#!/bin/bash
#
# ServerKit bootstrap installer.
#
#   curl -fsSL https://serverkit.ai/install.sh | bash
#
# By default the script clones the repository and builds from source. Two
# environment switches change that:
#
#   INSTALL_FROM_RELEASE=1   fetch a pre-built tarball instead of compiling
#   BUILD_FROM_SOURCE=1      force a source build even when a release exists
#   SERVERKIT_SKIP_SSL=1     run on plain HTTP (no HTTPS / no certbot attempt)
#
# The Flask backend runs straight on the host (it needs real system access);
# the React frontend is built to static files and served by the host nginx.
#
set -euo pipefail

# ---------------------------------------------------------------------------
# Settings and environment contract
# ---------------------------------------------------------------------------
SERVERKIT_DIR="${SERVERKIT_DIR:-/opt/serverkit}"
INSTALL_DIR="$SERVERKIT_DIR"
BASE_NAME="$(basename "$INSTALL_DIR")"
BASE_DIR="$(dirname "$INSTALL_DIR")"
DIR_A="$BASE_DIR/${BASE_NAME}-a"
DIR_B="$BASE_DIR/${BASE_NAME}-b"
VENV_DIR="${SERVERKIT_VENV_DIR:-$INSTALL_DIR/venv}"
LOG_DIR="/var/log/serverkit"
DATA_DIR="/var/lib/serverkit"
BACKUP_DIR="/var/backups/serverkit"
CONFIG_DIR="/etc/serverkit"

PYTHON_MIN="3.11"
PYTHON_MAX="3.12"
PYTHON_BIN=""

GITHUB_REPO="${GITHUB_REPO:-jhd3197/ServerKit}"
INSTALL_FROM_RELEASE="${INSTALL_FROM_RELEASE:-0}"
BUILD_FROM_SOURCE="${BUILD_FROM_SOURCE:-0}"
SERVERKIT_VERSION="${SERVERKIT_VERSION:-}"
VERSION="${VERSION:-${SERVERKIT_VERSION:-1.4.11}}"
CHANNEL="${CHANNEL:-Stable}"

PANEL_DOMAIN="${PANEL_DOMAIN:-}"
PANEL_PORT="${PANEL_PORT:-80}"
SERVERKIT_SKIP_SSL="${SERVERKIT_SKIP_SSL:-0}"
SERVERKIT_OFFLINE_TARBALL="${SERVERKIT_OFFLINE_TARBALL:-}"
SERVERKIT_MIRROR_URL="${SERVERKIT_MIRROR_URL:-}"

# Runtime state populated as we go (declared up-front for `set -u`).
OS_FAMILY="unknown"
ARCH=""
DL_ARCH=""
PKG_MGR=""
SAFE_MODE=false
SSL_MODE="insecure"
FIRST_SLOT="$DIR_A"

# Resolve where this script (and thus the bundled scripts/lib helpers) lives so
# shared libraries load whether we run from a clone, a release tree, or piped
# through `curl | bash`. The clone-relative path is tried first; once the source
# is on disk under $INSTALL_DIR that path works too.
SELF_DIR="$(cd "$(dirname "${BASH_SOURCE[0]:-$0}")" 2>/dev/null && pwd || true)"
load_serverkit_lib() {
    local name="$1" d
    for d in "$SELF_DIR/scripts/lib" "$INSTALL_DIR/scripts/lib"; do
        if [ -n "$d" ] && [ -f "$d/$name" ]; then
            # shellcheck source=/dev/null
            source "$d/$name"
            return 0
        fi
    done
    return 1
}

# ---------------------------------------------------------------------------
# Terminal styling
#
# Truecolor is used when the stream is an interactive terminal that has not
# opted out. The ServerKit identity is a violet ramp (V1 brightest .. V5
# deepest); status colors sit alongside it. Everything degrades to plain text
# when colour is unavailable so piped logs stay readable.
# ---------------------------------------------------------------------------
if [ -t 1 ] && [ -z "${NO_COLOR:-}" ] && [ "${TERM:-dumb}" != "dumb" ]; then
    ESC=$'\033'
    RST="${ESC}[0m"; BLD="${ESC}[1m"; DIMM="${ESC}[2m"
    paint() { printf '%s[38;2;%d;%d;%dm' "$ESC" "$1" "$2" "$3"; }
else
    RST=''; BLD=''; DIMM=''
    paint() { :; }
fi

V1="$(paint 196 181 253)"; V2="$(paint 167 139 250)"; V3="$(paint 139 92 246)"
V4="$(paint 124 58 237)";  V5="$(paint 109 40 217)"
PAPER="$(paint 237 233 254)"; ASH="$(paint 165 160 190)"; FOG="$(paint 113 108 140)"
HUE_OK="$(paint 52 211 153)"; HUE_WARN="$(paint 250 204 21)"
HUE_ERR="$(paint 248 113 113)"; HUE_LINK="$(paint 103 232 249)"

# Line-level reporting. Distinct verbs, distinct marks, single indent.
good()  { printf '  %s✔%s %s\n'  "$HUE_OK"   "$RST" "$1"; }
warn()  { printf '  %s▴%s %s\n'  "$HUE_WARN" "$RST" "$1"; }
halt()  { printf '  %s✘%s %s\n'  "$HUE_ERR"  "$RST" "$1" >&2; exit 1; }
step()  { printf '  %s❯%s %s\n'  "$HUE_LINK" "$RST" "$1"; }
faint() { printf '  %s%s%s\n'    "$FOG" "$1" "$RST"; }

# ---------------------------------------------------------------------------
# Phase headers
#
# Each major stage prints a numbered, time-stamped header followed by a violet
# rule. There is no global step total — the index plus elapsed clock is enough
# to read progress, and it never drifts out of sync with the actual path taken
# (source vs. release installs run different stages).
# ---------------------------------------------------------------------------
STARTED_AT=0
PHASE_N=0

clock() {
    [ "$STARTED_AT" -gt 0 ] || { printf ''; return; }
    local secs=$(( $(date +%s) - STARTED_AT ))
    printf '%dm %02ds' "$((secs / 60))" "$((secs % 60))"
}

phase() {
    PHASE_N=$((PHASE_N + 1))
    local t; t="$(clock)"
    printf '\n  %s%s%02d%s  %s%s%s  %s%s%s\n' \
        "$BLD" "$V3" "$PHASE_N" "$RST" "$BLD" "$1" "$RST" "$FOG" "$t" "$RST"
    printf '  %s%s%s\n\n' "$V4" "──────────────────────────────────────" "$RST"
}

# ---------------------------------------------------------------------------
# Masthead
# ---------------------------------------------------------------------------
masthead() {
    printf '\n'
    printf '  %s%s▖▌▌%s  %s%sServerKit%s  %sv%s%s  %s•%s %s%s%s\n' \
        "$BLD" "$V2" "$RST" "$BLD" "$PAPER" "$RST" "$FOG" "$VERSION" "$RST" \
        "$HUE_OK" "$RST" "$ASH" "$CHANNEL" "$RST"
    printf '  %s%s▌▖▌%s  %sSelf-hosted infrastructure, made simple.%s\n' \
        "$BLD" "$V3" "$RST" "$ASH" "$RST"
    printf '  %s%s▌▌▖%s  %sWeb apps · Databases · Docker · Email · DNS · Security%s\n' \
        "$BLD" "$V4" "$RST" "$FOG" "$RST"
    printf '  %s%s▘▘▘%s  %sPython + React, one command · serverkit.ai%s\n' \
        "$BLD" "$V5" "$RST" "$FOG" "$RST"
    printf '\n'
}

# ---------------------------------------------------------------------------
# Pre-flight: disk, memory, privileges
# ---------------------------------------------------------------------------
preflight() {
    step "Running pre-flight checks..."

    # Root first: every check and phase after this point may write to the
    # host (choose_pkg_manager drops an apt config file), so a non-root run
    # must die on THIS friendly message, not on the first raw
    # "Permission denied". (I11)
    if [ "$EUID" -ne 0 ]; then
        halt "Please run this installer as root (use sudo)."
    fi

    # Source builds need more headroom than unpacking a release.
    local need_kb=5242880
    [ "$INSTALL_FROM_RELEASE" = "1" ] && need_kb=2097152

    # Probe the filesystem that will actually hold the install — the target
    # tree rarely exists yet, so walk up to the nearest existing ancestor —
    # and use POSIX -Pk output so a long device name cannot wrap the line
    # and skew the awk parse. (I14)
    local probe="$INSTALL_DIR" parent
    while [ ! -d "$probe" ]; do
        parent="$(dirname "$probe")"
        [ "$parent" != "$probe" ] || break
        probe="$parent"
    done
    local free_kb
    free_kb=$(df -Pk "$probe" 2>/dev/null | awk 'NR==2 {print $4}') || free_kb=""
    if [ -n "$free_kb" ] && [ "$free_kb" -lt "$need_kb" ]; then
        halt "Need at least $((need_kb / 1024 / 1024))GB free on $probe; less is available."
    fi

    # `free` is missing from some LXC templates — skip the advisory memory
    # check rather than aborting on the bare assignment. (I14)
    local free_mem=""
    if command -v free &>/dev/null; then
        free_mem=$(free -m 2>/dev/null | awk '/^Mem:/ {print $7}') || free_mem=""
    else
        warn "'free' not found — skipping the memory check."
    fi
    if [ -n "$free_mem" ] && [ "$free_mem" -lt 256 ]; then
        warn "Under 256MB memory free — the install may run slowly."
    fi

    good "Pre-flight checks passed."
}

# ---------------------------------------------------------------------------
# Identify the OS family and CPU architecture
# ---------------------------------------------------------------------------
# Pure mapping from /etc/os-release ID (+ ID_LIKE fallback) to a ServerKit
# family. Kept as a standalone function so it is unit-testable without a real
# /etc/os-release. Echoes: debian|fedora|rhel|suse|arch|alpine|unknown.
os_family_from() {
    local id="$1" id_like="$2"
    case "$id" in
        ubuntu|linuxmint|pop|raspbian|elementary|zorin|debian|devuan)
            printf 'debian\n'; return ;;
        fedora|nobara)
            printf 'fedora\n'; return ;;
        rocky|almalinux|rhel|centos|ol|oracle|eurolinux)
            printf 'rhel\n'; return ;;
        opensuse*|sles|sled|suse|sle-micro)
            printf 'suse\n'; return ;;
        arch|manjaro|endeavouros|cachyos)
            printf 'arch\n'; return ;;
        alpine)
            printf 'alpine\n'; return ;;
    esac
    # Unknown ID — map via ID_LIKE to the closest supported family. Check rhel
    # before fedora: RHEL clones advertise ID_LIKE="rhel centos fedora" and want
    # the RHEL Docker repo, whereas a pure Fedora spin only lists "fedora".
    case " $id_like " in
        *debian*|*ubuntu*) printf 'debian\n' ;;
        *rhel*|*centos*)   printf 'rhel\n' ;;
        *fedora*)          printf 'fedora\n' ;;
        *suse*)            printf 'suse\n' ;;
        *arch*)            printf 'arch\n' ;;
        *alpine*)          printf 'alpine\n' ;;
        *)                 printf 'unknown\n' ;;
    esac
}

identify_system() {
    phase "Detecting System"

    local os_release="${SERVERKIT_OS_RELEASE:-/etc/os-release}"
    [ -f "$os_release" ] || halt "Cannot detect OS — $os_release is missing."
    # os-release defines its own VERSION ("24.04.1 LTS ..."), which would
    # clobber the installer's version string; ID/PRETTY_NAME are wanted
    # globals (provision_python keys off ID), so source in place and restore
    # just our VERSION afterwards. (I22)
    local sk_version="$VERSION"
    . "$os_release"
    VERSION="$sk_version"

    OS_FAMILY="$(os_family_from "${ID:-}" "${ID_LIKE:-}")"
    case "$OS_FAMILY" in
        unknown)
            warn "Untested OS '${ID:-unknown}' (ID_LIKE='${ID_LIKE:-}') — continuing anyway." ;;
        *)
            if [ "${ID:-}" = "$OS_FAMILY" ] || \
               { [ "$OS_FAMILY" = "debian" ] && [ "${ID:-}" = "ubuntu" ]; }; then
                good "Detected: ${PRETTY_NAME:-$ID} ($OS_FAMILY family)"
            else
                warn "Detected: ${PRETTY_NAME:-${ID:-unknown}} — treating as '$OS_FAMILY' family."
            fi
            ;;
    esac

    ARCH=$(uname -m)
    case "$ARCH" in
        x86_64)          DL_ARCH="amd64"; good "Architecture: x86_64" ;;
        aarch64|arm64)   DL_ARCH="arm64"; good "Architecture: ARM64" ;;
        *)               halt "Unsupported architecture: $ARCH" ;;
    esac
}

# ---------------------------------------------------------------------------
# Package manager abstraction (apt / dnf / yum)
# ---------------------------------------------------------------------------
# Detection order mirrors scripts/lib/pkg.sh. These run during the early
# dependency phase — before the repo (and thus scripts/lib) is on disk in the
# `curl | bash` path — so the logic is inline here and kept in sync with the lib.
choose_pkg_manager() {
    if command -v apt-get &>/dev/null; then
        PKG_MGR="apt"
        # unattended-upgrades can hold the dpkg lock right after boot; tell
        # apt to wait for it rather than failing outright.
        mkdir -p /etc/apt/apt.conf.d
        cat > /etc/apt/apt.conf.d/99-serverkit-lock-wait.conf <<'APT_EOF'
DPkg::Lock::Timeout "300";
APT_EOF
    elif command -v dnf &>/dev/null; then
        PKG_MGR="dnf"
    elif command -v yum &>/dev/null; then
        PKG_MGR="yum"
    elif command -v zypper &>/dev/null; then
        PKG_MGR="zypper"
    elif command -v pacman &>/dev/null; then
        PKG_MGR="pacman"
    elif command -v apk &>/dev/null; then
        PKG_MGR="apk"
    else
        halt "No supported package manager found (need apt, dnf, yum, zypper, pacman, or apk)."
    fi
}

refresh_pkg_index() {
    # Best-effort by design (mirrors scripts/lib/pkg.sh pkg_refresh): a failed
    # index refresh — flaky mirror, momentary lock — must never abort the
    # install, so every arm is guarded and the function always returns 0.
    # The --refresh flag is dnf-only; classic yum has no such flag, so its arm
    # is a plain makecache (same as pkg.sh).
    case "$PKG_MGR" in
        apt)    apt-get update -y >/dev/null 2>&1 || true ;;
        dnf)    dnf makecache --refresh >/dev/null 2>&1 || true ;;
        yum)    yum makecache >/dev/null 2>&1 || true ;;
        zypper) zypper --non-interactive refresh >/dev/null 2>&1 || true ;;
        pacman) pacman -Sy --noconfirm >/dev/null 2>&1 || true ;;
        apk)    apk update >/dev/null 2>&1 || true ;;
    esac
    return 0
}

# Warn-and-continue package install. Output is captured so a failure can be
# reported with the manager's last lines — and that capture carries an
# `|| rc=$?` guard because a bare `out=$(apt-get ...)` assignment is itself
# an abort point under `set -e`: the old body died on the assignment, before
# it could print anything at all. Always returns 0; callers that *require* a
# package must probe the resulting state (command -v, locate_python, ...)
# rather than this exit code.
pkg_add() {
    local out="" rc=0
    case "$PKG_MGR" in
        apt)    out=$(apt-get install -y "$@" 2>&1) || rc=$? ;;
        dnf)    out=$(dnf install -y "$@" 2>&1) || rc=$? ;;
        yum)    out=$(yum install -y "$@" 2>&1) || rc=$? ;;
        zypper) out=$(zypper --non-interactive install "$@" 2>&1) || rc=$? ;;
        pacman) out=$(pacman -S --noconfirm "$@" 2>&1) || rc=$? ;;
        apk)    out=$(apk add "$@" 2>&1) || rc=$? ;;
        *)      warn "No supported package manager — cannot install: $*"; return 0 ;;
    esac
    if [ "$rc" -ne 0 ]; then
        warn "Could not install: $* (exit $rc)"
        printf '%s\n' "$out" | tail -5 >&2 || true
    fi
    return 0
}

# ---------------------------------------------------------------------------
# RHEL-family (Rocky/Alma/RHEL/CentOS 9): upgrade openssh + openssl TOGETHER,
# up front, before any other dnf transaction runs.
#
# Rocky 9 images ship openssh linked against openssl-libs 3.0.x while the
# updates stream carries openssl-libs 3.5.x plus a matching openssh rebuild.
# Any later `dnf install` that pulls dependencies can transitively upgrade
# openssl-libs; if openssh is not upgraded in the SAME transaction, every new
# sshd fork dies with "OpenSSL version mismatch" — remote installs over SSH
# then cut themselves off mid-run. Upgrading both together lets openssh's
# scriptlet restart sshd against the matched libssl (KillMode=process keeps
# the live SSH session alive). Do NOT rewrite this with --exclude=openssl
# shapes; they fail on python3-libs symbol requirements. Best-effort: a box
# without the updates repo (or already current) is a clean no-op.
# ---------------------------------------------------------------------------
upgrade_rhel_crypto_stack() {
    [ "$OS_FAMILY" = "rhel" ] || return 0
    command -v dnf &>/dev/null || return 0
    step "Upgrading openssh/openssl together (avoids sshd 'OpenSSL version mismatch')..."
    dnf upgrade -y openssh openssh-server openssh-clients openssl openssl-libs openssl-devel 2>/dev/null || true
    return 0
}

# ---------------------------------------------------------------------------
# Memory tuning: low-RAM safe mode and a swap fallback
# ---------------------------------------------------------------------------
gauge_memory() {
    # `free` is missing from some LXC templates — degrade to "no safe mode"
    # instead of aborting on the bare assignment under pipefail. (I14)
    local total=""
    if command -v free &>/dev/null; then
        total=$(free -m 2>/dev/null | awk '/^Mem:/ {print $2}') || total=""
    fi
    if [ -z "$total" ]; then
        SAFE_MODE=false
        warn "Cannot read total memory ('free' missing) — skipping the low-RAM check."
        return 0
    fi
    if [ "$total" -le 700 ]; then
        SAFE_MODE=true
        warn "Low RAM (${total}MB) — enabling VPS safe mode."
    else
        SAFE_MODE=false
    fi
}

ensure_swap() {
    # No `free` (some LXC templates) → cannot gauge swap; skip quietly. (I14)
    if ! command -v free &>/dev/null; then
        warn "'free' not found — skipping the swap check."
        return 0
    fi
    # The swapfile path and /proc/swaps are overridable so the unit tests can
    # exercise this against fixtures (same pattern as SERVERKIT_NGINX_DIR).
    local swapfile="${SERVERKIT_SWAPFILE:-/swapfile}"
    local proc_swaps="${SERVERKIT_PROC_SWAPS:-/proc/swaps}"
    local swap
    swap=$(free -m 2>/dev/null | awk '/^Swap:/ {print $2}') || swap=""
    [ -n "$swap" ] || return 0
    if [ "$swap" -lt 512 ]; then
        step "Adding 1GB of swap..."
        # Every arm is guarded: fallocate is unsupported on some filesystems,
        # dd dies on a full disk, and swapon fails outright on btrfs/zfs and
        # in most containers. The old body claimed "Swap active." no matter
        # what and the Vite build then OOM'd — verify via swapon --show /
        # /proc/swaps before saying so, and degrade to a warning when no swap
        # could actually be brought up. (I19)
        if [ ! -f "$swapfile" ]; then
            if fallocate -l 1G "$swapfile" 2>/dev/null || \
               dd if=/dev/zero of="$swapfile" bs=1M count=1024 status=none 2>/dev/null; then
                chmod 600 "$swapfile" 2>/dev/null || true
                mkswap "$swapfile" >/dev/null 2>&1 || true
            else
                # A dd that died on a full disk leaves a partial file behind.
                rm -f "$swapfile" 2>/dev/null || true
            fi
        fi
        swapon "$swapfile" 2>/dev/null || true
        if swapon --show 2>/dev/null | grep -q "$swapfile" || \
           grep -qs "$swapfile" "$proc_swaps"; then
            good "Swap active."
        else
            warn "Could not activate swap (full disk, unsupported filesystem, or container limits)."
            warn "Continuing without it — a low-RAM box may need swap for the frontend build."
        fi
    fi
    return 0
}

# ---------------------------------------------------------------------------
# Python 3.11/3.12 — detect a usable interpreter or build one
# ---------------------------------------------------------------------------
ver_in_range() {
    # true when $1 is >= PYTHON_MIN and <= PYTHON_MAX
    printf '%s\n%s' "$PYTHON_MIN" "$1" | sort -C -V && \
    printf '%s\n%s' "$1" "$PYTHON_MAX" | sort -C -V
}

# True when <python> can actually create virtual environments. Debian/Ubuntu
# minimal images split the venv module (ensurepip) into pythonX.Y-venv, so an
# otherwise-valid interpreter still dies much later at `python -m venv` with
# "ensurepip is not available" — probe up front instead. (I8)
py_venv_ok() {
    "$1" -m venv --help >/dev/null 2>&1
}

locate_python() {
    # Prefer an explicit minor version, newest first, then bare python3. This
    # mirrors scripts/update.sh so a box that has python3.11 (Debian 12) but a
    # too-new/too-old default python3 is still recognized. A candidate must
    # also be venv-capable (py_venv_ok); on Debian-family boxes the missing
    # pythonX.Y-venv package is installed on demand before the candidate is
    # given up on. Sets PYTHON_BIN and returns 0 on success; returns 1
    # (without aborting) when nothing fits.
    local c v
    for c in python3.12 python3.11 python3; do
        if command -v "$c" &>/dev/null; then
            v=$("$c" -c 'import sys;print(".".join(map(str,sys.version_info[:2])))' 2>/dev/null || true)
            if [ -n "$v" ] && ver_in_range "$v"; then
                if ! py_venv_ok "$c" && [ "$OS_FAMILY" = "debian" ]; then
                    step "Installing python${v}-venv (the venv module is missing)..."
                    pkg_add "python${v}-venv"
                    py_venv_ok "$c" || pkg_add python3-venv
                fi
                if ! py_venv_ok "$c"; then
                    warn "$c (Python $v) cannot create virtualenvs (no venv/ensurepip) — skipping it."
                    continue
                fi
                PYTHON_BIN="$c"
                good "Using $c (Python $v)"
                return 0
            fi
        fi
    done
    PYTHON_BIN=""
    return 1
}

build_python_from_source() {
    cd /tmp
    wget -q https://www.python.org/ftp/python/3.12.8/Python-3.12.8.tgz
    tar xzf Python-3.12.8.tgz
    cd Python-3.12.8
    ./configure --enable-optimizations --prefix=/usr/local 2>&1 | tail -1
    make -j"$(nproc)" 2>&1 | tail -1
    make altinstall 2>&1 | tail -1
    cd /tmp && rm -rf Python-3.12.8 Python-3.12.8.tgz
}

provision_python() {
    phase "Installing Python"

    # Already have a supported interpreter? Nothing to do.
    if locate_python; then
        return
    fi

    warn "No supported Python ($PYTHON_MIN–$PYTHON_MAX) found — installing one."

    # Prefer the distro's own package over a source compile. Debian 12 ships
    # python3.11; Ubuntu 24.04 ships python3.12 (older Ubuntu falls back to the
    # deadsnakes PPA); Fedora/RHEL provide 3.12 or 3.11 in their repos. A slow,
    # fragile source build is now strictly the last resort. pkg_add is
    # warn-and-continue (always returns 0), so each attempt is followed by a
    # state probe (command -v) to decide whether the next fallback is needed.
    if [ "$OS_FAMILY" = "debian" ]; then
        if [ "${ID:-}" = "ubuntu" ]; then
            pkg_add python3.12 python3.12-venv python3.12-dev
            if ! command -v python3.12 &>/dev/null; then
                step "Adding deadsnakes PPA for Python 3.12..."
                pkg_add software-properties-common
                add-apt-repository -y ppa:deadsnakes/ppa || true
                refresh_pkg_index
                pkg_add python3.12 python3.12-venv python3.12-dev
            fi
        else
            # Debian (and Debian-like): python3.11 lives in the main repo.
            refresh_pkg_index
            pkg_add python3.11 python3.11-venv python3.11-dev
            command -v python3.11 &>/dev/null || \
                pkg_add python3.12 python3.12-venv python3.12-dev
        fi
    elif [ "$OS_FAMILY" = "fedora" ] || [ "$OS_FAMILY" = "rhel" ]; then
        pkg_add python3.12 python3.12-devel
        command -v python3.12 &>/dev/null || pkg_add python3.11 python3.11-devel
    elif [ "$OS_FAMILY" = "suse" ]; then
        pkg_add python311 python311-devel
        command -v python3.11 &>/dev/null || pkg_add python312 python312-devel
    elif [ "$OS_FAMILY" = "arch" ]; then
        # Rolling release — `python` is already 3.11+.
        pkg_add python
    elif [ "$OS_FAMILY" = "alpine" ]; then
        pkg_add python3 python3-dev
    fi

    # Did a distro package give us something usable?
    if locate_python; then
        good "Python ready: $PYTHON_BIN"
        return
    fi

    # Last resort: compile from source.
    warn "Distro packages did not provide a supported Python — building from source."
    if [ "$OS_FAMILY" = "debian" ]; then
        pkg_add wget zlib1g-dev libbz2-dev libreadline-dev \
            libsqlite3-dev libncurses5-dev libncursesw5-dev \
            xz-utils tk-dev liblzma-dev libffi-dev libssl-dev
    else
        pkg_add wget zlib-devel bzip2-devel readline-devel \
            sqlite-devel ncurses-devel xz-devel tk-devel libffi-devel
    fi
    build_python_from_source
    PYTHON_BIN="python3.12"

    command -v "$PYTHON_BIN" &>/dev/null || \
        halt "Could not install a supported Python — install Python 3.11 or 3.12 by hand."
    good "Python installed ($PYTHON_BIN)."
}

# ---------------------------------------------------------------------------
# Docker engine + compose plugin
# ---------------------------------------------------------------------------
# Add Docker's upstream .repo file, handling both config-manager generations:
# classic dnf4 uses `--add-repo URL`, while dnf5 (Fedora 41+) removed that
# flag in favour of `addrepo --from-repofile=URL`. Warn-and-continue: when
# neither works the docker-ce install below fails too (also non-fatally). (I10)
docker_repo_add() {
    local url="$1"
    if dnf config-manager --add-repo "$url" >/dev/null 2>&1; then
        return 0
    fi
    if dnf config-manager addrepo --from-repofile="$url" >/dev/null 2>&1; then
        return 0
    fi
    warn "Could not add the Docker repository ($url)."
    return 0
}

provision_docker() {
    phase "Docker"

    if command -v docker &>/dev/null; then
        good "Docker already present: $(docker --version | head -1)"
        return
    fi

    step "Installing Docker..."
    case "$OS_FAMILY" in
        fedora)
            pkg_add dnf-plugins-core
            docker_repo_add https://download.docker.com/linux/fedora/docker-ce.repo
            pkg_add docker-ce docker-ce-cli containerd.io docker-compose-plugin docker-buildx-plugin
            ;;
        rhel)
            pkg_add dnf-plugins-core
            docker_repo_add https://download.docker.com/linux/rhel/docker-ce.repo
            pkg_add docker-ce docker-ce-cli containerd.io docker-compose-plugin docker-buildx-plugin
            ;;
        suse)
            pkg_add docker docker-compose
            ;;
        arch)
            pkg_add docker docker-compose
            ;;
        alpine)
            pkg_add docker docker-cli-compose
            ;;
        *)
            # Docker's convenience script (the default Debian/Ubuntu path).
            # Stage it to a temp file with retries instead of piping curl
            # straight into sh — a connection dropped mid-download would
            # otherwise execute half a script. Warn-and-continue on failure,
            # falling back to the distro package (docker.io on Debian). (I13)
            local dget drc=0
            dget="$(mktemp 2>/dev/null)" || dget="/tmp/serverkit-get-docker.sh"
            if curl -fsSL --retry 3 https://get.docker.com -o "$dget"; then
                sh "$dget" || drc=$?
            else
                drc=1
            fi
            rm -f "$dget" 2>/dev/null || true
            if [ "$drc" -ne 0 ]; then
                warn "The get.docker.com install script failed — trying the distro package instead."
                pkg_add docker.io docker-compose-v2
            fi
            ;;
    esac

    # Enable + start across init systems (systemd on most families, OpenRC on
    # Alpine). Guarded so a non-systemd box doesn't abort the install here.
    if command -v systemctl &>/dev/null && [ -d /run/systemd/system ]; then
        systemctl enable docker 2>/dev/null || true
        systemctl start docker 2>/dev/null || true
    elif command -v rc-update &>/dev/null; then
        rc-update add docker default 2>/dev/null || true
        rc-service docker start 2>/dev/null || true
    fi
    # Don't claim success the old unconditional way — probe. Docker stays
    # best-effort here (managed app deploys need it, the panel itself runs
    # without it), so a miss is a loud warning, not a halt. (I13)
    if command -v docker &>/dev/null; then
        good "Docker installed."
    else
        warn "Docker could not be installed — managed app deployments need it."
        warn "Install it manually (https://docs.docker.com/engine/install/) when you need containers."
    fi
}

ensure_compose_plugin() {
    if docker compose version &>/dev/null; then
        good "Docker Compose plugin present."
        return
    fi
    step "Installing Docker Compose plugin..."
    # Fallback chain (I9): when Docker came from the distro repo (docker.io),
    # Docker's own repo was never configured, so 'docker-compose-plugin' does
    # not exist there — Ubuntu ships the same plugin as 'docker-compose-v2'.
    # Probe after each attempt; if neither lands, warn and continue (the box
    # may have compose v1, or the operator can add it later).
    pkg_add docker-compose-plugin
    if ! docker compose version &>/dev/null; then
        pkg_add docker-compose-v2
    fi
    if docker compose version &>/dev/null; then
        good "Docker Compose plugin installed."
    else
        warn "Could not install the Docker Compose plugin — 'docker compose' is unavailable."
        warn "Managed app deployments need it; install docker-compose-plugin or docker-compose-v2 manually."
    fi
}

# ---------------------------------------------------------------------------
# Node.js 20 (only needed for source builds — releases ship a built frontend)
# ---------------------------------------------------------------------------
# Node 18+ is the floor for the Vite frontend build. Distro nodejs on every
# currently-supported target (Ubuntu 24.04, Debian 12, Fedora 40+) already meets
# it, so we install the distro package first and only pipe NodeSource into bash
# when the distro can't deliver a new-enough Node + npm.
node_major()  { node --version 2>/dev/null | sed -E 's/^v([0-9]+).*/\1/'; }
node_ready()  {
    command -v node &>/dev/null && command -v npm &>/dev/null || return 1
    local m; m="$(node_major)"
    [ -n "$m" ] && [ "$m" -ge 18 ] 2>/dev/null
}

provision_node() {
    phase "Node.js"

    if [ "$INSTALL_FROM_RELEASE" = "1" ]; then
        good "Skipping Node.js — the release ships a pre-built frontend."
        return
    fi

    if node_ready; then
        good "Node.js already present: $(node --version)"
        return
    fi

    step "Installing Node.js (distro repo first)..."
    # Debian/Ubuntu split npm into its own package; Fedora bundles it.
    pkg_add nodejs npm 2>/dev/null || pkg_add nodejs 2>/dev/null || true
    command -v npm &>/dev/null || pkg_add npm 2>/dev/null || true

    if ! node_ready; then
        warn "Distro Node.js is missing or older than 18 — falling back to NodeSource 20."
        if [ "$OS_FAMILY" = "debian" ]; then
            curl -fsSL https://deb.nodesource.com/setup_20.x | bash - >/dev/null 2>&1 || true
        else
            curl -fsSL https://rpm.nodesource.com/setup_20.x | bash - >/dev/null 2>&1 || true
        fi
        pkg_add nodejs || true
    fi

    node_ready || \
        halt "Node.js 18+ (with npm) is required but could not be installed. Install Node 20 LTS and re-run."
    good "Node.js $(node --version) installed."
}

# ---------------------------------------------------------------------------
# Live-state carry: keep .env + backend/instance/ across a slot rewrite
# ---------------------------------------------------------------------------
# fetch_release and sync_source both rebuild $FIRST_SLOT with an rm -rf. On a
# re-run over an existing install that tree holds irreplaceable state: the
# generated .env (SECRET_KEY / JWT_SECRET_KEY / SERVERKIT_ENCRYPTION_KEY —
# losing that key orphans every encrypted secret) and backend/instance/ (the
# SQLite database). Copy them aside before the rewrite and restore them after,
# mirroring scripts/update.sh's deploy_source carry-forward. Both helpers are
# best-effort and always return 0 — preservation must never abort an install.
stash_live_state() {
    # Echoes a stash directory holding the live state, or nothing when there
    # is nothing to preserve (fresh install) or no stash could be created.
    local src="$1" stash
    if [ ! -f "$src/.env" ] && [ ! -d "$src/backend/instance" ]; then
        return 0
    fi
    stash="$(mktemp -d 2>/dev/null || true)"
    [ -n "$stash" ] || return 0
    cp -a "$src/.env" "$stash/.env" 2>/dev/null || true
    cp -a "$src/backend/instance" "$stash/instance" 2>/dev/null || true
    printf '%s' "$stash"
    return 0
}

restore_live_state() {
    local stash="$1" dest="$2"
    [ -n "$stash" ] || return 0
    if [ -f "$stash/.env" ]; then
        cp -a "$stash/.env" "$dest/.env" 2>/dev/null || true
    fi
    if [ -d "$stash/instance" ]; then
        mkdir -p "$dest/backend" 2>/dev/null || true
        rm -rf "$dest/backend/instance" 2>/dev/null || true
        cp -a "$stash/instance" "$dest/backend/instance" 2>/dev/null || true
    fi
    rm -rf "$stash" 2>/dev/null || true
    good "Preserved the existing .env and database across the rewrite."
    return 0
}

# ---------------------------------------------------------------------------
# Release tarball path
# ---------------------------------------------------------------------------
resolve_release_tag() {
    if [ -n "$SERVERKIT_VERSION" ]; then
        printf '%s' "$SERVERKIT_VERSION"
        return
    fi
    # Primary: the releases/latest redirect. Its Location header carries the
    # tag and — unlike api.github.com, which allows only 60 requests/hour per
    # IP and is routinely exhausted behind shared cloud NAT — it has no API
    # quota. The API lookup stays as the fallback. Both arms are guarded so
    # an unresolvable tag comes back as EMPTY output (the caller warns loudly)
    # instead of a set -e abort. (I15)
    local tag=""
    tag=$(curl -sfLI -o /dev/null -w '%{url_effective}' \
            "https://github.com/${GITHUB_REPO}/releases/latest" 2>/dev/null \
        | sed -n 's|.*/releases/tag/||p') || tag=""
    if [ -n "$tag" ]; then
        printf '%s' "$tag"
        return 0
    fi
    curl -sf "https://api.github.com/repos/${GITHUB_REPO}/releases/latest" 2>/dev/null \
        | grep '"tag_name"' | head -1 | cut -d'"' -f4 || true
}

fetch_release() {
    phase "Downloading Pre-built Release"

    local tag tarball tmp_dir unpacked

    if [ -n "$SERVERKIT_OFFLINE_TARBALL" ]; then
        [ -f "$SERVERKIT_OFFLINE_TARBALL" ] || halt "Offline tarball not found: $SERVERKIT_OFFLINE_TARBALL"
        tag="offline"
        tarball="$SERVERKIT_OFFLINE_TARBALL"
        good "Using offline tarball: $tarball"
    else
        tag=$(resolve_release_tag) || tag=""
        if [ -z "$tag" ]; then
            # Loud on purpose: this used to be a silent downgrade that turned
            # a 2-minute release install into a full compile. (I15)
            warn "Could not resolve the latest release tag (GitHub unreachable or API rate-limited)."
            warn "FALLING BACK TO A FULL SOURCE BUILD — much slower, and it compiles the frontend here."
            warn "To install a release instead, pin one: SERVERKIT_VERSION=vX.Y.Z"
            INSTALL_FROM_RELEASE=0
            return 1
        fi
        good "Latest release: $tag"

        local base
        if [ -n "$SERVERKIT_MIRROR_URL" ]; then
            base="$SERVERKIT_MIRROR_URL"
        else
            base="https://github.com/${GITHUB_REPO}/releases/download/${tag}"
        fi

        tarball="/tmp/serverkit-${tag}-linux-${DL_ARCH}.tar.gz"
        step "Fetching release tarball (${DL_ARCH})..."
        if ! curl -sfL "${base}/serverkit-${tag}-linux-${DL_ARCH}.tar.gz" -o "$tarball"; then
            warn "No release tarball for this platform — falling back to source."
            INSTALL_FROM_RELEASE=0
            return 1
        fi

        step "Verifying checksum..."
        if curl -sfL "${base}/checksums.txt" -o "/tmp/serverkit-checksums-${tag}.txt"; then
            if ! (cd /tmp && sha256sum -c <(grep "serverkit-${tag}-linux-${DL_ARCH}.tar.gz" "serverkit-checksums-${tag}.txt") >/dev/null 2>&1); then
                halt "Checksum verification failed for release tarball."
            fi
            good "Checksum verified"
        else
            warn "Could not download checksums.txt — skipping verification"
        fi
    fi

    step "Unpacking release..."
    tmp_dir="$(mktemp -d)"
    # A failed unpack (corrupt download, disk full) must take the clean
    # source fallback, not "succeed" into a half-written tree. (I16)
    if ! tar xzf "$tarball" -C "$tmp_dir"; then
        warn "Could not unpack the release tarball (corrupt download or disk full) — falling back to source."
        rm -rf "$tmp_dir"
        INSTALL_FROM_RELEASE=0
        return 1
    fi

    unpacked="$tmp_dir/serverkit"
    [ ! -d "$unpacked" ] && unpacked="$tmp_dir/opt/serverkit"
    if [ ! -d "$unpacked" ]; then
        unpacked="$(find "$tmp_dir" -maxdepth 2 -type d -name serverkit | head -n1)"
    fi
    [ -d "$unpacked" ] || halt "Release tarball layout is unrecognized (expected serverkit/ or opt/serverkit/)."

    ensure_install_layout

    # A re-run over a live install must never destroy its secrets or database
    # (the old bare rm -rf below did exactly that). Stash them, rewrite,
    # restore. (I4)
    local live_dir stash
    live_dir="$(readlink -f "$INSTALL_DIR" 2>/dev/null || echo "$FIRST_SLOT")"
    [ -d "$live_dir" ] || live_dir="$FIRST_SLOT"
    stash="$(stash_live_state "$live_dir")"

    rm -rf "$FIRST_SLOT"
    # Disk full mid-copy: a half-written slot must not masquerade as a
    # success. Put the live state back and hand control to the caller's
    # source fallback. (I16)
    if ! cp -a "$unpacked" "$FIRST_SLOT"; then
        warn "Could not copy the release into $FIRST_SLOT (disk full?) — falling back to source."
        rm -rf "$tmp_dir"
        mkdir -p "$FIRST_SLOT" 2>/dev/null || true
        restore_live_state "$stash" "$FIRST_SLOT"
        INSTALL_FROM_RELEASE=0
        return 1
    fi
    rm -rf "$tmp_dir"
    restore_live_state "$stash" "$FIRST_SLOT"

    [ -L "$INSTALL_DIR" ] || ln -s "$FIRST_SLOT" "$INSTALL_DIR"

    chmod +x "$INSTALL_DIR/serverkit"
    chmod +x "$INSTALL_DIR/scripts/"*.sh 2>/dev/null || true
    good "Release unpacked into $FIRST_SLOT"
}

# ---------------------------------------------------------------------------
# Source path: fetch / refresh the repository
# ---------------------------------------------------------------------------
sync_source() {
    phase "Source Code"

    # Source installs clone with git, but minimal images don't guarantee it
    # and the preflight never checked — install it on demand, and halt only
    # if that fails too (a source install cannot proceed without git). (I7)
    if ! command -v git &>/dev/null; then
        step "Installing git..."
        pkg_add git
        command -v git &>/dev/null || \
            halt "git is required for a source install but could not be installed."
    fi

    ensure_install_layout

    if [ -d "$FIRST_SLOT/.git" ]; then
        step "Refreshing the existing checkout..."
        cd "$FIRST_SLOT"
        if ! git pull --ff-only; then
            warn "Fast-forward failed (local edits?) — hard-resetting to origin/main."
            git fetch origin
            git reset --hard origin/main
        fi
    else
        step "Cloning ServerKit..."
        # Same live-state carry as fetch_release: the non-git tree replaced
        # here may still be a live install (e.g. one installed from a release
        # tarball) holding the generated .env and the database. (I4)
        local stash
        stash="$(stash_live_state "$FIRST_SLOT")"
        rm -rf "$FIRST_SLOT"
        git clone --depth 1 "https://github.com/${GITHUB_REPO}.git" "$FIRST_SLOT"
        restore_live_state "$stash" "$FIRST_SLOT"
        cd "$FIRST_SLOT"
    fi
    [ -L "$INSTALL_DIR" ] || ln -sfn "$FIRST_SLOT" "$INSTALL_DIR"
    good "Repository ready."
}

# ---------------------------------------------------------------------------
# On-disk layout (blue/green slots + symlink)
# ---------------------------------------------------------------------------
ensure_install_layout() {
    # Migrate legacy real-directory installs into the blue/green layout.
    if [ -d "$INSTALL_DIR" ] && [ ! -L "$INSTALL_DIR" ]; then
        step "Migrating to blue/green install layout..."
        # A stale slot left by an aborted earlier run would make `mv` NEST
        # the live tree inside it ($FIRST_SLOT/serverkit). The live install
        # is $INSTALL_DIR (a real dir here, so nothing links to the slot) —
        # clear the stale slot before moving. (I18)
        if [ -e "$FIRST_SLOT" ]; then
            warn "Removing a stale $FIRST_SLOT left by an earlier run."
            rm -rf "$FIRST_SLOT"
        fi
        mv "$INSTALL_DIR" "$FIRST_SLOT"
        ln -s "$FIRST_SLOT" "$INSTALL_DIR"
        good "Active install is now $INSTALL_DIR → $FIRST_SLOT"
    fi

    mkdir -p "$DIR_A" "$DIR_B"
    [ -L "$INSTALL_DIR" ] || ln -s "$FIRST_SLOT" "$INSTALL_DIR"
}

make_directories() {
    phase "Creating Directories"

    ensure_install_layout

    local d
    for d in "$LOG_DIR" "$DATA_DIR" "$BACKUP_DIR" "$CONFIG_DIR" "$INSTALL_DIR/backend/instance"; do
        mkdir -p -m 0750 "$d"
    done
    for d in "$INSTALL_DIR/nginx/ssl" /etc/serverkit/templates /var/serverkit/apps \
             /var/www/acme /etc/nginx/serverkit-locations; do
        mkdir -p -m 0755 "$d"
    done

    good "Directories created."
}

# ---------------------------------------------------------------------------
# Python virtual environment + dependencies
# ---------------------------------------------------------------------------
build_virtualenv() {
    phase "Python Environment"

    # If the release shipped a pre-built venv at the expected path, use it.
    if [ "$INSTALL_FROM_RELEASE" = "1" ] && [ -f "$FIRST_SLOT/venv/bin/activate" ] && [ -x "$FIRST_SLOT/venv/bin/python" ]; then
        step "Using pre-built virtual environment from release..."
        # In the default layout $INSTALL_DIR is a symlink to $FIRST_SLOT, so
        # $VENV_DIR *is* $FIRST_SLOT/venv — the rm -rf below would delete the
        # very venv it is about to "copy", and the cp would then fail. When
        # source and destination resolve to the same directory the venv is
        # already in place; verify and keep it. (I3)
        local src_venv dst_venv
        src_venv="$(readlink -f "$FIRST_SLOT/venv" 2>/dev/null || echo "$FIRST_SLOT/venv")"
        dst_venv="$(readlink -f "$VENV_DIR" 2>/dev/null || echo "$VENV_DIR")"
        if [ "$src_venv" = "$dst_venv" ]; then
            good "Virtual environment already in place from the release."
            return
        fi
        rm -rf "$VENV_DIR"
        cp -a "$FIRST_SLOT/venv" "$VENV_DIR"
        good "Virtual environment installed from release."
        return
    fi

    step "Creating the virtual environment..."
    $PYTHON_BIN -m venv "$VENV_DIR"
    if [ ! -f "$VENV_DIR/bin/activate" ]; then
        halt "Virtual environment creation failed: $VENV_DIR/bin/activate not found."
    fi
    source "$VENV_DIR/bin/activate"

    step "Installing Python dependencies..."
    pip install --upgrade pip --quiet
    if [ "$SAFE_MODE" = true ]; then
        pip install --no-cache-dir -r "$INSTALL_DIR/backend/requirements.txt" --quiet
    else
        pip install -r "$INSTALL_DIR/backend/requirements.txt" --quiet
    fi
    pip install gunicorn gevent gevent-websocket --quiet

    good "Python environment ready."
}

# ---------------------------------------------------------------------------
# Application configuration and generated secrets
# ---------------------------------------------------------------------------
write_config() {
    phase "Configuration"

    if [ -f "$INSTALL_DIR/.env" ]; then
        warn ".env already exists — leaving the current configuration in place."
        # ...except the SSL mode, which reflects THIS run's outcome (a re-run
        # may have gained or lost HTTPS). Refresh just that key so the
        # panel's HSTS gate matches /etc/serverkit/ssl-mode instead of a
        # stale value from the previous install. (I24)
        if grep -q '^SERVERKIT_SSL_MODE=' "$INSTALL_DIR/.env"; then
            sed -i "s|^SERVERKIT_SSL_MODE=.*|SERVERKIT_SSL_MODE=$SSL_MODE|" "$INSTALL_DIR/.env"
        else
            printf 'SERVERKIT_SSL_MODE=%s\n' "$SSL_MODE" >> "$INSTALL_DIR/.env"
        fi
        return
    fi

    step "Generating configuration..."
    local secret_key jwt_secret encryption_key
    secret_key=$(openssl rand -hex 32)
    jwt_secret=$(openssl rand -hex 32)
    encryption_key=$("${PYTHON_BIN:-python3}" -c 'import base64, os; print(base64.urlsafe_b64encode(os.urandom(32)).decode())')

    # Widen CORS / advertise a public URL when a panel domain is known.
    local public_url="" cors_origins="http://localhost,https://localhost"
    local url_scheme="http"
    if [ -n "$PANEL_DOMAIN" ]; then
        if [ "$SSL_MODE" = "secure" ]; then
            url_scheme="https"
            cors_origins="http://localhost,https://localhost,https://$PANEL_DOMAIN"
        else
            url_scheme="http"
            cors_origins="http://localhost,https://localhost,http://$PANEL_DOMAIN"
        fi
        public_url="${url_scheme}://$PANEL_DOMAIN"
    fi

    cat > "$INSTALL_DIR/.env" <<EOF
# ServerKit Configuration
# Generated on $(date)

# Security Keys (auto-generated, keep secret!)
SECRET_KEY=$secret_key
JWT_SECRET_KEY=$jwt_secret
SERVERKIT_ENCRYPTION_KEY=$encryption_key

# Database (SQLite by default)
DATABASE_URL=sqlite:///$INSTALL_DIR/backend/instance/serverkit.db

# CORS Origins (comma-separated, add your domain)
CORS_ORIGINS=$cors_origins

# Public URL for agents and install commands (optional)
${public_url:+# SERVERKIT_PUBLIC_URL=$public_url}

# SSL mode (secure|insecure) — gates the panel's HSTS header so HTTPS stays
# optional. Mirrors /etc/serverkit/ssl-mode; set to 'secure' only when this
# server terminates real end-to-end HTTPS.
SERVERKIT_SSL_MODE=$SSL_MODE

# Ports
PORT=80
SSL_PORT=443

# Environment
FLASK_ENV=production
EOF
    chmod 600 "$INSTALL_DIR/.env"
    good "Configuration generated."

    # When a domain is configured, bounce bare-IP visitors to it.
    if [ -n "$PANEL_DOMAIN" ]; then
        mkdir -p /etc/nginx/serverkit-conf.d
        cat > /etc/nginx/serverkit-conf.d/canonical-domain.conf <<EOF
# Auto-generated by ServerKit install.sh
# Redirect direct IP access to the canonical panel domain.
server {
    listen 80 default_server;
    server_name _;
    if (\$host ~* ^[0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+\$) {
        return 301 ${url_scheme}://$PANEL_DOMAIN\$request_uri;
    }
}
EOF
        good "Canonical-domain redirect configured for $PANEL_DOMAIN"
    fi
}

# ---------------------------------------------------------------------------
# Frontend build (skipped on release installs)
# ---------------------------------------------------------------------------
build_frontend() {
    phase "Frontend Build"

    if [ "$INSTALL_FROM_RELEASE" = "1" ]; then
        good "Using the pre-built frontend from the release."
        return
    fi

    step "Installing npm packages..."
    cd "$INSTALL_DIR/frontend"
    npm ci --prefer-offline 2>&1 | tail -3

    step "Compiling the frontend bundle..."
    NODE_OPTIONS="--max-old-space-size=1024" npm run build 2>&1 | tail -5
    good "Frontend built."
}

# ---------------------------------------------------------------------------
# Firewall: open 80/443 so the panel is reachable from the outside, and record
# exactly what we opened in /etc/serverkit/install-state.json so uninstall can
# undo only those rules. Fresh RHEL-family boxes run firewalld by default, which
# is the #1 reason an otherwise-good install looks "broken" (port 80 blocked).
# ---------------------------------------------------------------------------
configure_firewall() {
    phase "Firewall"

    if ! load_serverkit_lib firewall.sh; then
        warn "Firewall helper not found — open ports 80/443 manually if needed."
        return 0
    fi
    load_serverkit_lib state.sh || true

    local backend
    backend="$(firewall_detect)"
    if [ "$backend" = "none" ]; then
        warn "No active firewall detected — assuming ports 80/443 are already open."
        return 0
    fi

    step "Opening HTTP/HTTPS (80, 443) via $backend..."
    firewall_open "$backend" 80/tcp 443/tcp
    if [ "${FW_DRY_RUN:-0}" != "1" ] && command -v state_set >/dev/null 2>&1; then
        # Best-effort, exactly like update.sh's ensure_firewall: failing to
        # RECORD the opened ports must not abort an install whose firewall
        # work already succeeded. (I21)
        state_set firewall_backend "$backend" || true
        state_append firewall_ports 80/tcp || true
        state_append firewall_ports 443/tcp || true
    fi
    good "Firewall configured ($backend): 80/tcp and 443/tcp open."
}

# ---------------------------------------------------------------------------
# Init-system probe + tiny service verbs (mirrors scripts/lib/init.sh)
# ---------------------------------------------------------------------------
# install.sh runs pre-clone in the `curl | bash` path, so it cannot source
# scripts/lib/init.sh — the detection is inline here and kept in sync with the
# lib: systemd when /run/systemd/system exists, then OpenRC/SysV fallbacks.
# INIT_OVERRIDE (same contract as init.sh) forces the answer for unit tests.
# Best-effort: on a box none of these can drive (containers, WSL) the verbs
# warn and return 0 — a missing init system must never abort the install. (I17)
svc_has_systemd() {
    if [ -n "${INIT_OVERRIDE:-}" ]; then
        [ "$INIT_OVERRIDE" = "systemd" ]
        return
    fi
    [ -d /run/systemd/system ] && command -v systemctl &>/dev/null
}

svc_enable() {
    local svc="$1"
    if svc_has_systemd; then
        systemctl enable "$svc" 2>/dev/null || warn "Could not enable $svc at boot."
    elif command -v rc-update &>/dev/null; then
        rc-update add "$svc" default 2>/dev/null || warn "Could not enable $svc at boot."
    elif command -v chkconfig &>/dev/null; then
        chkconfig "$svc" on 2>/dev/null || warn "Could not enable $svc at boot."
    elif command -v update-rc.d &>/dev/null; then
        update-rc.d "$svc" enable 2>/dev/null || warn "Could not enable $svc at boot."
    else
        warn "No init system found to enable $svc — enable it at boot manually."
    fi
    return 0
}

svc_start() {
    local svc="$1"
    if svc_has_systemd; then
        systemctl start "$svc" 2>/dev/null || warn "Could not start $svc."
    elif command -v rc-service &>/dev/null; then
        rc-service "$svc" start 2>/dev/null || warn "Could not start $svc."
    elif command -v service &>/dev/null; then
        service "$svc" start 2>/dev/null || warn "Could not start $svc."
    else
        warn "No init system found to start $svc — start it manually."
    fi
    return 0
}

# ---------------------------------------------------------------------------
# nginx site + reverse-proxy wiring
# ---------------------------------------------------------------------------
configure_nginx() {
    phase "Nginx"

    if command -v nginx &>/dev/null; then
        good "Nginx already installed."
    else
        step "Installing Nginx..."
        pkg_add nginx
        svc_enable nginx
        good "Nginx installed."
    fi

    systemctl stop nginx 2>/dev/null || true
    rm -f /etc/nginx/sites-enabled/default

    mkdir -p /etc/nginx/sites-available /etc/nginx/sites-enabled /etc/nginx/serverkit-conf.d /var/www/certbot

    # Fedora/RHEL nginx.conf doesn't include sites-enabled by default.
    if ! grep -q "sites-enabled" /etc/nginx/nginx.conf; then
        sed -i '/http {/a \    include /etc/nginx/sites-enabled/*;' /etc/nginx/nginx.conf
    fi

    # Server-wide TLS floor: harden ssl_protocols/ssl_ciphers in the main
    # nginx.conf so even the default server and vhosts ServerKit did not
    # generate cannot negotiate TLS 1.0/1.1 or weak ciphers.
    harden_global_tls

    # Drop any foreign catch-all vhost that would shadow the panel.
    for conf in /etc/nginx/sites-enabled/*; do
        [ -f "$conf" ] || continue
        local name; name=$(basename "$conf")
        case "$name" in serverkit-*|serverkit.conf) continue ;; esac
        if grep -Eq 'server_name[[:space:]]+_;' "$conf" 2>/dev/null; then
            warn "Removing conflicting catch-all vhost: $name"
            rm -f "/etc/nginx/sites-enabled/$name" "/etc/nginx/sites-available/$name"
        fi
    done

    cp "$INSTALL_DIR/nginx/sites-available/serverkit.conf" /etc/nginx/sites-available/
    cp "$INSTALL_DIR/nginx/sites-available/serverkit-insecure.conf" /etc/nginx/sites-available/
    cp "$INSTALL_DIR/nginx/sites-available/example.conf.template" /etc/nginx/sites-available/

    # The panel frontend is served as static files by host nginx (no container).
    # The shipped config roots at the default /opt/serverkit; point it at the real
    # install dir when SERVERKIT_DIR was customised.
    apply_frontend_root /etc/nginx/sites-available/serverkit.conf \
                        /etc/nginx/sites-available/serverkit-insecure.conf

    # Decide whether we can use HTTPS. SSL is best-effort: if certbot fails or
    # no domain is given, we fall back to plain HTTP rather than forcing the
    # user to fix DNS/certs before they can use ServerKit.
    choose_ssl_mode
    install_nginx_config_for_mode

    # SELinux: let nginx make upstream connections to the app containers AND read
    # the SPA bundle it now serves from $INSTALL_DIR (default /opt, which is not
    # httpd_sys_content_t by default — without this nginx 403s every panel asset).
    if { [ "$OS_FAMILY" = "fedora" ] || [ "$OS_FAMILY" = "rhel" ]; } && command -v setsebool &>/dev/null; then
        setsebool -P httpd_can_network_connect 1 2>/dev/null || true
    fi
    selinux_label_frontend_dist

    good "Nginx configured ($SSL_MODE)."
}

# ---------------------------------------------------------------------------
# Choose secure or insecure mode. Never block the install because of SSL.
# ---------------------------------------------------------------------------
choose_ssl_mode() {
    if [ "$SERVERKIT_SKIP_SSL" = "1" ]; then
        SSL_MODE="insecure"
        warn "SERVERKIT_SKIP_SSL=1 — using plain HTTP."
        return
    fi

    if [ -z "$PANEL_DOMAIN" ]; then
        SSL_MODE="insecure"
        warn "No panel domain provided — using plain HTTP (access by IP)."
        warn "Set PANEL_DOMAIN and re-run the installer to try HTTPS automatically."
        return
    fi

    if ! command -v certbot &>/dev/null; then
        SSL_MODE="insecure"
        warn "Certbot not installed — cannot request SSL automatically."
        warn "Continuing with plain HTTP. Install certbot and run: certbot --nginx -d $PANEL_DOMAIN"
        return
    fi

    # Temporarily use the insecure config so certbot's webroot challenge can
    # answer on port 80.
    ln -sf /etc/nginx/sites-available/serverkit-insecure.conf /etc/nginx/sites-enabled/serverkit.conf
    step "Attempting Let's Encrypt certificate for $PANEL_DOMAIN..."
    if systemctl start nginx 2>/dev/null && \
       certbot certonly --webroot -w /var/www/certbot -d "$PANEL_DOMAIN" \
           --non-interactive --agree-tos --register-unsafely-without-email 2>/dev/null; then
        SSL_MODE="secure"
        good "Let's Encrypt certificate issued for $PANEL_DOMAIN."
    else
        SSL_MODE="insecure"
        warn "Could not obtain SSL certificate for $PANEL_DOMAIN."
        warn "Common causes: DNS not pointing to this server, port 80 not reachable, or rate limits."
        warn "Continuing with plain HTTP. Retry later with: certbot --nginx -d $PANEL_DOMAIN"
    fi
    systemctl stop nginx 2>/dev/null || true
}

# ---------------------------------------------------------------------------
# Install the nginx config matching the chosen SSL mode.
# ---------------------------------------------------------------------------
install_nginx_config_for_mode() {
    # Dirs are overridable so the unit tests can exercise this against
    # fixtures (same pattern as harden_global_tls / update.sh's NGINX_DIR).
    local nginx_dir="${SERVERKIT_NGINX_DIR:-/etc/nginx}"
    local config_dir="${SERVERKIT_CONFIG_DIR:-/etc/serverkit}"
    if [ "$SSL_MODE" = "secure" ]; then
        sed -i "s|/etc/letsencrypt/live/YOUR_DOMAIN/|/etc/letsencrypt/live/$PANEL_DOMAIN/|g" \
            "$nginx_dir/sites-available/serverkit.conf"
        ln -sf "$nginx_dir/sites-available/serverkit.conf" "$nginx_dir/sites-enabled/serverkit.conf"
    else
        ln -sf "$nginx_dir/sites-available/serverkit-insecure.conf" "$nginx_dir/sites-enabled/serverkit.conf"
    fi
    mkdir -p "$config_dir"
    printf '%s\n' "$SSL_MODE" > "$config_dir/ssl-mode"
    # Persist the domain so update.sh can re-apply the cert path on upgrades
    # without depending on the (commented-out) .env public URL. An empty
    # domain (the default no-domain install) is simply not persisted — and as
    # the LAST statement of the function this must be an `if`, not a
    # `[ -n ] && ...` list: the list form returned 1 on an empty domain and
    # set -e killed every no-domain install right here. (I1)
    if [ -n "$PANEL_DOMAIN" ]; then
        printf '%s\n' "$PANEL_DOMAIN" > "$config_dir/panel-domain"
    fi
}

# Point the static-frontend `root` at the real install dir. The shipped nginx
# config defaults to /opt/serverkit; only a customised SERVERKIT_DIR needs the
# rewrite. update.sh's refresh_config carries the same logic across upgrades.
apply_frontend_root() {
    [ "$INSTALL_DIR" = "/opt/serverkit" ] && return 0
    local f
    for f in "$@"; do
        # `if`, not a `[ -f ] && ...` list: with the list form a missing conf
        # as the LAST file made the loop (and thus the function) return 1,
        # and set -e killed the custom-SERVERKIT_DIR install right here —
        # the same species as I1/I2.
        if [ -f "$f" ]; then
            sed -i "s|/opt/serverkit/frontend/dist|$INSTALL_DIR/frontend/dist|g" "$f"
        fi
    done
    return 0
}

# Label the SPA bundle so SELinux-enforcing hosts (Fedora/RHEL) let nginx read
# it. /opt is not httpd_sys_content_t by default, so without this every panel
# asset 403s. Label the *real* slot path (blue/green resolves through a symlink).
# Best-effort: a permissive/disabled box, or one without the tools, just no-ops.
selinux_label_frontend_dist() {
    command -v selinuxenabled &>/dev/null && selinuxenabled 2>/dev/null || return 0
    local real dist
    real="$(readlink -f "$INSTALL_DIR" 2>/dev/null || echo "$INSTALL_DIR")"
    dist="${real}/frontend/dist"
    [ -d "$dist" ] || return 0
    if command -v semanage &>/dev/null && command -v restorecon &>/dev/null; then
        semanage fcontext -a -t httpd_sys_content_t "${dist}(/.*)?" 2>/dev/null \
            || semanage fcontext -m -t httpd_sys_content_t "${dist}(/.*)?" 2>/dev/null || true
        restorecon -R "$dist" 2>/dev/null || true
    elif command -v chcon &>/dev/null; then
        chcon -R -t httpd_sys_content_t "$dist" 2>/dev/null || true
    fi
}

# ---------------------------------------------------------------------------
# Server-wide TLS floor — force every HTTPS listener onto TLS 1.2/1.3 with
# AEAD-only ciphers, so even the default server and non-ServerKit vhosts can't
# negotiate weak TLS.
#
# Preferred: drop a self-contained /etc/nginx/conf.d/serverkit-tls.conf snippet
# — ServerKit-owned, trivially reversible on uninstall, and never touches the
# distro's nginx.conf. BUT a snippet is `include`d into the same http{} context,
# so if nginx.conf ALREADY declares ssl_protocols (Debian/Ubuntu do) a second
# declaration is a "duplicate ssl_protocols" error. In that case we fall back to
# rewriting the existing directives in place. Idempotent either way.
# ---------------------------------------------------------------------------
harden_global_tls() {
    local nginx_dir="${SERVERKIT_NGINX_DIR:-/etc/nginx}"
    local conf="$nginx_dir/nginx.conf"
    [ -f "$conf" ] || return 0
    local ciphers='ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384'

    # Does the main config already declare these in http{}? (Debian/Ubuntu yes,
    # RHEL/Fedora/SUSE typically no.)
    local has_proto=0 has_ciphers=0
    grep -qE '^[[:space:]]*ssl_protocols[[:space:]]' "$conf" && has_proto=1
    grep -qE '^[[:space:]]*ssl_ciphers[[:space:]]'   "$conf" && has_ciphers=1

    # The conf.d snippet is only safe when neither directive already exists AND
    # nginx.conf includes conf.d/*.conf inside http{} (the default on every
    # supported family).
    if [ "$has_proto" = "0" ] && [ "$has_ciphers" = "0" ] && \
       grep -qE 'include[[:space:]]+/etc/nginx/conf\.d/\*\.conf' "$conf"; then
        mkdir -p "$nginx_dir/conf.d"
        cat > "$nginx_dir/conf.d/serverkit-tls.conf" <<EOF
# Auto-generated by ServerKit — server-wide TLS floor. Safe to remove.
ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers ${ciphers};
EOF
        return 0
    fi

    # Fall back to editing nginx.conf in place (a snippet would duplicate the
    # existing directive). Remove any stale snippet we may have dropped before.
    rm -f "$nginx_dir/conf.d/serverkit-tls.conf" 2>/dev/null || true
    if [ "$has_proto" = "1" ]; then
        sed -i -E 's|^([[:space:]]*)ssl_protocols[[:space:]].*|\1ssl_protocols TLSv1.2 TLSv1.3;|' "$conf"
    else
        sed -i '/http {/a \    ssl_protocols TLSv1.2 TLSv1.3;' "$conf"
    fi
    if [ "$has_ciphers" = "1" ]; then
        sed -i -E "s|^([[:space:]]*)ssl_ciphers[[:space:]].*|\1ssl_ciphers ${ciphers};|" "$conf"
    else
        sed -i "/http {/a \\    ssl_ciphers ${ciphers};" "$conf"
    fi
}

# ---------------------------------------------------------------------------
# systemd unit + CLI symlink
# ---------------------------------------------------------------------------
# Render the systemd unit from the template to <out>, substituting the resolved
# install/venv/log paths so a custom SERVERKIT_DIR is honored (the old hardcoded
# unit baked in /opt/serverkit). The unit references the /opt/serverkit symlink,
# so blue/green switches need no re-render. Returns 1 if no template/unit exists.
render_service_unit() {
    local out="$1"
    local template="$INSTALL_DIR/templates/serverkit-backend.service.in"
    if [ -f "$template" ]; then
        sed -e "s|@SERVERKIT_DIR@|$INSTALL_DIR|g" \
            -e "s|@SERVERKIT_VENV_DIR@|$VENV_DIR|g" \
            -e "s|@PORT@|5000|g" \
            -e "s|@USER@|root|g" \
            -e "s|@LOG_DIR@|$LOG_DIR|g" \
            "$template" > "$out"
        return 0
    elif [ -f "$INSTALL_DIR/serverkit-backend.service" ]; then
        cp "$INSTALL_DIR/serverkit-backend.service" "$out"
        return 0
    fi
    return 1
}

install_service() {
    phase "Systemd Service"

    render_service_unit /etc/systemd/system/serverkit.service || \
        halt "No systemd unit template found at $INSTALL_DIR/templates/serverkit-backend.service.in"
    chmod 644 /etc/systemd/system/serverkit.service

    chmod +x "$INSTALL_DIR/serverkit"
    ln -sf "$INSTALL_DIR/serverkit" /usr/local/bin/serverkit

    # Bash tab-completion (best-effort — not every distro ships bash-completion).
    if [ -d /etc/bash_completion.d ]; then
        bash "$INSTALL_DIR/serverkit" completion > /etc/bash_completion.d/serverkit 2>/dev/null \
            || rm -f /etc/bash_completion.d/serverkit
    fi

    # Without systemd (LXC/WSL/containers) we can't enable the unit — say so
    # clearly instead of failing cryptically (Goal G5). The probe is inline
    # (svc_has_systemd) so it holds even when scripts/lib never made it to
    # disk, where the old env.sh-based check silently skipped itself. (I17)
    if ! svc_has_systemd; then
        warn "systemd not detected — installed the unit but cannot enable/start it here."
        warn "Start the backend with a supervisor, or run it in the foreground; see docs/ARCHITECTURE.md."
        return 0
    fi

    systemctl daemon-reload
    systemctl enable serverkit
    good "Systemd service installed."
}

# ---------------------------------------------------------------------------
# App templates
# ---------------------------------------------------------------------------
sync_templates() {
    phase "App Templates"

    if [ -d "$INSTALL_DIR/backend/templates" ]; then
        cp -r "$INSTALL_DIR/backend/templates/"*.yaml /etc/serverkit/templates/ 2>/dev/null || true
        cp -r "$INSTALL_DIR/backend/templates/"*.yml  /etc/serverkit/templates/ 2>/dev/null || true
        good "Installed $(ls /etc/serverkit/templates/*.yaml 2>/dev/null | wc -l) app templates."
    else
        warn "No app templates found."
    fi
}

# ---------------------------------------------------------------------------
# Bring services up
# ---------------------------------------------------------------------------
launch_services() {
    phase "Starting Services"

    step "Starting the backend..."
    svc_start serverkit

    # The frontend is static files served by host nginx (built into
    # frontend/dist by build_frontend) — no container to build or start.
    step "Starting nginx..."
    svc_start nginx
    good "Services started."
}

# ---------------------------------------------------------------------------
# Health probe + automatic rollback
# ---------------------------------------------------------------------------
revert_install() {
    warn "Health check failed — rolling back..."

    systemctl stop serverkit 2>/dev/null || true
    systemctl stop nginx 2>/dev/null || true

    local active
    active="$(readlink -f "$INSTALL_DIR" 2>/dev/null || echo "$INSTALL_DIR")"
    if [ -d "$active.backup" ]; then
        rm -rf "$active"
        cp -a "$active.backup" "$active"
        warn "Restored the previous installation from $active.backup"
    fi

    systemctl daemon-reload
    systemctl start serverkit 2>/dev/null || true
    systemctl start nginx 2>/dev/null || true
    halt "Install rolled back. Inspect logs: journalctl -u serverkit -n 50"
}

await_health() {
    phase "Health Check"

    step "Waiting for the backend to answer..."
    local waited=0
    while [ "$waited" -lt 30 ]; do
        if curl -sf --max-time 5 http://127.0.0.1:5000/api/v1/system/health >/dev/null 2>&1; then
            good "Backend healthy."
            return 0
        fi
        sleep 2
        waited=$((waited + 2))
    done

    warn "Backend did not respond on port 5000."
    return 1
}

# ---------------------------------------------------------------------------
# Safety copy of an existing install before we touch it
# ---------------------------------------------------------------------------
snapshot_existing() {
    local active
    active="$(readlink -f "$INSTALL_DIR" 2>/dev/null || echo "$INSTALL_DIR")"
    [ -d "$active" ] || return 0
    if [ ! -d "$active.backup" ]; then
        step "Backing up the existing installation..."
        cp -a "$active" "$active.backup"
        good "Backup saved to $active.backup"
        return 0
    fi
    # A .backup left by an earlier run is what revert_install restores — a
    # stale one would silently roll the box back to a months-old tree.
    # Refresh it: build the new copy first and swap only on success, so a
    # failed copy never costs us the backup we already have. (I20)
    step "Refreshing the existing installation backup..."
    rm -rf "$active.backup.new" 2>/dev/null || true
    if cp -a "$active" "$active.backup.new" 2>/dev/null; then
        rm -rf "$active.backup"
        mv "$active.backup.new" "$active.backup"
        good "Backup refreshed at $active.backup"
    else
        rm -rf "$active.backup.new" 2>/dev/null || true
        warn "Could not refresh $active.backup — keeping the previous backup."
    fi
}

# ---------------------------------------------------------------------------
# Closing summary
# ---------------------------------------------------------------------------
print_outro() {
    local ip
    ip=$(curl -sf --max-time 5 https://api.ipify.org 2>/dev/null || \
         hostname -I 2>/dev/null | awk '{print $1}' || echo "YOUR_SERVER_IP")

    printf '\n'
    printf '  %s%s✔  ServerKit installed successfully%s   %s%s%s\n' \
        "$BLD" "$HUE_OK" "$RST" "$FOG" "$(clock)" "$RST"
    printf '  %s%s%s\n\n' "$V4" "──────────────────────────────────────" "$RST"

    if [ -n "$PANEL_DOMAIN" ]; then
        if [ "$SSL_MODE" = "secure" ]; then
            printf '  %sPanel URL%s      https://%s\n' "$BLD" "$RST" "$PANEL_DOMAIN"
        else
            printf '  %sPanel URL%s      http://%s\n' "$BLD" "$RST" "$PANEL_DOMAIN"
        fi
    else
        printf '  %sPanel URL%s      http://%s\n' "$BLD" "$RST" "$ip"
    fi

    if [ "$SSL_MODE" != "secure" ]; then
        printf '\n  %sWARNING%s        Running without HTTPS. Passwords and tokens will be\n' "$BLD" "$RST"
        printf '                 transmitted unencrypted. Set PANEL_DOMAIN and run\n'
        printf '                 certbot, or set SERVERKIT_SKIP_SSL=1 to suppress this warning.\n'
    fi

    printf '\n  %sFirst step%s     create an admin user\n\n' "$BLD" "$RST"

    printf '  %sCLI%s            serverkit status\n' "$BLD" "$RST"
    printf '                 serverkit create-admin\n'
    printf '                 serverkit --help\n\n'

    printf '  %sService%s        systemctl status serverkit\n' "$BLD" "$RST"
    printf '                 journalctl -u serverkit -f\n'
    printf '                 systemctl restart serverkit\n\n'

    printf '  %sPaths%s          install : %s\n' "$BLD" "$RST" "$INSTALL_DIR"
    printf '                 config  : %s/.env\n' "$INSTALL_DIR"
    printf '                 backups : %s\n\n' "$BACKUP_DIR"

    printf '  %sUpdate%s         sudo serverkit update\n\n' "$HUE_WARN" "$RST"
}

# ---------------------------------------------------------------------------
# Anonymous install ping (best-effort)
# ---------------------------------------------------------------------------
ping_telemetry() {
    # Guarded: a missing VERSION file fails the pipeline under pipefail, and
    # this runs AFTER a successful install — it must never abort it. (I23)
    local v
    v=$(cat "$INSTALL_DIR/VERSION" 2>/dev/null | tr -d '\n\r ') || v=""
    curl -s "https://serverkit.ai/track/install?v=${v}" >/dev/null 2>&1 || true
}

# ---------------------------------------------------------------------------
# Ask for a panel domain when running interactively
# ---------------------------------------------------------------------------
prompt_for_domain() {
    # Nothing to ask when a domain is already set, or when there is no
    # interactive stdin to ask on (curl | bash). SERVERKIT_FORCE_PROMPT=1
    # lets the unit tests drive the prompt from a pipe.
    [ -z "$PANEL_DOMAIN" ] || return 0
    if [ ! -t 0 ] && [ "${SERVERKIT_FORCE_PROMPT:-0}" != "1" ]; then
        return 0
    fi
    printf '\n'
    printf '%sEnter your panel domain (e.g. panel.example.com)%s\n' "$BLD" "$RST"
    printf 'Leave blank to access via IP (no SSL attempt)\n'
    printf '%sTip:%s set PANEL_DOMAIN=... in the environment to skip this prompt\n' "$BLD" "$RST"
    printf '      set SERVERKIT_SKIP_SSL=1 to disable HTTPS entirely\n'
    printf '> '
    read -r PANEL_DOMAIN || true
    PANEL_DOMAIN=$(printf '%s' "$PANEL_DOMAIN" | tr -d ' ')
    # A blank answer (plain Enter) is the documented default — and as the
    # LAST statement of the function this must be an `if`, not a
    # `[ -n ] && ...` list: the list form returned 1 on a blank answer and
    # set -e killed every interactive no-domain install right here. (I2)
    if [ -n "$PANEL_DOMAIN" ]; then
        PANEL_PORT="80"
    fi
}

# ---------------------------------------------------------------------------
# Orchestration
# ---------------------------------------------------------------------------
# Decide whether a fresh install should default to a release tarball. An
# EXISTING install must never flip to release mode by default: fetch_release
# rewrites the whole slot. The old check tested $INSTALL_DIR/backend/src — a
# path that never existed (the tree is backend/app) — so every re-run over a
# live install picked release mode and rm -rf'd it, .env and database
# included. Probe the real tree and the generated .env instead. (I4)
should_default_to_release() {
    [ "$BUILD_FROM_SOURCE" != "1" ] || return 1
    [ -z "${SERVERKIT_VERSION:-}" ] || return 1
    [ ! -d "$INSTALL_DIR/backend/app" ] || return 1
    [ ! -f "$INSTALL_DIR/.env" ] || return 1
    return 0
}

main() {
    STARTED_AT=$(date +%s)
    masthead

    # Default to a release install unless an install is already present or
    # the caller forced a source build / pinned a version.
    if should_default_to_release; then
        INSTALL_FROM_RELEASE=1
    fi

    identify_system
    # preflight's root check must run before choose_pkg_manager, which
    # writes the apt lock-wait drop-in to /etc. (I11)
    preflight
    choose_pkg_manager
    gauge_memory
    ensure_swap
    prompt_for_domain
    snapshot_existing

    # RHEL 9 family: keep sshd alive across the dnf work below (see the
    # function's comment for the full openssl/openssh mismatch story).
    upgrade_rhel_crypto_stack

    provision_docker
    ensure_compose_plugin
    provision_node

    if [ "$INSTALL_FROM_RELEASE" = "1" ]; then
        fetch_release || warn "Falling back to a source build."
    fi

    if [ "$INSTALL_FROM_RELEASE" != "1" ]; then
        provision_python
        sync_source
        make_directories
        build_virtualenv
        build_frontend
    else
        make_directories
        # Release tarballs now ship a pre-built, relocatable venv. If one is
        # present, build_virtualenv will use it; otherwise it falls back to a
        # local build.
        provision_python
        build_virtualenv
    fi

    sync_templates
    configure_nginx
    configure_firewall
    write_config
    install_service

    # Tolerate failures through start + health so rollback can run.
    set +e
    launch_services
    await_health || revert_install
    set -e

    ping_telemetry
    print_outro
}

# Sourcing this file (e.g. from scripts/test/test_install.sh) defines every
# function above for unit testing without running an install. Only a direct
# execution falls through to the run below.
[ "${BASH_SOURCE[0]}" = "${0}" ] || return 0

main "$@"