#!/usr/bin/env bash
# LuxStats background launcher for Arch Linux
#
# * Auto-detects every installed CPython 3 and uses the newest one
# * Runs WITHOUT a venv when the system python already has the deps
#   (pacman: python-pyqt5 python-pyserial python-psutil)
# * Otherwise creates/uses a managed venv at
#   ${XDG_DATA_HOME:-~/.local/share}/luxstats/venv and installs deps there
# * Launches the configurator detached from the terminal, logging to
#   ${XDG_STATE_HOME:-~/.local/state}/luxstats/luxstats.log
#
# Usage:  ./luxstats.sh            start in the background
#         ./luxstats.sh stop      stop a running instance
#         ./luxstats.sh status    show whether it's running

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# works both from the repo root (host/ beside this script) and from packaging/
if [[ -f "$SCRIPT_DIR/host/luxstats_configurator.py" ]]; then
    APP="$SCRIPT_DIR/host/luxstats_configurator.py"
elif [[ -f "$SCRIPT_DIR/../host/luxstats_configurator.py" ]]; then
    APP="$(cd "$SCRIPT_DIR/../host" && pwd)/luxstats_configurator.py"
else
    echo "luxstats: cannot locate host/luxstats_configurator.py" >&2
    exit 1
fi

DATA_DIR="${XDG_DATA_HOME:-$HOME/.local/share}/luxstats"
STATE_DIR="${XDG_STATE_HOME:-$HOME/.local/state}/luxstats"
VENV="$DATA_DIR/venv"
LOG="$STATE_DIR/luxstats.log"
PIDFILE="$STATE_DIR/luxstats.pid"
DEPS_IMPORT='import PyQt5, serial, psutil'
mkdir -p "$DATA_DIR" "$STATE_DIR"

find_newest_python() {
    local best="" bestver=0 py ver base
    # scan PATH + common locations for pythonN.M binaries
    for py in $(compgen -c python3 | sort -u) /usr/bin/python3 \
              /usr/local/bin/python3.*; do
        base="$(basename "$py" 2>/dev/null || true)"
        [[ "$base" =~ ^python3(\.[0-9]+)?$ ]] || continue
        command -v "$py" >/dev/null 2>&1 || [[ -x "$py" ]] || continue
        ver="$("$py" -c 'import sys;print(sys.version_info[0]*1000+sys.version_info[1])' \
              2>/dev/null)" || continue
        if (( ver > bestver )); then bestver=$ver; best="$py"; fi
    done
    [[ -n "$best" ]] || { echo "luxstats: no python3 found" >&2; return 1; }
    echo "$best"
}

pick_interpreter() {
    local sys_py; sys_py="$(find_newest_python)"
    echo "using system interpreter candidate: $sys_py" \
         "($("$sys_py" -V 2>&1))" >&2
    if "$sys_py" -c "$DEPS_IMPORT" 2>/dev/null; then
        echo "$sys_py"                       # no venv needed
        return
    fi
    echo "system python lacks PyQt5/pyserial/psutil - using managed venv" >&2
    echo "(tip: 'sudo pacman -S python-pyqt5 python-pyserial python-psutil'" \
         "avoids the venv entirely)" >&2
    if [[ ! -x "$VENV/bin/python" ]] \
            || ! "$VENV/bin/python" -c "$DEPS_IMPORT" 2>/dev/null; then
        "$sys_py" -m venv --clear "$VENV"
        "$VENV/bin/pip" install --quiet --upgrade pip
        "$VENV/bin/pip" install --quiet PyQt5 pyserial psutil
    fi
    echo "$VENV/bin/python"
}

is_running() {
    [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null
}

case "${1:-start}" in
    start)
        if is_running; then
            echo "luxstats already running (pid $(cat "$PIDFILE"))"
            exit 0
        fi
        PY="$(pick_interpreter)"
        echo "launching with $PY"
        setsid "$PY" "$APP" >>"$LOG" 2>&1 < /dev/null &
        echo $! > "$PIDFILE"
        disown
        echo "luxstats started in the background (pid $(cat "$PIDFILE"))"
        echo "log: $LOG"
        ;;
    stop)
        if is_running; then
            kill "$(cat "$PIDFILE")" && rm -f "$PIDFILE"
            echo "luxstats stopped"
        else
            echo "luxstats is not running"
        fi
        ;;
    status)
        if is_running; then
            echo "running (pid $(cat "$PIDFILE"))"
        else
            echo "not running"
        fi
        ;;
    *)
        echo "usage: $0 [start|stop|status]" >&2
        exit 1
        ;;
esac