#!/usr/bin/env python3
"""
TechDJ production process manager.

Usage:
    python production.py start    — start TechDJ in the background
    python production.py stop     — stop TechDJ
    python production.py restart  — restart TechDJ
    python production.py status   — show whether TechDJ is running
    python production.py logs     — tail the live log output
"""
import sys
import os
import signal
import subprocess
import time
import json

BASE_DIR     = os.path.dirname(os.path.abspath(__file__))
PID_FILE     = os.path.join(BASE_DIR, 'techdj.pid')
LOG_FILE     = os.path.join(BASE_DIR, 'techdj.log')
CONF_FILE    = os.path.join(BASE_DIR, 'gunicorn.conf.py')
SERVER_MOD   = 'server:dj_app'

# Prefer the venv's gunicorn if it exists.
_venv_gunicorn = os.path.join(BASE_DIR, '.venv', 'bin', 'gunicorn')
GUNICORN = _venv_gunicorn if os.path.exists(_venv_gunicorn) else 'gunicorn'


# ── Helpers ───────────────────────────────────────────────────────────────────

def _load_config():
    try:
        with open(os.path.join(BASE_DIR, 'config.json')) as f:
            return json.load(f)
    except Exception:
        return {}


def _read_pid():
    try:
        with open(PID_FILE) as f:
            return int(f.read().strip())
    except (FileNotFoundError, ValueError):
        return None


def _is_running(pid):
    if pid is None:
        return False
    try:
        os.kill(pid, 0)
        return True
    except (ProcessLookupError, PermissionError):
        return False


def _check_gunicorn():
    try:
        subprocess.check_call(
            [GUNICORN, '--version'],
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
        )
    except (FileNotFoundError, subprocess.CalledProcessError):
        print(f"ERROR: gunicorn not found at '{GUNICORN}'.")
        print("       Install it with:  pip install gunicorn")
        sys.exit(1)


# ── Commands ──────────────────────────────────────────────────────────────────

def start():
    pid = _read_pid()
    if _is_running(pid):
        print(f"TechDJ is already running (PID {pid})")
        return

    _check_gunicorn()

    cfg  = _load_config()
    host = cfg.get('host', '0.0.0.0')
    port = cfg.get('dj_port', 5000)
    lport = cfg.get('listener_port', 5001)

    print(f"Starting TechDJ...")
    print(f"  DJ panel  : http://{host}:{port}")
    print(f"  Listener  : http://{host}:{lport}")
    print(f"  Log file  : {LOG_FILE}")

    cmd = [
        GUNICORN,
        '--config',      CONF_FILE,
        '--daemon',
        '--pid',         PID_FILE,
        '--access-logfile', LOG_FILE,
        '--error-logfile',  LOG_FILE,
        SERVER_MOD,
    ]

    try:
        subprocess.check_call(cmd, cwd=BASE_DIR)
    except subprocess.CalledProcessError as exc:
        print(f"ERROR: gunicorn exited with code {exc.returncode}. Check {LOG_FILE}")
        sys.exit(1)

    # Give gunicorn a moment to write the PID file.
    for _ in range(10):
        time.sleep(0.5)
        pid = _read_pid()
        if _is_running(pid):
            break
    else:
        print(f"ERROR: TechDJ did not start. Check logs:")
        _tail_log(20)
        sys.exit(1)

    print(f"TechDJ started (PID {pid})")


def stop():
    pid = _read_pid()
    if not _is_running(pid):
        print("TechDJ is not running.")
        if os.path.exists(PID_FILE):
            os.remove(PID_FILE)
        return

    print(f"Stopping TechDJ (PID {pid})...")
    os.kill(pid, signal.SIGTERM)

    for _ in range(20):
        time.sleep(0.5)
        if not _is_running(pid):
            break
    else:
        print("  Graceful shutdown timed out — sending SIGKILL.")
        try:
            os.kill(pid, signal.SIGKILL)
        except ProcessLookupError:
            pass

    if os.path.exists(PID_FILE):
        os.remove(PID_FILE)

    print("TechDJ stopped.")


def restart():
    stop()
    time.sleep(1)
    start()


def status():
    pid = _read_pid()
    if _is_running(pid):
        cfg   = _load_config()
        host  = cfg.get('host', '0.0.0.0')
        port  = cfg.get('dj_port', 5000)
        lport = cfg.get('listener_port', 5001)
        print(f"TechDJ is running  (PID {pid})")
        print(f"  DJ panel  : http://{host}:{port}")
        print(f"  Listener  : http://{host}:{lport}")
        print(f"  Log file  : {LOG_FILE}")
    else:
        print("TechDJ is NOT running.")


def _tail_log(lines=50):
    if not os.path.exists(LOG_FILE):
        print(f"No log file at {LOG_FILE}")
        return
    subprocess.call(['tail', f'-{lines}', LOG_FILE])


def logs():
    if not os.path.exists(LOG_FILE):
        print(f"No log file at {LOG_FILE}")
        sys.exit(1)
    # Replace this process with tail -f so Ctrl+C works cleanly.
    os.execvp('tail', ['tail', '-f', LOG_FILE])


# ── Entry point ───────────────────────────────────────────────────────────────

COMMANDS = {
    'start':   start,
    'stop':    stop,
    'restart': restart,
    'status':  status,
    'logs':    logs,
}

if __name__ == '__main__':
    cmd = sys.argv[1] if len(sys.argv) > 1 else 'status'
    if cmd not in COMMANDS:
        print(f"Usage: python production.py [{'|'.join(COMMANDS)}]")
        sys.exit(1)
    COMMANDS[cmd]()