"""CMBot update launcher (docs/10-lan-update.md stage 3/4).

Compiled to Launcher.exe (PyInstaller onefile) and run instead of launching
app/CMBot.exe directly. On each start it:

  1. seeds default config/templates into ~/.cmbot on first run;
  2. reads update_source / credentials from ~/.cmbot/config/app_config.json;
  3. checks the manifest and, when a newer version is advertised, downloads the
     release zip, verifies SHA-256, extracts it, and swaps it into app\\ while
     keeping the previous version in app.old\\ for rollback;
  4. launches app\\CMBot.exe.

Degrades safely: an unreachable source, a bad download, or a non-writable
install root leaves the existing app\\ in place and launches it. The running
program's data lives in ~/.cmbot (get_data_dir), so updates never touch it.
"""
import argparse
import hashlib
import logging
import shutil
import subprocess
import sys
import zipfile
from pathlib import Path
from urllib import error

# Make 'services' importable both frozen (PyInstaller --paths src) and from source.
sys.path.insert(0, str(Path(__file__).resolve().parent))

from services.update_service import check_for_update, download  # noqa: E402
from services.file_service import get_data_dir                  # noqa: E402
from services.config_service import load_config                 # noqa: E402

APP_EXE = "CMBot.exe"
VERSION_FILE = "version.txt"
CONFIG_FILES = ("app_config.json", "templates.json")

logger = logging.getLogger("launcher")


# ── helpers ──────────────────────────────────────────────────────────────────

def _read_version(app_dir):
    """Return the version recorded in app/version.txt, or '' if absent."""
    try:
        # utf-8-sig tolerates a BOM written by PowerShell.
        return (app_dir / VERSION_FILE).read_text(encoding="utf-8-sig").strip()
    except OSError:
        return ""


def seed_defaults(app_dir, data_dir):
    """First run: copy factory config/templates from app\\config into the data
    root, without overwriting any existing user file."""
    src = app_dir / "config"
    if not src.is_dir():
        return
    dst = data_dir / "config"
    dst.mkdir(parents=True, exist_ok=True)
    for name in CONFIG_FILES:
        s, d = src / name, dst / name
        if s.exists() and not d.exists():
            shutil.copy2(str(s), str(d))
            logger.info("Seeded default %s into %s", name, dst)


def is_writable(path):
    """True if a file can be created under *path* (so self-update can proceed)."""
    try:
        path.mkdir(parents=True, exist_ok=True)
        probe = path / ".write_test"
        probe.write_text("x", encoding="ascii")
        probe.unlink()
        return True
    except OSError:
        return False


def _sha256(path):
    h = hashlib.sha256()
    with open(str(path), "rb") as f:
        for chunk in iter(lambda: f.read(65536), b""):
            h.update(chunk)
    return h.hexdigest()


def _rm(path):
    if path.is_dir():
        shutil.rmtree(str(path), ignore_errors=True)
    elif path.exists():
        path.unlink()


def _find_package_root(extract_dir):
    """Locate the folder that holds CMBot.exe inside an extracted zip.

    Handles both a flat zip (exe at root) and one wrapped in a single folder.
    """
    if (extract_dir / APP_EXE).exists():
        return extract_dir
    subs = [p for p in extract_dir.iterdir() if p.is_dir()]
    if len(subs) == 1 and (subs[0] / APP_EXE).exists():
        return subs[0]
    return None


def _swap_in(app_dir, old_dir, package_root):
    """Rename app->app.old, then package_root->app. Roll back on failure.

    Never overwrites a running app dir: if app\\CMBot.exe is locked (running),
    the rename raises and the caller degrades to the existing version.
    """
    if old_dir.exists():
        shutil.rmtree(str(old_dir))
    if app_dir.exists():
        app_dir.rename(old_dir)
    try:
        package_root.rename(app_dir)
    except OSError:
        if not app_dir.exists() and old_dir.exists():
            old_dir.rename(app_dir)   # restore previous version
        raise


# ── update flow ──────────────────────────────────────────────────────────────

def _try_update(install_root, app_dir, source, user, password, local_version):
    info = check_for_update(source, local_version, user, password)
    if info is None:
        return   # no update / unreachable / not newer — already logged

    if not is_writable(install_root):
        logger.warning("Install root not writable, skipping update: %s", install_root)
        return

    staging = install_root / "staging"
    staging.mkdir(parents=True, exist_ok=True)
    zip_path = staging / "{}.zip".format(info.version)
    extract_dir = staging / "app.new"
    _rm(zip_path)
    _rm(extract_dir)

    logger.info("Downloading v%s from %s", info.version, info.source)
    download(info.source, zip_path, user, password)

    if info.size and zip_path.stat().st_size != info.size:
        raise ValueError("download size mismatch: got {}, expected {}".format(
            zip_path.stat().st_size, info.size))
    if info.sha256 and _sha256(zip_path).lower() != info.sha256.lower():
        raise ValueError("sha256 mismatch")

    with zipfile.ZipFile(str(zip_path)) as z:
        z.extractall(str(extract_dir))
    package_root = _find_package_root(extract_dir)
    if not package_root:
        raise ValueError("downloaded package does not contain {}".format(APP_EXE))
    pkg_version = _read_version(package_root)
    if pkg_version != info.version:
        raise ValueError("package version '{}' != manifest '{}'".format(
            pkg_version, info.version))

    _swap_in(app_dir, install_root / "app.old", package_root)
    _rm(zip_path)
    _rm(extract_dir)
    logger.info("Installed and switched to v%s", info.version)


def run(install_root, no_launch=False):
    """Seed config, attempt an update, then launch the app. Returns exit code."""
    install_root = Path(install_root)
    app_dir = install_root / "app"
    data_dir = get_data_dir()

    seed_defaults(app_dir, data_dir)

    cfg = load_config()
    source = cfg.get("update_source", "")
    user = cfg.get("update_user", "")
    password = cfg.get("update_pass", "")

    local_version = _read_version(app_dir)
    if source:
        try:
            _try_update(install_root, app_dir, source, user, password, local_version)
        except (OSError, ValueError, error.URLError) as exc:
            logger.warning("Update skipped (using local version): %s", exc)
    else:
        logger.info("No update_source configured, skipping update check.")

    exe = app_dir / APP_EXE
    if not exe.exists():
        logger.error("Executable not found: %s", exe)
        return 1
    if no_launch:
        logger.info("NoLaunch: would start %s (data=%s)", exe, data_dir)
        return 0
    logger.info("Launching %s", exe)
    subprocess.Popen([str(exe)], cwd=str(exe.parent))
    return 0


def _default_install_root():
    if getattr(sys, "frozen", False):
        return Path(sys.executable).resolve().parent
    return Path.cwd()


def main(argv=None):
    parser = argparse.ArgumentParser(description="CMBot update launcher")
    parser.add_argument("--install-root", default=None,
                        help="install root (default: Launcher.exe's folder)")
    parser.add_argument("--no-launch", action="store_true",
                        help="update only, do not start the app")
    args = parser.parse_args(argv)

    root = Path(args.install_root) if args.install_root else _default_install_root()
    logging.basicConfig(
        level=logging.INFO,
        format="%(asctime)s  %(message)s",
        handlers=[
            logging.StreamHandler(),
            logging.FileHandler(str(root / "launcher.log"), encoding="utf-8"),
        ],
    )
    return run(root, no_launch=args.no_launch)


if __name__ == "__main__":
    sys.exit(main())