"""Export sandcage repo to a public standalone repository.

Usage:
    uv run python scripts/export.py push [--dry-run] [--remote URL]
"""
from __future__ import annotations

import argparse
import contextlib
import os
import shutil
import subprocess
import sys
from dataclasses import dataclass, field
from pathlib import Path

try:
    import tomllib
except ModuleNotFoundError:
    import tomli as tomllib  # type: ignore[no-redef]

SCRIPT_DIR = Path(__file__).resolve().parent
REPO_ROOT = SCRIPT_DIR.parent
CONFIG_PATH = SCRIPT_DIR / "export.toml"


@dataclass(frozen=True)
class ExportConfig:
    branch: str
    remote_env: str
    assets: Path
    exclude: list[str] = field(default_factory=list)


def load_config(path: Path = CONFIG_PATH) -> ExportConfig:
    with open(path, "rb") as f:
        raw = tomllib.load(f)
    entry = raw["export"]
    return ExportConfig(
        branch=entry["branch"],
        remote_env=entry["remote_env"],
        assets=REPO_ROOT / entry["assets"],
        exclude=entry.get("exclude", []),
    )


def load_asset_bundle(assets_dir: Path) -> dict[str, bytes]:
    bundle: dict[str, bytes] = {}
    if not assets_dir.exists():
        return bundle
    for path in assets_dir.rglob("*"):
        if path.is_file():
            rel = path.relative_to(assets_dir).as_posix()
            bundle[rel] = path.read_bytes()
    return bundle


def materialize_assets(target: Path, bundle: dict[str, bytes]) -> None:
    for relpath, content in bundle.items():
        dst = target / relpath
        dst.parent.mkdir(parents=True, exist_ok=True)
        dst.write_bytes(content)


def remove_excluded_paths(target: Path, exclude: list[str]) -> None:
    for pattern in exclude:
        path = target / pattern
        if path.is_dir():
            shutil.rmtree(path)
        elif path.is_file():
            path.unlink()


def _run(cmd: list[str], cwd: Path, check: bool = True) -> subprocess.CompletedProcess:
    result = subprocess.run(cmd, cwd=cwd, check=False, capture_output=True, encoding="utf-8", errors="replace")
    if check and result.returncode != 0:
        detail = (result.stderr or result.stdout or "").strip()
        if detail:
            print(f"  stderr: {detail}", file=sys.stderr)
        raise SystemExit(
            f"error: command failed (exit {result.returncode}): {' '.join(cmd)}"
        )
    return result


@contextlib.contextmanager
def export_worktree(repo_root: Path):
    wt_path = repo_root / ".export-worktrees" / "sandcage"
    wt_path.parent.mkdir(parents=True, exist_ok=True)

    _run(["git", "worktree", "prune"], cwd=repo_root, check=False)
    _run(["git", "worktree", "remove", "--force", str(wt_path)],
         cwd=repo_root, check=False)
    if wt_path.exists():
        shutil.rmtree(wt_path, ignore_errors=True)

    _run(["git", "worktree", "add", "--detach", str(wt_path), "HEAD"],
         cwd=repo_root)
    try:
        yield wt_path
    finally:
        _run(["git", "worktree", "remove", "--force", str(wt_path)],
             cwd=repo_root, check=False)
        if wt_path.exists():
            shutil.rmtree(wt_path, ignore_errors=True)
        _run(["git", "worktree", "prune"], cwd=repo_root, check=False)


def _git_push(remote: str, branch: str, target: str, cwd: Path) -> None:
    fetch = _run(["git", "fetch", remote, target], cwd=cwd, check=False)
    if fetch.returncode == 0:
        expected = _run(["git", "rev-parse", "FETCH_HEAD"], cwd=cwd).stdout.strip()
        _run(["git", "push", f"--force-with-lease={target}:{expected}",
              remote, f"{branch}:{target}"], cwd=cwd)
    else:
        _run(["git", "push", remote, f"{branch}:{target}"], cwd=cwd)


def run_export(*, repo_root: Path, cfg: ExportConfig,
               remote: str | None, dry_run: bool) -> None:
    if not dry_run and remote is None:
        raise SystemExit(
            f"error: remote required for push (set {cfg.remote_env} or pass --remote)"
        )

    bundle = load_asset_bundle(cfg.assets)
    source_sha = _run(
        ["git", "rev-parse", "--short", "HEAD"], cwd=repo_root,
    ).stdout.strip()

    with export_worktree(repo_root) as worktree:
        branch_exists = _run(
            ["git", "rev-parse", "--verify", cfg.branch],
            cwd=repo_root, check=False,
        ).returncode == 0

        if branch_exists:
            _run(["git", "checkout", cfg.branch], cwd=worktree)
            _run(["git", "rm", "-rf", "."], cwd=worktree, check=False)
            _run(["git", "checkout", source_sha, "--", "."], cwd=worktree)
        else:
            _run(["git", "checkout", "--orphan", cfg.branch], cwd=worktree)

        remove_excluded_paths(worktree, cfg.exclude)
        materialize_assets(worktree, bundle)

        _run(["git", "add", "-A"], cwd=worktree)
        diff = _run(["git", "diff", "--cached", "--quiet"],
                     cwd=worktree, check=False)
        if diff.returncode != 0:
            _run(["git", "-c", "user.email=export@sandcage", "-c", "user.name=sandcage-export",
                  "commit", "-m",
                  f"\U0001f947 export from upstream ({source_sha})"],
                 cwd=worktree)

        if dry_run:
            print(f"dry-run: skipping push. Branch '{cfg.branch}' is ready locally.")
            return

        assert remote is not None
        print(f"force-with-lease push {cfg.branch} -> {remote}:main")
        _git_push(remote, cfg.branch, "main", worktree)


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser(
        prog="export", description="Export sandcage to public repo",
    )
    sub = parser.add_subparsers(dest="cmd", required=True)

    p_push = sub.add_parser("push", help="export to standalone repo")
    p_push.add_argument("--remote", default=None)
    p_push.add_argument("--dry-run", action="store_true")

    args = parser.parse_args(argv)
    cfg = load_config()

    if args.cmd == "push":
        remote = args.remote or os.environ.get(cfg.remote_env)
        run_export(repo_root=REPO_ROOT, cfg=cfg, remote=remote, dry_run=args.dry_run)

    return 0


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