#!/usr/bin/env python3
"""Create or verify the immutable source manifest used by long experiments."""

from __future__ import annotations

import argparse
import hashlib
import json
from pathlib import Path
from typing import Any


SCHEMA_VERSION = 1
ROOT_FILES = (
    "pyproject.toml",
    "requirements-runtime.txt",
    "requirements-dev.txt",
)
TREE_PATTERNS = (
    ("gmnet", "*.py"),
    ("scripts", "*.py"),
    ("scripts", "*.sh"),
    ("configs", "*.yaml"),
)


def file_sha256(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def stable_sha256(value: Any) -> str:
    payload = json.dumps(
        value, sort_keys=True, separators=(",", ":"), ensure_ascii=True
    ).encode("utf-8")
    return hashlib.sha256(payload).hexdigest()


def build_manifest(root: Path) -> dict[str, Any]:
    root = root.resolve()
    paths = [root / name for name in ROOT_FILES]
    for directory, pattern in TREE_PATTERNS:
        paths.extend((root / directory).rglob(pattern))
    paths = sorted({path.resolve() for path in paths if path.is_file()})
    records = [
        {
            "path": path.relative_to(root).as_posix(),
            "size": path.stat().st_size,
            "sha256": file_sha256(path),
        }
        for path in paths
    ]
    manifest: dict[str, Any] = {
        "schema_version": SCHEMA_VERSION,
        "fingerprint_scope": "training_source_configs_and_environment_specs",
        "files": records,
    }
    manifest["code_sha256"] = stable_sha256(manifest)
    return manifest


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        "--root", type=Path, default=Path(__file__).resolve().parents[1]
    )
    action = parser.add_mutually_exclusive_group()
    action.add_argument("--write", type=Path)
    action.add_argument("--check", type=Path)
    action.add_argument("--print", dest="print_fingerprint", action="store_true")
    return parser.parse_args()


def main() -> int:
    args = parse_args()
    manifest = build_manifest(args.root)
    if args.write is not None:
        args.write.parent.mkdir(parents=True, exist_ok=True)
        args.write.write_text(
            json.dumps(manifest, indent=2, sort_keys=True) + "\n", encoding="utf-8"
        )
    elif args.check is not None:
        expected = json.loads(args.check.read_text(encoding="utf-8"))
        if expected != manifest:
            expected_hash = expected.get("code_sha256")
            raise SystemExit(
                "code manifest mismatch: "
                f"expected {expected_hash}, computed {manifest['code_sha256']}"
            )
    if args.print_fingerprint or args.write is not None or args.check is not None:
        print(manifest["code_sha256"])
    else:
        print(json.dumps(manifest, indent=2, sort_keys=True))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())