"""Per-file SHA-256 manifests + per-game version-history helpers.

Ported from: JoshSteam CDN/Utils/manifest.py
Bug fixes during port:
    - Hardcoded GAMES_DIR removed; uses `mist.core.paths` instead.

NOTE: the version-history-as-JSON functions (`update_game_version_manifest`,
`get_latest_version_from_game_manifest`, `is_direct_update`) are kept as
**legacy fallbacks**. The Postgres `Version` model is the new source of
truth. Callsites are expected to migrate; the JSON path remains for
emergency manual operations on the NAS.
"""

from __future__ import annotations

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

from mist.core import paths


def file_checksum(file_path: Path | str) -> str:
    """SHA-256 of a file, computed in 4KB chunks."""
    sha256_hash = hashlib.sha256()
    with open(file_path, "rb") as f:
        for byte_block in iter(lambda: f.read(4096), b""):
            sha256_hash.update(byte_block)
    return sha256_hash.hexdigest()


def generate_manifest(game_title: str, version: str, depot_path: Path | str) -> Path:
    """Walk `depot_path`, compute SHA-256 for every file, write to manifests/<version>.json."""
    depot_path = Path(depot_path)
    manifest: dict[str, dict[str, str]] = {}
    for root, _, files in __import__("os").walk(depot_path):
        for file in files:
            file_path = Path(root) / file
            checksum = file_checksum(file_path)
            relative_path = str(file_path.relative_to(depot_path))
            manifest[relative_path] = {"checksum": checksum, "path": relative_path}

    out_path = paths.manifest_path(game_title, version)
    out_path.parent.mkdir(parents=True, exist_ok=True)
    with open(out_path, "w") as f:
        json.dump(manifest, f, indent=4)
    return out_path


def load_manifest(manifest_file: Path | str) -> dict[str, dict[str, str]]:
    """Load a per-version manifest file."""
    with open(manifest_file) as f:
        return json.load(f)


# ---- Legacy version-history JSON helpers (preserved for manual ops) ----


def update_game_version_manifest(game_title: str, version: str) -> None:
    """Append a version to the per-game version-history JSON. Legacy."""
    history_file = paths.game_version_history_path(game_title)
    if history_file.exists():
        with open(history_file) as f:
            history: list[str] = json.load(f)
    else:
        history = []
    history.append(version)
    history_file.parent.mkdir(parents=True, exist_ok=True)
    with open(history_file, "w") as f:
        json.dump(history, f, indent=4)


def get_latest_version_from_game_manifest(game_title: str) -> str | None:
    """Last entry in the legacy version-history JSON."""
    history_file = paths.game_version_history_path(game_title)
    if not history_file.exists():
        return None
    with open(history_file) as f:
        versions: list[str] = json.load(f)
    return versions[-1] if versions else None


def get_earliest_version_from_game_manifest(game_title: str) -> str | None:
    """First entry in the legacy version-history JSON."""
    history_file = paths.game_version_history_path(game_title)
    if not history_file.exists():
        return None
    with open(history_file) as f:
        versions: list[str] = json.load(f)
    return versions[0] if versions else None


def is_direct_update(game_title: str, version1: str, version2: str) -> bool:
    """True iff version1 is the immediate predecessor of version2. Legacy."""
    history_file = paths.game_version_history_path(game_title)
    if not history_file.exists():
        return False
    with open(history_file) as f:
        versions: list[str] = json.load(f)
    if version1 not in versions or version2 not in versions:
        return False
    return versions.index(version1) + 1 == versions.index(version2)


# ---- Manifest verification ----


def verify_files(game_dir: Path | str, manifest_file: Path | str) -> dict[str, Any]:
    """Verify every file under `game_dir` against the SHA-256s in `manifest_file`.

    Returns a dict with `missing_files`, `mismatched_checksums`, `all_files_verified`.
    """
    game_dir = Path(game_dir)
    manifest_file = Path(manifest_file)
    if not manifest_file.exists():
        raise FileNotFoundError(f"Manifest not found at {manifest_file}")

    with open(manifest_file) as f:
        manifest_data: dict[str, dict[str, str]] = json.load(f)

    results: dict[str, Any] = {
        "missing_files": [],
        "mismatched_checksums": [],
        "all_files_verified": True,
    }

    for _, file_info in manifest_data.items():
        file_path = game_dir / file_info["path"]
        if not file_path.exists():
            results["missing_files"].append(str(file_path))
            results["all_files_verified"] = False
            continue
        actual = file_checksum(file_path)
        if actual != file_info["checksum"]:
            results["mismatched_checksums"].append(
                {"file": str(file_path), "expected": file_info["checksum"], "actual": actual}
            )
            results["all_files_verified"] = False

    return results