#!/usr/bin/env python3
"""只读扫描来源目录中的 Skill，并输出稳定的 JSON 清单。"""

from __future__ import annotations

import argparse
import hashlib
import json
import subprocess
from datetime import datetime, timezone
from pathlib import Path


def file_hash(path: Path) -> str:
    """按二进制内容计算单文件 SHA-256。"""
    digest = hashlib.sha256()
    with path.open("rb") as stream:
        for block in iter(lambda: stream.read(65536), b""):
            digest.update(block)
    return digest.hexdigest()


def directory_hash(root: Path) -> tuple[str, int]:
    """把相对路径和文件内容共同纳入哈希，确保结构变化也可被识别。"""
    digest = hashlib.sha256()
    files = sorted(path for path in root.rglob("*") if path.is_file())
    for path in files:
        relative = path.relative_to(root).as_posix()
        digest.update(relative.encode("utf-8"))
        digest.update(b"\0")
        digest.update(bytes.fromhex(file_hash(path)))
    return digest.hexdigest(), len(files)


def read_skill_name(skill_md: Path) -> str:
    """从 YAML frontmatter 中读取 name；解析失败时回退为目录名。"""
    for line in skill_md.read_text(encoding="utf-8-sig").splitlines():
        if line.startswith("name:"):
            return line.split(":", 1)[1].strip().strip("'\"") or skill_md.parent.name
    return skill_md.parent.name


def git_commit(root: Path) -> str | None:
    """尽力读取来源提交；非 Git 目录时返回空值，不阻塞文件扫描。"""
    result = subprocess.run(
        ["git", "-c", f"safe.directory={root.as_posix()}", "-C", str(root), "rev-parse", "HEAD"],
        capture_output=True,
        text=True,
        check=False,
    )
    return result.stdout.strip() if result.returncode == 0 else None


def scan_source(source_id: str, root: Path) -> dict:
    """扫描单个来源，结果仅包含相对路径和指纹，不包含本地绝对路径。"""
    if not root.is_dir():
        raise ValueError(f"来源目录不存在：{root}")
    skills = []
    for skill_md in sorted(root.rglob("SKILL.md")):
        skill_root = skill_md.parent
        digest, file_count = directory_hash(skill_root)
        children = sorted(
            child.name for child in skill_root.iterdir() if child.is_dir()
        )
        skills.append(
            {
                "name": read_skill_name(skill_md),
                "relativePath": skill_root.relative_to(root).as_posix(),
                "sha256": digest,
                "fileCount": file_count,
                "resources": children,
            }
        )
    return {
        "id": source_id,
        "commit": git_commit(root),
        "skillCount": len(skills),
        "skills": skills,
    }


def parse_source(value: str) -> tuple[str, Path]:
    """解析 id=path 参数，避免把本地路径写入输出文件。"""
    if "=" not in value:
        raise argparse.ArgumentTypeError("来源参数必须使用 id=path 格式")
    source_id, raw_path = value.split("=", 1)
    if not source_id.strip() or not raw_path.strip():
        raise argparse.ArgumentTypeError("来源标识和路径均不能为空")
    return source_id.strip(), Path(raw_path).expanduser().resolve()


def main() -> None:
    parser = argparse.ArgumentParser(description="只读扫描 Skill 来源目录")
    parser.add_argument("--source", action="append", required=True, type=parse_source)
    parser.add_argument("--output", type=Path, help="可选 JSON 输出路径；省略时输出到终端")
    args = parser.parse_args()
    payload = {
        "schemaVersion": 1,
        "generatedAt": datetime.now(timezone.utc).isoformat(),
        "sources": [scan_source(source_id, root) for source_id, root in args.source],
    }
    content = json.dumps(payload, ensure_ascii=False, indent=2) + "\n"
    if args.output:
        args.output.parent.mkdir(parents=True, exist_ok=True)
        args.output.write_text(content, encoding="utf-8")
    else:
        print(content, end="")


if __name__ == "__main__":
    main()