#!/usr/bin/env python3
"""
vendor.py — minimal but extensible vendoring tool for GitHub files

Examples:
    # Fetch and record to manifest
    vendor.py --github user/repo path/to/file.txt

    # Fetch from specific commit
    vendor.py --github user/repo path/to/file.txt --commit abc1234

    # Update all vendored files
    vendor.py update
"""

import argparse
import os
import sys
import json
import urllib.request
from pathlib import Path

DEFAULT_VENDOR_DIR = "vendor"
MANIFEST_FILE = "vendor.json"


def load_manifest():
    if Path(MANIFEST_FILE).is_file():
        with open(MANIFEST_FILE, "r", encoding="utf-8") as f:
            return json.load(f)
    return []


def save_manifest(entries):
    with open(MANIFEST_FILE, "w", encoding="utf-8") as f:
        json.dump(entries, f, indent=2)
    print(f"Manifest saved to {MANIFEST_FILE}")


def fetch_github_file(repo, file_path, ref, out_path):
    """Fetch a file from GitHub and save to out_path."""
    raw_url = f"https://raw.githubusercontent.com/{repo}/{ref}/{file_path}"
    print(f"Fetching: {raw_url}")
    try:
        with urllib.request.urlopen(raw_url) as resp:
            data = resp.read()
    except Exception as e:
        print(f"Error: Failed to fetch from {raw_url}\n{e}", file=sys.stderr)
        sys.exit(1)

    os.makedirs(os.path.dirname(out_path), exist_ok=True)
    with open(out_path, "wb") as f:
        f.write(data)
    print(f"Saved to: {out_path}")


def add_to_manifest(provider, repo, file_path, ref, out_path):
    manifest = load_manifest()
    entry = {
        "provider": provider,
        "repo": repo,
        "file_path": file_path,
        "ref": ref,
        "out_path": out_path
    }
    # Avoid duplicates
    if entry not in manifest:
        manifest.append(entry)
        save_manifest(manifest)


def update_all():
    manifest = load_manifest()
    if not manifest:
        print("No vendored files found in manifest.")
        return
    for entry in manifest:
        if entry["provider"] == "github":
            fetch_github_file(
                entry["repo"],
                entry["file_path"],
                entry["ref"],
                entry["out_path"]
            )
        else:
            print(f"Unknown provider: {entry['provider']}", file=sys.stderr)


def parse_args():
    parser = argparse.ArgumentParser(
        description="Vendor single files from GitHub (with manifest tracking)."
    )

    subparsers = parser.add_subparsers(dest="command")

    # Fetch command
    fetch_parser = subparsers.add_parser(
        "fetch", help="Fetch a file and record in manifest."
    )
    fetch_parser.add_argument(
        "--github",
        nargs=2,
        metavar=("USER/REPO", "FILE_PATH"),
        help="Fetch from GitHub repository (example: user/repo path/to/file.txt).",
        required=True
    )
    fetch_parser.add_argument(
        "--branch", help="Branch to fetch from (default: master)."
    )
    fetch_parser.add_argument(
        "--tag", help="Tag to fetch from."
    )
    fetch_parser.add_argument(
        "--commit", help="Commit SHA to fetch from."
    )
    fetch_parser.add_argument(
        "--out",
        help=f"Output path (default: {DEFAULT_VENDOR_DIR}/<filename>)."
    )

    # Update command
    subparsers.add_parser("update", help="Update all files in manifest.")

    return parser.parse_args()


def main():
    args = parse_args()

    if args.command == "fetch":
        repo, file_path = args.github

        # Pick ref in priority order
        ref = args.commit or args.tag or args.branch or "master"

        out_path = args.out or os.path.join(
            DEFAULT_VENDOR_DIR, os.path.basename(file_path)
        )

        fetch_github_file(repo, file_path, ref, out_path)
        add_to_manifest("github", repo, file_path, ref, out_path)

    elif args.command == "update":
        update_all()

    else:
        print("No command specified. Use -h for help.", file=sys.stderr)
        sys.exit(1)


if __name__ == "__main__":
    main()