#!/usr/bin/env python3
"""Fetch GitHub star counts and owner info for all GitHub repos in README.md."""

import json
import os
import re
import sys
from datetime import datetime, timezone
from pathlib import Path

import httpx

from build import extract_github_repo

CACHE_MAX_AGE_DAYS = 7
DATA_DIR = Path(__file__).parent / "data"
CACHE_FILE = DATA_DIR / "github_stars.json"
README_PATH = Path(__file__).parent.parent / "README.md"
GRAPHQL_URL = "https://api.github.com/graphql"
BATCH_SIZE = 100


def extract_github_repos(text: str) -> set[str]:
    """Extract unique owner/repo pairs from GitHub URLs in markdown text."""
    repos = set()
    for url in re.findall(r"https?://github\.com/[^\s)\]]+", text):
        repo = extract_github_repo(url.split("#")[0].rstrip("/"))
        if repo:
            repos.add(repo)
    return repos


def load_cache() -> dict:
    """Load the star cache from disk. Returns empty dict if missing or corrupt."""
    if CACHE_FILE.exists():
        try:
            return json.loads(CACHE_FILE.read_text(encoding="utf-8"))
        except json.JSONDecodeError:
            print(f"Warning: corrupt cache at {CACHE_FILE}, starting fresh.", file=sys.stderr)
            return {}
    return {}


def save_cache(cache: dict) -> None:
    """Write the star cache to disk, creating data/ dir if needed."""
    DATA_DIR.mkdir(parents=True, exist_ok=True)
    CACHE_FILE.write_text(
        json.dumps(cache, indent=2, ensure_ascii=False) + "\n",
        encoding="utf-8",
    )


def build_graphql_query(repos: list[str]) -> str:
    """Build a GraphQL query with aliases for up to 100 repos."""
    if not repos:
        return ""
    parts = []
    for i, repo in enumerate(repos):
        owner, name = repo.split("/", 1)
        if '"' in owner or '"' in name:
            continue
        parts.append(
            f'repo_{i}: repository(owner: "{owner}", name: "{name}") '
            f"{{ stargazerCount pushedAt owner {{ login }} }}"
        )
    if not parts:
        return ""
    return "query { " + " ".join(parts) + " }"


def parse_graphql_response(
    data: dict,
    repos: list[str],
) -> dict[str, dict]:
    """Parse GraphQL response into {owner/repo: {stars, owner}} dict."""
    result = {}
    for i, repo in enumerate(repos):
        node = data.get(f"repo_{i}")
        if node is None:
            continue
        result[repo] = {
            "stars": node.get("stargazerCount", 0),
            "owner": node.get("owner", {}).get("login", ""),
            "pushed_at": node.get("pushedAt", ""),
        }
    return result


def fetch_batch(
    repos: list[str], *, client: httpx.Client,
) -> dict[str, dict]:
    """Fetch star data for a batch of repos via GitHub GraphQL API."""
    query = build_graphql_query(repos)
    if not query:
        return {}
    resp = client.post(GRAPHQL_URL, json={"query": query})
    resp.raise_for_status()
    result = resp.json()
    if "errors" in result:
        for err in result["errors"]:
            print(f"  Warning: {err.get('message', err)}", file=sys.stderr)
    data = result.get("data", {})
    return parse_graphql_response(data, repos)


def main() -> None:
    """Fetch GitHub stars for all repos in README.md, updating the JSON cache."""
    token = os.environ.get("GITHUB_TOKEN", "")
    if not token:
        print("Error: GITHUB_TOKEN environment variable is required.", file=sys.stderr)
        sys.exit(1)

    readme_text = README_PATH.read_text(encoding="utf-8")
    current_repos = extract_github_repos(readme_text)
    print(f"Found {len(current_repos)} GitHub repos in README.md")

    cache = load_cache()
    now = datetime.now(timezone.utc)

    # Prune entries not in current README
    pruned = {k: v for k, v in cache.items() if k in current_repos}
    if len(pruned) < len(cache):
        print(f"Pruned {len(cache) - len(pruned)} stale cache entries")
    cache = pruned

    # Determine which repos need fetching (missing or stale)
    to_fetch = []
    for repo in sorted(current_repos):
        entry = cache.get(repo)
        if entry and "fetched_at" in entry:
            fetched = datetime.fromisoformat(entry["fetched_at"])
            age_days = (now - fetched).days
            if age_days < CACHE_MAX_AGE_DAYS:
                continue
        to_fetch.append(repo)

    print(f"{len(to_fetch)} repos to fetch ({len(current_repos) - len(to_fetch)} cached)")

    if not to_fetch:
        save_cache(cache)
        print("Cache is up to date.")
        return

    # Fetch in batches
    fetched_count = 0
    skipped_repos: list[str] = []

    with httpx.Client(
        headers={"Authorization": f"bearer {token}", "Content-Type": "application/json"},
        transport=httpx.HTTPTransport(retries=2),
        timeout=30,
    ) as client:
        for i in range(0, len(to_fetch), BATCH_SIZE):
            batch = to_fetch[i : i + BATCH_SIZE]
            batch_num = i // BATCH_SIZE + 1
            total_batches = (len(to_fetch) + BATCH_SIZE - 1) // BATCH_SIZE
            print(f"Fetching batch {batch_num}/{total_batches} ({len(batch)} repos)...")

            try:
                results = fetch_batch(batch, client=client)
            except httpx.HTTPStatusError as e:
                print(f"HTTP error {e.response.status_code}", file=sys.stderr)
                if e.response.status_code == 401:
                    print("Error: Invalid GITHUB_TOKEN.", file=sys.stderr)
                    sys.exit(1)
                print("Saving partial cache and exiting.", file=sys.stderr)
                save_cache(cache)
                sys.exit(1)

            now_iso = now.isoformat()
            for repo in batch:
                if repo in results:
                    cache[repo] = {
                        "stars": results[repo]["stars"],
                        "owner": results[repo]["owner"],
                        "pushed_at": results[repo]["pushed_at"],
                        "fetched_at": now_iso,
                    }
                    fetched_count += 1
                else:
                    skipped_repos.append(repo)

            # Save after each batch in case of interruption
            save_cache(cache)

    if skipped_repos:
        print(f"Skipped {len(skipped_repos)} repos (deleted/private/renamed)")
    print(f"Done. Fetched {fetched_count} repos, {len(cache)} total cached.")


if __name__ == "__main__":
    main()