"""Stale PR monitor — auto-close extraction PRs that produced no claims.

Catches the failure mode where batch-extract creates a PR but extraction
produces only source-file updates (no actual claims). These PRs sit open
indefinitely, consuming merge queue bandwidth and confusing metrics.

Rules:
  - PR branch starts with "extract/"
  - PR is open for >30 minutes
  - PR diff contains 0 files in domains/*/ or decisions/*/
  → Auto-close with comment, log to audit_log as stale_extraction_closed

  - If same source branch has been stale-closed 2+ times
  → Mark source as extraction_failed in pipeline.db sources table

Called from the pipeline daemon (piggyback on validate_cycle interval)
or standalone via: python3 -m lib.stale_pr

Owner: Epimetheus
"""

import logging
import json
import os
import re
import sqlite3
import urllib.request
from datetime import datetime, timedelta, timezone

from . import config

logger = logging.getLogger("pipeline.stale_pr")

STALE_THRESHOLD_MINUTES = 30
MAX_STALE_FAILURES = 2  # After this many stale closures, mark source as failed


def _forgejo_api(method: str, path: str, body: dict | None = None) -> dict | list | None:
    """Call Forgejo API. Returns parsed JSON or None on failure."""
    token_file = config.FORGEJO_TOKEN_FILE
    if not token_file.exists():
        logger.error("No Forgejo token at %s", token_file)
        return None
    token = token_file.read_text().strip()

    url = f"{config.FORGEJO_URL}/api/v1/{path}"
    data = json.dumps(body).encode() if body else None
    req = urllib.request.Request(
        url,
        data=data,
        headers={
            "Authorization": f"token {token}",
            "Content-Type": "application/json",
        },
        method=method,
    )
    try:
        with urllib.request.urlopen(req, timeout=15) as resp:
            return json.loads(resp.read())
    except Exception as e:
        logger.warning("Forgejo API %s %s failed: %s", method, path, e)
        return None


def _pr_has_claim_files(pr_number: int) -> bool:
    """Check if a PR's diff contains any files in domains/ or decisions/."""
    diff_data = _forgejo_api("GET", f"repos/{config.FORGEJO_OWNER}/{config.FORGEJO_REPO}/pulls/{pr_number}/files")
    if not diff_data or not isinstance(diff_data, list):
        return False

    for file_entry in diff_data:
        filename = file_entry.get("filename", "")
        if filename.startswith("domains/") or filename.startswith("decisions/"):
            # Check it's a .md file, not a directory marker
            if filename.endswith(".md"):
                return True
    return False


def _close_pr(pr_number: int, reason: str) -> bool:
    """Close a PR with a comment explaining why."""
    # Add comment
    _forgejo_api("POST",
        f"repos/{config.FORGEJO_OWNER}/{config.FORGEJO_REPO}/issues/{pr_number}/comments",
        {"body": f"Auto-closed by stale PR monitor: {reason}\n\nPentagon-Agent: Epimetheus"},
    )
    # Close PR
    result = _forgejo_api("PATCH",
        f"repos/{config.FORGEJO_OWNER}/{config.FORGEJO_REPO}/pulls/{pr_number}",
        {"state": "closed"},
    )
    return result is not None


def _log_audit(conn: sqlite3.Connection, pr_number: int, branch: str):
    """Log stale closure to audit_log."""
    try:
        conn.execute(
            "INSERT INTO audit_log (timestamp, stage, event, detail) VALUES (datetime('now'), ?, ?, ?)",
            ("monitor", "stale_extraction_closed", json.dumps({"pr": pr_number, "branch": branch})),
        )
        conn.commit()
    except Exception as e:
        logger.warning("Audit log write failed: %s", e)


def _count_stale_closures(conn: sqlite3.Connection, branch: str) -> int:
    """Count how many times this branch has been stale-closed."""
    try:
        row = conn.execute(
            "SELECT COUNT(*) FROM audit_log WHERE event = 'stale_extraction_closed' AND detail LIKE ?",
            (f'%"branch": "{branch}"%',),
        ).fetchone()
        return row[0] if row else 0
    except Exception:
        return 0


def _mark_source_failed(conn: sqlite3.Connection, branch: str):
    """Mark the source as extraction_failed after repeated stale closures."""
    # Extract source name from branch: extract/source-name → source-name
    source_name = branch.removeprefix("extract/")
    try:
        conn.execute(
            "UPDATE sources SET status = 'extraction_failed', last_error = 'repeated_stale_extraction', updated_at = datetime('now') WHERE path LIKE ?",
            (f"%{source_name}%",),
        )
        conn.commit()
        logger.info("Marked source %s as extraction_failed (repeated stale closures)", source_name)
    except Exception as e:
        logger.warning("Failed to mark source as failed: %s", e)


def check_stale_prs(conn: sqlite3.Connection) -> tuple[int, int]:
    """Check for and close stale extraction PRs.

    Returns (closed_count, error_count).
    """
    closed = 0
    errors = 0

    # Fetch all open PRs (paginated)
    page = 1
    all_prs = []
    while True:
        prs = _forgejo_api("GET",
            f"repos/{config.FORGEJO_OWNER}/{config.FORGEJO_REPO}/pulls?state=open&limit=50&page={page}")
        if not prs:
            break
        all_prs.extend(prs)
        if len(prs) < 50:
            break
        page += 1

    now = datetime.now(timezone.utc)

    for pr in all_prs:
        branch = pr.get("head", {}).get("ref", "")
        if not branch.startswith("extract/"):
            continue

        # Check age
        created_str = pr.get("created_at", "")
        if not created_str:
            continue
        try:
            # Forgejo returns ISO format with Z suffix
            created = datetime.fromisoformat(created_str.replace("Z", "+00:00"))
        except ValueError:
            continue

        age_minutes = (now - created).total_seconds() / 60
        if age_minutes < STALE_THRESHOLD_MINUTES:
            continue

        pr_number = pr["number"]

        # Check if PR has claim files
        if _pr_has_claim_files(pr_number):
            continue  # PR has claims — not stale

        # PR is stale — close it
        logger.info("Stale PR #%d: branch=%s, age=%.0f min, no claim files — closing",
                     pr_number, branch, age_minutes)

        if _close_pr(pr_number, f"No claim files after {int(age_minutes)} minutes. Branch: {branch}"):
            closed += 1
            _log_audit(conn, pr_number, branch)

            # Check for repeated failures
            failure_count = _count_stale_closures(conn, branch)
            if failure_count >= MAX_STALE_FAILURES:
                _mark_source_failed(conn, branch)
                logger.warning("Source %s marked as extraction_failed after %d stale closures",
                               branch, failure_count)
        else:
            errors += 1
            logger.warning("Failed to close stale PR #%d", pr_number)

    if closed:
        logger.info("Stale PR monitor: closed %d PRs", closed)

    return closed, errors


# Allow standalone execution
if __name__ == "__main__":
    import sys
    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")

    db_path = config.DB_PATH
    if not db_path.exists():
        print(f"ERROR: Database not found at {db_path}", file=sys.stderr)
        sys.exit(1)

    conn = sqlite3.connect(str(db_path))
    conn.row_factory = sqlite3.Row
    closed, errs = check_stale_prs(conn)
    print(f"Stale PR monitor: {closed} closed, {errs} errors")
    conn.close()