#!/usr/bin/env python3
"""Backfill: normalize all cluster payload timestamps to ISO 8601 UTC.

Reads every cluster payload from the DB, normalizes timestamp fields
(cluster-level and article-level), and writes back only changed payloads.

Usage:
  ./.venv/bin/python scripts/normalize_cluster_timestamps.py [--dry-run] [--db PATH]

Safe to re-run: only writes rows whose payload actually changed.
"""

from __future__ import annotations

import argparse
import json
import sqlite3
import sys
from datetime import datetime, timezone, timedelta
from email.utils import parsedate_to_datetime
from pathlib import Path
from typing import Any

ROOT = Path(__file__).resolve().parents[1]
sys.path.insert(0, str(ROOT))

from news_mcp.config import DB_PATH


def _normalize_ts(ts: Any) -> str:
    """Parse any timestamp string and return ISO 8601 UTC. Returns "" if unparseable."""
    if ts is None:
        return ""
    if isinstance(ts, (int, float)):
        try:
            dt = datetime.fromtimestamp(float(ts), tz=timezone.utc)
            return dt.strftime("%Y-%m-%dT%H:%M:%S+00:00")
        except Exception:
            return ""
    text = str(ts).strip()
    if not text:
        return ""
    # ISO 8601
    try:
        dt = datetime.fromisoformat(text.replace("Z", "+00:00"))
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=timezone.utc)
        return dt.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%S+00:00")
    except Exception:
        pass
    # RFC 2822 / HTTP-date
    try:
        dt = parsedate_to_datetime(text)
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=timezone.utc)
        return dt.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%S+00:00")
    except Exception:
        pass
    return text  # leave unparseable values as-is


def _normalize_payload(payload: dict[str, Any]) -> dict[str, Any]:
    """Return a new dict with all timestamp fields normalized. Returns same ref if no changes."""
    changed = False
    out = dict(payload)

    # Article-level timestamps
    articles = out.get("articles") or []
    if articles:
        new_articles = []
        for a in articles:
            if isinstance(a, dict) and "timestamp" in a and a["timestamp"]:
                normed = _normalize_ts(a["timestamp"])
                if normed != a["timestamp"]:
                    a = dict(a)
                    a["timestamp"] = normed
                    changed = True
            new_articles.append(a)
        out["articles"] = new_articles

    # Cluster-level timestamp fields
    for field in ("timestamp", "first_seen", "last_updated"):
        if field in out and out[field]:
            normed = _normalize_ts(out[field])
            if normed != out[field]:
                out[field] = normed
                changed = True

    return out


def main() -> None:
    parser = argparse.ArgumentParser(description="Normalize all cluster payload timestamps to ISO 8601")
    parser.add_argument("--db", type=Path, default=DB_PATH)
    parser.add_argument("--dry-run", action="store_true")
    parser.add_argument("--limit", type=int, default=None)
    args = parser.parse_args()

    db_path = str(args.db)
    print(f"Database: {db_path}")
    print(f"Dry run:  {args.dry_run}")

    with sqlite3.connect(db_path) as conn:
        conn.execute("PRAGMA journal_mode=WAL")
        rows = conn.execute(
            "SELECT cluster_id, topic, payload FROM clusters ORDER BY updated_at ASC"
        ).fetchall()
        if args.limit:
            rows = rows[: args.limit]

    total = len(rows)
    changed_count = 0
    errors = 0

    with sqlite3.connect(db_path) as conn:
        conn.execute("PRAGMA journal_mode=WAL")
        for i, (cluster_id, topic, payload_json) in enumerate(rows):
            try:
                payload = json.loads(payload_json)
            except Exception:
                errors += 1
                continue

            normalized = _normalize_payload(payload)

            if normalized is not payload:  # identity check: _normalize_payload returns same ref if no changes
                changed_count += 1
                if not args.dry_run:
                    new_json = json.dumps(normalized, ensure_ascii=False)
                    conn.execute(
                        "UPDATE clusters SET payload=?, updated_at=? WHERE cluster_id=?",
                        (new_json, datetime.now(timezone.utc).isoformat(), cluster_id),
                    )

            if (i + 1) % 500 == 0 or i == total - 1:
                print(f"  Processed {i+1}/{total}... ({changed_count} changed, {errors} errors)", flush=True)

        if not args.dry_run:
            conn.commit()

    print(f"\nDone. {changed_count}/{total} payloads normalized, {errors} errors.")
    if args.dry_run:
        print("  (dry run — no changes written)")


if __name__ == "__main__":
    main()