#!/usr/bin/env python3
"""
Migrate existing transaction records to a new TTL.

Reads all .json record files in the given storage directory and rewrites
expires_at to processed_at + ttl_days. Records that have already expired
are left untouched (they will be cleaned up on next startup).

Usage:
    python migrate_ttl.py <storage_dir> <ttl_days>

Example (run on the server):
    python migrate_ttl.py /opt/data/transaction_records 14
"""
import json
import os
import sys
from datetime import datetime, timedelta


def migrate(storage_dir: str, ttl_days: int) -> None:
    if not os.path.isdir(storage_dir):
        print(f"Directory not found: {storage_dir}")
        sys.exit(1)

    now = datetime.now()
    updated = skipped = errors = 0

    for filename in os.listdir(storage_dir):
        if not filename.endswith(".json"):
            continue
        path = os.path.join(storage_dir, filename)
        try:
            with open(path) as f:
                record = json.load(f)

            processed_at = datetime.fromisoformat(record["processed_at"])
            current_expires = datetime.fromisoformat(record["expires_at"])

            if current_expires <= now:
                skipped += 1
                continue

            new_expires = processed_at + timedelta(days=ttl_days)
            if new_expires <= current_expires:
                skipped += 1
                continue

            record["expires_at"] = new_expires.isoformat()
            with open(path, "w") as f:
                json.dump(record, f)
            updated += 1

        except (json.JSONDecodeError, KeyError, ValueError, OSError) as e:
            print(f"  ERROR {filename}: {e}")
            errors += 1

    print(f"Done: {updated} updated, {skipped} skipped (already expired or TTL already sufficient), {errors} errors")


if __name__ == "__main__":
    if len(sys.argv) != 3:
        print(__doc__)
        sys.exit(1)
    migrate(sys.argv[1], int(sys.argv[2]))