from __future__ import annotations

import argparse
import asyncio
import json
import sys
from decimal import Decimal

from sqlalchemy import text

from app.enums.credit_balance import CreditBalanceSourceType, CreditLevel
from app.enums.credit_record import CreditRecordType
from app.models.base import async_session
from app.services.credit.ledger_service import grant_credits
from app.services.credit.time_policy import add_natural_months
from app.services.credit.utils import to_credit_decimal, utc_now


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="将 users.credits 一次性迁移到动态积分余额表。")
    parser.add_argument("--batch-size", type=int, default=500)
    parser.add_argument("--dry-run", action="store_true")
    parser.add_argument("--commit", action="store_true")
    parser.add_argument("--after-id", default="")
    return parser


async def amain(argv: list[str]) -> int:
    args = build_parser().parse_args(argv)
    if args.dry_run and args.commit:
        raise SystemExit("--dry-run 和 --commit 不能同时使用")
    do_commit = bool(args.commit)
    batch_size = max(1, min(int(args.batch_size or 500), 5000))
    migration_time = utc_now()
    cursor = str(args.after_id or "")
    stats = {"positive_users": 0, "zero_users": 0, "negative_reset_users": 0, "migrated_credits": "0.00", "last_id": cursor}
    total = Decimal("0.00")

    while True:
        async with async_session() as db:
            rows = (await db.execute(
                text("SELECT id, credits FROM users WHERE id > :cursor ORDER BY id ASC LIMIT :limit"),
                {"cursor": cursor, "limit": batch_size},
            )).mappings().all()
            if not rows:
                break
            try:
                for row in rows:
                    user_id = str(row["id"])
                    legacy = to_credit_decimal(row.get("credits") or 0)
                    cursor = user_id
                    stats["last_id"] = cursor
                    if legacy > 0:
                        stats["positive_users"] += 1
                        total += legacy
                        if do_commit:
                            await grant_credits(
                                db,
                                user_id=user_id,
                                amount=legacy,
                                description="历史用户积分迁移",
                                source_type=CreditBalanceSourceType.LEGACY_MIGRATION.value,
                                valid_from=migration_time,
                                expires_at=add_natural_months(migration_time, 12),
                                credit_level=CreditLevel.GENERAL.value,
                                source_id=user_id,
                                related_id=user_id,
                                record_type=CreditRecordType.RECHARGE.value,
                                biz_key=f"legacy-user-credits:{user_id}",
                                metadata_json={"legacy_credits": str(legacy), "migration_time": migration_time.isoformat()},
                                request_time=migration_time,
                            )
                    elif legacy < 0:
                        stats["negative_reset_users"] += 1
                    else:
                        stats["zero_users"] += 1
                if do_commit:
                    await db.commit()
                else:
                    await db.rollback()
            except Exception:
                await db.rollback()
                raise
    stats["migrated_credits"] = str(total.quantize(Decimal("0.01")))
    stats["migration_time"] = migration_time.isoformat()
    stats["mode"] = "commit" if do_commit else "dry-run"
    print(json.dumps(stats, ensure_ascii=False, indent=2))
    return 0


def main() -> int:
    return asyncio.run(amain(sys.argv[1:]))


if __name__ == "__main__":
    raise SystemExit(main())