"""Create a minimal local SQLite snapshot for offline backtest research.

Copies only the data required by app.services.backtest_service.run_backtest:
tickers, OHLCV bars, SPY benchmark closes, and activation/recommendation
settings. Other system settings are intentionally skipped to avoid copying
secrets into local snapshot files.
"""

from __future__ import annotations

import argparse
import asyncio
import os
import sys
from pathlib import Path

from sqlalchemy import func, insert, or_, select
from sqlalchemy.engine import make_url
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

ROOT = Path(__file__).resolve().parents[1]
if str(ROOT) not in sys.path:
    sys.path.insert(0, str(ROOT))


def _normalize_postgres_url(url: str) -> str:
    if url.startswith("postgresql+asyncpg://"):
        return url
    if url.startswith("postgresql://"):
        return "postgresql+asyncpg://" + url[len("postgresql://") :]
    if url.startswith("postgres://"):
        return "postgresql+asyncpg://" + url[len("postgres://") :]
    return url


def _sqlite_url(path: Path) -> str:
    return f"sqlite+aiosqlite:///{path.resolve().as_posix()}"


def _hide_password(url: str) -> str:
    return make_url(url).render_as_string(hide_password=True)


def _parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        "--database-url",
        default=os.getenv("DATABASE_URL"),
        help="Source Postgres URL. Defaults to DATABASE_URL, then app .env database_url.",
    )
    parser.add_argument(
        "--output",
        default="backtest_snapshots/prod-backtest.sqlite",
        help="SQLite snapshot path to create.",
    )
    parser.add_argument("--batch-size", type=int, default=5000)
    parser.add_argument("--force", action="store_true", help="Overwrite an existing snapshot file.")
    return parser.parse_args()


async def _copy_table(
    source: AsyncSession,
    dest: AsyncSession,
    model: type,
    *,
    batch_size: int,
    where=None,
) -> int:
    table = model.__table__
    columns = list(table.columns)

    count_stmt = select(func.count()).select_from(table)
    stmt = select(*columns)
    if where is not None:
        count_stmt = count_stmt.where(where)
        stmt = stmt.where(where)
    primary_key_columns = list(table.primary_key.columns)
    if primary_key_columns:
        stmt = stmt.order_by(*primary_key_columns)

    expected = int((await source.execute(count_stmt)).scalar_one())
    if expected == 0:
        print(f"{table.name}: 0 rows")
        return 0

    copied = 0
    stream = await source.stream(stmt.execution_options(yield_per=batch_size))
    async for partition in stream.partitions(batch_size):
        rows = [dict(row._mapping) for row in partition]
        if not rows:
            continue
        await dest.execute(insert(table), rows)
        await dest.commit()
        copied += len(rows)
        print(f"{table.name}: {copied}/{expected}", end="\r")

    print(f"{table.name}: {copied} rows")
    return copied


async def _main() -> None:
    args = _parse_args()

    from app.config import settings
    from app.database import Base
    import app.models  # noqa: F401 - registers all metadata tables
    from app.models.benchmark_price import BenchmarkPrice
    from app.models.ohlcv import OHLCVRecord
    from app.models.settings import SystemSetting
    from app.models.ticker import Ticker

    source_url = _normalize_postgres_url(args.database_url or settings.database_url)
    output = Path(args.output)
    if output.exists():
        if not args.force:
            raise SystemExit(f"{output} already exists. Pass --force to overwrite it.")
        output.unlink()
    output.parent.mkdir(parents=True, exist_ok=True)

    source_engine = create_async_engine(
        source_url,
        pool_pre_ping=True,
        connect_args={"server_settings": {"default_transaction_read_only": "on"}},
    )
    dest_engine = create_async_engine(_sqlite_url(output))
    SourceSession = async_sessionmaker(source_engine, class_=AsyncSession, expire_on_commit=False)
    DestSession = async_sessionmaker(dest_engine, class_=AsyncSession, expire_on_commit=False)

    print(f"Source: {_hide_password(source_url)}")
    print(f"Snapshot: {output}")

    try:
        async with dest_engine.begin() as conn:
            await conn.run_sync(Base.metadata.create_all)

        async with SourceSession() as source, DestSession() as dest:
            counts = {
                "tickers": await _copy_table(source, dest, Ticker, batch_size=args.batch_size),
                "system_settings": await _copy_table(
                    source,
                    dest,
                    SystemSetting,
                    batch_size=args.batch_size,
                    where=or_(
                        SystemSetting.key.like("activation_%"),
                        SystemSetting.key.like("recommendation_%"),
                    ),
                ),
                "benchmark_prices": await _copy_table(source, dest, BenchmarkPrice, batch_size=args.batch_size),
                "ohlcv_records": await _copy_table(source, dest, OHLCVRecord, batch_size=args.batch_size),
            }
    finally:
        await source_engine.dispose()
        await dest_engine.dispose()

    print("Done:")
    for name, count in counts.items():
        print(f"  {name}: {count}")


if __name__ == "__main__":
    asyncio.run(_main())