"""Trade calendar interface.

Fetch trading calendar data from Tushare to determine market open/close dates.
With local caching for performance optimization.
"""

import pandas as pd
from typing import Optional, Literal
from pathlib import Path
from src.data.client import TushareClient
from src.config.settings import get_settings

# Module-level flag to track if cache has been synced in this session
_cache_synced = False


# Trading calendar cache file path
def _get_cache_path() -> Path:
    """Get the cache file path for trade calendar."""
    cfg = get_settings()
    return cfg.data_path_resolved / "trade_cal.h5"


def _save_to_cache(data: pd.DataFrame) -> None:
    """Save trade calendar data to local cache.

    Args:
        data: Trade calendar DataFrame
    """
    if data.empty:
        return

    cache_path = _get_cache_path()
    cache_path.parent.mkdir(parents=True, exist_ok=True)

    try:
        with pd.HDFStore(cache_path, mode="a") as store:
            store.put("trade_cal", data, format="table")
        print(f"[trade_cal] Saved {len(data)} records to cache: {cache_path}")
    except Exception as e:
        print(f"[trade_cal] Error saving to cache: {e}")


def _load_from_cache() -> pd.DataFrame:
    """Load trade calendar data from local cache.

    Returns:
        Trade calendar DataFrame or empty DataFrame if cache doesn't exist
    """
    cache_path = _get_cache_path()

    if not cache_path.exists():
        return pd.DataFrame()

    try:
        with pd.HDFStore(cache_path, mode="r") as store:
            # HDF5 keys include leading slash (e.g., '/trade_cal')
            if "/trade_cal" in store.keys():
                data = store["/trade_cal"]
                print(f"[trade_cal] Loaded {len(data)} records from cache")
                return data
    except Exception as e:
        print(f"[trade_cal] Error loading from cache: {e}")

    return pd.DataFrame()


def _get_cached_date_range() -> tuple[Optional[str], Optional[str]]:
    """Get the date range of cached trade calendar.

    Returns:
        Tuple of (min_date, max_date) or (None, None) if cache empty
    """
    data = _load_from_cache()
    if data.empty or "cal_date" not in data.columns:
        return (None, None)

    return (str(data["cal_date"].min()), str(data["cal_date"].max()))


def sync_trade_cal_cache(
    start_date: str = "20180101",
    end_date: Optional[str] = None,
    force: bool = False,
) -> pd.DataFrame:
    """Sync trade calendar data to local cache with incremental updates.

    This function checks if we have cached data and only fetches new data
    from the last cached date onwards.

    Args:
        start_date: Initial start date for full sync (default: 20180101)
        end_date: End date (defaults to today)
        force: If True, force sync even if already synced in this session

    Returns:
        Full trade calendar DataFrame (cached + new)
    """
    global _cache_synced

    # Skip if already synced in this session (unless forced)
    if _cache_synced and not force:
        return _load_from_cache()

    if end_date is None:
        from datetime import datetime

        end_date = datetime.now().strftime("%Y%m%d")

    client = TushareClient()

    # Check cached data range
    cached_min, cached_max = _get_cached_date_range()

    if cached_min and cached_max:
        print(f"[trade_cal] Cache found: {cached_min} to {cached_max}")
        # Only fetch new data after the cached max date
        fetch_start = str(int(cached_max) + 1)
        print(f"[trade_cal] Fetching incremental data from {fetch_start} to {end_date}")

        if int(fetch_start) > int(end_date):
            print("[trade_cal] Cache is up-to-date, no new data needed")
            return _load_from_cache()

        # Fetch new data
        new_data = client.query(
            "trade_cal",
            start_date=fetch_start,
            end_date=end_date,
            exchange="SSE",
        )

        if new_data.empty:
            print("[trade_cal] No new data returned")
            return _load_from_cache()

        print(f"[trade_cal] Fetched {len(new_data)} new records")

        # Load cached data and merge
        cached_data = _load_from_cache()
        if not cached_data.empty:
            combined = pd.concat([cached_data, new_data], ignore_index=True)
            # Remove duplicates by cal_date
            combined = combined.drop_duplicates(
                subset=["cal_date", "exchange"], keep="first"
            )
            combined = combined.sort_values("cal_date").reset_index(drop=True)
        else:
            combined = new_data

        # Save combined data to cache
        # Mark as synced to avoid redundant syncs in this session
        _cache_synced = True
        _save_to_cache(combined)
        return combined
    else:
        # No cache, fetch all data
        print(f"[trade_cal] No cache found, fetching from {start_date} to {end_date}")
        data = client.query(
            "trade_cal",
            start_date=start_date,
            end_date=end_date,
            exchange="SSE",
        )

        if data.empty:
            print("[trade_cal] No data returned")
            return data

        # Mark as synced to avoid redundant syncs in this session
        _cache_synced = True
        _save_to_cache(data)
        return data


def get_trade_cal(
    start_date: str,
    end_date: str,
    exchange: Literal["SSE", "SZSE", "BSE"] = "SSE",
    is_open: Optional[Literal["0", "1"]] = None,
    use_cache: bool = True,
) -> pd.DataFrame:
    """Fetch trading calendar data with optional local caching.

    This interface retrieves trading calendar information including
    whether each date is a trading day. Uses cached data when available
    to reduce API calls and improve performance.

    Args:
        start_date: Start date in YYYYMMDD format
        end_date: End date in YYYYMMDD format
        exchange: Exchange - SSE (Shanghai), SZSE (Shenzhen), BSE (Beijing)
        is_open: Open status - "1" for trading day, "0" for non-trading day
        use_cache: Whether to use and update local cache (default: True)

    Returns:
        pd.DataFrame with trade calendar containing:
        - cal_date: Calendar date (YYYYMMDD)
        - exchange: Exchange code
        - is_open: Whether it's a trading day (1/0)
        - pretrade_date: Previous trading day

    Example:
        >>> # Get all trading days in January 2024
        >>> cal = get_trade_cal('20240101', '20240131')
        >>> trading_days = cal[cal['is_open'] == '1']
        >>>
        >>> # Get first and last trading day of a period
        >>> cal = get_trade_cal('20180101', '20240101')
        >>> first_trade_day = cal[cal['is_open'] == '1'].iloc[0]['cal_date']
        >>> last_trade_day = cal[cal['is_open'] == '1'].iloc[-1]['cal_date']
    """
    # Use cache if enabled
    if use_cache and exchange == "SSE":
        # Sync cache first (incremental)
        sync_trade_cal_cache()

        # Load from cache and filter by date range
        cached_data = _load_from_cache()
        if not cached_data.empty and "cal_date" in cached_data.columns:
            # Filter by date range and exchange
            filtered = cached_data[
                (cached_data["cal_date"] >= start_date)
                & (cached_data["cal_date"] <= end_date)
                & (cached_data["exchange"] == exchange)
            ]

            # Apply is_open filter if specified
            if is_open is not None:
                # Handle type mismatch: HDF5 stores is_open as int, but API returns str
                filtered = filtered[filtered["is_open"].astype(str) == str(is_open)]

            if not filtered.empty:
                print(f"[get_trade_cal] Retrieved {len(filtered)} records from cache")
                return filtered

    # Fallback to API if cache not available or disabled
    client = TushareClient()

    # Build parameters
    params = {
        "start_date": start_date,
        "end_date": end_date,
        "exchange": exchange,
    }

    if is_open is not None:
        params["is_open"] = is_open

    # Fetch data
    data = client.query("trade_cal", **params)

    if data.empty:
        print("[get_trade_cal] No data returned")

    return data


def get_trading_days(
    start_date: str,
    end_date: str,
    exchange: Literal["SSE", "SZSE", "BSE"] = "SSE",
) -> list:
    """Get list of trading days in a date range.

    Args:
        start_date: Start date in YYYYMMDD format
        end_date: End date in YYYYMMDD format
        exchange: Exchange code

    Returns:
        List of trading dates (YYYYMMDD strings)
    """
    cal = get_trade_cal(start_date, end_date, exchange=exchange, is_open="1")
    if cal.empty:
        return []
    return cal["cal_date"].tolist()


def get_first_trading_day(
    start_date: str,
    end_date: str,
    exchange: Literal["SSE", "SZSE", "BSE"] = "SSE",
) -> Optional[str]:
    """Get the first trading day in a date range.

    Args:
        start_date: Start date in YYYYMMDD format
        end_date: End date in YYYYMMDD format
        exchange: Exchange code

    Returns:
        First trading date (YYYYMMDD) or None if no trading days
    """
    trading_days = get_trading_days(start_date, end_date, exchange)
    if not trading_days:
        return None
    # Return the earliest trading day
    return min(trading_days)


def get_last_trading_day(
    start_date: str,
    end_date: str,
    exchange: Literal["SSE", "SZSE", "BSE"] = "SSE",
) -> Optional[str]:
    """Get the last trading day in a date range.

    Args:
        start_date: Start date in YYYYMMDD format
        end_date: End date in YYYYMMDD format
        exchange: Exchange code

    Returns:
        Last trading date (YYYYMMDD) or None if no trading days
    """
    trading_days = get_trading_days(start_date, end_date, exchange)
    if not trading_days:
        return None
    # Return the latest trading day
    return max(trading_days)


if __name__ == "__main__":
    # Example usage
    start = "20180101"
    end = "20240101"

    print(f"Trade calendar from {start} to {end}")

    cal = get_trade_cal(start, end)
    print(f"Total records: {len(cal)}")

    first_day = get_first_trading_day(start, end)
    last_day = get_last_trading_day(start, end)
    print(f"First trading day: {first_day}")
    print(f"Last trading day: {last_day}")