"""
This script provides functionalities to download financial market data
and save it in a structured, partitioned Parquet format. Data is fetched
from MetaTrader 5 (MT5) for specified symbols and date ranges, with options
to handle existing files intelligently. It includes a user-friendly GUI prompt
to manage overwriting existing data, robust logging with 'loguru', and secure
credential management using environment variables. The script is designed to be
run as a standalone application for data acquisition, ensuring that the account
used for downloading matches the account used for loading data later.

FUntionality is provided for loading downloaded files into a DataFrame for analysis,
with options to specify columns and date ranges. The script is optimized for memory
usage and provides a clear directory structure for easy data management.

Features:
- Downloads data for a given list of symbols and a date range.
- Organizes saved data into a clear directory structure: path/symbol/year/month.parquet
- Implements a user-friendly, timed GUI prompt to ask for overwriting existing files.
- Uses 'loguru' for robust logging to both console and a file.
- Secures credentials using environment variables.
- Verifies account consistency for both downloading and loading data.
- Designed to be run as a standalone script for data acquisition.
"""

import json
import os
import sys
from concurrent.futures import ProcessPoolExecutor, as_completed
from pathlib import Path

import numpy as np
import pandas as pd
import MetaTrader5 as mt5
from dask import dataframe as dd
from dotenv import load_dotenv
from loguru import logger
from tqdm import tqdm

from ..util.misc import date_conversion, is_first_weekday, is_last_weekday, log_df_info
from .clean_data import clean_tick_data

# --- Credential and Login Management ---


def get_credentials_from_env(account):
    """
    Retrieves MT5 credentials from environment variables.

    Args:
        account (str): The account name (e.g., 'MyAccount').

    Returns:
        tuple: (login, password, server) or (None, None, None) if not found.
    """
    load_dotenv()  # Load environment variables from .env file if present
    prefix = f"MT5_ACCOUNT_{account.upper()}"
    login = os.environ.get(f"{prefix}_LOGIN")
    password = os.environ.get(f"{prefix}_PASSWORD")
    server = os.environ.get(f"{prefix}_SERVER")

    if not all([login, password, server]):
        logger.error(
            f"Missing one or more environment variables for account '{account}'."
        )
        logger.error(
            f"Please set {prefix}_LOGIN, {prefix}_PASSWORD, and {prefix}_SERVER."
        )
        return None, None, None

    if login.isnumeric():
        login = int(login)

    return login, password, server


def login_mt5(account, timeout=60000, verbose=True):
    """
    Logs in to a MetaTrader5 account using credentials from environment variables.

    Args:
        account (str): Account name to log in to.
        timeout (int): Connection timeout in milliseconds.
        verbose (bool): Whether to print detailed connection information.

    Returns:
        str: The account name if login is successful, otherwise None.
    """
    import MetaTrader5 as mt5

    logger.info(f"Attempting to log in to MT5 with account: {account}")
    login, password, server = get_credentials_from_env(account)

    if not login:
        return None

    if not mt5.initialize(
        login=login, password=password, server=server, timeout=timeout
    ):
        logger.error(
            f"MT5 initialize() failed for account {account}. Error: {mt5.last_error()}"
        )
        mt5.shutdown()
        return

    logger.success(f"Successfully logged in to MT5 as {account}.")
    if verbose:
        logger.info(f"MT5 Version: {mt5.version()}")
        terminal_info = mt5.terminal_info()
        if terminal_info:
            logger.info(f"Connected to {terminal_info.name} at {terminal_info.path}")
        else:
            logger.warning("Could not retrieve terminal info.")

    return account


# --- Data Validation and Verification ---


def verify_or_create_account_info(data_path, current_account_name):
    """
    Checks if the data directory is associated with the correct account.
    If no account info exists, it creates it.

    Args:
        data_path (Path): The root path of the data directory.
        current_account_name (str): The name of the account currently in use.

    Returns:
        bool: True if the account is verified, False otherwise.
    """
    account_info_file = data_path / "account_info.json"
    current_account_name = current_account_name.upper()

    if account_info_file.exists():
        try:
            with open(account_info_file, "r") as f:
                stored_info = json.load(f)
                stored_name = stored_info.get("account_name")

            if stored_name and stored_name != current_account_name:
                logger.error(
                    f"Account Mismatch! This directory ('{data_path.name}') is for account '{stored_name}'."
                )
                logger.error(
                    f"Current operation is for account '{current_account_name}'. Aborting to prevent data errors."
                )
                return False
            elif not stored_name:
                # File exists but is malformed, so we fix it.
                logger.warning(
                    "Account info file is malformed. Overwriting with current account."
                )
                with open(account_info_file, "w") as f:
                    json.dump({"account_name": current_account_name}, f, indent=4)

        except json.JSONDecodeError:
            logger.warning(
                f"Could not read account info file. Overwriting with current account: '{current_account_name}'."
            )
            with open(account_info_file, "w") as f:
                json.dump({"account_name": current_account_name}, f, indent=4)
    else:
        logger.info(
            f"First time use for this directory. Associating it with account '{current_account_name}'."
        )
        with open(account_info_file, "w") as f:
            json.dump({"account_name": current_account_name}, f, indent=4)

    return True


# --- Data Fetching and Saving ---


def get_ticks(symbol, start_date, end_date, datetime_index=True, verbose=True):
    """
    Downloads tick data from the MT5 terminal for a given period.

    Args:
        symbol (str): The financial instrument symbol (e.g., 'EURUSD').
        start_date (pd.Timestamp): The timezone-aware start date for the data range.
        end_date (pd.Timestamp): The timezone-aware end date for the data range.
        datetime_index (bool): Set 'time' column to DatetimeIndex.

    Returns:
        pd.DataFrame: A DataFrame containing the tick data, or an empty DataFrame if
                      no data is found or an error occurs.
    """
    import MetaTrader5 as mt5

    if not mt5.terminal_info():  # Check if connection is still active
        logger.error("MT5 connection lost. Cannot download data.")
        return pd.DataFrame()

    try:
        start_date, end_date = date_conversion(start_date, end_date)
        mt5.symbol_select(symbol, True)
        ticks = mt5.copy_ticks_range(symbol, start_date, end_date, mt5.COPY_TICKS_ALL)
        if ticks is None or len(ticks) == 0:
            logger.warning(
                f"No tick data returned for {symbol} from {start_date.date()} to {end_date.date()}."
            )
            return pd.DataFrame()

        df = pd.DataFrame(ticks)
        df["time"] = pd.to_datetime(df["time_msc"], unit="ms", utc=True)
        df.drop(columns=["time_msc"], inplace=True)

        if datetime_index:
            df.set_index("time", inplace=True)

        # Keep only columns with meaningful data
        df = df.loc[:, df.any()]

        # Optimize memory usage
        for col in ["bid", "ask"]:
            if col in df.columns:
                df[col] = df[col].astype("float32")

        if verbose:
            log_df_info(df)

        return df

    except Exception as e:
        logger.error(f"An error occurred while getting ticks for {symbol}: {e}")
        return pd.DataFrame()


def get_bars(
    symbol, timeframe, start_date, end_date, datetime_index=True, verbose=True
):
    """
    Downloads bar (OHLCV) data from the MT5 terminal for a given period.

    Args:
        symbol (str): The financial instrument symbol (e.g., 'EURUSD').
        timeframe (int): MT5 timeframe constant (e.g., mt5.TIMEFRAME_M1, mt5.TIMEFRAME_H1).
        start_date (pd.Timestamp): Timezone-aware start date.
        end_date (pd.Timestamp): Timezone-aware end date.
        datetime_index (bool): Set 'time' column to DatetimeIndex.
        verbose (bool): Print DataFrame info.

    Returns:
        pd.DataFrame: A DataFrame containing OHLCV data, or empty if no data/error.
    """
    import MetaTrader5 as mt5

    if not mt5.terminal_info():
        logger.error("MT5 connection lost. Cannot download data.")
        return pd.DataFrame()

    try:
        start_date, end_date = date_conversion(start_date, end_date)
        timeframe = getattr(mt5, f"TIMEFRAME_{timeframe}")
        mt5.symbol_select(symbol, True)
        bars = mt5.copy_rates_range(symbol, timeframe, start_date, end_date)
        if bars is None or len(bars) == 0:
            logger.warning(
                f"No bar data returned for {symbol} from {start_date.date()} to {end_date.date()}."
            )
            return pd.DataFrame()

        df = pd.DataFrame(bars)
        df["time"] = pd.to_datetime(df["time"], unit="s", utc=True)

        if datetime_index:
            df.set_index("time", inplace=True)

        # Optimize memory usage
        for col in [
            "open",
            "high",
            "low",
            "close",
            "tick_volume",
            "spread",
            "real_volume",
        ]:
            if col in df.columns:
                df[col] = df[col].astype("float32")

        if verbose:
            log_df_info(df)

        return df

    except Exception as e:
        logger.error(f"An error occurred while getting bars for {symbol}: {e}")
        return pd.DataFrame()


def process_symbol(symbol, start_dt, end_dt, data_path, account_name):
    """Worker function to download data for a single symbol."""
    try:
        login_mt5(account_name)  # Each worker needs its own login
    except Exception as e:
        return {symbol: f"login_failed: {e}"}

    symbol_path = data_path / symbol
    
    # Generate month starts for the range
    dates_from = pd.date_range(
        start=start_dt.replace(day=1), 
        end=end_dt, 
        freq="MS", 
        tz="UTC"
    )
    
    # Generate month ends
    dates_to = []
    for d in dates_from:
        # End of the current month
        m_end = (d + pd.offsets.MonthEnd(0)).replace(hour=23, minute=59, second=59)
        # But don't go past the global end_dt
        dates_to.append(min(m_end, end_dt))
    
    # Adjust the first start date if it's after the month start
    dates_from_list = list(dates_from)
    if dates_from_list:
        dates_from_list[0] = max(dates_from_list[0], start_dt)

    missing_data = []

    for start, end in zip(dates_from_list, dates_to):
        year_path = symbol_path / str(start.year)
        year_path.mkdir(parents=True, exist_ok=True)

        file = year_path / f"month-{start.month:02d}.parquet"
        log_msg_prefix = f"{symbol}  -> Month {start.strftime('%Y-%m')}..."

        if file.exists():
            df0 = pd.read_parquet(file)
            if not df0.empty:
                first, start = [x.date() for x in df0.index[[0, -1]]]
                if is_first_weekday(first) and is_last_weekday(start):
                    logger.info(f"{log_msg_prefix} Exists—Skipping download")
                    continue
                else:
                    logger.info(
                        f"{log_msg_prefix} Exists—Appending from {start} to {end}"
                    )
        else:
            df0 = pd.DataFrame()

        df1 = get_ticks(symbol, start, end, verbose=False)
        df = pd.concat([df0, df1])

        if not df.empty:
            df = clean_tick_data(df)
            df.to_parquet(file, engine="pyarrow", compression="zstd")
            logger.success(f"{log_msg_prefix} Saved {len(df):,} rows")
        else:
            logger.warning(f"{log_msg_prefix} No data found")
            missing_data.append(start.strftime("%Y-%m"))
            try:
                year_path.rmdir()
            except Exception as e:
                logger.error(f"Could not remove empty directory {year_path}: {e}")


    return {symbol: missing_data}


def save_data_to_parquet(symbols, start_date, end_date, account_name, path=None):
    """
    Downloads and saves tick data to a partitioned Parquet structure.

    Args:
        symbols (Union[str, list, tuple]): A single symbol or a collection of symbols to download.
        start_date (Union[str, dt, pd.Timestamp]): The start date for the data range.
        end_date (Union[str, dt, pd.Timestamp]): The end date for the data range.
        account_name (str): The name of the account used for the download.
        path (Union[str, Path]): The root folder where data will be saved.
    Returns:
        None
    """

    data_path = Path(path) if path is not None else Path().home() / "tick_data_parquet"
    data_path.mkdir(parents=True, exist_ok=True)

    date_range = date_conversion(start_date, end_date)
    if not date_range:
        return
    start_dt, end_dt = date_range

    if isinstance(symbols, str):
        symbols = [symbols]

    missing_data = {}

    for symbol in tqdm(symbols, desc="Downloading symbols"):
        try:
            result = process_symbol(symbol, start_dt, end_dt, data_path, account_name)
            missing_data.update(result)
        except Exception as e:
            logger.critical(f"Worker for {symbol} failed: {e}")

    # Summary logging
    logger.info("Download process finished.")
    if missing_data and any(missing_data.values()):
        logger.warning("Missing data summary:")
        for symbol, months in missing_data.items():
            logger.warning(f"  - {symbol}: {', '.join(months)}")

    logger.success(f"All operations complete. Files saved to {data_path}")


# --- Loading Data from Files ---


def load_tick_data(
    symbol,
    start_date,
    end_date,
    account_name,
    path=None,
    columns=None,
    verbose=True,
):
    """
    Loads tick data from a partitioned Parquet structure after verifying account.

    Args:
        path (Union[str, Path]): The root folder where the data is stored.
        symbol (str): The financial instrument symbol to load.
        start_date (Union[str, dt, pd.Timestamp]): The start date of the desired data range.
        end_date (Union[str, dt, pd.Timestamp]): The end date of the desired data range.
        account_name (str): The account name to verify against the data directory.
        columns (Optional[list]): A list of specific columns to load. Loads all if None.
        verbose (bool): If True, logs detailed DataFrame info upon successful load.

    Returns:
        pd.DataFrame: A DataFrame with the requested tick data, or an empty DataFrame
                      if the account verification fails, dates are invalid, or an error occurs.
    """
    try:
        root_path = Path(path)
    except TypeError:
        root_path = Path.home() / "tick_data_parquet"

    if not verify_or_create_account_info(root_path, account_name):
        return pd.DataFrame()

    date_range = date_conversion(start_date, end_date)
    if date_range:
        start_dt, end_dt = date_range
        fname = root_path / symbol.upper()
    else:
        return pd.DataFrame()

    try:
        filters = [("time", ">=", start_dt), ("time", "<=", end_dt)]

        if not fname.exists():
            logger.error(f"Data directory {fname} not found for {symbol}")
            return pd.DataFrame()

        ddf = dd.read_parquet(fname, columns=columns, filters=filters, engine="pyarrow")
        df = ddf.compute()

        if df.empty:
            logger.warning(
                f"No tick data found for {symbol} between {start_dt} and {end_dt} "
                f"in account {account_name}"
            )
            return pd.DataFrame()

        size = df.memory_usage(deep=True).sum() / 1024**2
        logger.success(
            f"Loaded {len(df):,} rows of {symbol} ({size:,.2f} MB) tick data for account {account_name}"
        )

        to_drop = []
        for col in df.columns:
            # Drop columns
            if any(np.isnan(df[col].unique())):
                to_drop.append(col)
            # Optimise dtype of flags column for memory
            if col == "flags":
                mem = df.memory_usage(deep=True).sum()  # memory before downcasting
                dtype_orig = df["flags"].dtype
                limit = df["flags"].max()
                for x in (8, 16, 32):
                    dtype = f"uint{x}"
                    if dtype_orig != dtype and np.iinfo(dtype).max >= limit:
                        df = df.astype({"flags": dtype})
                        mem = (mem - df.memory_usage(deep=True).sum()) / 1024**2
                        logger.info(
                            f"Converted flags from {dtype_orig} to {df['flags'].dtype} saving {mem:,.1f} MB"
                        )
                        break

        if to_drop:
            df.drop(columns=to_drop, inplace=True)
            logger.info(f"Dropped empty columns {to_drop}")

        if not df.index.is_monotonic_increasing:
            df.sort_index(inplace=True)

        if verbose:
            log_df_info(df)

        return df

    except Exception as e:
        logger.error(f"Failed to load data for {symbol}. Error: {e}")
        return pd.DataFrame()


# --- Main Execution Block ---
if __name__ == "__main__":
    import MetaTrader5 as mt5
    
    MAJORS = [
        "EURUSD",
        "USDJPY",
        "GBPUSD",
        "USDCHF",
        "AUDUSD",
        "USDCAD",
        "NZDUSD",
        "XAUUSD",
    ]

    CRYPTO = [
        "ADAUSD",
        "BTCUSD",
        "DOGUSD",
        "ETHUSD",
        "LNKUSD",
        "LTCUSD",
        "XLMUSD",
        "XMRUSD",
        "XRPUSD",
    ]

    # --- 1. User Configuration ---
    CONFIG = {
        "save_path": Path.home() / "tick_data_parquet",
        "symbols_to_download": MAJORS + CRYPTO,
        "account_to_use": "FundedNext_STLR2_6K",  # This name MUST match the one used in your environment variables
        "start_date": "2016-01-01",
        "end_date": "2017-12-31",
        "verbose_login": True,
    }

    # --- 2. Setup Logging ---
    # Configure logger to output to console and a file for persistent records.
    logger.add(
        sys.stderr,
        format="<green>{time:YYYY-MM-DD HH:mm:ss}</green> | "
        "<level>{level: <8}</level> | "
        "<cyan>{name}</cyan>:<cyan>{function}</cyan>:<cyan>{line}</cyan> - "
        "<level>{message}</level>",
        colorize=True,
        backtrace=True,
        diagnose=True,
        enqueue=True,
    )
    log_path = CONFIG["save_path"] / "data_download.log"
    log_path.parent.mkdir(parents=True, exist_ok=True)

    # The default logger is console-only. Add a file sink.
    logger.add(
        log_path,
        rotation="10 MB",
        retention="30 days",
        level="INFO",
        format="{time:YYYY-MM-DD HH:mm:ss.SSS} | {level: <8} | {name}:{function}:{line} - {message}",
        enqueue=True,
    )
    logger.info("--- Starting New Data Download Session ---")

    # --- 3. Login to MT5 ---
    logged_in_account = login_mt5(
        account=CONFIG["account_to_use"], verbose=CONFIG["verbose_login"]
    )

    # --- 4. Run Downloader ---
    if logged_in_account:
        save_data_to_parquet(
            symbols=CONFIG["symbols_to_download"],
            start_date=CONFIG["start_date"],
            end_date=CONFIG["end_date"],
            account_name=logged_in_account,
            path=CONFIG["save_path"],
        )

        # --- 6. Shutdown MT5 Connection ---
        mt5.shutdown()
        logger.info("--- MT5 Connection Closed. Session End ---")

    else:
        logger.critical("Could not log in to MetaTrader 5. Aborting all operations.")