"""
Time bucket implementation for building OHLCV candles.

This module provides the TimeframeBucket class which accumulates trades
within a specific time period and calculates OHLCV data incrementally.
"""

from datetime import datetime, timedelta
from decimal import Decimal
from typing import Optional, List

from ..data_types import StandardizedTrade, OHLCVCandle
from .utils import parse_timeframe


class TimeframeBucket:
    """
    Time bucket for building OHLCV candles from trades.
    
    This class accumulates trades within a specific time period
    and calculates OHLCV data incrementally.
    
    IMPORTANT: Uses RIGHT-ALIGNED timestamps
    - start_time: Beginning of the interval (inclusive)
    - end_time: End of the interval (exclusive) - this becomes the candle timestamp
    - Example: 09:00:00 - 09:05:00 bucket -> candle timestamp = 09:05:00
    """
    
    def __init__(self, symbol: str, timeframe: str, start_time: datetime, exchange: str = "unknown"):
        """
        Initialize time bucket for candle aggregation.
        
        Args:
            symbol: Trading symbol (e.g., 'BTC-USDT')
            timeframe: Time period (e.g., '1m', '5m', '1h')
            start_time: Start time for this bucket (inclusive)
            exchange: Exchange name
        """
        self.symbol = symbol
        self.timeframe = timeframe
        self.start_time = start_time
        self.end_time = self._calculate_end_time(start_time, timeframe)
        self.exchange = exchange
        
        # OHLCV data
        self.open: Optional[Decimal] = None
        self.high: Optional[Decimal] = None
        self.low: Optional[Decimal] = None
        self.close: Optional[Decimal] = None
        self.volume: Decimal = Decimal('0')
        self.trade_count: int = 0
        
        # Tracking
        self.first_trade_time: Optional[datetime] = None
        self.last_trade_time: Optional[datetime] = None
        self.trades: List[StandardizedTrade] = []
    
    def add_trade(self, trade: StandardizedTrade) -> bool:
        """
        Add trade to this bucket if it belongs to this time period.
        
        Args:
            trade: Standardized trade data
            
        Returns:
            True if trade was added, False if outside time range
        """
        # Check if trade belongs in this bucket (start_time <= trade.timestamp < end_time)
        if not (self.start_time <= trade.timestamp < self.end_time):
            return False
        
        # First trade sets open price
        if self.open is None:
            self.open = trade.price
            self.high = trade.price
            self.low = trade.price
            self.first_trade_time = trade.timestamp
        
        # Update OHLCV
        self.high = max(self.high, trade.price)
        self.low = min(self.low, trade.price)
        self.close = trade.price  # Last trade sets close
        self.volume += trade.size
        self.trade_count += 1
        self.last_trade_time = trade.timestamp
        
        # Store trade for detailed analysis if needed
        self.trades.append(trade)
        
        return True
    
    def to_candle(self, is_complete: bool = True) -> OHLCVCandle:
        """
        Convert bucket to OHLCV candle.
        
        IMPORTANT: Candle timestamp = end_time (right-aligned, industry standard)
        """
        return OHLCVCandle(
            symbol=self.symbol,
            timeframe=self.timeframe,
            start_time=self.start_time,
            end_time=self.end_time,
            open=self.open or Decimal('0'),
            high=self.high or Decimal('0'),
            low=self.low or Decimal('0'),
            close=self.close or Decimal('0'),
            volume=self.volume,
            trade_count=self.trade_count,
            exchange=self.exchange,
            is_complete=is_complete,
            first_trade_time=self.first_trade_time,
            last_trade_time=self.last_trade_time
        )
    
    @staticmethod
    def _parse_timeframe_to_timedelta(timeframe: str) -> timedelta:
        """
        Parse a timeframe string (e.g., '5m', '1h', '10s', '1d') into a timedelta object.
        Supported units: 's' (seconds), 'm' (minutes), 'h' (hours), 'd' (days).
        Args:
            timeframe: Timeframe string (e.g., '5m', '1h')
        Returns:
            timedelta: Corresponding timedelta object
        Raises:
            ValueError: If the timeframe format or unit is unsupported
        """
        number, unit = parse_timeframe(timeframe)
        if unit == 's':
            return timedelta(seconds=number)
        elif unit == 'm':
            return timedelta(minutes=number)
        elif unit == 'h':
            return timedelta(hours=number)
        elif unit == 'd':
            return timedelta(days=number)
        else:
            raise ValueError(f"Unsupported timeframe unit: {unit}")

    def _calculate_end_time(self, start_time: datetime, timeframe: str) -> datetime:
        """
        Calculate end time for this timeframe (right-aligned timestamp) using parsing-based logic.
        Args:
            start_time: The start datetime of the bucket
            timeframe: Timeframe string (e.g., '5m', '1h')
        Returns:
            datetime: The end time of the bucket
        Raises:
            ValueError: If the timeframe is malformed or unsupported
        """
        return start_time + self._parse_timeframe_to_timedelta(timeframe)


__all__ = ['TimeframeBucket']