"""
Data Transformation Module

Handles DataFrame transformations and CSV loading.
"""

import logging
import html
import re
from typing import List, Optional, Union
from pathlib import Path
import pandas as pd
import numpy as np

from ..core.columns import column_registry, ColumnType
from ..core.config import settings

logger = logging.getLogger(__name__)


def parse_parameter_string(value: Union[str, float, int]) -> Optional[float]:
    """
    Parse parameter strings like '307M', '1B', '1.7B', '4B' to numeric values.
    
    Args:
        value: Parameter string (e.g., '307M', '1B', '1.7B') or numeric value.
        
    Returns:
        Numeric value (in millions for consistency) or None if parsing fails.
    """
    if pd.isna(value):
        return None
    
    # If already numeric, return as-is
    if isinstance(value, (int, float)):
        return float(value)
    
    value_str = str(value).strip().upper()
    
    # Handle special cases
    if value_str in ('', 'N/A', 'NA', 'NAN', 'NONE', '∞'):
        return None
    
    # Pattern to match numbers with optional suffix (K, M, B, T)
    pattern = r'^([\d.]+)\s*([KMBT])?$'
    match = re.match(pattern, value_str)
    
    if not match:
        return None
    
    try:
        number = float(match.group(1))
        suffix = match.group(2)
        
        # Convert to raw count based on suffix
        multipliers = {
            None: 1,
            'K': 1_000,
            'M': 1_000_000,
            'B': 1_000_000_000,
            'T': 1_000_000_000_000
        }
        
        return number * multipliers.get(suffix, 1)
    except (ValueError, TypeError):
        return None


def format_parameter_count(value: Union[float, int, None]) -> str:
    """
    Format a numeric parameter count to human-readable string.
    
    Args:
        value: Numeric parameter count.
        
    Returns:
        Formatted string like '307M', '1.7B', '4B'.
    """
    if pd.isna(value) or value is None:
        return ''
    
    try:
        value = float(value)
    except (ValueError, TypeError):
        return str(value)
    
    if value >= 1_000_000_000_000:
        formatted = value / 1_000_000_000_000
        return f"{formatted:.1f}T" if formatted != int(formatted) else f"{int(formatted)}T"
    elif value >= 1_000_000_000:
        formatted = value / 1_000_000_000
        return f"{formatted:.1f}B" if formatted != int(formatted) else f"{int(formatted)}B"
    elif value >= 1_000_000:
        formatted = value / 1_000_000
        return f"{formatted:.0f}M" if formatted >= 10 else f"{formatted:.1f}M".rstrip('0').rstrip('.')+"M" if formatted != int(formatted) else f"{int(formatted)}M"
    elif value >= 1_000:
        formatted = value / 1_000
        return f"{formatted:.0f}K" if formatted >= 10 else f"{formatted:.1f}K"
    else:
        return str(int(value))


class DataTransformer:
    """
    Transforms data between different formats.
    
    Handles CSV -> DataFrame conversions and display preparation.
    """
    
    @staticmethod
    def create_empty_dataframe() -> pd.DataFrame:
        """Create an empty DataFrame with all column definitions."""
        return pd.DataFrame(columns=column_registry.all_columns)
    
    @staticmethod
    def load_from_csv(file_path: Path = None) -> pd.DataFrame:
        """
        Load leaderboard data from CSV file.
        
        Args:
            file_path: Path to CSV file (uses default if None).
            
        Returns:
            DataFrame with leaderboard data.
        """
        path = file_path or settings.data.csv_file
        
        if not path.exists():
            logger.warning(f"CSV file not found: {path}")
            return DataTransformer.create_empty_dataframe()
        
        try:
            df = pd.read_csv(path)
            logger.info(f"Loaded {len(df)} records from {path}")
            
            # Convert to display format
            df = DataTransformer._normalize_columns(df)
            df = DataTransformer._convert_parameters_to_numeric(df)
            df = DataTransformer._sort_by_rank(df)
            
            return df
            
        except Exception as e:
            logger.error(f"Error loading CSV: {e}")
            return DataTransformer.create_empty_dataframe()
    
    @staticmethod
    def _normalize_columns(df: pd.DataFrame) -> pd.DataFrame:
        """Normalize column names from CSV variations to standard names."""
        # Column name mappings for variations
        column_mappings = {
            "Mean (TaskType)": "MTEB Score",
            "Score(Legal)": "Legal Score",
            "Embedding Dimensions": "Embed Dim",
            "Embedding Dim": "Embed Dim",
            "Max Tokens": "Max Sequence Length",
            "Max Seq Length": "Max Sequence Length",
            "Number of Parameters": "Parameters",
            "PairClassification": "Pair Classification",
            "Vocabulary Size": "Vocab Size",
            "Vocabulary": "Vocab Size",
        }
        
        df = df.copy()
        
        # Rename columns based on mappings
        for old_name, new_name in column_mappings.items():
            if old_name in df.columns and new_name not in df.columns:
                df = df.rename(columns={old_name: new_name})
        
        return df
    
    @staticmethod
    def _sort_by_rank(df: pd.DataFrame) -> pd.DataFrame:
        """Sort DataFrame by MTEB Score descending and recalculate ranks."""
        if "MTEB Score" in df.columns:
            # Sort by MTEB Score descending (higher is better)
            df = df.sort_values("MTEB Score", ascending=False, na_position='last').reset_index(drop=True)
            # Recalculate ranks as 1, 2, 3, 4... (no ties)
            df["Rank"] = range(1, len(df) + 1)
        elif "Rank" in df.columns:
            # Fallback to existing rank if MTEB Score not available
            df = df.sort_values("Rank", ascending=True).reset_index(drop=True)
        return df
    
    @staticmethod
    def _convert_parameters_to_numeric(df: pd.DataFrame) -> pd.DataFrame:
        """
        Convert Parameters column from string format to numeric for proper sorting.
        
        Converts values like '307M', '1B', '1.7B' to numeric values.
        """
        if "Parameters" not in df.columns:
            return df
        
        df = df.copy()
        df["Parameters"] = df["Parameters"].apply(parse_parameter_string)
        return df
    
    @staticmethod
    def add_model_links(df: pd.DataFrame) -> pd.DataFrame:
        """Add clickable HuggingFace links to Model column."""
        if "Model" not in df.columns:
            return df
        
        df = df.copy()
        df["Model"] = df["Model"].apply(
            lambda x: f'<a href="https://huggingface.co/{html.escape(str(x))}" target="_blank" '
                     f'style="color: #2563eb; text-decoration: underline;">{html.escape(str(x))}</a>'
        )
        return df
    
    @staticmethod
    def ensure_numeric_columns(df: pd.DataFrame) -> pd.DataFrame:
        """Convert numeric columns to proper types."""
        df = df.copy()
        
        for col_name in column_registry.numeric_columns:
            if col_name not in df.columns:
                continue
            
            col_def = column_registry.get(col_name)
            if col_def is None:
                continue
            
            # Handle "N/A" and empty values
            df[col_name] = df[col_name].replace("N/A", pd.NA)
            df[col_name] = pd.to_numeric(df[col_name], errors='coerce')
            
            # Round to specified decimals
            if col_def.decimals == 0:
                # Keep as float to preserve NaN, format later
                pass
            else:
                df[col_name] = df[col_name].round(col_def.decimals)
        
        return df
    
    @staticmethod
    def filter_columns(df: pd.DataFrame, columns: List[str]) -> pd.DataFrame:
        """Filter DataFrame to only include specified columns (preserves order)."""
        available = [col for col in columns if col in df.columns]
        return df[available]
    
    @classmethod
    def prepare_for_display(
        cls, 
        df: pd.DataFrame, 
        columns: List[str] = None,
        add_links: bool = True
    ) -> pd.DataFrame:
        """
        Prepare DataFrame for Gradio display.
        
        Args:
            df: Source DataFrame.
            columns: Columns to include (preserves order passed in).
            add_links: Whether to add HuggingFace links.
            
        Returns:
            Prepared DataFrame.
        """
        if df is None or df.empty:
            return cls.create_empty_dataframe()
        
        # Work with a copy
        result = df.copy()
        
        # Filter columns if specified (preserves the order passed in)
        if columns:
            result = cls.filter_columns(result, columns)
        
        # Convert numeric columns
        result = cls.ensure_numeric_columns(result)
        
        # Add model links
        if add_links and "Model" in result.columns:
            result = cls.add_model_links(result)
        
        return result