"""
Leaderboard Styling Module

Handles color gradients and visual styling for the leaderboard.
"""

import logging
import html
from typing import Dict, Tuple, List
import pandas as pd
from matplotlib.colors import LinearSegmentedColormap

from ..core.columns import column_registry
from .transformer import format_parameter_count

logger = logging.getLogger(__name__)


class LeaderboardStyler:
    """
    Applies visual styling to leaderboard DataFrames.
    
    Uses Excel-like Red-Yellow-Green color gradients for score columns.
    """
    
    # Excel-style color gradient: Red -> Yellow -> Green
    GRADIENT_COLORS = [
        (0.9, 0.1, 0.2),       # Red (low scores)
        (1.0, 1.0, 0.0),       # Yellow (medium scores)
        (0/255, 176/255, 80/255)  # Excel Green (high scores)
    ]
    
    def __init__(self):
        self._colormap = LinearSegmentedColormap.from_list(
            "ExcelRedYellowGreen",
            self.GRADIENT_COLORS,
            N=256
        )
    
    @staticmethod
    def rgb_to_hex(rgb: Tuple[float, float, float]) -> str:
        """Convert RGB tuple (0-1 range) to hex color."""
        r = int(rgb[0] * 255)
        g = int(rgb[1] * 255)
        b = int(rgb[2] * 255)
        return f"#{r:02x}{g:02x}{b:02x}"
    
    def get_color_for_value(self, value: float, min_val: float, max_val: float) -> str:
        """Get hex color for a value within a range."""
        if max_val == min_val:
            normalized = 0.5
        else:
            normalized = (value - min_val) / (max_val - min_val)
        
        # Clamp to [0, 0.999] to avoid edge case at exactly 1.0
        normalized = max(0, min(0.999, normalized))
        
        rgba = self._colormap(normalized)
        return self.rgb_to_hex(rgba[:3])
    
    def calculate_color_ranges(self, df: pd.DataFrame) -> Dict[str, Dict[str, float]]:
        """Calculate min/max for each score column."""
        ranges = {}
        
        for col_name in column_registry.score_columns:
            if col_name not in df.columns:
                continue
            
            numeric_values = pd.to_numeric(df[col_name], errors='coerce')
            if numeric_values.isna().all():
                continue
            
            ranges[col_name] = {
                'min': numeric_values.min(),
                'max': numeric_values.max()
            }
        
        return ranges
    
    def apply_styling(self, df: pd.DataFrame) -> "pd.io.formats.style.Styler":
        """
        Apply color styling to DataFrame.
        
        Returns a pandas Styler object that Gradio can render.
        """
        if df.empty:
            return df.style
        
        df_copy = df.copy()
        
        # Convert "N/A" to NaN for proper formatting
        for col in column_registry.score_columns:
            if col in df_copy.columns:
                df_copy[col] = df_copy[col].replace("N/A", pd.NA)
                df_copy[col] = pd.to_numeric(df_copy[col], errors='coerce')
        
        # Calculate color ranges
        color_ranges = self.calculate_color_ranges(df_copy)
        
        # Create style function
        def apply_gradient(val, col_name: str):
            if col_name not in color_ranges:
                return ''
            
            if pd.isna(val):
                return ''
            
            try:
                min_val = color_ranges[col_name]['min']
                max_val = color_ranges[col_name]['max']
                color_hex = self.get_color_for_value(float(val), min_val, max_val)
                return f'background-color: {color_hex}; text-align: center; font-weight: bold; color: #333;'
            except (ValueError, TypeError):
                return ''
        
        # Apply styling
        styler = df_copy.style
        
        for col in column_registry.score_columns:
            if col in df_copy.columns:
                styler = styler.map(
                    lambda val, c=col: apply_gradient(val, c), 
                    subset=[col]
                )
        
        # Format numeric columns
        format_dict = {}
        for col_name in column_registry.numeric_columns:
            if col_name in df_copy.columns:
                col_def = column_registry.get(col_name)
                # Special handling for Parameters column - use human-readable format
                if col_name == "Parameters":
                    format_dict[col_name] = format_parameter_count
                elif col_def and col_def.decimals == 0:
                    format_dict[col_name] = '{:.0f}'
                elif col_def and col_def.decimals == 3:
                    format_dict[col_name] = '{:.3f}'
                else:
                    format_dict[col_name] = '{:.2f}'

        # Format model column as hyperlink without mutating the underlying data
        if "Model" in df_copy.columns:
            def _model_link_formatter(value: object) -> str:
                model_name = html.escape(str(value))
                return (
                    f'<a href="https://huggingface.co/{model_name}" target="_blank" '
                    f'style="color: #2563eb; text-decoration: underline;">{model_name}</a>'
                )

            format_dict["Model"] = _model_link_formatter
        
        if format_dict:
            # Don't replace NA values - let them display as they are in the CSV
            styler = styler.format(format_dict, na_rep='', escape=None)
        
        return styler
    
    def get_datatypes(self, columns: List[str]) -> List[str]:
        """Get Gradio datatypes for columns."""
        return column_registry.get_datatypes(columns)
    
    def get_column_widths(self, columns: List[str]) -> List[str]:
        """Get column widths for columns."""
        return column_registry.get_widths(columns)