import 'package:flutter/material.dart';
import 'package:fl_chart/fl_chart.dart';
import 'package:intl/intl.dart'; // For number formatting

import '../models/category.dart'; // Keep using the Category model for UI structure

// Changed to StatefulWidget to manage its own selection state
class SpendingPieChart extends StatefulWidget {
  final List<Category> categories; // Expect List<Category> from database calculation
  final double totalExpenses;
  final Animation<double> animation; // For fade/scale animation

  const SpendingPieChart({
    Key? key,
    required this.categories,
    required this.totalExpenses,
    required this.animation,
    // Removed selectedPieIndex and onSelectPieCategory
  }) : super(key: key);

  @override
  State<SpendingPieChart> createState() => _SpendingPieChartState();
}

class _SpendingPieChartState extends State<SpendingPieChart> {
  // State for the selected index is now managed internally
  int _selectedPieIndex = -1;

  // Handles selection logic internally
  void _handlePieTap(int index) {
    setState(() {
      // If the same index is selected, deselect (-1), otherwise select the new index
      _selectedPieIndex = (_selectedPieIndex == index) ? -1 : index;
    });
  }

  @override
  Widget build(BuildContext context) {
    final isDark = Theme.of(context).brightness == Brightness.dark;
    final theme = Theme.of(context);
    final currencyFormatter = NumberFormat.currency(locale: 'en_US', symbol: '\$'); // Or your preferred locale/symbol

    // Handle the case where there are no categories to display
     if (widget.categories.isEmpty) {
       return AnimatedBuilder( // Still use animation for consistency
         animation: widget.animation,
         builder: (context, child) => Opacity(
           opacity: widget.animation.value,
           child: Container(
             height: 230, // Maintain similar height to the chart version
             alignment: Alignment.center,
             padding: const EdgeInsets.all(16),
             child: Text(
               'No spending data for this period.',
               textAlign: TextAlign.center,
               style: theme.textTheme.bodyMedium?.copyWith(color: Colors.grey),
             ),
           ),
         ),
       );
     }

    // Use AnimatedBuilder to apply the fade/scale animation
    return AnimatedBuilder(
      animation: widget.animation,
      builder: (context, child) {
        return Transform.scale(
          scale: widget.animation.value, // Apply scale animation
          child: Opacity(
            opacity: widget.animation.value, // Apply fade animation
            child: Container(
              padding: const EdgeInsets.symmetric(vertical: 8.0), // Reduced vertical padding
              height: 230, // Fixed height for the chart and legend area
              child: Row(
                children: [
                  // --- Pie Chart ---
                  Expanded(
                    flex: 5, // Give more space to the chart itself
                    child: Stack( // Use Stack to overlay text on the chart center
                      alignment: Alignment.center,
                      children: [
                        PieChart(
                          PieChartData(
                            // Handle touch events on the pie chart
                            pieTouchData: PieTouchData(
                              touchCallback: (FlTouchEvent event, PieTouchResponse? pieTouchResponse) {
                                // We are only interested in TapUp events to trigger selection changes
                                if (event is FlTapUpEvent) {
                                  final section = pieTouchResponse?.touchedSection;
                                  if (section != null) {
                                    // Tap occurred ON a section
                                    final touchedIndex = section.touchedSectionIndex;
                                    // Use internal handler to update state
                                    _handlePieTap(touchedIndex);
                                  } else {
                                    // Tap occurred OUTSIDE any section
                                    // Deselect if something was selected
                                    if (_selectedPieIndex != -1) {
                                      _handlePieTap(-1); // Pass -1 to deselect
                                    }
                                  }
                                }
                              },
                            ),
                            borderData: FlBorderData(show: false), // No border around the chart
                            sectionsSpace: 2, // Space between slices
                            centerSpaceRadius: 50, // Radius of the center hole
                            sections: _generatePieSections(context), // Generate slices data
                            startDegreeOffset: -90, // Start chart from the top (12 o'clock)
                          ),
                          // Optional animation when data changes
                          swapAnimationDuration: const Duration(milliseconds: 250),
                          swapAnimationCurve: Curves.easeInOut,
                        ),
                        // --- Center Text (Displayed when a slice is selected) ---
                        if (_selectedPieIndex != -1)
                          _buildCenterText(context, currencyFormatter)
                        else // Optional: Display total or default text when nothing is selected
                          _buildDefaultCenterText(context, currencyFormatter),
                      ],
                    ),
                  ),
                  const SizedBox(width: 8), // Spacing between chart and legend

                  // --- Legend ---
                  Expanded(
                    flex: 4, // Allocate space for the legend
                    // Use ListView for scrollable legend if many categories
                    child: ListView.builder(
                      itemCount: widget.categories.length,
                      padding: const EdgeInsets.only(right: 8), // Padding for legend items
                      itemBuilder: (context, index) => _buildPieLegendItem(context, index),
                    ),
                  ),
                ],
              ),
            ),
          ),
        );
      },
    );
  }

  // Builds the text displayed in the center when a slice is selected
  Widget _buildCenterText(BuildContext context, NumberFormat formatter) {
    final theme = Theme.of(context);
    // Check if selectedPieIndex is valid before accessing categories
    if (_selectedPieIndex < 0 || _selectedPieIndex >= widget.categories.length) {
      // Return an empty container or default text if index is invalid
      return _buildDefaultCenterText(context, formatter);
    }
    final selectedCategory = widget.categories[_selectedPieIndex];
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text(
          selectedCategory.name,
          style: theme.textTheme.bodyMedium?.copyWith(
            fontWeight: FontWeight.bold,
            color: theme.textTheme.bodyLarge?.color?.withOpacity(0.8),
          ),
          textAlign: TextAlign.center,
          overflow: TextOverflow.ellipsis,
        ),
        const SizedBox(height: 4),
        Text(
          formatter.format(selectedCategory.amount), // Format the amount as currency
          style: theme.textTheme.titleMedium?.copyWith(
            fontWeight: FontWeight.bold,
            color: selectedCategory.colorCode, // Use category color for amount
          ),
          textAlign: TextAlign.center,
        ),
      ],
    );
  }

  // Builds the default text displayed in the center when no slice is selected
  Widget _buildDefaultCenterText(BuildContext context, NumberFormat formatter) {
      final theme = Theme.of(context);
      return Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
              Text(
                  'Total', // Label for the total amount
                  style: theme.textTheme.bodyMedium?.copyWith(
                      fontWeight: FontWeight.bold,
                      color: theme.textTheme.bodyLarge?.color?.withOpacity(0.7),
                  ),
                  textAlign: TextAlign.center,
              ),
              const SizedBox(height: 4),
              Text(
                  formatter.format(widget.totalExpenses), // Display total expenses
                  style: theme.textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.bold,
                      color: theme.textTheme.bodyLarge?.color // Use default text color
                  ),
                  textAlign: TextAlign.center,
              ),
          ],
      );
  }


  // Builds a single item for the legend
  Widget _buildPieLegendItem(BuildContext context, int index) {
    final isDark = Theme.of(context).brightness == Brightness.dark;
    final theme = Theme.of(context);
    final isSelected = index == _selectedPieIndex; // Check if this item is selected using internal state
    // Check if index is valid before accessing categories
    if (index < 0 || index >= widget.categories.length) {
      return const SizedBox.shrink(); // Return empty if index is invalid
    }
    final category = widget.categories[index];
    // Calculate percentage, handle totalExpenses being zero
    final percentage = widget.totalExpenses > 0 ? (category.amount / widget.totalExpenses * 100) : 0.0;

    // Use InkWell for tap feedback and GestureDetector for tap logic
    return InkWell(
      onTap: () => _handlePieTap(index), // Use internal handler on tap
      borderRadius: BorderRadius.circular(8), // Match border radius
      child: AnimatedContainer(
        duration: const Duration(milliseconds: 200), // Animation for selection change
        margin: const EdgeInsets.symmetric(vertical: 3.0), // Spacing between legend items
        padding: const EdgeInsets.symmetric(horizontal: 10.0, vertical: 6.0), // Padding inside item
        decoration: BoxDecoration(
          // Highlight background if selected
          color: isSelected
              ? category.colorCode.withOpacity(isDark ? 0.3 : 0.15)
              : Colors.transparent,
          borderRadius: BorderRadius.circular(8),
          // Add border if selected
          border: Border.all(
            color: isSelected ? category.colorCode.withOpacity(0.8) : Colors.transparent,
            width: 1.5,
          ),
        ),
        child: Row(
          children: [
            // Color indicator dot
            Container(
              width: 10,
              height: 10,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: category.colorCode.withOpacity(isDark ? 0.9 : 1.0), // Use category color
              ),
            ),
            const SizedBox(width: 8), // Spacing
            // Category name
            Expanded(
              child: Text(
                category.name,
                style: theme.textTheme.bodyMedium?.copyWith(
                  fontWeight: isSelected ? FontWeight.bold : FontWeight.normal, // Bold if selected
                  color: theme.textTheme.bodyLarge?.color, // Use default body text color
                ),
                overflow: TextOverflow.ellipsis, // Prevent long names from wrapping
              ),
            ),
            const SizedBox(width: 8), // Spacing
            // Percentage text
            Text(
              '${percentage.toStringAsFixed(1)}%', // Format percentage
              style: theme.textTheme.bodySmall?.copyWith(
                fontWeight: isSelected ? FontWeight.bold : FontWeight.normal, // Bold if selected
                color: theme.textTheme.bodyMedium?.color?.withOpacity(0.7), // Slightly faded color
              ),
            ),
          ],
        ),
      ),
    );
  }

  // Generates the data for each slice (PieChartSectionData) of the pie chart
  List<PieChartSectionData> _generatePieSections(BuildContext context) {
    final isDark = Theme.of(context).brightness == Brightness.dark;

    return List.generate(widget.categories.length, (i) {
      // Check if index is valid before accessing categories
      if (i < 0 || i >= widget.categories.length) {
        // This should ideally not happen if List.generate is used correctly,
        // but adding a safeguard.
        return PieChartSectionData(); // Return an empty section
      }
      final isTouched = i == _selectedPieIndex; // Check if this slice is selected using internal state
      // Make selected slice slightly larger
      final double radius = isTouched ? 65 : 55;
      // Make title font slightly larger when selected
      final double titleFontSize = isTouched ? 14 : 12;
      final category = widget.categories[i];
      // Calculate percentage for the title
      final percentage = widget.totalExpenses > 0 ? (category.amount / widget.totalExpenses * 100) : 0;

      return PieChartSectionData(
        color: category.colorCode.withOpacity(isDark ? 0.85 : 1.0), // Use category color
        value: category.amount, // Value determines the slice size
        title: '${percentage.toStringAsFixed(0)}%', // Display percentage as title
        radius: radius, // Apply radius (larger if touched)
        titleStyle: TextStyle(
          fontSize: titleFontSize, // Apply font size (larger if touched)
          fontWeight: FontWeight.bold,
          color: Colors.white.withOpacity(0.9), // White text for contrast on colored slices
          shadows: const [Shadow(color: Colors.black38, blurRadius: 2)], // Subtle shadow for readability
        ),
        // Add border to selected slice for emphasis
        borderSide: isTouched
            ? BorderSide(color: isDark ? Colors.white60 : Colors.black54, width: 2)
            : BorderSide(color: category.colorCode.withOpacity(0.5), width: 1),
        // Optional: Add badge (icon) to the selected slice
        // badgeWidget: isTouched ? Icon(category.icon, color: Colors.white, size: 16) : null,
        // badgePositionPercentageOffset: .98,
      );
    });
  }
}