/// This file defines the `BalancesTab` widget, which is responsible for displaying a list of user balances
/// in a group. Each balance is represented as a card, showing the user's name, the amount they have paid,
/// the amount they owe, and their overall balance status (to pay, to receive, or balanced).
///
/// The widget handles both light and dark themes and provides a fallback UI for empty balance lists.

import 'package:flutter/material.dart';
import '../../models/user_balance.dart';

/// A stateless widget that displays a list of user balances in a group.
///
/// The `BalancesTab` widget takes a list of `UserBalance` objects and renders them as cards in a scrollable list.
/// Each card provides detailed information about the user's financial status within the group.
///
/// If the list of balances is empty, a placeholder message is displayed.
class BalancesTab extends StatelessWidget {
  /// The list of user balances to display.
  final List<UserBalance> balances;

  /// Creates a `BalancesTab` widget.
  ///
  /// The [balances] parameter must not be null.
  const BalancesTab({
    super.key,
    required this.balances,
  });

  @override
  Widget build(BuildContext context) {
    // Check if the balances list is empty and display a placeholder message if true.
    if (balances.isEmpty) {
      return const Center(
        child: Text('Aucune balance à afficher'),
      );
    }

    // Render the list of balances as a scrollable list.
    return ListView.builder(
      padding: const EdgeInsets.all(16),
      itemCount: balances.length,
      itemBuilder: (context, index) {
        final balance = balances[index];
        return _buildBalanceCard(context, balance);
      },
    );
  }

  /// Builds a card widget to display a single user's balance information.
  ///
  /// The card includes the user's name, their total paid and owed amounts, and their balance status.
  /// The card's appearance adapts to the app's current theme (light or dark).
  Widget _buildBalanceCard(BuildContext context, UserBalance balance) {
    // Determine if the app is in dark mode.
    final isDark = Theme.of(context).brightness == Brightness.dark;

    // Define variables for the balance's color, icon, and status text.
    Color balanceColor;
    IconData balanceIcon;
    String balanceText;

    // Determine the balance status and corresponding UI elements.
    if (balance.shouldReceive) {
      balanceColor = Colors.green;
      balanceIcon = Icons.arrow_downward;
      balanceText = 'À recevoir';
    } else if (balance.shouldPay) {
      balanceColor = Colors.red;
      balanceIcon = Icons.arrow_upward;
      balanceText = 'À payer';
    } else {
      balanceColor = Colors.grey;
      balanceIcon = Icons.check_circle;
      balanceText = 'Équilibré';
    }

    // Build and return the card widget.
    return Card(
      margin: const EdgeInsets.only(bottom: 12),
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Row(
          children: [
            // Display the user's initial in a circular avatar.
            CircleAvatar(
              radius: 24,
              backgroundColor: isDark ? Colors.grey[800] : Colors.grey[200],
              child: Text(
                balance.userName.isNotEmpty
                    ? balance.userName[0].toUpperCase()
                    : '?',
                style: const TextStyle(
                  fontSize: 20,
                  fontWeight: FontWeight.bold,
                ),
              ),
            ),
            const SizedBox(width: 16),
            // Display the user's name and financial details.
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  // User's name.
                  Text(
                    balance.userName,
                    style: const TextStyle(
                      fontSize: 16,
                      fontWeight: FontWeight.bold,
                    ),
                  ),
                  const SizedBox(height: 4),
                  // User's total paid and owed amounts.
                  Text(
                    'Payé: ${balance.totalPaid.toStringAsFixed(2)} € • Doit: ${balance.totalOwed.toStringAsFixed(2)} €',
                    style: TextStyle(
                      fontSize: 12,
                      color: isDark ? Colors.grey[400] : Colors.grey[600],
                    ),
                  ),
                ],
              ),
            ),
            // Display the user's balance status and amount.
            Column(
              crossAxisAlignment: CrossAxisAlignment.end,
              children: [
                Row(
                  children: [
                    // Icon indicating the balance status.
                    Icon(balanceIcon, size: 16, color: balanceColor),
                    const SizedBox(width: 4),
                    // User's absolute balance amount.
                    Text(
                      '${balance.absoluteBalance.toStringAsFixed(2)} €',
                      style: TextStyle(
                        fontSize: 18,
                        fontWeight: FontWeight.bold,
                        color: balanceColor,
                      ),
                    ),
                  ],
                ),
                // Text indicating the balance status (e.g., "À recevoir").
                Text(
                  balanceText,
                  style: TextStyle(
                    fontSize: 12,
                    color: balanceColor,
                  ),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}