/// Accessibility Wrapper
///
/// Enforces WCAG 3.0+ accessibility on all wrapped widgets.
/// AI agents: wrap generated UI components with these helpers
/// to guarantee accessibility compliance.
library;

import 'package:flutter/material.dart';

/// Wraps any widget to enforce minimum touch target size
/// Per WCAG 3.0+ and platform guidelines: 44x44 logical pixels minimum
class AccessibleTouchTarget extends StatelessWidget {
  final Widget child;
  final String semanticLabel;

  static const double minSize = 44.0;

  const AccessibleTouchTarget({
    super.key,
    required this.child,
    required this.semanticLabel,
  });

  @override
  Widget build(BuildContext context) {
    return Semantics(
      label: semanticLabel,
      child: ConstrainedBox(
        constraints: const BoxConstraints(
          minWidth: minSize,
          minHeight: minSize,
        ),
        child: child,
      ),
    );
  }
}

/// Focus-aware wrapper that provides visible focus indicators
/// Per WCAG 3.0+: 3px outline with 3:1 contrast ratio
class AccessibleFocusWrapper extends StatelessWidget {
  final Widget child;
  final Color focusColor;
  final double focusWidth;

  const AccessibleFocusWrapper({
    super.key,
    required this.child,
    this.focusColor = Colors.blue,
    this.focusWidth = 3.0,
  });

  @override
  Widget build(BuildContext context) {
    return Focus(
      child: Builder(
        builder: (context) {
          final hasFocus = Focus.of(context).hasFocus;
          return Container(
            decoration: hasFocus
                ? BoxDecoration(
                    border: Border.all(
                      color: focusColor,
                      width: focusWidth,
                    ),
                    borderRadius: BorderRadius.circular(4),
                  )
                : null,
            child: child,
          );
        },
      ),
    );
  }
}

/// Screen reader announcement helper
/// Use this when state changes need to be announced
class AccessibleAnnouncement {
  /// Announce a state change to screen readers
  static void announce(BuildContext context, String message) {
    SemanticsService.announce(message, TextDirection.ltr);
  }

  /// Announce a polite update (doesn't interrupt current speech)
  static void announcePolite(BuildContext context, String message) {
    SemanticsService.announce(message, TextDirection.ltr);
  }
}

/// Contrast checker utility
/// Validates that text/background combinations meet WCAG AAA (7:1)
class ContrastChecker {
  static const double wcagAAA = 7.0;
  static const double wcagAA = 4.5;

  /// Calculate contrast ratio between two colors
  static double contrastRatio(Color foreground, Color background) {
    final fgLuminance = foreground.computeLuminance();
    final bgLuminance = background.computeLuminance();
    final lighter = fgLuminance > bgLuminance ? fgLuminance : bgLuminance;
    final darker = fgLuminance > bgLuminance ? bgLuminance : fgLuminance;
    return (lighter + 0.05) / (darker + 0.05);
  }

  /// Check if a color pair meets WCAG AAA
  static bool meetsAAA(Color foreground, Color background) {
    return contrastRatio(foreground, background) >= wcagAAA;
  }

  /// Check if a color pair meets WCAG AA
  static bool meetsAA(Color foreground, Color background) {
    return contrastRatio(foreground, background) >= wcagAA;
  }
}