import 'package:flutter/material.dart';

/// Native Flutter profile avatar that displays either:
/// 1. User's avatar image URL (if provided)
/// 2. Initials derived from full name (fallback)
///
/// Pass [heroTag] to participate in a Hero transition to/from a destination
/// that uses the same tag (e.g., the profile screen's large avatar).
class ProfileAvatar extends StatelessWidget {
  const ProfileAvatar({
    super.key,
    required this.fullName,
    this.avatarUrl,
    this.radius = 18,
    this.heroTag,
  });

  final String fullName;
  final String? avatarUrl;
  final double radius;

  /// When non-null, wraps the avatar in a [Hero] with this tag.
  final Object? heroTag;

  String _getInitials() {
    final trimmed = fullName.trim();
    if (trimmed.isEmpty) return 'U';

    final parts = trimmed.split(RegExp(r'\s+'));
    if (parts.length == 1) {
      return parts[0].substring(0, 1).toUpperCase();
    }

    // Get first letter of first and last name
    return '${parts.first[0]}${parts.last[0]}'.toUpperCase();
  }

  /// Returns a (background, foreground) pair from the M3 tonal palette.
  ///
  /// Uses a deterministic hash of the initials to cycle through the scheme's
  /// semantic container colors so every avatar is theme-aware and accessible.
  (Color, Color) _getTonalColors(String initials, ColorScheme cs) {
    final hash =
        initials.codeUnitAt(0) +
        (initials.length > 1 ? initials.codeUnitAt(1) * 256 : 0);

    // Six M3-compliant container pairs (background / on-color text).
    final pairs = [
      (cs.primaryContainer, cs.onPrimaryContainer),
      (cs.secondaryContainer, cs.onSecondaryContainer),
      (cs.tertiaryContainer, cs.onTertiaryContainer),
      (cs.errorContainer, cs.onErrorContainer),
      (cs.primary, cs.onPrimary),
      (cs.secondary, cs.onSecondary),
    ];

    return pairs[hash % pairs.length];
  }

  @override
  Widget build(BuildContext context) {
    final initials = _getInitials();

    Widget avatar;

    // If avatar URL is provided, attempt to load the image
    if (avatarUrl != null && avatarUrl!.isNotEmpty) {
      avatar = CircleAvatar(
        radius: radius,
        backgroundImage: NetworkImage(avatarUrl!),
        onBackgroundImageError: (_, _) {
          // Silently fall back to initials if image fails
        },
        child: null, // Image will display if loaded successfully
      );
    } else {
      final (bg, fg) = _getTonalColors(
        initials,
        Theme.of(context).colorScheme,
      );

      // Fallback to initials
      avatar = CircleAvatar(
        radius: radius,
        backgroundColor: bg,
        child: Text(
          initials,
          style: TextStyle(
            color: fg,
            fontSize: radius * 0.8,
            fontWeight: FontWeight.w600,
          ),
        ),
      );
    }

    if (heroTag != null) {
      return Hero(tag: heroTag!, child: avatar);
    }
    return avatar;
  }
}