import 'package:flutter/material.dart';

import '../services/offer_thumbnail.dart' show decodeDataUri;
import 'avatar.dart';
import 'seed_glyph.dart';

/// A small round avatar for a person. When they've set an avatar ([picture] — a
/// `data:` photo thumbnail or a `tane:seed:<glyph>` illustration) it's shown;
/// otherwise it falls back to a deterministic disc coloured from their [pubkey],
/// with the first letter of their [name] (else a person glyph). Same pubkey →
/// same colour on every device, so a person stays visually recognizable.
class PeerAvatar extends StatelessWidget {
  const PeerAvatar({
    required this.pubkey,
    this.name,
    this.picture,
    this.radius = 14,
    super.key,
  });

  final String pubkey;
  final String? name;

  /// The person's chosen avatar value; null/empty → the coloured-initial disc.
  final String? picture;
  final double radius;

  @override
  Widget build(BuildContext context) {
    final pic = picture?.trim() ?? '';

    if (pic.startsWith('data:')) {
      final bytes = decodeDataUri(pic);
      if (bytes != null) {
        return CircleAvatar(radius: radius, backgroundImage: MemoryImage(bytes));
      }
    } else if (pic.startsWith(avatarGlyphPrefix)) {
      final glyph = avatarGlyphChar(pic.substring(avatarGlyphPrefix.length));
      if (glyph != null) {
        return CircleAvatar(
          radius: radius,
          backgroundColor: peerAvatarColor(pubkey),
          child: SeedGlyph(glyph, size: radius * 1.15, color: Colors.white),
        );
      }
    }

    final letter = _initial(name);
    return CircleAvatar(
      radius: radius,
      backgroundColor: peerAvatarColor(pubkey),
      child: letter == null
          ? Icon(Icons.person_outline, size: radius, color: Colors.white)
          : Text(
              letter,
              style: TextStyle(
                color: Colors.white,
                fontSize: radius,
                fontWeight: FontWeight.w600,
              ),
            ),
    );
  }

  static String? _initial(String? name) {
    if (name == null) return null;
    final trimmed = name.trim();
    if (trimmed.isEmpty) return null;
    // characters.first handles emoji/combining marks safely.
    return trimmed.characters.first.toUpperCase();
  }
}

/// A deterministic, readable avatar colour derived from [pubkey]. Hashes the
/// key to a hue, then fixes saturation/lightness so white text stays legible on
/// top. Pure and stable — exposed for testing.
Color peerAvatarColor(String pubkey) {
  // FNV-1a over the code units — cheap, stable, well-spread across hues.
  var hash = 0x811c9dc5;
  for (final unit in pubkey.codeUnits) {
    hash = (hash ^ unit) * 0x01000193;
    hash &= 0xffffffff;
  }
  final hue = (hash % 360).toDouble();
  return HSLColor.fromAHSL(1, hue, 0.45, 0.42).toColor();
}