import 'package:dicebear_core/dicebear_core.dart' show Avatar, Style;
import 'package:dicebear_styles/thumbs.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';

import '../services/offer_thumbnail.dart' show decodeDataUri;
import '../services/profile_cache.dart';
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 [GeneratedAvatar] drawn deterministically from
/// their [pubkey]. Same pubkey → same picture on every device, so a person
/// stays visually recognizable without sharing anything.
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 [GeneratedAvatar].
  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),
        );
      }
    }

    return GeneratedAvatar(pubkey: pubkey, name: name, radius: radius);
  }
}

/// The `thumbs` DiceBear style, parsed once — [Style.parse] validates the style
/// definition against its schema, which is not free to repeat per build.
final _thumbsStyle = Style.parse(thumbs);

/// Rendered-SVG memo keyed by pubkey, so a person's avatar is generated once and
/// reused across every rebuild and list row rather than re-rendered each time.
final _svgCache = <String, String>{};

/// Strips the `<metadata>` block (the style's CC0 licence notice) that
/// flutter_svg cannot parse and logs a warning for; CC0 requires no attribution
/// in the rendered image, and the licence still ships with the package source.
final _metadataElement = RegExp(r'<metadata\b[^>]*>.*?</metadata>', dotAll: true);

String _renderThumbs(String pubkey) =>
    Avatar(_thumbsStyle, {'seed': pubkey}).svg.replaceAll(_metadataElement, '');

/// The deterministic default avatar for a person with no chosen [picture]: a
/// friendly DiceBear "thumbs" face (CC0) seeded from their [pubkey], so the same
/// key yields the same face on every device with nothing shared. Rendered as an
/// SVG (no network, no assets). Exposes [pubkey] so call sites/tests can find it.
class GeneratedAvatar extends StatelessWidget {
  const GeneratedAvatar({
    required this.pubkey,
    this.name,
    this.radius = 14,
    super.key,
  });

  final String pubkey;
  final String? name;
  final double radius;

  @override
  Widget build(BuildContext context) {
    final svg = _svgCache[pubkey] ??= _renderThumbs(pubkey);
    return Semantics(
      label: name,
      image: true,
      child: ClipOval(
        child: SizedBox.square(
          dimension: radius * 2,
          child: SvgPicture.string(svg, fit: BoxFit.cover),
        ),
      ),
    );
  }
}

/// A [PeerAvatar] that looks the person's published avatar up from the
/// [ProfileCache] (their kind:0 `picture`), falling back to the generated
/// pattern while it loads or when none is cached / no cache is available. Use at
/// list/row sites (one avatar each); for many avatars of the same few people
/// (chat bubbles) resolve the picture once into state instead.
class CachedAvatar extends StatelessWidget {
  const CachedAvatar({
    required this.pubkey,
    this.name,
    this.cache,
    this.radius = 14,
    super.key,
  });

  final String pubkey;
  final String? name;
  final ProfileCache? cache;
  final double radius;

  @override
  Widget build(BuildContext context) {
    final c = cache;
    if (c == null) {
      return PeerAvatar(pubkey: pubkey, name: name, radius: radius);
    }
    return FutureBuilder<String?>(
      future: c.picture(pubkey),
      builder: (context, snap) => PeerAvatar(
        pubkey: pubkey,
        name: name,
        picture: snap.data,
        radius: radius,
      ),
    );
  }
}

/// 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();
}