// SPDX-FileCopyrightText: 2026 TatuChat
//
// SPDX-License-Identifier: AGPL-3.0-or-later

/// Names of the `<meta>` tags a mini app document must declare to be
/// installable. They act as the mini app's manifest.
const String miniAppMetaIdTag = 'mini-app-id';
const String miniAppMetaNameTag = 'mini-app-name';
const String miniAppMetaCategoryTag = 'mini-app-category';
const String miniAppMetaDescriptionTag = 'mini-app-description';
const String miniAppMetaLogoTag = 'mini-app-logo';
const String miniAppMetaInChatTag = 'mini-app-in-chat';

const List<String> miniAppMetaTags = [
  miniAppMetaIdTag,
  miniAppMetaNameTag,
  miniAppMetaCategoryTag,
  miniAppMetaDescriptionTag,
  miniAppMetaLogoTag,
  miniAppMetaInChatTag,
];

/// Manifest of a mini app, extracted from its `<meta>` tags.
///
/// [id] is mandatory and non-empty. It is used as the account data key under
/// which the app's store and HTML source are persisted
/// (`im.tatuchat.miniapps.data.<id>` / `im.tatuchat.miniapps.source.<id>`).
class MiniAppMeta {
  final String id;
  final String name;
  final String category;
  final String description;
  final String logo;

  /// Whether the mini app can run inside a chat room. `false` by default.
  final bool inChat;

  const MiniAppMeta({
    required this.id,
    required this.name,
    this.category = '',
    this.description = '',
    this.logo = '',
    this.inChat = false,
  });
}

/// Extracts the meta tags of an HTML document into a `name -> content` map
/// (names normalized to lower case). Attribute order and quoting style are
/// irrelevant.
Map<String, String> extractMetaTags(String html) {
  final result = <String, String>{};
  final metaRegex = RegExp(r'<meta\b[^>]*>', caseSensitive: false);
  final attrRegex = RegExp(
    r"""(name|content)\s*=\s*["']([^"']*)["']""",
    caseSensitive: false,
  );
  for (final match in metaRegex.allMatches(html)) {
    final attributes = <String, String>{};
    for (final attr in attrRegex.allMatches(match.group(0)!)) {
      attributes[attr.group(1)!.toLowerCase()] = attr.group(2)!;
    }
    final name = attributes['name'];
    final content = attributes['content'];
    if (name != null && content != null) {
      result[name.toLowerCase()] = content;
    }
  }
  return result;
}

/// Parses the mini app manifest out of the `<meta>` tags of [html].
///
/// All [miniAppMetaTags] must be present (their content may be empty), except
/// `mini-app-id` and `mini-app-name`, which must also be non-empty. Throws a
/// [FormatException] with a human readable reason otherwise.
MiniAppMeta parseMiniAppMeta(String html) {
  final tags = extractMetaTags(html);
  final missing = [
    for (final tag in miniAppMetaTags)
      if (!tags.containsKey(tag)) tag,
  ];
  if (missing.isNotEmpty) {
    throw FormatException(
      'This document is missing the required meta tag(s): '
      '${missing.join(', ')}',
    );
  }
  final id = tags[miniAppMetaIdTag]!.trim();
  final name = tags[miniAppMetaNameTag]!.trim();
  if (id.isEmpty) {
    throw FormatException(
      'The meta tag "$miniAppMetaIdTag" must not be empty',
    );
  }
  if (name.isEmpty) {
    throw FormatException(
      'The meta tag "$miniAppMetaNameTag" must not be empty',
    );
  }
  return MiniAppMeta(
    id: id,
    name: name,
    category: tags[miniAppMetaCategoryTag]!.trim(),
    description: tags[miniAppMetaDescriptionTag]!.trim(),
    logo: tags[miniAppMetaLogoTag]!.trim(),
    inChat: tags[miniAppMetaInChatTag]!.trim().toLowerCase() == 'true',
  );
}