build method

Implementation

ChatMessage build() {
  // Create universal text content, excluding tools blocks and empty text blocks
  final textBlocks = _blocks.where(
      (block) => block is! ToolsBlock && block.displayText.trim().isNotEmpty);
  final content = textBlocks.map((block) => block.displayText).join('\n');

  // Group blocks by provider
  final extensions = <String, dynamic>{};

  final providerGroups = <String, List<ContentBlock>>{};
  final universalTools = <ToolsBlock>[];

  for (final block in _blocks) {
    if (block.providerId == 'universal') {
      // Special handling for ToolsBlock - they might need to be moved to anthropic extension
      if (block is ToolsBlock) {
        universalTools.add(block);
      }
      continue;
    }

    providerGroups.putIfAbsent(block.providerId, () => []).add(block);
  }

  // Check if we have Anthropic cache markers and tools that need to be combined
  if (providerGroups.containsKey('anthropic') && universalTools.isNotEmpty) {
    final anthropicBlocks = providerGroups['anthropic']!;

    // Check if there's a cache marker (empty text block with cache_control)
    final hasCacheMarker = anthropicBlocks.any((block) {
      final json = block.toJson();
      return json['cache_control'] != null && json['text'] == '';
    });

    if (hasCacheMarker) {
      // Move tools to anthropic extension for caching
      // Create AnthropicToolsBlock from universal ToolsBlock
      for (final toolsBlock in universalTools) {
        // Create a new block that will be treated as anthropic-specific
        final anthropicToolsBlock =
            _AnthropicToolsBlockWrapper(toolsBlock.tools);
        anthropicBlocks.add(anthropicToolsBlock);
      }
    }
  }

  // Create extensions for each provider
  for (final entry in providerGroups.entries) {
    extensions[entry.key] = {
      'contentBlocks': entry.value.map((block) => block.toJson()).toList(),
    };
  }

  return ChatMessage(
    role: _role,
    messageType: const TextMessage(),
    content: content,
    name: _name,
    extensions: extensions,
  );
}