Function buildPartsFromEvents

packages/studio/src/store/chat/parts-builder.ts:159–314

(events: StreamEvent[])

// -- Builder --

export function buildPartsFromEvents(events: StreamEvent[]): MessagePart[] {
  const parts: MessagePart[] = [];
  let suppressTextAfterPlayTool = false;

  /** Find the last tool part that is still "running". */
  function findRunningTool(): ToolExecution | undefined {
    for (let i = parts.length - 1; i >= 0; i--) {
      const p = parts[i];
      if (p.type === "tool" && p.execution.status === "running") return p.execution;
    }
    return undefined;
  }

  function appendThinking(content: string): void {
    const last = parts[parts.length - 1];
    if (last?.type === "thinking") {
      last.content += content;
    } else {
      parts.push({ type: "thinking", content, streaming: false });
    }
  }

  for (const event of events) {
    switch (event.type) {
      case "thinking:start": {
        parts.push({ type: "thinking", content: "", streaming: true });
        break;
      }

      case "thinking:delta": {
        // Append to last thinking part
        const last = parts[parts.length - 1];
        if (last?.type === "thinking") {
          last.content += event.text;
        }
        break;
      }

      case "thinking:end": {
        const last = parts[parts.length - 1];
        if (last?.type === "thinking") {
          last.streaming = false;
        }
        break;
      }

      case "draft:delta": {
        if (suppressTextAfterPlayTool) {
          if (event.text.trim()) appendThinking(event.text);
          break;
        }
        // Append to last text part, or create a new one
        const last = parts[parts.length - 1];
        if (last?.type === "text") {
          last.content += event.text;
        } else {
          parts.push({ type: "text", content: event.text });
        }