/**
 * Calls the given Gemini model with the given image and/or text
 * parts, streaming output (as a generator function).
 */
export async function* streamGemini({
    model = 'gemini-pro', // use 'gemini-pro' for text -> text
    contents = [],
  } = {}) {
    // Send the prompt to the Python backend
    // Call API defined in main.py
    let response = await fetch("/api/generate", {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ model, contents })
    });
  
    yield* streamResponseChunks(response);
  }
  
  /**
   * A helper that streams text output chunks from a fetch() response.
   */
  async function* streamResponseChunks(response) {
    let buffer = '';
  
    const CHUNK_SEPARATOR = '\n\n';
  
    let processBuffer = async function* (streamDone = false) {
      while (true) {
        let flush = false;
        let chunkSeparatorIndex = buffer.indexOf(CHUNK_SEPARATOR);
        if (streamDone && chunkSeparatorIndex < 0) {
          flush = true;
          chunkSeparatorIndex = buffer.length;
        }
        if (chunkSeparatorIndex < 0) {
          break;
        }
  
        let chunk = buffer.substring(0, chunkSeparatorIndex);
        buffer = buffer.substring(chunkSeparatorIndex + CHUNK_SEPARATOR.length);
        chunk = chunk.replace(/^data:\s*/, '').trim();
        if (!chunk) {
          if (flush) break;
          continue;
        }
        let { error, text } = JSON.parse(chunk);
        if (error) {
          console.error(error);
          throw new Error(error?.message || JSON.stringify(error));
        }
        yield text;
        if (flush) break;
      }
    };
  
    const reader = response.body.getReader();
    try {
      while (true) {
        const { done, value } = await reader.read()
        if (done) break;
        buffer += new TextDecoder().decode(value);
        console.log(new TextDecoder().decode(value));
        yield* processBuffer();
      }
    } finally {
      reader.releaseLock();
    }
  
    yield* processBuffer(true);
  }