// OpenAI-shaped response builders for the GitLab Duo executor. Extracted from
// gitlab.ts (leaf module — must not import from gitlab.ts) so the executor stays
// under the file-size cap. Covers plain text (streaming + JSON) and the
// tool_calls emulation variants added for #6051.

function buildSseChunk(data: unknown): string {
  return `data: ${JSON.stringify(data)}\n\n`;
}

export function buildStreamingResponse(
  content: string,
  model: string,
  id: string,
  created: number
): Response {
  const encoder = new TextEncoder();

  const body = new ReadableStream<Uint8Array>({
    start(controller) {
      controller.enqueue(
        encoder.encode(
          buildSseChunk({
            id,
            object: "chat.completion.chunk",
            created,
            model,
            choices: [{ index: 0, delta: { role: "assistant" }, finish_reason: null }],
          })
        )
      );

      if (content) {
        controller.enqueue(
          encoder.encode(
            buildSseChunk({
              id,
              object: "chat.completion.chunk",
              created,
              model,
              choices: [{ index: 0, delta: { content }, finish_reason: null }],
            })
          )
        );
      }

      controller.enqueue(
        encoder.encode(
          buildSseChunk({
            id,
            object: "chat.completion.chunk",
            created,
            model,
            choices: [{ index: 0, delta: {}, finish_reason: "stop" }],
          })
        )
      );
      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
      controller.close();
    },
  });

  return new Response(body, {
    status: 200,
    headers: { "Content-Type": "text/event-stream" },
  });
}

export function buildJsonCompletion(
  content: string,
  model: string,
  id: string,
  created: number
): Response {
  const estimated = Math.max(1, Math.ceil(content.length / 4));
  return new Response(
    JSON.stringify({
      id,
      object: "chat.completion",
      created,
      model,
      choices: [
        {
          index: 0,
          message: { role: "assistant", content },
          finish_reason: "stop",
        },
      ],
      usage: {
        prompt_tokens: estimated,
        completion_tokens: estimated,
        total_tokens: estimated * 2,
      },
    }),
    {
      status: 200,
      headers: { "Content-Type": "application/json" },
    }
  );
}

export function buildToolJsonCompletion(
  message: Record<string, unknown>,
  finishReason: string,
  model: string,
  id: string,
  created: number
): Response {
  const contentForEstimate = typeof message.content === "string" ? message.content : "";
  const estimated = Math.max(1, Math.ceil(contentForEstimate.length / 4));
  return new Response(
    JSON.stringify({
      id,
      object: "chat.completion",
      created,
      model,
      choices: [
        {
          index: 0,
          message,
          finish_reason: finishReason,
        },
      ],
      usage: {
        prompt_tokens: estimated,
        completion_tokens: estimated,
        total_tokens: estimated * 2,
      },
    }),
    {
      status: 200,
      headers: { "Content-Type": "application/json" },
    }
  );
}

export function buildToolStreamingResponse(
  message: Record<string, unknown>,
  finishReason: string,
  model: string,
  id: string,
  created: number
): Response {
  const encoder = new TextEncoder();

  const body = new ReadableStream<Uint8Array>({
    start(controller) {
      controller.enqueue(
        encoder.encode(
          buildSseChunk({
            id,
            object: "chat.completion.chunk",
            created,
            model,
            choices: [{ index: 0, delta: { role: "assistant" }, finish_reason: null }],
          })
        )
      );

      controller.enqueue(
        encoder.encode(
          buildSseChunk({
            id,
            object: "chat.completion.chunk",
            created,
            model,
            choices: [{ index: 0, delta: message, finish_reason: null }],
          })
        )
      );

      controller.enqueue(
        encoder.encode(
          buildSseChunk({
            id,
            object: "chat.completion.chunk",
            created,
            model,
            choices: [{ index: 0, delta: {}, finish_reason: finishReason }],
          })
        )
      );
      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
      controller.close();
    },
  });

  return new Response(body, {
    status: 200,
    headers: { "Content-Type": "text/event-stream" },
  });
}