/**
 * Utilities for sending messages to an agent via conversations
 **/

import type { Stream } from "@letta-ai/letta-client/core/streaming";
import type { MessageCreate } from "@letta-ai/letta-client/resources/agents/agents";
import type {
  ApprovalCreate,
  LettaStreamingResponse,
} from "@letta-ai/letta-client/resources/agents/messages";
import { getClientToolsFromRegistry } from "../tools/manager";
import { isTimingsEnabled } from "../utils/timing";
import { getClient } from "./client";

// Symbol to store timing info on the stream object
export const STREAM_REQUEST_START_TIME = Symbol("streamRequestStartTime");

/**
 * Send a message to a conversation and return a streaming response.
 * Uses the conversations API for proper message isolation per session.
 *
 * For the "default" conversation (agent's primary message history without
 * an explicit conversation object), pass conversationId="default" and
 * provide agentId in opts. This uses the agents messages API instead.
 */
export async function sendMessageStream(
  conversationId: string,
  messages: Array<MessageCreate | ApprovalCreate>,
  opts: {
    streamTokens?: boolean;
    background?: boolean;
    agentId?: string; // Required when conversationId is "default"
  } = { streamTokens: true, background: true },
  // TODO: Re-enable once issues are resolved - disabled retries were causing problems
  // Disable SDK retries by default - state management happens outside the stream,
  // so retries would violate idempotency and create race conditions
  // requestOptions: { maxRetries?: number } = { maxRetries: 0 },
  requestOptions: { maxRetries?: number } = {},
): Promise<Stream<LettaStreamingResponse>> {
  // Capture request start time for TTFT measurement when timings are enabled
  const requestStartTime = isTimingsEnabled() ? performance.now() : undefined;

  const client = await getClient();

  let stream: Stream<LettaStreamingResponse>;

  if (process.env.DEBUG) {
    console.log(
      `[DEBUG] sendMessageStream: conversationId=${conversationId}, useAgentsRoute=${conversationId === "default"}`,
    );
  }

  if (conversationId === "default") {
    // Use agents route for default conversation (agent's primary message history)
    if (!opts.agentId) {
      throw new Error(
        "agentId is required in opts when using default conversation",
      );
    }
    stream = await client.agents.messages.create(
      opts.agentId,
      {
        messages: messages,
        streaming: true,
        stream_tokens: opts.streamTokens ?? true,
        background: opts.background ?? true,
        client_tools: getClientToolsFromRegistry(),
      },
      requestOptions,
    );
  } else {
    // Use conversations route for explicit conversations
    stream = await client.conversations.messages.create(
      conversationId,
      {
        messages: messages,
        streaming: true,
        stream_tokens: opts.streamTokens ?? true,
        background: opts.background ?? true,
        client_tools: getClientToolsFromRegistry(),
      },
      requestOptions,
    );
  }

  // Attach start time to stream for TTFT calculation in drainStream
  if (requestStartTime !== undefined) {
    (stream as unknown as Record<symbol, number>)[STREAM_REQUEST_START_TIME] =
      requestStartTime;
  }

  return stream;
}