/**
 * Extracted handler for the list_messages control request.
 *
 * Returns a ControlResponse object (caller does console.log + JSON.stringify).
 * Accepting a minimal client interface makes the handler fully testable with
 * mock objects — no real network or process required.
 */

import { randomUUID } from "node:crypto";
import type {
  ControlResponse,
  ListMessagesControlRequest,
  ListMessagesResponsePayload,
} from "../types/protocol";
import { resolveListMessagesRoute } from "./listMessagesRouting";

// ─────────────────────────────────────────────────────────────────────────────
// Minimal client interface — only what the handler needs
// ─────────────────────────────────────────────────────────────────────────────

export interface ConversationsMessagesPage {
  getPaginatedItems(): unknown[];
}

export interface ListMessagesHandlerClient {
  conversations: {
    messages: {
      list(
        conversationId: string,
        opts: {
          limit: number;
          order: "asc" | "desc";
          agent_id?: string;
          before?: string;
          after?: string;
        },
      ): Promise<ConversationsMessagesPage>;
    };
  };
}

export interface HandleListMessagesParams {
  listReq: ListMessagesControlRequest;
  /** Session's current resolved conversationId ("default" or a real conv id). */
  sessionConversationId: string;
  /** Session's agentId — used as fallback for the agents path. */
  sessionAgentId: string;
  sessionId: string;
  requestId: string;
  client: ListMessagesHandlerClient;
}

// ─────────────────────────────────────────────────────────────────────────────
// Handler
// ─────────────────────────────────────────────────────────────────────────────

/**
 * Execute a list_messages control request and return the ControlResponse.
 *
 * Caller is responsible for serialising + writing to stdout:
 *   console.log(JSON.stringify(await handleListMessages(params)));
 */
export async function handleListMessages(
  params: HandleListMessagesParams,
): Promise<ControlResponse> {
  const {
    listReq,
    sessionConversationId,
    sessionAgentId,
    sessionId,
    requestId,
    client,
  } = params;

  const limit = listReq.limit ?? 50;
  const order = listReq.order ?? "desc";
  const cursorOpts = {
    ...(listReq.before ? { before: listReq.before } : {}),
    ...(listReq.after ? { after: listReq.after } : {}),
  };

  try {
    const route = resolveListMessagesRoute(
      listReq,
      sessionConversationId,
      sessionAgentId,
    );

    const page = await client.conversations.messages.list(
      route.conversationId,
      {
        limit,
        order,
        ...(route.agentId ? { agent_id: route.agentId } : {}),
        ...cursorOpts,
      },
    );
    const items = page.getPaginatedItems();

    const hasMore = items.length >= limit;
    const oldestId =
      items.length > 0
        ? (items[items.length - 1] as { id?: string })?.id
        : undefined;

    const payload: ListMessagesResponsePayload = {
      messages: items,
      next_before: oldestId ?? null,
      has_more: hasMore,
    };

    return {
      type: "control_response",
      response: {
        subtype: "success",
        request_id: requestId,
        response: payload as unknown as Record<string, unknown>,
      },
      session_id: sessionId,
      uuid: randomUUID(),
    };
  } catch (err) {
    return {
      type: "control_response",
      response: {
        subtype: "error",
        request_id: requestId,
        error: err instanceof Error ? err.message : "list_messages failed",
      },
      session_id: sessionId,
      uuid: randomUUID(),
    };
  }
}