import { defineEventHandler, getQuery } from "h3";
import { R } from "#server/utils/response";
import { getCurrentUser } from "#server/utils/context";
import { getTempTokenFromCookie } from "#server/service/agent/temp-token";
import { getSessionByIdAndUser } from "#server/service/agent/session";
import { getStreamBuffer, subscribeToBuffer } from "#server/service/agent/stream-buffer";
import log4js from "logger";

const logger = log4js.getLogger("APP");

export default defineEventHandler(async (event) => {
  const user = await getCurrentUser(event);
  const tempToken = getTempTokenFromCookie(event);

  if (!user && !tempToken) {
    throw createError({ statusCode: 401, statusMessage: "请先登录或创建临时会话" });
  }

  const query = getQuery(event);
  const sessionId = query.sessionId as string | undefined;

  if (!sessionId) {
    throw createError({ statusCode: 400, statusMessage: "缺少 sessionId 参数" });
  }

  const session = await getSessionByIdAndUser(sessionId, user?.id ?? null, tempToken);
  if (!session) {
    throw createError({ statusCode: 404, statusMessage: "会话不存在" });
  }

  const buf = getStreamBuffer(sessionId);

  if (!buf) {
    return R.success({ active: false, reason: "no-buffer" });
  }

  if (buf.done) {
    return R.success({ active: false, reason: "already-done", modelId: buf.modelId });
  }

  const stream = new ReadableStream<Uint8Array>({
    start(controller) {
      for (const chunk of buf.chunks) {
        controller.enqueue(chunk);
      }

      if (buf.done) {
        controller.close();
        return;
      }

      const unsubscribe = subscribeToBuffer(
        sessionId,
        (chunk) => {
          try {
            controller.enqueue(chunk);
          } catch (e) {
            logger.error("[STREAM-RESUME] enqueue error: %s", e instanceof Error ? e.message : String(e));
          }
        },
        () => {
          try {
            controller.close();
          } catch {
          }
        },
      );

      event.node.req.on("close", () => {
        unsubscribe();
        try {
          controller.close();
        } catch {
        }
      });
    },
  });

  return new Response(stream, {
    headers: {
      "Content-Type": "text/event-stream; charset=utf-8",
      "Cache-Control": "no-cache",
      "Connection": "keep-alive",
      "X-Stream-Resume": "true",
      "X-Stream-Model-Id": String(buf.modelId ?? ""),
      "X-Stream-User-Message-Id": buf.userMessageId ?? "",
    },
  });
});