(function () {
  const STORAGE_KEY = "lapp.pendingItemUpdates";

  function readQueue() {
    try {
      return JSON.parse(localStorage.getItem(STORAGE_KEY) || "[]");
    } catch (error) {
      return [];
    }
  }

  function writeQueue(queue) {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(queue));
  }

  function queueRequest(request) {
    const queue = readQueue();
    const queuedRequest = {
      url: request.url,
      method: request.method || "GET",
      coalesceKey: request.coalesceKey || null,
      clientUpdatedAt: request.clientUpdatedAt || Date.now()
    };

    if (queuedRequest.coalesceKey) {
      const existingIndex = queue.findIndex(function (item) {
        return item.coalesceKey === queuedRequest.coalesceKey;
      });
      if (existingIndex >= 0) {
        queue[existingIndex] = queuedRequest;
      } else {
        queue.push(queuedRequest);
      }
    } else {
      queue.push(queuedRequest);
    }

    writeQueue(queue);
  }

  async function sendRequest(request) {
    const url = new URL(request.url, window.location.origin);
    if (request.clientUpdatedAt) {
      url.searchParams.set("client_updated_at", request.clientUpdatedAt);
    }

    const response = await fetch(url.toString(), {
      method: request.method || "GET",
      cache: "no-store",
      credentials: "same-origin"
    });

    if (response.redirected && new URL(response.url).pathname === "/login") {
      const error = new Error("Login required");
      error.retryable = true;
      throw error;
    }

    if (!response.ok) {
      const error = new Error("Request failed: " + response.status);
      error.retryable = response.status >= 500 || response.status === 408 || response.status === 429;
      throw error;
    }
    return response;
  }

  async function queueableItemRequest(url, options) {
    const request = Object.assign({}, options || {}, {
      url: url,
      clientUpdatedAt: Date.now()
    });
    try {
      await sendRequest(request);
      flushItemUpdateQueue();
      return true;
    } catch (error) {
      if (error.retryable !== false) {
        queueRequest(request);
      }
      return false;
    }
  }

  async function flushItemUpdateQueue() {
    if (flushItemUpdateQueue.running) {
      return;
    }
    flushItemUpdateQueue.running = true;

    const queue = readQueue();
    const remaining = [];

    for (const request of queue) {
      try {
        await sendRequest(request);
      } catch (error) {
        if (error.retryable !== false) {
          remaining.push(request);
        }
      }
    }

    writeQueue(remaining);
    flushItemUpdateQueue.running = false;
  }

  window.lappQueueItemRequest = queueableItemRequest;
  window.lappFlushItemUpdateQueue = flushItemUpdateQueue;

  window.addEventListener("online", flushItemUpdateQueue);
  document.addEventListener("visibilitychange", function () {
    if (!document.hidden) {
      flushItemUpdateQueue();
    }
  });
  document.addEventListener("DOMContentLoaded", flushItemUpdateQueue);
})();