(function (root) {
  "use strict";

  function createBackgroundController(api) {
    const tabStates = new Map();

    function validTabId(tabId) {
      return Number.isInteger(tabId) && tabId >= 0;
    }

    async function broadcast(tabId, enabled) {
      try {
        await api.tabs.sendMessage(tabId, {
          type: "glagolify:set-enabled",
          enabled
        });
        return true;
      } catch (error) {
        return false;
      }
    }

    api.runtime.onMessage.addListener((message, sender) => {
      if (!message || typeof message.type !== "string") {
        return undefined;
      }

      if (message.type === "glagolify:document-ready") {
        const tabId = sender && sender.tab && sender.tab.id;
        return Promise.resolve({
          enabled: validTabId(tabId) && tabStates.get(tabId) === true
        });
      }

      if (message.type === "glagolify:get-tab-state") {
        const tabId = message.tabId;
        if (!validTabId(tabId)) {
          return Promise.resolve({ enabled: false, available: false });
        }

        const enabled = tabStates.get(tabId) === true;
        return broadcast(tabId, enabled).then((available) => ({ enabled, available }));
      }

      if (message.type === "glagolify:set-tab-enabled") {
        const tabId = message.tabId;
        if (!validTabId(tabId) || typeof message.enabled !== "boolean") {
          return Promise.resolve({ enabled: false, available: false });
        }

        tabStates.set(tabId, message.enabled);
        return broadcast(tabId, message.enabled).then((available) => ({
          enabled: message.enabled,
          available
        }));
      }

      return undefined;
    });

    api.tabs.onRemoved.addListener((tabId) => {
      tabStates.delete(tabId);
    });

    return { tabStates, broadcast };
  }

  const exported = Object.freeze({ createBackgroundController });

  if (typeof browser === "object" && browser.runtime && browser.tabs) {
    createBackgroundController(browser);
  }

  if (typeof module === "object" && module.exports) {
    module.exports = exported;
  }

  root.GlagolifyBackground = exported;
})(typeof globalThis === "object" ? globalThis : this);