(function () {
  const DB_NAME = "md-hub-cache";
  const DB_VERSION = 1;
  const STORE_DOCUMENTS = "documents";
  const STORE_CONTENT = "content";

  function openDB() {
    return new Promise(function (resolve, reject) {
      const request = indexedDB.open(DB_NAME, DB_VERSION);
      request.onerror = function () {
        reject(request.error);
      };
      request.onsuccess = function () {
        resolve(request.result);
      };
      request.onupgradeneeded = function (event) {
        const db = event.target.result;
        if (!db.objectStoreNames.contains(STORE_DOCUMENTS)) {
          db.createObjectStore(STORE_DOCUMENTS, { keyPath: "path" });
        }
        if (!db.objectStoreNames.contains(STORE_CONTENT)) {
          db.createObjectStore(STORE_CONTENT, { keyPath: "path" });
        }
      };
    });
  }

  function cacheDocuments(documents) {
    return openDB().then(function (db) {
      return new Promise(function (resolve, reject) {
        const tx = db.transaction(STORE_DOCUMENTS, "readwrite");
        const store = tx.objectStore(STORE_DOCUMENTS);
        documents.forEach(function (doc) {
          store.put(doc);
        });
        tx.oncomplete = function () {
          resolve();
        };
        tx.onerror = function () {
          reject(tx.error);
        };
      });
    });
  }

  function cacheContent(path, html, title) {
    return openDB().then(function (db) {
      return new Promise(function (resolve, reject) {
        const tx = db.transaction(STORE_CONTENT, "readwrite");
        const store = tx.objectStore(STORE_CONTENT);
        store.put({ path: path, html: html, title: title, cachedAt: Date.now() });
        tx.oncomplete = function () {
          resolve();
        };
        tx.onerror = function () {
          reject(tx.error);
        };
      });
    });
  }

  function getCachedDocuments() {
    return openDB().then(function (db) {
      return new Promise(function (resolve, reject) {
        const tx = db.transaction(STORE_DOCUMENTS, "readonly");
        const store = tx.objectStore(STORE_DOCUMENTS);
        const request = store.getAll();
        request.onsuccess = function () {
          resolve(request.result);
        };
        request.onerror = function () {
          reject(request.error);
        };
      });
    });
  }

  function getCachedContent(path) {
    return openDB().then(function (db) {
      return new Promise(function (resolve, reject) {
        const tx = db.transaction(STORE_CONTENT, "readonly");
        const store = tx.objectStore(STORE_CONTENT);
        const request = store.get(path);
        request.onsuccess = function () {
          resolve(request.result);
        };
        request.onerror = function () {
          reject(request.error);
        };
      });
    });
  }

  window.MDHubCache = {
    cacheDocuments: cacheDocuments,
    cacheContent: cacheContent,
    getCachedDocuments: getCachedDocuments,
    getCachedContent: getCachedContent,
  };
})();