/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

/* globals browser */

if (!window.smartblockTwitterShimInitialized) {
  // Guard against this script running multiple times
  window.smartblockTwitterShimInitialized = true;

  const SHIM_ID = "TwitterEmbed";

  const SHIM_EMBED_CLASSES = ["twitter-tweet", "twitter-timeline"];
  const SHIM_CLASS_SELECTORS = SHIM_EMBED_CLASSES.map(
    className => `.${className}`
  ).join(",");

  // Original URL of the embed script.
  const ORIGINAL_URL = "https://platform.twitter.com/widgets.js";
  const LOGO_URL = "https://smartblock.firefox.etp/x-logo.svg";

  // Timeout for observing new changes to the page
  const OBSERVER_TIMEOUT_MS = 10000;
  let observerTimeout;
  let newEmbedObserver;

  let originalEmbedContainers = [];
  let embedPlaceholders = [];

  function sendMessageToAddon(message) {
    return browser.runtime.sendMessage({ message, shimId: SHIM_ID });
  }

  function addonMessageHandler(message) {
    let { topic, shimId } = message;
    // Only react to messages which are targeting this shim.
    if (shimId != SHIM_ID) {
      return;
    }

    if (topic === "smartblock:unblock-embed") {
      if (newEmbedObserver) {
        newEmbedObserver.disconnect();
        newEmbedObserver = null;
      }

      if (observerTimeout) {
        clearTimeout(observerTimeout);
      }

      // remove embed placeholders
      embedPlaceholders.forEach((p, idx) => {
        p.replaceWith(originalEmbedContainers[idx]);
      });

      // recreate scripts
      let scriptElement = document.createElement("script");

      // Set the script element's src with the website's principal instead of
      // the content script principal to ensure the tracker script is not loaded
      // via the content script's expanded principal.
      scriptElement.wrappedJSObject.src = ORIGINAL_URL;
      document.body.appendChild(scriptElement);
    }
  }

  /**
   * Replaces embeds with a SmartBlock Embed placeholder. Optionally takes a list
   * of embeds to replace, otherwise will search for all embeds on the page.
   *
   * @param {HTMLElement[]} embedContainers - Array of elements to replace with placeholders.
   *                                  If the array is empty, this function will search
   *                                  for and replace all embeds on the page.
   */
  async function createShimPlaceholders(embedContainers = []) {
    const [titleString, descriptionString, buttonString] =
      await sendMessageToAddon("smartblockGetFluentString");

    if (!embedContainers.length) {
      // No containers were passed in, do own search for containers
      embedContainers = document.querySelectorAll(SHIM_CLASS_SELECTORS);
    }

    embedContainers.forEach(originalContainer => {
      // this string has to be defined within this function to avoid linting errors
      // see: https://github.com/mozilla/eslint-plugin-no-unsanitized/issues/259
      const SMARTBLOCK_PLACEHOLDER_HTML_STRING = `
      <style>
        #smartblock-placeholder-wrapper {
          min-height: 225px;
          width: 400px;
          padding: 32px 24px;

          display: block;
          align-content: center;
          text-align: center;

          background-color: light-dark(rgb(255, 255, 255), rgb(28, 27, 34));
          color: light-dark(rgb(43, 42, 51), rgb(251, 251, 254));

          border-radius: 8px;
          border: 2px dashed #0250bb;

          font-size: 14px;
          line-height: 1.2;
          font-family: system-ui;
        }

        #smartblock-placeholder-button {
          min-height: 32px;
          padding: 8px 14px;

          border-radius: 4px;
          font-weight: 600;
          border: 0;

          /* Colours match light/dark theme from
            https://searchfox.org/mozilla-central/source/browser/themes/addons/light/manifest.json
            https://searchfox.org/mozilla-central/source/browser/themes/addons/dark/manifest.json */
          background-color: light-dark(rgb(0, 97, 224), rgb(0, 221, 255));
          color: light-dark(rgb(251, 251, 254), rgb(43, 42, 51));
        }

        #smartblock-placeholder-button:hover {
          /* Colours match light/dark theme from
            https://searchfox.org/mozilla-central/source/browser/themes/addons/light/manifest.json
            https://searchfox.org/mozilla-central/source/browser/themes/addons/dark/manifest.json */
          background-color: light-dark(rgb(2, 80, 187), rgb(128, 235, 255));
        }

        #smartblock-placeholder-button:hover:active {
          /* Colours match light/dark theme from
            https://searchfox.org/mozilla-central/source/browser/themes/addons/light/manifest.json
            https://searchfox.org/mozilla-central/source/browser/themes/addons/dark/manifest.json */
          background-color: light-dark(rgb(5, 62, 148), rgb(170, 242, 255));
        }

        #smartblock-placeholder-title {
          margin-block: 14px;
          font-size: 16px;
          font-weight: bold;
        }

        #smartblock-placeholder-desc {
          margin-block: 14px;
        }
      </style>
      <div id="smartblock-placeholder-wrapper">
        <img id="smartblock-placeholder-image" width="24" height="24" />
        <p id="smartblock-placeholder-title"></p>
        <p id="smartblock-placeholder-desc"></p>
        <button id="smartblock-placeholder-button"></button>
      </div>`;

      // Create the placeholder inside a shadow dom
      const placeholderDiv = document.createElement("div");

      const shadowRoot = placeholderDiv.attachShadow({ mode: "closed" });

      shadowRoot.innerHTML = SMARTBLOCK_PLACEHOLDER_HTML_STRING;
      shadowRoot.getElementById("smartblock-placeholder-image").src = LOGO_URL;
      shadowRoot.getElementById("smartblock-placeholder-title").textContent =
        titleString;
      shadowRoot.getElementById("smartblock-placeholder-desc").textContent =
        descriptionString;
      shadowRoot.getElementById("smartblock-placeholder-button").textContent =
        buttonString;

      // Wait for user to opt-in.
      shadowRoot
        .getElementById("smartblock-placeholder-button")
        .addEventListener("click", ({ isTrusted }) => {
          if (!isTrusted) {
            return;
          }
          // Send a message to the addon to allow loading tracking resources
          // needed by the embed.
          sendMessageToAddon("embedClicked");
        });

      // Save the original embed element and the newly created placeholder
      embedPlaceholders.push(placeholderDiv);
      originalEmbedContainers.push(originalContainer);

      // Replace the embed with the placeholder
      originalContainer.replaceWith(placeholderDiv);

      sendMessageToAddon("smartblockEmbedReplaced");
    });
  }

  // Listen for messages from the background script.
  browser.runtime.onMessage.addListener(request => {
    addonMessageHandler(request);
  });

  // Monitor for new embeds being added after page load so we can replace them
  // with placeholders.
  newEmbedObserver = new MutationObserver(mutations => {
    for (let { addedNodes, target, type } of mutations) {
      const nodes = type === "attributes" ? [target] : addedNodes;
      for (const node of nodes) {
        if (
          SHIM_EMBED_CLASSES.some(className =>
            node.classList?.contains(className)
          )
        ) {
          // If node is an embed, replace with placeholder
          createShimPlaceholders([node]);
        } else {
          // If node is not an embed, check if any children are
          // and replace if needed
          let maybeEmbedNodeList =
            node.querySelectorAll?.(SHIM_CLASS_SELECTORS);
          if (maybeEmbedNodeList) {
            createShimPlaceholders(maybeEmbedNodeList);
          }
        }
      }
    }
  });

  newEmbedObserver.observe(document.documentElement, {
    childList: true,
    subtree: true,
    attributes: true,
    attributeFilter: ["class"],
  });

  // Disconnect the mutation observer after a fixed (long) timeout to conserve resources.
  observerTimeout = setTimeout(
    () => newEmbedObserver.disconnect(),
    OBSERVER_TIMEOUT_MS
  );

  createShimPlaceholders();
}