/* 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 <http://mozilla.org/MPL/2.0/>. */

/**
 * Tabs reducer
 */

export function initialTabState({ urls = [], prettyPrintedURLs = [] } = {}) {
  return {
    // List of source URL's which should be automatically opened in a tab.
    // This array will be stored as-is in the persisted async storage.
    // The order of URLs in this list is important and will be used to restore
    // tabs in the same order.
    //
    // Array<String>
    urls,

    // List of sources which are pretty printed.
    //
    // Set<String>
    // (converted into Array in the asyncStorage)
    prettyPrintedURLs,

    // List of sources for which tabs should be currently displayed.
    // This is transient data, specific to the current document and at this precise time.
    //
    // Array<Source objects>
    openedSources: [],
  };
}

function update(state = initialTabState(), action) {
  switch (action.type) {
    case "ADD_TAB":
      return updateTabsWithNewActiveSource(state, [action.source], true);

    case "MOVE_TAB":
      return moveTabInList(state, action.url, action.tabIndex);

    case "MOVE_TAB_BY_SOURCE_ID":
      return moveTabInListBySourceId(state, action.sourceId, action.tabIndex);

    case "CLOSE_TABS_FOR_SOURCES":
      return closeTabsForSources(state, action.sources, true);

    case "ADD_ORIGINAL_SOURCES": {
      return updateTabsWithNewActiveSource(
        state,
        action.originalSources,
        false
      );
    }

    case "INSERT_SOURCE_ACTORS": {
      const sources = action.sourceActors.map(
        sourceActor => sourceActor.sourceObject
      );
      return updateTabsWithNewActiveSource(state, sources, false);
    }

    case "REMOVE_SOURCES": {
      return closeTabsForSources(state, action.sources, false);
    }

    case "REMOVE_PRETTY_PRINTED_SOURCE": {
      return removePrettyPrintedSource(state, action.source);
    }

    default:
      return state;
  }
}

/**
 * Allow unregistering pretty printed source earlier than source unregistering.
 */
function removePrettyPrintedSource(state, source) {
  const prettyPrintedURLs = new Set(state.prettyPrintedURLs);
  prettyPrintedURLs.delete(source.generatedSource.url);
  return { ...state, prettyPrintedURLs };
}

/**
 * Update the tab list for a given set of sources.
 * Either when the user adds a tab (forceAdding will be true),
 * or when sources are registered (forceAdding will be false).
 *
 * @param {Object} state
 * @param {Array<Source>} sources
 * @param {Boolean} forceAdding
 *        If true, a tab should be opened for all the passed sources,
 *        even if the source has no url.
 *        If false, only sources matching a previously opened URL
 *        will be restored.
 * @return {Object} Modified state object
 */
function updateTabsWithNewActiveSource(state, sources, forceAdding = false) {
  let { urls, openedSources, prettyPrintedURLs } = state;
  for (let source of sources) {
    // When we are adding a pretty printed source, we don't add a new tab.
    // We  only ensure the tab for the minimized/generated source is opened.
    //
    // We then rely on `prettyPrintedURLs` to pick the right source in the editor.
    if (source.isPrettyPrinted) {
      source = source.generatedSource;

      // Also ensure bookeeping that the source has been pretty printed.
      if (state.prettyPrintedURLs == prettyPrintedURLs) {
        prettyPrintedURLs = new Set(prettyPrintedURLs);
      }
      prettyPrintedURLs.add(source.url);
    }

    const { url } = source;
    // Ignore the source if it is already opened.
    // Also, when we are adding the tab (forceAdding=true), we want to add the tab for source,
    // even if they don't have a URL.
    // Otherwise, when we are simply registering a new active source (forceAdding=false),
    // we only want to show a tab if the source is in the persisted state.urls list.
    if (
      openedSources.includes(source) ||
      (!forceAdding && (!url || !urls.includes(url)))
    ) {
      continue;
    }

    // If we are pass that point in the for loop, we are opening a tab for the current source
    if (openedSources === state.openedSources) {
      openedSources = [...openedSources];
    }

    let index = -1;
    if (url) {
      if (!urls.includes(url)) {
        // Ensure adding the url to the persisted list
        if (urls === state.urls) {
          urls = [...state.urls];
        }
        // Newly opened tabs are always added first.
        urls.unshift(url);
      } else {
        // In this branch, we are restoring a previously opened tab.
        // We lookup for the position of this source in the persisted list (state.urls),
        // then find the index for the first persisted source which has an opened tab before it.
        const indexInUrls = urls.indexOf(url);
        for (let i = indexInUrls - 1; i >= 0; i--) {
          const previousSourceUrl = urls[i];
          index = openedSources.findIndex(s => s.url === previousSourceUrl);
          if (index != -1) {
            break;
          }
        }
      }
    }

    if (index == -1) {
      // Newly opened tabs are always added first.
      openedSources.unshift(source);
    } else {
      // Otherwise add the source at the expected location.
      // i.e. right after the source already opened which is before the currently added source in the persistent list of URLs (state.urls)
      openedSources.splice(index + 1, 0, source);
    }
  }

  if (
    openedSources != state.openedSources ||
    urls != state.urls ||
    prettyPrintedURLs != state.prettyPrintedURLs
  ) {
    return { ...state, urls, openedSources, prettyPrintedURLs };
  }
  return state;
}

function closeTabsForSources(state, sources, permanent = false) {
  if (!sources.length) {
    return state;
  }
  // Pretty printed source have their tab refering to the minimized source
  const tabSources = sources.map(s =>
    s.isPrettyPrinted ? s.generatedSource : s
  );

  const newOpenedSources = state.openedSources.filter(source => {
    return !tabSources.includes(source);
  });

  // Bails out if no tab has changed
  if (newOpenedSources.length == state.openedSources.length) {
    return state;
  }

  // Also remove from the url list, if the tab closing is permanent.
  // i.e. when the user requested to close the tab, and not when a source is simply unregistered from the store.
  let { urls, prettyPrintedURLs } = state;
  if (permanent) {
    const sourceURLs = tabSources.map(source => source.url);
    urls = state.urls.filter(url => !sourceURLs.includes(url));

    // In case of pretty printing, tab's always refer to the minimized source.
    // So it is fair to unregister the tab's source's URL from `prettyPrintedURLs`
    // which contains the urls of the minmized source.
    prettyPrintedURLs = new Set(state.prettyPrintedURLs);
    for (const url of sourceURLs) {
      prettyPrintedURLs.delete(url);
    }
  }
  return { ...state, urls, prettyPrintedURLs, openedSources: newOpenedSources };
}

function moveTabInList(state, url, newIndex) {
  const currentIndex = state.openedSources.findIndex(
    source => source.url == url
  );
  return moveTab(state, currentIndex, newIndex);
}

function moveTabInListBySourceId(state, sourceId, newIndex) {
  const currentIndex = state.openedSources.findIndex(
    source => source.id == sourceId
  );
  return moveTab(state, currentIndex, newIndex);
}

function moveTab(state, currentIndex, newIndex) {
  // Avoid any state change if we are on the same position or the new is invalid
  if (currentIndex == newIndex || isNaN(newIndex)) {
    return state;
  }

  const { openedSources } = state;
  const source = openedSources[currentIndex];

  const newOpenedSources = Array.from(openedSources);
  // Remove the tab from its current location
  newOpenedSources.splice(currentIndex, 1);
  // And add it to the new one
  newOpenedSources.splice(newIndex, 0, source);

  // If the tabs relates to a source with a URL, also move it in the list of URLs
  let newUrls = state.urls;
  const { url } = source;
  if (url) {
    const urlIndex = state.urls.indexOf(url);
    let newUrlIndex = 0;
    // Lookup for the previous tab with a URL in order to move the tab
    // just after that one in the list of all URLs.
    for (let i = newIndex; i >= 0; i--) {
      const previousTabUrl = newOpenedSources[i].url;
      if (previousTabUrl) {
        newUrlIndex = state.urls.indexOf(previousTabUrl);
        break;
      }
    }
    if (urlIndex != -1 && newUrlIndex != -1) {
      newUrls = Array.from(state.urls);
      // Remove the tab from its current location
      newUrls.splice(urlIndex, 1);
      // And add it to the new one
      newUrls.splice(newUrlIndex, 0, url);
    }
  }

  return { ...state, urls: newUrls, openedSources: newOpenedSources };
}

export default update;
