// ==UserScript==

// @name         AzDO Pull Request Improvements
// @version      2.22.0
// @author       Alejandro Barreto (National Instruments)
// @description  Adds sorting and categorization to the PR dashboard. Also adds minor improvements to the PR diff experience, such as a base update selector and per-file checkboxes.
// @license      MIT

// @namespace    https://github.com/alejandro5042
// @homepageURL  https://alejandro5042.github.io/azdo-userscripts/
// @supportURL   https://alejandro5042.github.io/azdo-userscripts/SUPPORT.html

// @contributionURL  https://github.com/alejandro5042/azdo-userscripts

// @include      https://dev.azure.com/*
// @include      https://*.visualstudio.com/*

// @run-at       document-end
// @require      https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js#sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=
// @require      https://cdnjs.cloudflare.com/ajax/libs/jquery-once/2.2.3/jquery.once.min.js#sha256-HaeXVMzafCQfVtWoLtN3wzhLWNs8cY2cH9OIQ8R9jfM=
// @require      https://cdnjs.cloudflare.com/ajax/libs/lscache/1.3.0/lscache.js#sha256-QVvX22TtfzD4pclw/4yxR0G1/db2GZMYG9+gxRM9v30=
// @require      https://cdnjs.cloudflare.com/ajax/libs/date-fns/1.30.1/date_fns.min.js#sha256-wCBClaCr6pJ7sGU5kfb3gQMOOcIZNzaWpWcj/lD9Vfk=
// @require      https://cdn.jsdelivr.net/npm/lodash@4.17.11/lodash.min.js#sha256-7/yoZS3548fXSRXqc/xYzjsmuW3sFKzuvOCHd06Pmps=

// @downloadURL none
// ==/UserScript==

(function () {
  'use strict';

  // All REST API calls should fail after a timeout, instead of going on forever.
  $.ajaxSetup({ timeout: 5000 });

  // Find out who is our current user. In general, we should avoid using pageData because it doesn't always get updated when moving between page-to-page in AzDO's single-page application flow. Instead, rely on the AzDO REST APIs to get information from stuff you find on the page or the URL. Some things are OK to get from pageData; e.g. stuff like the user which is available on all pages.
  const pageData = JSON.parse(document.getElementById('dataProviders').innerHTML).data;
  const currentUser = pageData['ms.vss-web.page-data'].user;

  // Because of CORS, we need to make sure we're querying the same hostname for our AzDO APIs.
  const azdoApiBaseUrl = `${window.location.origin}${pageData['ms.vss-tfs-web.header-action-data'].suiteHomeUrl}`;

  // Set a namespace for our local storage items.
  lscache.setBucket('acb-azdo/');

  // Call our event handler if we notice new elements being inserted into the DOM. This happens as the page is loading or updating dynamically based on user activity. We throttle new element events to avoid using up CPU when AzDO is adding a lot of elements during a short time (like on page load).
  document.addEventListener('DOMNodeInserted', _.throttle(onPageDOMNodeInserted, 400));

  // This is "main()" for this script. Runs periodically when the page updates.
  function onPageDOMNodeInserted(event) {
    // The page may not have refreshed when moving between URLs--sometimes AzDO acts as a single-page application. So we must always check where we are and act accordingly.
    if (/\/(pullrequest)\//i.test(window.location.pathname)) {
      addCheckboxesToFiles();
      addBaseUpdateSelector();
      makePullRequestDiffEasierToScroll();
    } else if (/\/(_pulls|pullrequests)/i.test(window.location.pathname)) {
      sortPullRequestDashboard();
    }
  }

  function makePullRequestDiffEasierToScroll() {
    addStyleOnce('pr-diff-improvements', /* css */ `
      .vc-change-summary-files .file-container {
        /* Make the divs float but clear them so they get stacked on top of each other. We float so that the divs expand to take up the width of the text in it. Finally, we remove the overflow property so that they don't have scrollbars and also such that we can have sticky elements (apparently, sticky elements don't work if the div has overflow). */
        float: left;
        clear: both;
        min-width: 95%;
        overflow: initial;
      }
      .vc-change-summary-files .file-row {
        /* Let the file name section of each diff stick to the top of the page if we're scrolling. */
        position: sticky;
        top: 0;
        z-index: 100000;
        padding-bottom: 10px;
        background: var(--background-color,rgba(255, 255, 255, 1));
      }
      .vc-change-summary-files .vc-diff-viewer {
        /* We borrowed padding from the diff to give to the bottom of the file row. So adjust accordingly (this value was originally 20px). */
        padding-top: 10px;
      }`);
  }

  // The func we'll call to continuously add checkboxes to the PR file listing, once initialization is over.
  let addCheckboxesToNewFilesFunc = () => { };

  // If we're on specific PR, add checkboxes to the file listing.
  function addCheckboxesToFiles() {
    $('.vc-sparse-files-tree').once('add-checkbox-support').each(async function () {
      addCheckboxesToNewFilesFunc = () => { };

      const filesTree = $(this);

      addStyleOnce('pr-file-checbox-support-css', /* css */ `
        :root {
          /* Set some constants for our CSS. */
          --file-to-review-color: var(--communication-foreground);
        }
        button.file-complete-checkbox {
          /* Make a checkbox out of a button. */
          cursor: pointer;
          width: 15px;
          height: 15px;
          line-height: 15px;
          margin: -3px 8px 0px 0px;
          padding: 0px;
          background: var(--palette-black-alpha-6);
          border-radius: 3px;
          border: 1px solid var(--palette-black-alpha-10);
          vertical-align: middle;
          display: inline-block;
          font-size: 0.75em;
          text-align: center;
          color: var(--text-primary-color);
        }
        button.file-complete-checkbox:hover {
          /* Make a checkbox out of a button. */
          background: var(--palette-black-alpha-10);
        }
        button.file-complete-checkbox.checked:after {
          /* Make a checkbox out of a button. */
          content: "✔";
        }
        .vc-sparse-files-tree .tree-row.file-to-review-row,
        .vc-sparse-files-tree .tree-row.file-to-review-row .file-name {
          /* Highlight files I need to review. */
          color: var(--file-to-review-color);
        }
        .vc-sparse-files-tree .tree-row.file-to-review-row .file-owners-role {
          /* Style the role of the user in the files table. */
          font-weight: bold;
          padding: 7px 10px;
          position: absolute;
          z-index: 100;
          float: right;
        }
        .file-to-review-diff {
          /* Highlight files I need to review. */
          border-left: 3px solid var(--file-to-review-color) !important;
          padding-left: 7px;
        }
        .files-container.hide-files-not-to-review .file-container:not(.file-to-review-diff) {
          /* Fade the header for files I don't have to review. */
          opacity: 0.2;
        }
        .files-container.hide-files-not-to-review .file-container:not(.file-to-review-diff) .item-details-body {
          /* Hide the diff for files I don't have to review. */
          display: none;
        }`);

      // Get the current iteration of the PR.
      const pr = await getPullRequest();
      const currentPullRequestIteration = (await $.get(`${pr.url}/iterations?api-version=5.0`)).count;

      // Get the current checkbox state for the PR at this URL.
      const checkboxStateId = `pr-file-iteration6/${window.location.pathname}`;

      // Stores the checkbox state for the current page. A map of files => iteration it was checked.
      const filesToIterationReviewed = lscache.get(checkboxStateId) || {};

      // Handle clicking on file checkboxes.
      filesTree.on('click', 'button.file-complete-checkbox', function (event) {
        const checkbox = $(this);

        // Toggle the look of the checkbox.
        checkbox.toggleClass('checked');

        // Save the iteration number the file was checked in our map. To save space, if it is unchecked, simply remove the entry.
        if (checkbox.hasClass('checked')) {
          filesToIterationReviewed[checkbox.attr('name')] = currentPullRequestIteration;
        } else {
          delete filesToIterationReviewed[checkbox.attr('name')];
        }

        // Save the current checkbox state to local storage.
        lscache.set(checkboxStateId, filesToIterationReviewed, 60 * 24 * 21);

        // Stop the click event here to avoid the checkbox click from selecting the PR row underneath, which changes the active diff in the right panel.
        event.stopPropagation();
      });

      // Get owners info for this PR.
      const ownersInfo = await getNationalInstrumentsPullRequestOwnersInfo(pr.url);

      // If we have owners info, add a button to filter out diffs that we don't need to review.
      if (ownersInfo && ownersInfo.currentUserFileCount > 0) {
        $('.changed-files-summary-toolbar').once('add-other-files-button').each(function () {
          $(this)
            .find('ul')
            .prepend('<li class="menu-item" role="button"><a href="#">Toggle other files</a></li>')
            .click((event) => {
              $('.files-container').toggleClass('hide-files-not-to-review');
            });
        });
      }

      addCheckboxesToNewFilesFunc = function () {
        // If we have owners info, tag the diffs that we don't need to review.
        if (ownersInfo && ownersInfo.currentUserFileCount > 0) {
          $('.file-container .file-path').once('filter-files-to-review').each(function () {
            const filePathElement = $(this);
            const path = filePathElement.text().replace(/\//, '');
            filePathElement.closest('.file-container').toggleClass('file-to-review-diff', ownersInfo.isCurrentUserResponsibleForFile(path));
          });
        }
        $('.vc-sparse-files-tree .vc-tree-cell').once('add-complete-checkbox').each(function () {
          const fileCell = $(this);
          const fileRow = fileCell.closest('.tree-row');
          const typeIcon = fileRow.find('.type-icon');

          // Don't put checkboxes on rows that don't represent files.
          if (!/bowtie-file\b/i.test(typeIcon.attr('class'))) {
            return;
          }

          const name = fileCell.attr('content'); // The 'content' attribute contains the file operation; e.g. "/src/file.cs [edit]".
          const iteration = filesToIterationReviewed[name] || 0;

          // Create the checkbox before the type icon.
          $('<button class="file-complete-checkbox" />')
            .attr('name', name)
            .toggleClass('checked', iteration > 0)
            .insertBefore(typeIcon);

          // If we have owners info, highlight the files we need to review and add role info.
          if (ownersInfo && ownersInfo.currentUserFileCount > 0) {
            const path = name.replace(/\s\[.*?\]$/i, '').replace(/^\//, '');
            if (ownersInfo.isCurrentUserResponsibleForFile(path)) {
              fileRow.addClass('file-to-review-row');
              $('<div class="file-owners-role" />').text(`${ownersInfo.currentUserFilesToRole[path]}:`).prependTo(fileRow);
            }
          }
        });
      };
    });

    addCheckboxesToNewFilesFunc();
  }

  // If we're on specific PR, add a base update selector.
  function addBaseUpdateSelector() {
    $('.vc-iteration-selector').once('add-base-selector').each(async function () {
      const toolbar = $(this);

      addStyleOnce('base-selector-css', /* css */ `
        .base-selector {
          color: var(--text-secondary-color);
          margin: 0px 5px 0px 0px;
        }
        .base-selector select {
          border: 1px solid transparent;
          padding: 2px 4px;
          width: 3em;
          height: 100%;
          text-align: center;
        }
        .base-selector select:hover {
          border-color: var(--palette-black-alpha-20);
        }
        .base-selector select option {
          background: var(--callout-background-color);
          color: var(--text-primary-color);
          font-family: Consolas, monospace;
        }
        .base-selector select option:disabled {
          display: none;
        }`);

      // Get the PR iterations.
      const pr = await getPullRequest();
      const iterations = (await $.get(`${pr.url}/iterations?api-version=5.0`)).value;

      // Create a dropdown with the first option being the icon we show to users. We use an HTML dropdown since its much easier to code than writing our own with divs/etc or trying to figure out how to use an AzDO dropdown.
      const selector = $('<select><option value="" disabled selected>↦</option></select>');

      // Add an option for each iteration in the dropdown, looking roughly the same as the AzDO update selector.
      for (const iteration of iterations.reverse()) {
        const date = Date.parse(iteration.createdDate);
        const truncatedDescription = iteration.description.length > 60 ? `${iteration.description.substring(0, 58)}...` : iteration.description;
        const optionText = `Update ${iteration.id.toString().padEnd(4)} ${truncatedDescription.padEnd(61)} ${dateFns.distanceInWordsToNow(date).padStart(15)} ago`;
        $('<option>').val(iteration.id).text(optionText).appendTo(selector);
      }

      // Add the last option to select the merge base as the diff base (essentially update zero).
      $('<option value="0">            === Merge Base ===</option>').appendTo(selector);

      // Replace spaces with non-breaking spaces (char 0xa0) to force the browser to not collapse it so that we can align the dates to the right of the dropdown. Apprently even `white-space: pre !important;` doesn't work on `option` element css.
      selector.children('option').each(function () { $(this).text((i, text) => text.replace(/ /g, '\xa0')); });

      // Finally add the dropdown to the toolbar.
      $('<div class="base-selector" />').append(selector).prependTo(toolbar);

      // When an option is selected, update the URL to include the selected base update.
      selector.on('change', function (event) {
        const currentUrl = new URL(window.location.href);
        currentUrl.searchParams.set('base', $(this).first().val());
        currentUrl.searchParams.set('iteration', currentUrl.searchParams.get('iteration') || iterations.length); // If we select a base without having an explicit iteration, compare the base to the latest.
        window.location.href = currentUrl.toString();
      });
    });
  }

  // The func we'll call to continuously sort new PRs into categories, once initialization is over.
  let sortEachPullRequestFunc = () => { };

  // If we're on a pull request page, attempt to sort it.
  function sortPullRequestDashboard() {
    // Find the reviews section for this user. Note the two selectors: 1) a repo dashboard; 2) the overall dashboard (e.g. https://dev.azure.com/*/_pulls).
    $("[aria-label='Assigned to me'][role='region'], .ms-GroupedList-group:has([aria-label='Assigned to me'])").once('reviews-sorted').each(function () {
      sortEachPullRequestFunc = () => { };

      const personalReviewSection = $(this);

      addStyleOnce('reviews-list-css', /* css */ `
        details.reviews-list {
          margin: 10px 30px;
          display: none;
        }
        details.reviews-list summary {
          padding: 10px;
          cursor: pointer;
          color: var(--text-secondary-color);
        }
        details.reviews-list > div.flex-container {
          display: flex;
          flex-direction: column-reverse;
        }`);


      // Disable the expanding button if we are on the overall PR dashboard. If enabled and the user hides/shows this section, it causes the AzDO page to re-add all the PRs, leading to duplicates in the sorted list.
      personalReviewSection.find('button.ms-GroupHeader-expand').prop('disabled', true).attr('title', 'AzDO Pull Request Improvements userscript disabled this button.');

      // Define what it means to be a notable PR after you have approved it.
      const peopleToNotApproveToCountAsNotableThread = 2;
      const commentsToCountAsNotableThread = 4;
      const wordsToCountAsNotableThread = 300;
      const notableUpdateDescription = `These are pull requests you've already approved, but since then, any of following events have happened:&#013    1) At least ${peopleToNotApproveToCountAsNotableThread} people voted Rejected or Waiting on Author&#013    2) A thread was posted with at least ${commentsToCountAsNotableThread} comments&#013    3) A thread was posted with at least ${wordsToCountAsNotableThread} words&#013Optional: To remove PRs from this list, simply vote again on the PR (even if it's the same vote).`;

      // Create review sections with counters.
      const sections = {
        blocking:
          $("<details class='reviews-list reviews-pending'><summary style='color: var(--status-error-foreground); font-weight: bold'>Blocking</summary></details>"),

        pending:
          $("<details class='reviews-list reviews-pending'><summary>Incomplete</summary></details>"),

        blocked:
          $("<details class='reviews-list reviews-incomplete-blocked'><summary>Incomplete but blocked</summary></details>"),

        approvedButNotable:
          $(`<details class='reviews-list reviews-approved-notable'><summary>Completed as Approved / Approved with Suggestions (<abbr title="${notableUpdateDescription}">with notable activity</abbr>)</summary></details>`),

        drafts:
          $("<details class='reviews-list reviews-drafts'><summary>Drafts</summary></details>"),

        waiting:
          $("<details class='reviews-list reviews-waiting'><summary>Completed as Waiting on Author</summary></details>"),

        rejected:
          $("<details class='reviews-list reviews-rejected'><summary>Completed as Rejected</summary></details>"),

        approved:
          $("<details class='reviews-list reviews-approved'><summary>Completed as Approved / Approved with Suggestions</summary></details>"),
      };

      // Load the subsection open/closed setting if it exists and setup a change handler to save the setting. We also add common elements to each sections.
      for (const section of Object.values(sections)) {
        const id = `pr-section-open/${section.attr('class')}`;
        section.children('summary').append(" (<span class='review-subsection-counter'>0</span>)");
        section.append("<div class='flex-container' />");
        section.prop('open', lscache.get(id));
        section.on('toggle', function () { lscache.set(id, $(this).prop('open')); });
        section.appendTo(personalReviewSection);
      }

      // Loop through the PRs that we've voted on.
      sortEachPullRequestFunc = () => $(personalReviewSection).find('[role="list"] [role="listitem"]').once('pr-sorted').each(async function () {
        const row = $(this);

        // Loop until AzDO has added the link to the PR into the row.
        let pullRequestHref;
        while (!pullRequestHref) {
          // Important! Do not remove this sleep, even on the first iteration. We need to give AzDO some time to finish making the row before moving it. If we don't sleep for some time, and we begin moving rows, AzDO may get confused and not create all the PR rows. That would cause some PRs to not be rendered in the list. The best solution is to wait until the list finishes to render via an event handler; except that I don't know how to hook into that without understanding AzDO JS infrastructure. The sleep time was chosen to balance first load time (don't wait too long before sorting) and what appears to be long enough to avoid the missing PR problem when sorting a 50+ PR dashboard, as determined by experimentation (refreshing the page a dozen or so times).
          // eslint-disable-next-line no-await-in-loop
          await sleep(300);
          pullRequestHref = row.find("a[href*='/pullrequest/']").attr('href');
        }

        try {
          // Hide the row while we are updating it.
          row.hide(150);

          // Sort the reviews in reverse; aka. show oldest reviews first then newer reviews. We do this by ordering the rows inside a reversed-order flex container.
          row.css('order', row.attr('data-list-index'));

          // Get the PR id.
          const pullRequestUrl = new URL(pullRequestHref, window.location.origin);
          const pullRequestId = parseInt(pullRequestUrl.pathname.substring(pullRequestUrl.pathname.lastIndexOf('/') + 1), 10);

          // Get complete information about the PR.
          const pr = await getPullRequest(pullRequestId);

          let missingVotes = 0;
          let waitingOrRejectedVotes = 0;
          let userVote = 0;

          // Count the number of votes.
          for (const reviewer of pr.reviewers) {
            if (reviewer.uniqueName === currentUser.uniqueName) {
              userVote = reviewer.vote;
            }
            if (reviewer.vote === 0) {
              missingVotes += 1;
            } else if (reviewer.vote < 0) {
              waitingOrRejectedVotes += 1;
            }
          }

          // See what section this PR should be filed under and style the row, if necessary.
          let section;
          let computeSize = false;

          if (pr.isDraft) {
            section = sections.drafts;
            computeSize = true;
          } else if (userVote === -5) {
            section = sections.waiting;
          } else if (userVote < 0) {
            section = sections.rejected;
          } else if (userVote > 0) {
            section = sections.approved;

            // If the user approved the PR, see if we need to resurface it as a notable PR.
            const pullRequestThreads = await $.get(`${pr.url}/threads?api-version=5.0`);

            let threadsWithLotsOfComments = 0;
            let threadsWithWordyComments = 0;
            let newNonApprovedVotes = 0;

            // Loop through the threads in reverse time order (newest first).
            for (const thread of pullRequestThreads.value.reverse()) {
              // If the thread is deleted, let's ignore it and move on to the next thread.
              if (thread.isDeleted) {
                break;
              }

              // See if this thread represents a non-approved vote.
              if (Object.prototype.hasOwnProperty.call(thread, 'CodeReviewThreadType')) {
                if (thread.properties.CodeReviewThreadType.$value === 'VoteUpdate') {
                  // Stop looking at threads once we find the thread that represents our vote.
                  const votingUser = thread.identities[thread.properties.CodeReviewVotedByIdentity.$value];
                  if (votingUser.uniqueName === currentUser.uniqueName) {
                    break;
                  }

                  if (thread.properties.CodeReviewVoteResult.$value < 0) {
                    newNonApprovedVotes += 1;
                  }
                }
              }

              // Count the number of comments and words in the thread.
              let wordCount = 0;
              let commentCount = 0;
              for (const comment of thread.comments) {
                if (comment.commentType !== 'system' && !comment.isDeleted && comment.content) {
                  commentCount += 1;
                  wordCount += comment.content.trim().split(/\s+/).length;
                }
              }

              if (commentCount >= commentsToCountAsNotableThread) {
                threadsWithLotsOfComments += 1;
              }
              if (wordCount >= wordsToCountAsNotableThread) {
                threadsWithWordyComments += 1;
              }
            }

            // See if we've tripped any of attributes that would make this PR notable.
            if (threadsWithLotsOfComments > 0 || threadsWithWordyComments > 0 || newNonApprovedVotes >= peopleToNotApproveToCountAsNotableThread) {
              section = sections.approvedButNotable;
            }
          } else {
            computeSize = true;
            if (waitingOrRejectedVotes > 0) {
              section = sections.blocked;
            } else if (missingVotes === 1) {
              section = sections.blocking;
            } else {
              section = sections.pending;
            }
          }

          // Compute the size of certain PRs; e.g. those we haven't reviewed yet. But first, sure we've created a merge commit that we can compute its size.
          if (computeSize && pr.lastMergeCommit) {
            let fileCount = 0;

            // See if this PR has owners info and count the files listed for the current user.
            const ownersInfo = await getNationalInstrumentsPullRequestOwnersInfo(pr.url);
            if (ownersInfo) {
              fileCount = ownersInfo.currentUserFileCount;
            }

            // If there is no owner info or if it returns zero files to review (since we may not be on the review explicitly), then count the number of files in the merge commit.
            if (fileCount === 0) {
              const mergeCommitInfo = await $.get(`${pr.lastMergeCommit.url}/changes?api-version=5.0`);
              fileCount = _(mergeCommitInfo.changes).filter(item => !item.item.isFolder).size();
            }

            const fileCountContent = `<span class="contributed-icon flex-noshrink fabric-icon ms-Icon--FileCode"></span>&nbsp;${fileCount}`;

            // Add the file count on the overall PR dashboard.
            row.find('div.vss-DetailsList--titleCellTwoLine').parent()
              .append(`<div style='margin: 0px 15px; width: 3em; text-align: left;'>${fileCountContent}</div>`);

            // Add the file count on a repo's PR dashboard.
            row.find('div.vc-pullrequest-entry-col-secondary')
              .after(`<div style='margin: 15px; width: 3.5em; display: flex; align-items: center; text-align: right;'>${fileCountContent}</div>`);
          }

          // If we identified a section, move the row.
          if (section) {
            section.find('.review-subsection-counter').text((i, value) => +value + 1);
            section.children('div.flex-container').append(row);
            section.show();
          }
        } finally {
          // No matter what--e.g. even on error--show the row again.
          row.show(150);
        }
      });
    });

    sortEachPullRequestFunc();
  }

  // Helper function to avoid adding CSS twice into a document.
  function addStyleOnce(id, style) {
    $(document.head).once(id).each(function () {
      $('<style type="text/css" />').html(style).appendTo(this);
    });
  }

  // Async helper function get info on a single PR. Defaults to the PR that's currently on screen.
  function getPullRequest(id = 0) {
    const actualId = id || window.location.pathname.substring(window.location.pathname.lastIndexOf('/') + 1);
    return $.get(`${azdoApiBaseUrl}/_apis/git/pullrequests/${actualId}?api-version=5.0`);
  }

  // Async helper function to sleep.
  function sleep(milliseconds) {
    return new Promise(resolve => setTimeout(resolve, milliseconds));
  }

  // Async helper function to get a specific PR property, otherwise return the default value.
  async function getPullRequestProperty(prUrl, key, defaultValue = null) {
    const properties = await $.get(`${prUrl}/properties?api-version=5.1-preview.1`);
    const property = properties.value[key];
    return property ? JSON.parse(property.$value) : defaultValue;
  }

  // Async helper function to return reviewer info specific to National Instruments workflows (where this script is used the most).
  async function getNationalInstrumentsPullRequestOwnersInfo(prUrl) {
    const reviewProperties = await getPullRequestProperty(prUrl, 'NI.ReviewProperties');

    // Not all repos have NI owner info.
    if (!reviewProperties) {
      return null;
    }

    // Only support the more recent PR owner info version, where full user info is stored in an identities table separate from files.
    if (reviewProperties.version < 4) {
      return null;
    }

    // Some PRs don't have complete owner info if it would be too large to fit in PR property storage.
    if (!reviewProperties.fileProperties) {
      return null;
    }

    const ownersInfo = {
      currentUserFilesToRole: {},
      currentUserFileCount: 0,
      isCurrentUserResponsibleForFile(path) {
        return Object.prototype.hasOwnProperty.call(this.currentUserFilesToRole, path);
      },
    };

    // See if the current user is listed in this PR.
    const currentUserListedInThisOwnerReview = _(reviewProperties.reviewerIdentities).some(r => r.email === currentUser.uniqueName);

    // Go through all the files listed in the PR.
    if (currentUserListedInThisOwnerReview) {
      for (const file of reviewProperties.fileProperties) {
        // Get the identities associated with each of the known roles.
        const owner = reviewProperties.reviewerIdentities[file.Owner - 1] || {};
        const alternate = reviewProperties.reviewerIdentities[file.Alternate - 1] || {}; // handle nulls everywhere
        const reviewers = file.Reviewers.map(r => reviewProperties.reviewerIdentities[r - 1]) || [];

        // Pick the highest role for the current user on this file, and track it.
        if (owner.email === currentUser.uniqueName) {
          ownersInfo.currentUserFilesToRole[file.Path] = 'O';
          ownersInfo.currentUserFileCount += 1;
        } else if (alternate.email === currentUser.uniqueName) {
          ownersInfo.currentUserFilesToRole[file.Path] = 'A';
          ownersInfo.currentUserFileCount += 1;
        } else if (_(reviewers).some(r => r.email === currentUser.uniqueName)) {
          ownersInfo.currentUserFilesToRole[file.Path] = 'R';
          ownersInfo.currentUserFileCount += 1;
        }
      }
    }

    return ownersInfo;
  }
}());