4 files changed, 93 insertions, 7 deletions

diff --git a/app/assets/javascripts/diffs/utils/diff_file.js b/app/assets/javascripts/diffs/utils/diff_file.js
index 69d0e49e501..ce0398e75fc 100644
--- a/app/assets/javascripts/diffs/utils/diff_file.js
+++ b/app/assets/javascripts/diffs/utils/diff_file.js
@@ -4,11 +4,12 @@ import {
   DIFF_FILE_MANUAL_COLLAPSE,
   DIFF_FILE_AUTOMATIC_COLLAPSE,
 } from '../constants';
+import { getDerivedMergeRequestInformation } from './merge_request';
 import { uuids } from './uuids';
 
 function fileSymlinkInformation(file, fileList) {
-  const duplicates = fileList.filter(iteratedFile => iteratedFile.file_hash === file.file_hash);
-  const includesSymlink = duplicates.some(iteratedFile => {
+  const duplicates = fileList.filter((iteratedFile) => iteratedFile.file_hash === file.file_hash);
+  const includesSymlink = duplicates.some((iteratedFile) => {
     return [iteratedFile.a_mode, iteratedFile.b_mode].includes(DIFF_FILE_SYMLINK_MODE);
   });
   const brokenSymlinkScenario = duplicates.length > 1 && includesSymlink;
@@ -34,8 +35,12 @@ function collapsed(file) {
 }
 
 function identifier(file) {
+  const { userOrGroup, project, id } = getDerivedMergeRequestInformation({
+    endpoint: file.load_collapsed_diff_url,
+  });
+
   return uuids({
-    seeds: [file.file_identifier_hash, file.blob?.id],
+    seeds: [userOrGroup, project, id, file.file_identifier_hash, file.blob?.id],
   })[0];
 }
 
@@ -48,10 +53,10 @@ export function prepareRawDiffFile({ file, allFiles, meta = false }) {
     },
   };
 
-  // It's possible, but not confirmed, that `content_sha` isn't available sometimes
+  // It's possible, but not confirmed, that `blob.id` isn't available sometimes
   // See: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/49506#note_464692057
   // We don't want duplicate IDs if that's the case, so we just don't assign an ID
-  if (!meta && file.blob?.id) {
+  if (!meta && file.blob?.id && file.load_collapsed_diff_url) {
     additionalProperties.id = identifier(file);
   }
 
diff --git a/app/assets/javascripts/diffs/utils/file_reviews.js b/app/assets/javascripts/diffs/utils/file_reviews.js
new file mode 100644
index 00000000000..0047955643a
--- /dev/null
+++ b/app/assets/javascripts/diffs/utils/file_reviews.js
@@ -0,0 +1,61 @@
+function getFileReviewsKey(mrPath) {
+  return `${mrPath}-file-reviews`;
+}
+
+export function getReviewsForMergeRequest(mrPath) {
+  const reviewsForMr = localStorage.getItem(getFileReviewsKey(mrPath));
+  let reviews = {};
+
+  if (reviewsForMr) {
+    try {
+      reviews = JSON.parse(reviewsForMr);
+    } catch (err) {
+      reviews = {};
+    }
+  }
+
+  return reviews;
+}
+
+export function setReviewsForMergeRequest(mrPath, reviews) {
+  localStorage.setItem(getFileReviewsKey(mrPath), JSON.stringify(reviews));
+
+  return reviews;
+}
+
+export function isFileReviewed(reviews, file) {
+  const fileReviews = reviews[file.file_identifier_hash];
+
+  return file?.id && fileReviews?.length ? new Set(fileReviews).has(file.id) : false;
+}
+
+export function reviewable(file) {
+  return Boolean(file.id) && Boolean(file.file_identifier_hash);
+}
+
+export function markFileReview(reviews, file, reviewed = true) {
+  const usableReviews = { ...(reviews || {}) };
+  let updatedReviews = usableReviews;
+  let fileReviews;
+
+  if (reviewable(file)) {
+    fileReviews = new Set([...(usableReviews[file.file_identifier_hash] || [])]);
+
+    if (reviewed) {
+      fileReviews.add(file.id);
+    } else {
+      fileReviews.delete(file.id);
+    }
+
+    updatedReviews = {
+      ...usableReviews,
+      [file.file_identifier_hash]: Array.from(fileReviews),
+    };
+
+    if (updatedReviews[file.file_identifier_hash].length === 0) {
+      delete updatedReviews[file.file_identifier_hash];
+    }
+  }
+
+  return updatedReviews;
+}
diff --git a/app/assets/javascripts/diffs/utils/merge_request.js b/app/assets/javascripts/diffs/utils/merge_request.js
new file mode 100644
index 00000000000..edb4304f558
--- /dev/null
+++ b/app/assets/javascripts/diffs/utils/merge_request.js
@@ -0,0 +1,20 @@
+const endpointRE = /^(\/?(.+?)\/(.+?)\/-\/merge_requests\/(\d+)).*$/i;
+
+export function getDerivedMergeRequestInformation({ endpoint } = {}) {
+  let mrPath;
+  let userOrGroup;
+  let project;
+  let id;
+  const matches = endpointRE.exec(endpoint);
+
+  if (matches) {
+    [, mrPath, userOrGroup, project, id] = matches;
+  }
+
+  return {
+    mrPath,
+    userOrGroup,
+    project,
+    id,
+  };
+}
diff --git a/app/assets/javascripts/diffs/utils/uuids.js b/app/assets/javascripts/diffs/utils/uuids.js
index 12448350e62..1fe5f9f6499 100644
--- a/app/assets/javascripts/diffs/utils/uuids.js
+++ b/app/assets/javascripts/diffs/utils/uuids.js
@@ -11,7 +11,7 @@
  * @typedef {String} UUIDv4
  */
 
-import MersenneTwister from 'mersenne-twister';
+import { MersenneTwister } from 'fast-mersenne-twister';
 import stringHash from 'string-hash';
 import { isString } from 'lodash';
 import { v4 } from 'uuid';
@@ -49,7 +49,7 @@ function randomValuesForUuid(prng) {
     const buffer = new ArrayBuffer(4);
     const view = new DataView(buffer);
 
-    view.setUint32(0, prng.random_int());
+    view.setUint32(0, prng.randomNumber());
 
     randomValues.push(view.getUint8(0), view.getUint8(1), view.getUint8(2), view.getUint8(3));
   }