test: post diff deletion tests

public/openapi/write.yaml

@@ -116,6 +116,8 @@ paths:
     $ref: 'write/posts/pid/diffs.yaml'
   /posts/{pid}/diffs/{since}:
     $ref: 'write/posts/pid/diffs/since.yaml'
+  /posts/{pid}/diffs/{timestamp}:
+    $ref: 'write/posts/pid/diffs/timestamp.yaml'
   /admin/settings/{setting}:
     $ref: 'write/admin/settings/setting.yaml'
   /files/:

public/openapi/write/posts/pid/diffs.yaml

@@ -39,3 +39,5 @@ get:
                           type: string
                   editable:
                     type: boolean
+                  deletable:
+                    type: boolean

public/openapi/write/posts/pid/diffs/timestamp.yaml

@@ -0,0 +1,37 @@
+delete:
+  tags:
+    - posts
+  summary: delete a post diff
+  description: This operation deletes a post diff from its history.
+  parameters:
+    - in: path
+      name: pid
+      schema:
+        type: string
+      required: true
+      description: a valid post id
+      example: 2
+    - in: path
+      name: timestamp
+      schema:
+        type: number
+      required: true
+      description: a valid UNIX timestamp
+      example: 1611850000000
+  responses:
+    '200':
+      description: Post diff successfully deleted
+      content:
+        application/json:
+          schema:
+            type: object
+            properties:
+              status:
+                $ref: ../../../../components/schemas/Status.yaml#/Status
+              response:
+                type: object
+                properties: {}
+    '400':
+      $ref: ../../../../components/responses/400.yaml#/400
+    '403':
+      $ref: ../../../../components/responses/403.yaml#/403

src/posts/diffs.js

@@ -84,6 +84,7 @@ module.exports = function (Posts) {
 		const lastTimestampIndex = timestamps.length - 1;
 
 		if (timestamp === String(post[0].timestamp)) {
+			// Deleting oldest diff, so history rewrite is not needed
 			return Promise.all([
 				db.delete(`diff:${pid}.${timestamps[lastTimestampIndex]}`),
 				db.listRemoveAll(`post:${pid}:diffs`, timestamps[lastTimestampIndex]),
@@ -102,6 +103,7 @@ module.exports = function (Posts) {
 
 		/* eslint-disable no-await-in-loop */
 		for (let i = lastTimestampIndex; i >= timestampIndex; --i) {
+			// Recreate older diffs with skipping the deleted diff
 			const newContentIndex = i === timestampIndex ? i - 2 : i - 1;
 			const timestampToUpdate = newContentIndex + 1;
 			const newContent = newContentIndex < 0 ? postContent : versionContents[timestamps[newContentIndex]];

test/posts.js

@@ -647,6 +647,29 @@ describe('Post\'s', function () {
 				done();
 			});
 		});
+
+		it('should not delete first diff of a post', async function () {
+			const timestamps = await posts.diffs.list(replyPid);
+			await assert.rejects(async () => {
+				await posts.diffs.delete(replyPid, timestamps[0], voterUid);
+			}, {
+				message: '[[error:invalid-data]]',
+			});
+		});
+
+		it('should delete a post diff', async function () {
+			await socketPosts.edit({ uid: voterUid }, { pid: replyPid, content: 'another edit has been made' });
+			await socketPosts.edit({ uid: voterUid }, { pid: replyPid, content: 'most recent edit' });
+			const timestamp = (await posts.diffs.list(replyPid)).pop();
+			await posts.diffs.delete(replyPid, timestamp, voterUid);
+			const differentTimestamp = (await posts.diffs.list(replyPid)).pop();
+			assert.notStrictEqual(timestamp, differentTimestamp);
+		});
+
+		it('should load (oldest) diff and reconstruct post correctly after a diff deletion', async function () {
+			const data = await posts.diffs.load(replyPid, 0, voterUid);
+			assert.strictEqual(data.content, 'A reply to edit');
+		});
 	});
 
 	describe('move', function () {