fix: truncate image descriptions (#7699)

* move truncate function to separate file to reuse it

* truncate image descriptions

* show image description limit in UI

* correctly treat null

Co-authored-by: nullobsi <me@nullob.si>

* make truncate Unicode-aware

The strings that truncate returns should now be valid Unicode.

PostgreSQL also counts Unicode Code Points instead of bytes so this
should be correct.

* move truncate to internal, validate in API

Truncating could also be done in src/services/drive/add-file.ts or
src/services/drive/upload-from-url.ts but those would also affect
local images. But local images should result in a hard error if the
image comment is too long.

* avoid overwriting

Co-authored-by: nullobsi <me@nullob.si>

src/remote/activitypub/models/image.ts

@@ -5,6 +5,8 @@ import { fetchMeta } from '@/misc/fetch-meta';
 import { apLogger } from '../logger';
 import { DriveFile } from '@/models/entities/drive-file';
 import { DriveFiles } from '@/models/index';
+import { truncate } from '@/misc/truncate';
+import { DM_MAX_IMAGE_COMMENT_LENGTH } from '@/misc/hard-limits';
 
 const logger = apLogger;
 
@@ -28,7 +30,7 @@ export async function createImage(actor: IRemoteUser, value: any): Promise<Drive
 	const instance = await fetchMeta();
 	const cache = instance.cacheRemoteFiles;
 
-	let file = await uploadFromUrl(image.url, actor, null, image.url, image.sensitive, false, !cache, image.name);
+	let file = await uploadFromUrl(image.url, actor, null, image.url, image.sensitive, false, !cache, truncate(image.name, DB_MAX_IMAGE_COMMENT_LENGTH));
 
 	if (file.isLink) {
 		// URLが異なっている場合、同じ画像が以前に異なるURLで登録されていたということなので、

src/remote/activitypub/models/person.ts

@@ -28,22 +28,13 @@ import { getConnection } from 'typeorm';
 import { toArray } from '@/prelude/array';
 import { fetchInstanceMetadata } from '@/services/fetch-instance-metadata';
 import { normalizeForSearch } from '@/misc/normalize-for-search';
+import { truncate } from '@/misc/truncate';
 
 const logger = apLogger;
 
 const nameLength = 128;
 const summaryLength = 2048;
 
-function truncate(input: string, size: number): string;
-function truncate(input: string | undefined, size: number): string | undefined;
-function truncate(input: string | undefined, size: number): string | undefined {
-	if (!input || input.length <= size) {
-		return input;
-	} else {
-		return input.substring(0, size);
-	}
-}
-
 /**
  * Validate and convert to actor object
  * @param x Fetched object