Remove the content cache's handling of an earlier version's live-photo ZIP (closes #151)

quak is pre-1.0 and keeps no handling of old data. The content cache no longer recognises or removes a live photo that an earlier quak version cached as one ZIP. A live-photo download no longer removes what was at its destination before renaming the image and video into place; the rename already replaces it. The README sentences and the tests about that old ZIP are gone. The two removed tests that also covered current behaviour are replaced by tests with no ZIP: the cache re-fetching a live photo recorded with no video, and the library telling the cache which files are live photos when it opens.

Model: opus-5-5

src/library/content.ts

@@ -29,14 +29,7 @@
 // the cache does not count as saved there, but is copied there rather than
 // fetched again.
 
-import {
-    closeSync,
-    existsSync,
-    openSync,
-    readFileSync,
-    readSync,
-    statSync,
-} from "node:fs";
+import { existsSync, readFileSync, statSync } from "node:fs";
 import {
     chmod,
     copyFile,
@@ -281,25 +274,6 @@ const fileSize = (path: string): number | undefined => {
 const hasContent = (path: string | undefined): boolean =>
     path !== undefined && (fileSize(path) ?? 0) > 0;
 
-// Whether the file at `path` begins as a ZIP does, with `PK\x03\x04`. False
-// when it cannot be read.
-const isZip = (path: string): boolean => {
-    try {
-        const fd = openSync(path, "r");
-        try {
-            const head = Buffer.alloc(4);
-            return (
-                readSync(fd, head, 0, 4, 0) === 4 &&
-                head.toString("latin1") === "PK\x03\x04"
-            );
-        } finally {
-            closeSync(fd);
-        }
-    } catch {
-        return false;
-    }
-};
-
 // A live photo's image and video are named with the extensions from inside its
 // ZIP, so their names alone do not say which is which. Wherever the cache or a
 // save path stores one, a JSON file of this name beside them names both.
@@ -713,8 +687,10 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
                     await this.touch(cached.path);
                 return { ...cached, bytes: size, cached: true };
             }
-            // A recorded file that has since gone, or a live photo an earlier
-            // version stored as one ZIP, re-fetches below.
+            // A recorded file that has since gone re-fetches below. So does a
+            // live photo recorded with no video: the cache opened before the
+            // library's records said it is a live photo, while its image and
+            // video had no JSON file beside them yet.
             known.delete(fileID);
         }
 
@@ -983,20 +959,14 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
             if (id === undefined || !existsSync(path)) continue;
             // A live photo's image and video are one entry, as the JSON file
             // beside them names them. A live photo's file with no such JSON
-            // file is not its original. If it is a ZIP, it is the one an
-            // earlier version stored under the image's name, and is removed.
-            // Any other is left alone: another process may have just stored
-            // it and not yet written the JSON file.
+            // file is not its original and is left alone: another process may
+            // have just stored it and not yet written the JSON file.
             const livePhoto = names.has(livePhotoJSONName(String(id)))
                 ? readLivePhotoJSON(dir, String(id))
                 : undefined;
             if (livePhoto !== undefined) {
                 into.set(id, livePhoto);
-            } else if (isLivePhoto(id)) {
-                if (isZip(path)) {
-                    await rm(path, { force: true }).catch(() => undefined);
-                }
-            } else {
+            } else if (!isLivePhoto(id)) {
                 into.set(id, { path });
             }
         }