Support resumable game folder uploads and remove DLC declarations

src/lib/ui/game-folder.ts

@@ -0,0 +1,38 @@
+export interface SelectedGameFile { path: string; file: File }
+export interface SelectedGameFolder { name: string; files: SelectedGameFile[]; size: number }
+
+/** Directory inputs include the selected folder in every relative path. Remove
+ * that one component and retain the complete game directory below it. */
+export function selectGameFolder(selection: Iterable<File>): SelectedGameFolder {
+    const files: SelectedGameFile[] = [];
+    const paths = new Set<string>();
+    let name = '';
+    let size = 0;
+    for (const file of selection) {
+        const [root, ...parts] = file.webkitRelativePath.split('/');
+        if (!root || root === '.' || root === '..' || !parts.length || name && root !== name) throw new Error('Choose one game folder with the folder picker.');
+        name = root;
+        const path = parts.join('/');
+        if (path.length > 1024 || /[\\\x00-\x1f\x7f:]/.test(path) || parts.some(part => !part || part === '.' || part === '..' || /[. ]$/.test(part))) {
+            throw new Error(`This file has an unsupported game path: ${file.webkitRelativePath}`);
+        }
+        const key = path.toLowerCase();
+        if (paths.has(key)) throw new Error(`This folder has duplicate game paths: ${path}`);
+        paths.add(key);
+        size += file.size;
+        if (!Number.isSafeInteger(size)) throw new Error('This folder exceeds the supported upload size.');
+        files.push({ path, file });
+        if (files.length > 200_000) throw new Error('Choose a folder with no more than 200,000 files.');
+    }
+    if (!files.length) throw new Error('The selected folder contains no files.');
+    for (const { path } of files) {
+        const parents = path.toLowerCase().split('/');
+        parents.pop();
+        while (parents.length) {
+            if (paths.has(parents.join('/'))) throw new Error(`This folder uses the same game path for a file and a directory: ${path}`);
+            parents.pop();
+        }
+    }
+    files.sort((a, b) => a.path < b.path ? -1 : a.path > b.path ? 1 : 0);
+    return { name, files, size };
+}