fix(txt): add stream() to RemoteFile to fix large TXT import on desktop, closes #3495 (#3502)

RemoteFile (used on all desktop platforms) extended File([]) with empty
data and overrode slice(), text(), arrayBuffer() but not stream(). The
large file path (>8MB) introduced in #3320 uses file.stream() to read
content incrementally, which returned empty data from the base File
class, causing "No chapters detected" for large TXT files.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

apps/readest-app/src/__tests__/utils/txt-converter.test.ts

@@ -260,6 +260,60 @@ describe('TxtToEpubConverter', () => {
     expect(result.chapterCount).toBe(2);
   });
 
+  it('convert large file should work when stream() is built from slice() like RemoteFile', async () => {
+    const converter = new TxtToEpubConverter() as unknown as TxtConverterFlowPrivateAPI;
+    const content = '第一章 开始\n这是第一章的内容。\n\n第二章 继续\n这是第二章的内容。';
+    const backingBlob = new Blob([content]);
+
+    // Simulate a fixed RemoteFile: stream() reads data via slice(), not from base File([])
+    const fixedFile = new File([], 'large.txt');
+    const fileSize = 9 * 1024 * 1024;
+    Object.defineProperty(fixedFile, 'size', { value: fileSize });
+    Object.defineProperty(fixedFile, 'slice', {
+      value: (start?: number, end?: number) => backingBlob.slice(start, end),
+    });
+    Object.defineProperty(fixedFile, 'stream', {
+      value: () => {
+        const CHUNK_SIZE = 1024 * 1024;
+        let offset = 0;
+        return new ReadableStream<Uint8Array>({
+          pull: async (controller) => {
+            if (offset >= fileSize) {
+              controller.close();
+              return;
+            }
+            const end = Math.min(offset + CHUNK_SIZE, fileSize);
+            const buf = await backingBlob.slice(offset, end).arrayBuffer();
+            controller.enqueue(new Uint8Array(buf));
+            offset = end;
+          },
+        });
+      },
+    });
+
+    converter.createEpub = async () => new Blob();
+
+    const result = await converter.convert({ file: fixedFile });
+    expect(result.chapterCount).toBeGreaterThanOrEqual(1);
+  });
+
+  it('convert large file should fail when stream() returns empty data (unfixed RemoteFile)', async () => {
+    const converter = new TxtToEpubConverter() as unknown as TxtConverterFlowPrivateAPI;
+
+    // Simulate the bug: RemoteFile with unoverridden stream() returns empty data
+    const brokenFile = new File([], 'large.txt');
+    Object.defineProperty(brokenFile, 'size', { value: 9 * 1024 * 1024 });
+    Object.defineProperty(brokenFile, 'slice', {
+      value: (start?: number, end?: number) =>
+        new Blob(['第一章 开始\n内容\n\n第二章 继续\n内容']).slice(start, end),
+    });
+    // stream() is NOT overridden — inherits base File's empty stream
+
+    converter.createEpub = async () => new Blob();
+
+    await expect(converter.convert({ file: brokenFile })).rejects.toThrow('No chapters detected');
+  });
+
   it('iterateSegmentsFromFile should cancel stream on early return', async () => {
     const converter = new TxtToEpubConverter() as unknown as TxtConverterFlowPrivateAPI & {
       iterateSegmentsFromFile(

apps/readest-app/src/utils/file.ts

@@ -453,6 +453,26 @@ export class RemoteFile extends File implements ClosableFile {
     return new DeferredBlob(dataPromise, contentType);
   }
 
+  override stream(): ReadableStream<Uint8Array<ArrayBuffer>> {
+    const CHUNK_SIZE = 1024 * 1024;
+    let offset = 0;
+
+    return new ReadableStream<Uint8Array<ArrayBuffer>>({
+      pull: async (controller) => {
+        if (offset >= this.size) {
+          controller.close();
+          return;
+        }
+
+        const end = Math.min(offset + CHUNK_SIZE, this.size);
+        const buffer = await this.fetchRange(offset, end - 1);
+
+        controller.enqueue(new Uint8Array(buffer));
+        offset = end;
+      },
+    });
+  }
+
   override async text() {
     const blob = this.slice(0, this.size);
     return blob.text();