feat: 🎸 start WriteStream implementation

package.json

@@ -84,7 +84,8 @@
     }
   },
   "dependencies": {
-    "fs-monkey": "^1.0.4"
+    "fs-monkey": "^1.0.4",
+    "thingies": "^1.11.1"
   },
   "devDependencies": {
     "@semantic-release/changelog": "^6.0.1",

src/fsa-to-node/FsaNodeFs.ts

@@ -40,6 +40,7 @@ import { constants } from '../constants';
 import { FsaNodeStats } from './FsaNodeStats';
 import process from '../process';
 import { FsSynchronousApi } from '../node/types/FsSynchronousApi';
+import {FsaNodeWriteStream} from './FsaNodeWriteStream';
 import type { FsCallbackApi, FsPromisesApi } from '../node/types';
 import type * as misc from '../node/types/misc';
 import type * as opts from '../node/types/options';
@@ -732,36 +733,45 @@ export class FsaNodeFs implements FsCallbackApi, FsSynchronousApi, FsCommonObjec
       );
   };
 
-  fchmod(fd: number, mode: misc.TMode, callback: misc.TCallback<void>): void {
+  public readonly fchmod: FsCallbackApi['fchmod'] = (fd: number, mode: misc.TMode, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
 
-  chmod(path: misc.PathLike, mode: misc.TMode, callback: misc.TCallback<void>): void {
+  public readonly chmod: FsCallbackApi['chmod'] = (path: misc.PathLike, mode: misc.TMode, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
 
-  lchmod(path: misc.PathLike, mode: misc.TMode, callback: misc.TCallback<void>): void {
+  public readonly lchmod: FsCallbackApi['lchmod'] = (path: misc.PathLike, mode: misc.TMode, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
 
-  fchown(fd: number, uid: number, gid: number, callback: misc.TCallback<void>): void {
+  public readonly fchown: FsCallbackApi['fchown'] = (fd: number, uid: number, gid: number, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
 
-  chown(path: misc.PathLike, uid: number, gid: number, callback: misc.TCallback<void>): void {
+  public readonly chown: FsCallbackApi['chown'] = (path: misc.PathLike, uid: number, gid: number, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
 
-  lchown(path: misc.PathLike, uid: number, gid: number, callback: misc.TCallback<void>): void {
+  public readonly lchown: FsCallbackApi['lchown'] = (path: misc.PathLike, uid: number, gid: number, callback: misc.TCallback<void>): void => {
     callback(null);
-  }
+  };
+
+  public readonly createWriteStream: FsCallbackApi['createWriteStream'] = (path: misc.PathLike, options?: opts.IWriteStreamOptions | string): FsaNodeWriteStream => {
+    const optionsObj: opts.IWriteStreamOptions = !options ? {} : typeof options === 'object' ? options : { encoding: options } as opts.IWriteStreamOptions;
+    const filename = pathToFilename(path);
+    const location = pathToLocation(filename);
+    const flags = flagsToNumber(optionsObj.flags);
+    const createIfMissing = !!(flags & FLAG.O_CREAT);
+    const handle = this.getFile(location[0], location[1], 'createWriteStream', createIfMissing);
+    return new FsaNodeWriteStream(handle, filename, optionsObj);
+  };
 
   public readonly symlink: FsCallbackApi['symlink'] = notSupported;
   public readonly link: FsCallbackApi['link'] = notSupported;
   public readonly watchFile: FsCallbackApi['watchFile'] = notSupported;
   public readonly unwatchFile: FsCallbackApi['unwatchFile'] = notSupported;
   public readonly createReadStream: FsCallbackApi['createReadStream'] = notSupported;
-  public readonly createWriteStream: FsCallbackApi['createWriteStream'] = notSupported;
   public readonly watch: FsCallbackApi['watch'] = notSupported;
 
   // --------------------------------------------------------- FsSynchronousApi
@@ -817,10 +827,10 @@ export class FsaNodeFs implements FsCallbackApi, FsSynchronousApi, FsCommonObjec
   public readonly constants = constants;
   public readonly Dirent = FsaNodeDirent;
   public readonly Stats = FsaNodeStats<any>;
+  public readonly WriteStream = FsaNodeWriteStream;
   public readonly StatFs = 0 as any;
   public readonly Dir = 0 as any;
   public readonly StatsWatcher = 0 as any;
   public readonly FSWatcher = 0 as any;
   public readonly ReadStream = 0 as any;
-  public readonly WriteStream = 0 as any;
 }

src/fsa-to-node/FsaNodeWriteStream.ts

@@ -0,0 +1,67 @@
+import {Writable} from 'stream';
+import {Defer} from 'thingies/es6/Defer';
+import type {IFileSystemFileHandle} from '../fsa/types';
+import type {IWriteStream} from '../node/types/misc';
+import type {IWriteStreamOptions} from '../node/types/options';
+
+/**
+ * This WriteStream implementation does not build on top of the `fs` module,
+ * but instead uses the lower-level `FileSystemFileHandle` interface. The reason
+ * is the different semantics in `fs` and FSA (File System Access API) write streams.
+ * 
+ * When data is written to an FSA file, a new FSA stream is created, it copies
+ * the file to a temporary swap file. After each written chunk, that swap file
+ * is closed and the original file is replaced with the swap file. This means,
+ * if WriteStream was built on top of `fs`, each chunk write would result in
+ * a file copy, write, close, rename operations, which is not what we want.
+ * 
+ * Instead this implementation hooks into the lower-level and closes the swap
+ * file only once the stream is closed. The downside is that the written data
+ * is not immediately visible to other processes (because it is written to the
+ * swap file), but that is the trade-off we have to make.
+ */
+export class FsaNodeWriteStream extends Writable implements IWriteStream {
+  protected __pending: boolean = true;
+  protected ready = new Defer<void>();
+  protected closed: boolean = false;
+
+  public constructor(protected readonly handle: Promise<IFileSystemFileHandle>, public readonly path: string, protected readonly options?: IWriteStreamOptions) {
+    super();
+    handle
+      .then(() => {
+        this.__pending = false;
+        this.ready.resolve();
+      })
+      .catch((error) => {
+        this.ready.reject(error);
+      });
+  }
+
+  // ------------------------------------------------------------- IWriteStream
+
+  public get bytesWritten(): number {
+    return 0;
+  }
+
+  public get pending(): boolean {
+    return this.__pending;
+  }
+
+  public close(): void {
+
+  }
+
+  // ----------------------------------------------------------------- Writable
+
+  _write(chunk: any, encoding: string, callback: (error?: Error | null) => void): void {
+
+  }
+
+  _writev(chunks: Array<{ chunk: any, encoding: string }>, callback: (error?: Error | null) => void): void {
+
+  }
+
+  _final(callback: (error?: Error | null) => void): void {
+
+  }
+}

src/node/types/misc.ts

@@ -94,8 +94,7 @@ export interface IReadStream extends Readable {
 export interface IWriteStream extends Writable {
   bytesWritten: number;
   path: string;
-  new (path: PathLike, options: IWriteStreamOptions);
-  open();
+  pending: boolean;
   close();
 }
 

src/node/types/options.ts

@@ -1,4 +1,4 @@
-import type { TEncodingExtended, TFlags, TMode } from './misc';
+import type { IFileHandle, TEncodingExtended, TFlags, TMode } from './misc';
 
 export interface IOptions {
   encoding?: BufferEncoding | TEncodingExtended;
@@ -72,10 +72,11 @@ export interface IReadStreamOptions {
 
 export interface IWriteStreamOptions {
   flags?: TFlags;
-  defaultEncoding?: BufferEncoding;
-  fd?: number;
+  encoding?: BufferEncoding;
+  fd?: number | IFileHandle;
   mode?: TMode;
   autoClose?: boolean;
+  emitClose?: boolean;
   start?: number;
 }
 

yarn.lock

@@ -6522,6 +6522,11 @@ text-table@~0.2.0:
   resolved "https://registry.yarnpkg.com/text-table/-/text-table-0.2.0.tgz#7f5ee823ae805207c00af2df4a84ec3fcfa570b4"
   integrity sha512-N+8UisAXDGk8PFXP4HAzVR9nbfmVJ3zYLAWiTIoqC5v5isinhr+r5uaO8+7r3BMfuNIufIsA7RdpVgacC2cSpw==
 
+thingies@^1.11.1:
+  version "1.11.1"
+  resolved "https://registry.yarnpkg.com/thingies/-/thingies-1.11.1.tgz#47a648e2b42c3bb011e493e0c99df20a2758c25d"
+  integrity sha512-SXWTuQA6TFjpfV4xiwPs4FkHashZShR/Hugosrm9sRMm63fAdgZaWKixt5YvuP6VwDaAROcDwf9cFeuw1DeekA==
+
 through2@^4.0.0:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/through2/-/through2-4.0.2.tgz#a7ce3ac2a7a8b0b966c80e7c49f0484c3b239764"