111 lines
3.3 KiB
TypeScript
111 lines
3.3 KiB
TypeScript
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/**
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* Represents a streaming response from a Rust bridge command.
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* Implements AsyncIterable to allow `for await...of` consumption of chunks,
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* and exposes `.result` for the final response once the stream ends.
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*
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* @typeParam TChunk - Type of each streamed chunk
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* @typeParam TResult - Type of the final result
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*/
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export class StreamingResponse<TChunk, TResult> implements AsyncIterable<TChunk> {
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/** Resolves with the final result when the stream ends successfully. */
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public readonly result: Promise<TResult>;
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private resolveResult!: (value: TResult) => void;
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private rejectResult!: (error: Error) => void;
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/** Buffered chunks not yet consumed by the iterator. */
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private buffer: TChunk[] = [];
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/** Waiting consumer resolve callback (when iterator is ahead of producer). */
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private waiting: ((value: IteratorResult<TChunk>) => void) | null = null;
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/** Waiting consumer reject callback. */
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private waitingReject: ((error: Error) => void) | null = null;
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private done = false;
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private error: Error | null = null;
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constructor() {
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this.result = new Promise<TResult>((resolve, reject) => {
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this.resolveResult = resolve;
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this.rejectResult = reject;
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});
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}
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/**
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* Push a chunk into the stream. Called internally by RustBridge.
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*/
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public pushChunk(chunk: TChunk): void {
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if (this.done) return;
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if (this.waiting) {
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// A consumer is waiting — deliver immediately
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const resolve = this.waiting;
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this.waiting = null;
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this.waitingReject = null;
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resolve({ value: chunk, done: false });
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} else {
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// No consumer waiting — buffer the chunk
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this.buffer.push(chunk);
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}
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}
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/**
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* End the stream successfully with a final result. Called internally by RustBridge.
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*/
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public finish(result: TResult): void {
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if (this.done) return;
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this.done = true;
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this.resolveResult(result);
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// If a consumer is waiting, signal end of iteration
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if (this.waiting) {
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const resolve = this.waiting;
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this.waiting = null;
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this.waitingReject = null;
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resolve({ value: undefined as any, done: true });
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}
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}
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/**
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* End the stream with an error. Called internally by RustBridge.
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*/
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public fail(error: Error): void {
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if (this.done) return;
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this.done = true;
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this.error = error;
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this.rejectResult(error);
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// If a consumer is waiting, reject it
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if (this.waitingReject) {
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const reject = this.waitingReject;
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this.waiting = null;
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this.waitingReject = null;
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reject(error);
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}
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}
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[Symbol.asyncIterator](): AsyncIterator<TChunk> {
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return {
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next: (): Promise<IteratorResult<TChunk>> => {
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// If there are buffered chunks, deliver one
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if (this.buffer.length > 0) {
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return Promise.resolve({ value: this.buffer.shift()!, done: false });
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}
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// If the stream is done, signal end
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if (this.done) {
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if (this.error) {
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return Promise.reject(this.error);
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}
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return Promise.resolve({ value: undefined as any, done: true });
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}
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// No buffered chunks and not done — wait for the next push
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return new Promise<IteratorResult<TChunk>>((resolve, reject) => {
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this.waiting = resolve;
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this.waitingReject = reject;
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});
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},
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};
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}
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}
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