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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
import { createLPS } from "./_common.ts";
/** Transform a stream into a stream where each chunk is divided by a given delimiter. * * ```ts * import { TextDelimiterStream } from "https://deno.land/std@$STD_VERSION/streams/text_delimiter_stream.ts"; * const res = await fetch("https://example.com"); * const parts = res.body! *   .pipeThrough(new TextDecoderStream()) *   .pipeThrough(new TextDelimiterStream("foo")); * ``` */export class TextDelimiterStream extends TransformStream<string, string> {  #buf = "";  #delimiter: string;  #inspectIndex = 0;  #matchIndex = 0;  #delimLPS: Uint8Array;
  constructor(delimiter: string) {    super({      transform: (chunk, controller) => {        this.#handle(chunk, controller);      },      flush: (controller) => {        controller.enqueue(this.#buf);      },    });
    this.#delimiter = delimiter;    this.#delimLPS = createLPS(new TextEncoder().encode(delimiter));  }
  #handle(    chunk: string,    controller: TransformStreamDefaultController<string>,  ) {    this.#buf += chunk;    let localIndex = 0;    while (this.#inspectIndex < this.#buf.length) {      if (chunk[localIndex] === this.#delimiter[this.#matchIndex]) {        this.#inspectIndex++;        localIndex++;        this.#matchIndex++;        if (this.#matchIndex === this.#delimiter.length) {          // Full match          const matchEnd = this.#inspectIndex - this.#delimiter.length;          const readyString = this.#buf.slice(0, matchEnd);          controller.enqueue(readyString);          // Reset match, different from KMP.          this.#buf = this.#buf.slice(this.#inspectIndex);          this.#inspectIndex = 0;          this.#matchIndex = 0;        }      } else {        if (this.#matchIndex === 0) {          this.#inspectIndex++;          localIndex++;        } else {          this.#matchIndex = this.#delimLPS[this.#matchIndex - 1];        }      }    }  }}