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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { createLPS } from "./_common.ts";
import type {  DelimiterDisposition,  DelimiterStreamOptions,} from "./delimiter_stream.ts";
/** * Transform a stream into a stream where each chunk is divided by a given delimiter. * * @example * ```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;  #disp: DelimiterDisposition;
  /** Constructs a new instance. */  constructor(delimiter: string, options?: DelimiterStreamOptions) {    super({      transform: (chunk, controller) => {        this.#handle(chunk, controller);      },      flush: (controller) => {        controller.enqueue(this.#buf);      },    });
    this.#delimiter = delimiter;    this.#delimLPS = createLPS(new TextEncoder().encode(delimiter));    this.#disp = options?.disposition ?? "discard";  }
  #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 start = this.#inspectIndex - this.#delimiter.length;          const end = this.#disp === "suffix" ? this.#inspectIndex : start;          const copy = this.#buf.slice(0, end);          controller.enqueue(copy);          const shift = this.#disp === "prefix" ? start : this.#inspectIndex;          this.#buf = this.#buf.slice(shift);          this.#inspectIndex = this.#disp === "prefix"            ? this.#delimiter.length            : 0;          this.#matchIndex = 0;        }      } else {        if (this.#matchIndex === 0) {          this.#inspectIndex++;          localIndex++;        } else {          this.#matchIndex = this.#delimLPS[this.#matchIndex - 1]!;        }      }    }  }}