// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
// Modified by Sukka (https://skk.moe) to increase compatibility and performance with Bun.

interface TextLineStreamOptions {
  /** Allow splitting by solo \r */
  allowCR: boolean;
}

/** Transform a stream into a stream where each chunk is divided by a newline,
 * be it `\n` or `\r\n`. `\r` can be enabled via the `allowCR` option.
 *
 * ```ts
 * import { TextLineStream } from 'https://deno.land/std@$STD_VERSION/streams/text_line_stream.ts';
 * const res = await fetch('https://example.com');
 * const lines = res.body!
 *   .pipeThrough(new TextDecoderStream())
 *   .pipeThrough(new TextLineStream());
 * ```
 */
export class TextLineStream extends TransformStream<string, string> {
  private __buf = '';

  constructor(options?: TextLineStreamOptions) {
    const allowCR = options?.allowCR ?? false;

    super({
      transform: (chunk, controller) => {
        chunk = this.__buf + chunk;

        for (; ;) {
          const lfIndex = chunk.indexOf('\n');

          if (allowCR) {
            const crIndex = chunk.indexOf('\r');

            if (
              crIndex !== -1 && crIndex !== (chunk.length - 1) &&
              (lfIndex === -1 || (lfIndex - 1) > crIndex)
            ) {
              controller.enqueue(chunk.slice(0, crIndex));
              chunk = chunk.slice(crIndex + 1);
              continue;
            }
          }

          if (lfIndex !== -1) {
            let crOrLfIndex = lfIndex;
            if (chunk[lfIndex - 1] === '\r') {
              crOrLfIndex--;
            }
            controller.enqueue(chunk.slice(0, crOrLfIndex));
            chunk = chunk.slice(lfIndex + 1);
            continue;
          }

          break;
        }

        this.__buf = chunk;
      },
      flush: (controller) => {
        if (this.__buf.length > 0) {
          if (allowCR && this.__buf[this.__buf.length - 1] === '\r') {
            controller.enqueue(this.__buf.slice(0, -1));
          } else {
            controller.enqueue(this.__buf);
          };
        }
      },
    });
  }
}