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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.import {  convertRowToObject,  defaultReadOptions,  type LineReader,  parseRecord,  type RowType,} from "../csv/_io.ts";import { TextDelimiterStream } from "../streams/text_delimiter_stream.ts";
export interface CsvStreamOptions {  separator?: string;  comment?: string;  skipFirstRow?: boolean;  columns?: string[];}
class StreamLineReader implements LineReader {  #reader: ReadableStreamDefaultReader<string>;  #done = false;  constructor(reader: ReadableStreamDefaultReader<string>) {    this.#reader = reader;  }
  async readLine(): Promise<string | null> {    const { value, done } = await this.#reader.read();    if (done) {      this.#done = true;      return null;    } else {      // NOTE: Remove trailing CR for compatibility with golang's `encoding/csv`      return stripLastCR(value!);    }  }
  isEOF(): Promise<boolean> {    return Promise.resolve(this.#done);  }
  cancel() {    this.#reader.cancel();  }}
function stripLastCR(s: string): string {  return s.endsWith("\r") ? s.slice(0, -1) : s;}
export class CsvStream<T extends CsvStreamOptions>  implements TransformStream<string, RowType<CsvStreamOptions, T>> {  readonly #readable: ReadableStream<    string[] | Record<string, string | unknown>  >;  readonly #options: CsvStreamOptions;  readonly #lineReader: StreamLineReader;  readonly #lines: TextDelimiterStream;  #lineIndex = 0;  #isFirstRow = true;
  #headers: string[] = [];
  constructor(options: T = defaultReadOptions as T) {    this.#options = {      ...defaultReadOptions,      ...options,    };
    this.#lines = new TextDelimiterStream("\n");    this.#lineReader = new StreamLineReader(this.#lines.readable.getReader());    this.#readable = new ReadableStream({      pull: (controller) => this.#pull(controller),      cancel: () => this.#lineReader.cancel(),    });  }
  async #pull(    controller: ReadableStreamDefaultController<      string[] | Record<string, string | unknown>    >,  ): Promise<void> {    const line = await this.#lineReader.readLine();    if (line === "") {      // Found an empty line      this.#lineIndex++;      return this.#pull(controller);    }    if (line === null) {      // Reached to EOF      controller.close();      this.#lineReader.cancel();      return;    }
    const record = await parseRecord(      line,      this.#lineReader,      this.#options,      this.#lineIndex,    );    if (record === null) {      controller.close();      this.#lineReader.cancel();      return;    }
    if (this.#isFirstRow) {      this.#isFirstRow = false;      if (this.#options.skipFirstRow || this.#options.columns) {        this.#headers = [];
        if (this.#options.skipFirstRow) {          const head = record;          this.#headers = head;        }
        if (this.#options.columns) {          this.#headers = this.#options.columns;        }      }
      if (this.#options.skipFirstRow) {        return this.#pull(controller);      }    }
    this.#lineIndex++;    if (record.length > 0) {      if (this.#options.skipFirstRow || this.#options.columns) {        controller.enqueue(convertRowToObject(          record,          this.#headers,          this.#lineIndex,        ));      } else {        controller.enqueue(record);      }    } else {      return this.#pull(controller);    }  }
  get readable() {    return this.#readable as ReadableStream<RowType<CsvStreamOptions, T>>;  }
  get writable(): WritableStream<string> {    return this.#lines.writable;  }}