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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.import { stringify } from "./stringify.ts";
export interface CsvStringifyStreamOptions {  /**   * Delimiter used to separate values.   *   * @default {","}   */  readonly separator?: string;
  /**   * A list of columns to be included in the output.   *   * If you want to stream objects, this option is required.   */  readonly columns?: Array<string>;}
/** * Convert each chunk to a CSV record. * * @example * ```ts * import { CsvStringifyStream } from "https://deno.land/std@$STD_VERSION/csv/csv_stringify_stream.ts"; * import { readableStreamFromIterable } from "https://deno.land/std@$STD_VERSION/streams/readable_stream_from_iterable.ts"; * * const file = await Deno.open("data.csv", { create: true, write: true }); * const readable = readableStreamFromIterable([ *   { id: 1, name: "one" }, *   { id: 2, name: "two" }, *   { id: 3, name: "three" }, * ]); * * await readable *   .pipeThrough(new CsvStringifyStream({ columns: ["id", "name"] })) *   .pipeThrough(new TextEncoderStream()) *   .pipeTo(file.writable); * ```` */export class CsvStringifyStream<TOptions extends CsvStringifyStreamOptions>  extends TransformStream<    TOptions["columns"] extends Array<string> ? Record<string, unknown>      : Array<unknown>,    string  > {  constructor(options?: TOptions) {    const {      separator,      columns = [],    } = options ?? {};
    super(      {        start(controller) {          if (columns && columns.length > 0) {            try {              controller.enqueue(                stringify([columns], { separator, headers: false }),              );            } catch (error) {              controller.error(error);            }          }        },        transform(chunk, controller) {          try {            controller.enqueue(              stringify([chunk], { separator, headers: false, columns }),            );          } catch (error) {            controller.error(error);          }        },      },    );  }}