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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
const NEWLINE_REGEXP = /\r\n|\r|\n/;const encoder = new TextEncoder();
/** * Represents a message in the Server-Sent Event (SSE) protocol. * * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#fields} */export interface ServerSentEventMessage {  /** Ignored by the client. */  comment?: string;  /** A string identifying the type of event described. */  event?: string;  /** The data field for the message. Split by new lines. */  data?: string;  /** The event ID to set the {@linkcode EventSource} object's last event ID value. */  id?: string | number;  /** The reconnection time. */  retry?: number;}
function assertHasNoNewline(value: string, varName: string) {  if (value.match(NEWLINE_REGEXP) !== null) {    throw new RangeError(`${varName} cannot contain a newline`);  }}
/** * Converts a server-sent message object into a string for the client. * * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#event_stream_format} */function stringify(message: ServerSentEventMessage): Uint8Array {  const lines = [];  if (message.comment) {    assertHasNoNewline(message.comment, "`message.comment`");    lines.push(`:${message.comment}`);  }  if (message.event) {    assertHasNoNewline(message.event, "`message.event`");    lines.push(`event:${message.event}`);  }  if (message.data) {    message.data.split(NEWLINE_REGEXP).forEach((line) =>      lines.push(`data:${line}`)    );  }  if (message.id) {    assertHasNoNewline(message.id.toString(), "`message.id`");    lines.push(`id:${message.id}`);  }  if (message.retry) lines.push(`retry:${message.retry}`);  return encoder.encode(lines.join("\n") + "\n\n");}
/** * Transforms server-sent message objects into strings for the client. * * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events} * * @example * ```ts * import { *   type ServerSentEventMessage, *   ServerSentEventStream, * } from "https://deno.land/std@$STD_VERSION/http/server_sent_event_stream.ts"; * * const stream = ReadableStream.from<ServerSentEventMessage>([ *   { data: "hello there" } * ]).pipeThrough(new ServerSentEventStream()); * new Response(stream, { *   headers: { *     "content-type": "text/event-stream", *     "cache-control": "no-cache", *   }, * }); * ``` */export class ServerSentEventStream  extends TransformStream<ServerSentEventMessage, Uint8Array> {  constructor() {    super({      transform: (message, controller) => {        controller.enqueue(stringify(message));      },    });  }}