import type {EventSourceParser, ParsedEvent} from './types.js'
import {createParser} from './parse.js'

/**
 * A TransformStream that ingests a stream of strings and produces a stream of ParsedEvents.
 *
 * @example
 * ```
 * const eventStream =
 *   response.body
 *     .pipeThrough(new TextDecoderStream())
 *     .pipeThrough(new EventSourceParserStream())
 * ```
 * @public
 */
export class EventSourceParserStream extends TransformStream<string, ParsedEvent> {
  constructor() {
    let parser!: EventSourceParser

    super({
      start(controller) {
        parser = createParser((event) => {
          if (event.type === 'event') {
            controller.enqueue(event)
          }
        })
      },
      transform(chunk) {
        parser.feed(chunk)
      },
    })
  }
}

export type {ParsedEvent} from './types.js'