1'use strict'
2
3const MinipassPipeline = require('minipass-pipeline')
4
5class CachingMinipassPipeline extends MinipassPipeline {
6  #events = []
7  #data = new Map()
8
9  constructor (opts, ...streams) {
10    // CRITICAL: do NOT pass the streams to the call to super(), this will start
11    // the flow of data and potentially cause the events we need to catch to emit
12    // before we've finished our own setup. instead we call super() with no args,
13    // finish our setup, and then push the streams into ourselves to start the
14    // data flow
15    super()
16    this.#events = opts.events
17
18    /* istanbul ignore next - coverage disabled because this is pointless to test here */
19    if (streams.length) {
20      this.push(...streams)
21    }
22  }
23
24  on (event, handler) {
25    if (this.#events.includes(event) && this.#data.has(event)) {
26      return handler(...this.#data.get(event))
27    }
28
29    return super.on(event, handler)
30  }
31
32  emit (event, ...data) {
33    if (this.#events.includes(event)) {
34      this.#data.set(event, data)
35    }
36
37    return super.emit(event, ...data)
38  }
39}
40
41module.exports = CachingMinipassPipeline
42