export class BenchmarkSuite {
  constructor() {
    this.state = 'initialized'
    this.cases = new CasesIterator([])
    this.reset()
    this.onChange = () => {}
  }

  reset() {
    this.cases.reset()
    this.stats = this.cases.getInitialStats()
  }

  setBenchmarkType(benchmarktype) {
    this.benchmarktype = benchmarktype
    this.onChange()
  }

  setCases(cases) {
    this.cases = new CasesIterator(cases)
    this.stats = this.cases.getInitialStats()
    this.onChange()
  }

  addStat(name, val) {
    this.stats[name] = [...this.stats[name], val]
  }

  async measureNext() {
    let currentCase = this.cases.next()
    this.benchmarktype.setCase(currentCase)
    this.addStat(currentCase.name, await this.benchmarktype.run())
  }

  async run() {
    while (this.state === 'running' && this.cases.hasNext()) {
      await this.measureNext()
      this.onChange()
      await freeEventLoop()
    }

    switch (this.state) {
      case 'running':
        this.state = 'finished'
        break
      case 'stop_requested':
        this.reset()
        this.state = 'initialized'
        break
      case 'pause_requested':
        this.state = this.cases.hasNext() ? 'paused' : 'finished'
        break
    }
    this.onChange()
  }

  start() {
    this.state = 'running'
    this.run()
  }

  pause() {
    this.state = 'pause_requested'
  }

  stop() {
    this.state = 'stop_requested'
    this.run()
  }
}

/**
 * Promise that uses setTimeout to resolve.
 * This is a hack to free the eventloop from microtasks.
 * Without this rendering blocks during benchmarks.
 */
async function freeEventLoop() {
  return new Promise(resolve => setTimeout(resolve, 0))
}

class CasesIterator {
  constructor(cases) {
    this.cases = cases
    this.idx = -1
  }

  current() {
    return this.cases[this.idx]
  }

  hasNext() {
    return this.idx + 1 < this.cases.length
  }

  next() {
    this.idx = this.idx + 1
    return this.idx < this.cases.length ? this.current() : null
  }

  reset() {
    this.idx = -1
  }

  getInitialStats() {
    let stats = {}
    for (let c of this.cases) {
      stats[c.name] = []
    }
    return stats
  }
}