require('bare-process/global')
const EventEmitter = require('bare-events')
const { CHUNK_TYPES, mediaStats } = require('../../_shared/media-streaming-base.js')

const PROTOCOL = 'chunk-scheduler-media/v1'

const PRIORITY = {
  [CHUNK_TYPES.KEYFRAME]: 100,
  [CHUNK_TYPES.BASE]: 80,
  [CHUNK_TYPES.AUDIO]: 70,
  [CHUNK_TYPES.ENHANCEMENT]: 50,
  [CHUNK_TYPES.DELTA]: 40
}

class HyperP2PChunkSchedulerMedia extends EventEmitter {
  constructor (opts = {}) {
    super()
    this._queue = []
    this._stats = { enqueued: 0, scheduled: 0 }
  }

  enqueue (chunk, priority = null) {
    if (!chunk || chunk.seq == null) throw new Error('chunk with seq required')
    const p = priority != null ? priority : (PRIORITY[chunk.type] ?? 30)
    const entry = { chunk, priority: p, enqueuedAt: Date.now() }
    this._queue.push(entry)
    this._stats.enqueued++
    this._sort()
    this.emit('enqueue', entry)
    return entry
  }

  _sort () {
    this._queue.sort((a, b) => b.priority - a.priority || a.chunk.seq - b.chunk.seq)
  }

  nextChunks (limit = 8) {
    const out = this._queue.splice(0, Math.max(0, limit | 0))
    this._stats.scheduled += out.length
    if (out.length) this.emit('schedule', { count: out.length })
    return out.map((e) => e.chunk)
  }

  prioritizeKeyframes () {
    for (const e of this._queue) {
      if (e.chunk.type === CHUNK_TYPES.KEYFRAME || e.chunk.keyframe) {
        e.priority = PRIORITY[CHUNK_TYPES.KEYFRAME]
      }
    }
    this._sort()
    return this._queue.length
  }

  schedulePlan () {
    const plan = { keyframes: 0, audio: 0, enhancement: 0, other: 0 }
    for (const e of this._queue) {
      if (e.chunk.type === CHUNK_TYPES.KEYFRAME) plan.keyframes++
      else if (e.chunk.type === CHUNK_TYPES.AUDIO) plan.audio++
      else if (e.chunk.type === CHUNK_TYPES.ENHANCEMENT) plan.enhancement++
      else plan.other++
    }
    return plan
  }

  pendingCount () { return this._queue.length }

  peek (n = 5) {
    return this._queue.slice(0, Math.max(0, n | 0)).map((e) => e.chunk)
  }

  dequeueSeq (seq) {
    const idx = this._queue.findIndex((e) => e.chunk.seq === seq)
    if (idx < 0) return null
    const [entry] = this._queue.splice(idx, 1)
    this._stats.scheduled++
    return entry.chunk
  }

  boostType (type, amount = 20) {
    for (const e of this._queue) {
      if (e.chunk.type === type) e.priority += amount
    }
    this._sort()
    return this._queue.length
  }

  enqueueBatch (chunks) {
    if (!Array.isArray(chunks)) throw new Error('chunks must be an array')
    return chunks.map((c) => this.enqueue(c.chunk || c, c.priority))
  }

  dropBelowPriority (minPriority) {
    const before = this._queue.length
    this._queue = this._queue.filter((e) => e.priority >= minPriority)
    return before - this._queue.length
  }

  clear () {
    const n = this._queue.length
    this._queue = []
    return n
  }

  getStats () {
    return mediaStats(this._stats, PROTOCOL, { pending: this._queue.length })
  }

  async ready () { return this }

  async close () {
    this._queue = []
    this.emit('closed')
  }
}

module.exports = { HyperP2PChunkSchedulerMedia, PROTOCOL }