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

const PROTOCOL = 'origin-hybrid-bridge/v1'

class HyperP2POriginHybridBridge extends EventEmitter {
  constructor (opts = {}) {
    super()
    this._origins = new Map()
    this._stats = { originBytes: 0, p2pBytes: 0 }
  }

  registerOrigin (streamId, url, weight = 1) {
    const sid = assertStreamId(streamId)
    if (!url) throw new Error('url required')
    const list = this._origins.get(sid) || []
    list.push({ url: String(url), weight: Math.max(0, weight), at: Date.now() })
    list.sort((a, b) => b.weight - a.weight)
    this._origins.set(sid, list)
    return list[0]
  }

  selectOrigin (streamId) {
    const list = this._origins.get(assertStreamId(streamId))
    return list && list.length ? list[0] : null
  }

  recordPull (bytes, via = 'origin') {
    const n = Math.max(0, bytes | 0)
    if (via === 'p2p') this._stats.p2pBytes += n
    else this._stats.originBytes += n
    this.emit('pull', { bytes: n, via })
    return n
  }

  p2pOffloadRatio () {
    const total = this._stats.originBytes + this._stats.p2pBytes
    if (!total) return 0
    return this._stats.p2pBytes / total
  }

  shouldFallbackP2P (coverage) {
    return coverage < 0.85
  }

  listOrigins (streamId) {
    return [...(this._origins.get(assertStreamId(streamId)) || [])]
  }

  removeOrigin (streamId, url) {
    const sid = assertStreamId(streamId)
    const list = this._origins.get(sid)
    if (!list) return false
    const idx = list.findIndex((o) => o.url === url)
    if (idx < 0) return false
    list.splice(idx, 1)
    if (!list.length) this._origins.delete(sid)
    return true
  }

  listStreamIds () {
    return [...this._origins.keys()]
  }

  weightedSelect (streamId) {
    const list = this._origins.get(assertStreamId(streamId))
    if (!list || !list.length) return null
    const total = list.reduce((s, o) => s + o.weight, 0)
    let r = Math.random() * total
    for (const o of list) {
      r -= o.weight
      if (r <= 0) return o
    }
    return list[0]
  }

  totalBytes () {
    return this._stats.originBytes + this._stats.p2pBytes
  }

  getStats () {
    return mediaStats(this._stats, PROTOCOL, {
      offloadRatio: this.p2pOffloadRatio(),
      streams: this._origins.size
    })
  }

  async ready () { return this }

  async close () {
    this._origins.clear()
    this.emit('closed')
  }
}

module.exports = { HyperP2POriginHybridBridge, PROTOCOL }