import buildUrl from 'build-url'

export default (context, inject) => {
  const engine = {
    context,
    lastFetched: [0, 0, 0, 0, 0],
    isActive: false,
    shouldStop: false,

    async start() {
      const { store, redirect } = this.context
      if (!store.state.engine.user) {
        if (!await this.fetchUserInfo()) {
          redirect('/')
        }
      }
      if (this.isActive) {
        console.warn('attempt to start already running engine!')
        return
      }

      this.isActive = true
      this.fetchUpdate()
    },

    stop() {
      if (!this.isActive) return
      this.shouldStop = true
    },

    async fetchUpdate() {
      const { store, $axios, $config } = this.context

      if (this.shouldStop || !this.isActive) {
        this.isActive = false
        this.shouldStop = false
        return
      }

      let delay = 0
      try {
        const url = buildUrl($config.serverBaseUrl, {
          path: '/api/sync',
          queryParams: {
            v: store.state.engine.version + 1,
            g: store.state.engine.user?.game,
          },
        })
        const response = await $axios.get(url)
        store.commit('engine/setJson', response.data)
      } catch (e) {
        const { status, statusText } = e.response
        if (status != 200) {
          console.warn(`HTTP ${status} ${statusText}`)
          delay = 5000
          store.commit('engine/setVersion', -1)
        }
      }

      const now = new Date().getTime()
      const last = this.lastFetched.splice(0, 1)
      this.lastFetched.push(now)

      if (now - last < 1000) {
        console.warn('engine: respawning too fast, throttling down')
        delay = 5000
      }
      window.setTimeout(() => {
        this.fetchUpdate()
      }, delay)
    },

    async fetchUserInfo() {
      const { store, $axios } = this.context

      try {
        const response = await $axios.get('/api/userinfo')
        store.commit('engine/setUser', response.data)
      } catch(e) {
        store.commit('engine/setUser', undefined)
        return false
      }

      return true
    },
  }
  
  inject('engine', engine)
}