knowyt/client/src/plugins/engine.js

export default (context, inject) => {
  const { store, $axios } = context

  const engine = {
    lastFetched: [0, 0, 0, 0, 0],
    start() {
      this.fetchUpdate()
    },
    async fetchUpdate() {
      let delay = 0
      try {
        const response = await $axios.get('http://localhost:3000/api/sync?v=' + (store.state.engine.version + 1))
        const json = response.data
        store.commit('engine/setJson', json)
      } catch (e) {
        const { status, statusText } = e.response
        if (status >= 500) {
          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)
    },

  }
  inject('engine', engine)
}