blockscout/apps/block_scout_web/assets/js/pages/blocks.js

import $ from 'jquery'
import _ from 'lodash'
import URI from 'urijs'
import humps from 'humps'
import socket from '../socket'
import { createStore, connectElements, listMorph } from '../utils'

export const initialState = {
  channelDisconnected: false,

  blocks: [],

  beyondPageOne: null
}

export const reducer = withMissingBlocks(baseReducer)

function baseReducer (state = initialState, action) {
  switch (action.type) {
    case 'PAGE_LOAD':
    case 'ELEMENTS_LOAD': {
      return Object.assign({}, state, _.omit(action, 'type'))
    }
    case 'CHANNEL_DISCONNECTED': {
      return Object.assign({}, state, {
        channelDisconnected: true
      })
    }
    case 'RECEIVED_NEW_BLOCK': {
      if (state.channelDisconnected || state.beyondPageOne) return state

      return Object.assign({}, state, {
        blocks: [
          action.msg,
          ...state.blocks
        ]
      })
    }
    default:
      return state
  }
}

function withMissingBlocks (reducer) {
  return (...args) => {
    const result = reducer(...args)

    if (result.blocks.length < 2) return result

    const maxBlock = _.first(result.blocks).blockNumber
    const minBlock = _.last(result.blocks).blockNumber

    return Object.assign({}, result, {
      blocks: _.rangeRight(minBlock, maxBlock + 1)
        .map((blockNumber) => _.find(result.blocks, ['blockNumber', blockNumber]) || {
          blockNumber,
          blockHtml: placeHolderBlock(blockNumber)
        })
    })
  }
}

const elements = {
  '[data-selector="channel-disconnected-message"]': {
    render ($el, state) {
      if (state.channelDisconnected) $el.show()
    }
  },
  '[data-selector="blocks-list"]': {
    load ($el) {
      return {
        blocks: $el.children().map((index, el) => ({
          blockNumber: parseInt(el.dataset.blockNumber),
          blockHtml: el.outerHTML
        })).toArray()
      }
    },
    render ($el, state, oldState) {
      if (oldState.blocks === state.blocks) return
      const container = $el[0]
      const newElements = _.map(state.blocks, ({ blockHtml }) => $(blockHtml)[0])
      listMorph(container, newElements, { key: 'dataset.blockNumber' })
    }
  }
}

const $blockListPage = $('[data-page="block-list"]')
if ($blockListPage.length) {
  const store = createStore(reducer)
  store.dispatch({
    type: 'PAGE_LOAD',
    beyondPageOne: !!humps.camelizeKeys(URI(window.location).query(true)).blockNumber
  })
  connectElements({ store, elements })

  const blocksChannel = socket.channel(`blocks:new_block`, {})
  blocksChannel.join()
  blocksChannel.onError(() => store.dispatch({
    type: 'CHANNEL_DISCONNECTED'
  }))
  blocksChannel.on('new_block', (msg) => store.dispatch({
    type: 'RECEIVED_NEW_BLOCK',
    msg: humps.camelizeKeys(msg)
  }))
}

function placeHolderBlock (blockNumber) {
  return `
    <div class="my-3" style="height: 98px;" data-selector="place-holder" data-block-number="${blockNumber}">
      <div
        class="tile tile-type-block d-flex align-items-center fade-up"
        style="height: 98px;"
      >
        <span class="loading-spinner-small ml-1 mr-4">
          <span class="loading-spinner-block-1"></span>
          <span class="loading-spinner-block-2"></span>
        </span>
        <div>
          <div class="tile-title">${blockNumber}</div>
          <div>${window.localized['Block Processing']}</div>
        </div>
      </div>
    </div>
  `
}