Thermostat Demo

This demo illustrates how to do cross-browser realtime update.

The state is globally shared (for all connections) and the logic are maintained on the server.

In addition, the document title is dynamically generated and updated in realtime.

Interactive UIs

Target: 24.5°
24.5°
idle
Source Code of thermostat.tsx
(import statements omitted for simplicity, click to expand)
import { Link } from '../components/router.js'
import { Style } from '../components/style.js'
import { o } from '../jsx/jsx.js'
import { sessions } from '../session.js'
import { Update, UpdateIn } from '../components/update.js'
import type { ServerMessage } from '../../../client/types'
import SourceCode from '../components/source-code.js'
import { Routes, StaticPageRoute } from '../routes.js'
import type { Node } from '../jsx/types'
import { apiEndpointTitle, title } from '../../config.js'
const UpdateInterval = 1000

type Status = 'cooling' | 'heating' | 'idle'

const StatusStyles: Record<Status, string> = {
  heating: `
background: #f83;
background: linear-gradient(180deg, #f83 0%, #f54 100%);
color: white;
`.replace(/\n/g, ' '),
  cooling: `
background: #6ae;
background: linear-gradient(180deg, #6ae 0%, #17d 100%);
color: white;
`.replace(/\n/g, ' '),
  idle: `
background: #eef;
background: radial-gradient(#fff 0%, #eef 100%);
color: black;
`.replace(/\n/g, ' '),
}

class State {
  private _current = 27
  private _target = 25.5
  private _status: Status = 'idle'
  private tick = () => {
    if (this.current === this.target) {
      this.status = 'idle'
      this.timer = null
      return
    }
    if (this.current > this.target) {
      this.status = 'cooling'
      this.current -= 0.5
    } else if (this.current < this.target) {
      this.status = 'heating'
      this.current += 0.5
    }
    this.timer = setTimeout(this.tick, UpdateInterval)
  }
  private timer: NodeJS.Timeout | null = setTimeout(this.tick)
  get status() {
    return this._status
  }
  set status(value: Status) {
    if (this._status === value) return
    this._status = value
    let messages: ServerMessage[] = [
      ['update-in', '#thermostat #status', value, this.title],
      [
        'update-attrs',
        '#thermostat .outer.circle',
        {
          style: StatusStyles[value],
        },
      ],
    ]
    update(['batch', messages])
  }
  get target() {
    return this._target
  }
  set target(value: number) {
    if (this._target === value) return
    this._target = value
    update(['update-in', '#thermostat #target', value.toFixed(1), this.title])
    if (!this.timer) {
      this.timer = setTimeout(this.tick)
    }
  }
  get current() {
    return this._current
  }
  set current(value: number) {
    if (this._current === value) return
    this._current = value
    update(['update-in', '#thermostat #current', value.toFixed(1), this.title])
  }
  get targetText() {
    return this.target.toFixed(1) + '°'
  }
  get currentText() {
    return this.current.toFixed(1) + '°'
  }
  get title() {
    return title(`C: ${this.currentText} | T: ${this.targetText} | Thermostat`)
  }
}
const state = new State()

function inc() {
  state.target += 0.5
  return (
    <UpdateIn
      to="/thermostat"
      selector="#thermostat #target"
      content={state.target.toFixed(1)}
      title={state.title}
    />
  )
}

function dec() {
  state.target -= 0.5
  return (
    <UpdateIn
      to="/thermostat"
      selector="#thermostat #target"
      content={state.target.toFixed(1)}
      title={state.title}
    />
  )
}

function update(message: ServerMessage) {
  sessions.forEach(session => {
    if (session.url === '/thermostat') {
      session.ws.send(message)
    }
  })
  return <Update to="/thermostat" message={message} />
}

/* the root node is statically built at boot-time (doesn't need to be reconstructed at request-time) */
let Thermostat: Node = (
  <div id="thermostat">
    {Style(/* css */ `
#thermostat button {
  margin: 0.25em;
  font-size: larger;
}
#thermostat [data-live=redirect] {
  display: block;
}
#thermostat .title {
  width: min(72vw,72vh);
  text-align: center;
}
#thermostat .circle.outer {
  --size: min(72vw,72vh);
  background-color: #eef;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
#thermostat .circle.outer > div {
  display: flex;
  flex-direction: row;
  justify-content: center;
}
#thermostat .circle.outer > .text-container {
  font-size: 1.25em;
  padding: min(3vw,3vh);
}
#thermostat .circle.middle {
  --size: min(48vw,48vh);
  display: flex;
  flex-direction: row;
  justify-content: center;
  background-color: #eee;
  color: black;
}
#thermostat .circle.middle > div {
  display: flex;
  flex-direction: column;
  justify-content: center;
}
#thermostat .circle.middle button {
  border: none;
  width: min(12vw,12vh);
  height: min(12vw,12vh);
  margin: 0;
  background-color: transparent;
  font-size: 2em;
  cursor: pointer;
}
#thermostat .circle.middle button:hover {
  outline: 1px solid gray;
}
#thermostat .circle.inner {
  --size: min(24vw,24vh);
  background-color: white;
  display: flex;
  flex-direction: column;
  text-align: center;
  justify-content: center;
  font-size: 1.6em;
}
#thermostat .circle {
  border-radius: 100%;
  border: 1px solid black;
  width: var(--size);
  height: var(--size);
}
`)}
    <h1>Thermostat Demo</h1>
    <p>This demo illustrates how to do cross-browser realtime update.</p>
    <p>
      The state is globally shared (for all connections) and the logic are
      maintained on the server.
    </p>
    <p>
      In addition, the document title is dynamically generated and updated in
      realtime.
    </p>
    <h2 class="title">Interactive UIs</h2>
    <div class="outer circle" style={StatusStyles[state.status]}>
      <div class="text-container">
        Target:&nbsp;
        <span title="Target temperature in celsius degree">
          <span id="target">
            {
              /* this fraction is wrapped in an inline functional component to evaluate the state at request-time */
              [() => state.target.toFixed(1)]
            }
          </span>
          &deg;
        </span>
      </div>
      <div>
        <div class="middle circle">
          <div>
            <Link
              href="/thermostat/dec"
              no-history
              title="Reduce target temperature by 0.5 celsius degree"
            >
              <button>-</button>
            </Link>
          </div>
          <div>
            <div class="inner circle">
              <span title="Current temperature in celsius degree">
                <span id="current">{[() => state.current.toFixed(1)]}</span>
                &deg;
              </span>
            </div>
          </div>
          <div>
            <Link
              href="/thermostat/inc"
              no-history
              title="Increase target temperature by 0.5 celsius degree"
            >
              <button>+</button>
            </Link>
          </div>
        </div>
      </div>
      <div class="text-container">
        <span id="status" title="Current status">
          {[() => state.status]}
        </span>
      </div>
    </div>
    <SourceCode page="thermostat.tsx" />
    <p>
      <a href="https://dockyard.com/blog/2018/12/12/phoenix-liveview-interactive-real-time-apps-no-need-to-write-javascript">
        Layout reference
      </a>
    </p>
  </div>
)

function index(): StaticPageRoute {
  return {
    title: state.title,
    description: `A realtime updated thermostat demo application. Current temperature: ${state.currentText}; target temperature: ${state.targetText}.`,
    node: Thermostat,
  }
}

let routes = {
  '/thermostat': {
    resolve: index,
    menuText: 'Thermostat',
  },
  '/thermostat/inc': {
    title: apiEndpointTitle,
    description: 'increase target temperature of the demo thermostat',
    node: [inc],
    streaming: false,
  },
  '/thermostat/dec': {
    title: apiEndpointTitle,
    description: 'decrease target temperature of the demo thermostat',
    node: [dec],
    streaming: false,
  },
} satisfies Routes

export default { routes }

Layout reference