import { useCallback, useEffect, useState } from 'react'
import { api, isDesktop, message } from './bridge.js'
import { usePolled } from './hooks.js'
import * as Icon from './ui/icons.jsx'
import logo from './assets/loyaly-mark.png'
import Login from './views/Login.jsx'
import Setup from './views/Setup.jsx'
import Live from './views/Live.jsx'
import Customers from './views/Customers.jsx'
import Cameras from './views/Cameras.jsx'

// Three screens, and the trim is by AUDIENCE rather than by taste.
//
// This window runs on a PC behind a counter, and the person in front of it can
// act on exactly three things: is it working, who is this customer, and is the
// camera set up. Footfall and Sales answer a different person's questions - an
// owner comparing shops, who is not standing in one - and they now live on the
// head-office platform where a comparison across sites is even possible. A
// month-on-month chart on a shop PC was a report nobody there could act on,
// competing for the attention of somebody with a customer waiting.
//
// `cloud` marks a screen that cannot work without head office. A PC set up on
// its own hides those rather than showing a screen that can only ever fail:
// the customer record lives on the server, the cameras and what this PC is
// seeing do not.
const VIEWS = [
  { id: 'live',      label: 'Live',      Glyph: Icon.Live,   View: Live },
  { id: 'customers', label: 'Customers', Glyph: Icon.People, View: Customers, cloud: true },
  { id: 'cameras',   label: 'Cameras',   Glyph: Icon.Camera, View: Cameras },
]

export default function App() {
  const [session, setSession] = useState(null)
  const [view, setView] = useState('live')
  const [booting, setBooting] = useState(true)
  // A standalone PC can join head office later. That is the same Setup screen,
  // reached deliberately rather than because the app will not open otherwise.
  const [linking, setLinking] = useState(false)

  useEffect(() => {
    (async () => {
      try { setSession(await api.session()) } catch { setSession(null) }
      setBooting(false)
    })()
  }, [])

  if (!isDesktop()) {
    // The frontend can be served by `npm run dev` for styling work, where the
    // Go bindings do not exist. Saying so beats a blank screen and a console
    // error nobody will read.
    return (
      <div className="login"><div className="box">
        <span className="mark"><img src={logo} alt="" /></span>
        <h1>Behavision</h1>
        <p className="lead">
          This is the Behavision window running outside the app, so it has no
          connection to the recognition engine. Launch the Behavision
          application instead.
        </p>
      </div></div>
    )
  }

  if (booting) return <div className="login"><p className="note">Starting…</p></div>
  // Which shop this PC IS comes before who is standing at it. An installer on a
  // brand new counter has a code and often no account yet, and every screen
  // behind here is about a shop this PC does not have one of. Unless there is
  // no head office at all, which is the other supported answer.
  if (!session?.claimed && !session?.standalone) return <Setup onDone={setSession} />
  if (!session?.standalone && !session?.logged_in) return <Login onDone={setSession} />

  const views = VIEWS.filter(v => !v.cloud || !session.standalone)
  const Current = views.find(v => v.id === view)?.View ?? Live

  if (linking) {
    return <Setup onDone={s => { setLinking(false); setSession(s) }}
                  onCancel={() => setLinking(false)} />
  }

  return (
    <div className="shell">
      <aside className="side">
        <div className="brand">
          <span className="mark"><img src={logo} alt="" /></span>
          <div className="id">
            <h1>Behavision</h1>
            <p>{session.site_name || session.user?.client_name || 'This shop'}</p>
          </div>
        </div>
        <nav className="nav">
          {views.map(({ id, label, Glyph }) => (
            <button key={id} onClick={() => setView(id)}
                    aria-current={id === view ? 'page' : undefined}>
              <Glyph size={17} />{label}
            </button>
          ))}
        </nav>
        <EngineBox />
        <div className="who">
          {session.standalone
            ? <>
                <div className="id">
                  <b>On its own</b>
                  <span>No head office</span>
                </div>
                <button className="btn sm icon" title="Link to head office"
                        onClick={() => setLinking(true)}>
                  <Icon.Link size={15} />
                </button>
              </>
            : <>
                <div className="id">
                  <b>Signed in</b>
                  <span>{session.user?.email}</span>
                </div>
                <button className="btn sm icon" title="Sign out"
                        onClick={async () => setSession(await api.logout())}>
                  <Icon.Logout size={15} />
                </button>
              </>}
        </div>
      </aside>
      <main className="main"><Current session={session} /></main>
    </div>
  )
}

// Always visible, because "is recognition actually running" is the question
// behind every other screen — an empty Live page means something completely
// different depending on the answer.
function EngineBox() {
  const { data, reload } = usePolled(() => api.engineStatus(), 5000)
  const [busy, setBusy] = useState(false)
  const s = data ?? { state: 'stopped' }

  const act = useCallback(async fn => {
    setBusy(true)
    try { await fn() } catch (e) { alert(message(e)) }
    finally { setBusy(false); reload() }
  }, [reload])

  const running = s.state === 'running'
  const cams = Object.values(s.cameras ?? {})
  const up = cams.filter(Boolean).length

  let tone = 'idle', text = 'Stopped'
  // Reachable but not ours: somebody started the engine outside this app, or a
  // previous copy is still up. Saying "Stopped" beside live camera feeds is the
  // two-surfaces-disagreeing bug the tray exists to avoid - and it is exactly
  // what this panel showed while recognition was visibly running.
  if (!running && s.reachable) { tone = 'warn'; text = 'Running outside the app' }
  else if (s.state === 'failed' || s.state === 'backoff') { tone = 'bad'; text = 'Not running' }
  else if (running && !s.reachable) { tone = 'warn'; text = 'Starting…' }
  else if (running && cams.length === 0) { tone = 'warn'; text = 'No cameras' }
  else if (running && up === 0) { tone = 'bad'; text = 'No camera connected' }
  else if (running && up < cams.length) { tone = 'warn'; text = `${up} of ${cams.length} cameras` }
  else if (running) { tone = 'ok'; text = `Watching ${up} camera${up === 1 ? '' : 's'}` }

  return (
    <div className="enginebox">
      <div className="row">
        <i className={`dot ${tone === 'ok' ? 'live' : tone}`} />
        <span className="state">{text}</span>
      </div>
      {s.recognition_model && <span className="label">{s.recognition_model}</span>}
      {s.error && <span className="label" style={{ color: 'var(--bad)' }}>{s.error}</span>}
      <div className="actions">
        <button className="btn sm" disabled={busy || running || s.reachable}
                onClick={() => act(api.startEngine)}>
          <Icon.Play size={13} />Start
        </button>
        <button className="btn sm" disabled={busy || !running}
                onClick={() => act(api.stopEngine)}>
          <Icon.Stop size={13} />Stop
        </button>
      </div>
    </div>
  )
}