import { useEffect, useRef, useState } from 'react'
import { api, streamArrivals } from '../api.js'
import { ago, Loading, Problem } from './Sites.jsx'
import Shot from './Shot.jsx'

// Who just walked in, pushed as it happens.
//
// The list is capped rather than unbounded: this screen is left open on a wall
// display for days, and an ever-growing array of arrivals — each holding an
// image URL — is a tab that eventually falls over. Older arrivals are in the
// reports; this view is about the last few minutes.
const KEEP = 60

export default function Live() {
  const [arrivals, setArrivals] = useState([])
  const [status, setStatus] = useState('connecting')
  const [error, setError] = useState(null)
  const seen = useRef(new Set())

  useEffect(() => {
    const ac = new AbortController()
    let stop = () => {}

    ;(async () => {
      try {
        // One poll for the recent window, so the screen is never blank while
        // waiting for the next person to walk through a door.
        const page = await api.arrivals({ limit: 30 })
        const rows = page.arrivals || []
        rows.forEach(a => seen.current.add(a.visit_id))
        setArrivals(rows.slice().reverse())
        setStatus('live')

        stop = streamArrivals({
          cursor: page.cursor,
          signal: ac.signal,
          onPage: (p) => {
            const fresh = (p.arrivals || []).filter(a => !seen.current.has(a.visit_id))
            if (!fresh.length) return
            fresh.forEach(a => seen.current.add(a.visit_id))
            setStatus('live')
            // Newest first on screen; the feed delivers oldest first.
            setArrivals(prev => [...fresh.reverse(), ...prev].slice(0, KEEP))
          },
          onError: () => setStatus('reconnecting'),
        })
      } catch (err) {
        setError(err)
      }
    })()

    return () => { ac.abort(); stop() }
  }, [])

  if (error) return <Problem error={error} />
  if (status === 'connecting' && !arrivals.length) return <Loading />

  return (
    <>
      <header className="head">
        <h1>Live</h1>
        <p className="sub">
          <span className={'dot ' + (status === 'live' ? 'ok' : 'warn')} aria-hidden="true" />
          {status === 'live' ? 'Connected' : 'Reconnecting…'}
          {' · '}last {KEEP} arrivals
        </p>
      </header>

      {arrivals.length === 0 ? (
        <div className="state">
          <h2>Nobody yet</h2>
          <p className="sub">
            Arrivals appear here the moment a camera recognises someone.
          </p>
        </div>
      ) : (
        <ul className="arrivals">
          {arrivals.map(a => <Arrival key={a.visit_id} a={a} />)}
        </ul>
      )}
    </>
  )
}

function Arrival({ a }) {
  const name = a.name || a.label || 'Unidentified'
  return (
    <li className="card arrival">
      <Face image={a.image} name={name} customerRef={a.visitor_ref} />
      <div className="who-col">
        <strong>{name}</strong>
        <span className="sub">
          {/* Only beside a name somebody typed. The auto label already IS the
              number, so "Visitor 13 · V-13" would read as two identifiers for
              one person. */}
          {a.name && a.visitor_ref ? `${a.visitor_ref} · ` : ''}
          {a.site}{a.camera_id ? ` · ${a.camera_id}` : ''} · {ago(a.occurred_at)}
        </span>
        {a.attributes && <Attributes attrs={a.attributes} />}
      </div>
      {a.is_new_visitor
        ? <span className="pill new">New</span>
        : <span className="pill">Returning</span>}
    </li>
  )
}

// Photos are off unless a shop turns them on, so "no photo" is the ordinary
// case. Initials, never an error state — a screen full of red for a system
// working exactly as configured teaches people to ignore it.
//
// The picture goes through Shot rather than a bare <img> because a face can
// now come from either of two places: a presigned link to object storage, or
// this server's own database on a deployment with no bucket. The second cannot
// be loaded by an <img> at all — it needs the session — so a plain src here
// showed a broken image on exactly the deployments that had just started
// storing photos.
// customerRef, not `ref`: React reserves that prop name, so it would never
// reach this component's props.
function Face({ image, name, customerRef }) {
  if (image?.available) {
    return <span className="face"><Shot image={image} alt="" /></span>
  }
  return (
    <span className="face initials" title={image?.reason || ''} aria-hidden="true">
      {avatarText(name, customerRef)}
    </span>
  )
}

// What goes in the circle when there is no photograph.
//
// Initials of a name a human typed; the NUMBER for a customer the system named
// itself. Running initials() over "Visitor 13" takes the first letter of each
// word and produces "V1" - which is also what "Visitor 10" and "Visitor 15"
// produce, so three different people wore the same badge, and it read as the
// V-1 reference for a fourth. Found by opening the page: every unit test here
// passes a human name.
function avatarText(name, customerRef) {
  const auto = /^Visitor (\d+)$/.exec(String(name).trim())
  if (auto) return auto[1]
  if (customerRef) {
    const n = /^V-(\d+)$/.exec(customerRef)
    if (n) return n[1]
  }
  return initials(name)
}

function initials(name) {
  const parts = String(name).trim().split(/\s+/).filter(Boolean)
  if (!parts.length) return '?'
  if (parts.length === 1) return parts[0].slice(0, 2).toUpperCase()
  return (parts[0][0] + parts[parts.length - 1][0]).toUpperCase()
}

function Attributes({ attrs }) {
  const bits = []
  if (attrs.gender) bits.push(attrs.gender)
  if (attrs.age) bits.push(`~${Math.round(attrs.age)}`)
  if (attrs.emotion) bits.push(attrs.emotion)
  if (!bits.length) return null
  return <span className="attrs">{bits.join(' · ')}</span>
}