import { useState, useEffect, useCallback, useRef } from 'react'
import { api } from './api'
import styles from './Platform.module.css'

const HEARTBEAT_MS = 25000  // §15 — "browser heartbeat every 20-30 seconds"
const POLL_MS = 5000

const HELP_CATEGORIES = [
  { value: 'lab_problem', label: 'Lab problem' },
  { value: 'dont_understand', label: "Don't understand the task" },
  { value: 'validation_failing', label: 'Validation failing' },
  { value: 'other', label: 'Other' },
]

// Phase 5A §22 — the live classroom experience. No live classroom -> a quiet "nothing live
// right now" state. Live -> title, current activity (guidance only — a link into the student's
// own Lab, never an auto-redirect), announcements, Need Help, and the student's own Lab status
// (reusing the exact same /api/environment/* the My Learning tab uses — no second Lab-status
// system). Heartbeats fire only while this tab is mounted and a classroom is actually joined.
export default function ClassroomTab() {
  const [live, setLive] = useState(null)
  const [detail, setDetail] = useState(null)
  const [envStatus, setEnvStatus] = useState(null)
  const [joined, setJoined] = useState(false)
  const [helpCategory, setHelpCategory] = useState('lab_problem')
  const [helpMessage, setHelpMessage] = useState('')
  const [helpSent, setHelpSent] = useState(false)
  const [error, setError] = useState(null)
  const heartbeatRef = useRef(null)
  const pollRef = useRef(null)

  const loadLive = useCallback(() => {
    api.liveClassroom().then((r) => setLive(r.classroom)).catch((e) => setError(e.message))
  }, [])
  useEffect(() => { loadLive() }, [loadLive])

  const loadDetail = useCallback((id) => {
    api.classroom(id).then(setDetail).catch((e) => setError(e.message))
    api.environmentStatus().then(setEnvStatus).catch(() => {})
  }, [])

  useEffect(() => {
    if (!live) return
    loadDetail(live.classroom_session_id)
    pollRef.current = setInterval(() => loadDetail(live.classroom_session_id), POLL_MS)
    return () => clearInterval(pollRef.current)
  }, [live, loadDetail])

  useEffect(() => {
    if (!joined || !live) return
    heartbeatRef.current = setInterval(() => api.classroomHeartbeat(live.classroom_session_id).catch(() => {}), HEARTBEAT_MS)
    api.classroomHeartbeat(live.classroom_session_id).catch(() => {}) // one immediately on join, not just after the first interval
    return () => clearInterval(heartbeatRef.current)
  }, [joined, live])

  const join = async () => {
    try { await api.joinClassroom(live.classroom_session_id); setJoined(true) }
    catch (e) { setError(e.message) }
  }

  const sendHelp = async (e) => {
    e.preventDefault()
    try {
      await api.requestHelp(live.classroom_session_id, helpCategory, helpMessage)
      setHelpSent(true); setHelpMessage('')
    } catch (e) { setError(e.message) }
  }

  const launchLab = async () => {
    try { setEnvStatus(await api.launchEnvironment()) } catch (e) { setError(e.message) }
  }

  if (!live) {
    return (
      <div className={styles.card}>
        <h2>Classroom</h2>
        <p className={styles.muted}>No live class right now. Check back at your scheduled class time.</p>
      </div>
    )
  }

  return (
    <div>
      <div className={styles.card}>
        <p className={styles.livePill}>LIVE NOW</p>
        <h2 style={{ margin: '0.4rem 0' }}>{live.title}</h2>
        {live.description && <p className={styles.muted}>{live.description}</p>}
        {live.meeting_url && (
          <p><a className={styles.primaryBtn} href={live.meeting_url} target="_blank" rel="noreferrer">Join Video Class</a></p>
        )}
        {!joined ? (
          <button className={styles.primaryBtn} onClick={join}>Join Classroom</button>
        ) : (
          <p className={styles.muted}>You're in this classroom.</p>
        )}
      </div>

      {joined && detail && (
        <>
          {detail.classroom.current_scenario_id && (
            <div className={styles.card}>
              <h3>Current class activity</h3>
              <p>{detail.classroom.current_scenario_id}</p>
              <p className={styles.muted}>Open it from the My Learning tab when you're ready — nothing here jumps you there automatically.</p>
            </div>
          )}

          <div className={styles.card}>
            <h3>Your Lab</h3>
            {envStatus?.status === 'running'
              ? <p><a className={styles.primaryBtn} href={envStatus.launch_path}>Open Lab</a></p>
              : <button className={styles.primaryBtn} onClick={launchLab} disabled={envStatus?.status === 'provisioning'}>
                  {envStatus?.status === 'provisioning' ? 'Starting…' : 'Launch Lab'}
                </button>}
          </div>

          <div className={styles.card}>
            <h3>Announcements</h3>
            {!detail.announcements.length ? <p className={styles.muted}>None yet.</p> : (
              <ul>
                {detail.announcements.map((a) => <li key={a.announcement_id}>{a.message}</li>)}
              </ul>
            )}
          </div>

          <div className={styles.card}>
            <h3>Need help?</h3>
            {helpSent ? <p className={styles.muted}>Help requested — your instructor has been notified.</p> : (
              <form onSubmit={sendHelp}>
                <label className={styles.label}>What's going on?</label>
                <select className={styles.select} value={helpCategory} onChange={(e) => setHelpCategory(e.target.value)}>
                  {HELP_CATEGORIES.map((c) => <option key={c.value} value={c.value}>{c.label}</option>)}
                </select>
                <label className={styles.label}>Details (optional)</label>
                <input className={styles.input} value={helpMessage} onChange={(e) => setHelpMessage(e.target.value)} />
                <button className={styles.primaryBtn} type="submit">Need Help</button>
              </form>
            )}
          </div>
        </>
      )}

      {error && <div className={styles.errorBox}>{error}</div>}
    </div>
  )
}