import { useState, useEffect, useCallback } from 'react'
import { adminApi } from './api'
import { StatusPill } from './CohortsView'
import styles from './Admin.module.css'

export default function StudentsView() {
  const [students, setStudents] = useState(null)
  const [selected, setSelected] = useState(null)
  const [error, setError] = useState(null)

  const reload = useCallback(() => {
    adminApi.students().then(setStudents).catch((e) => setError(e.message))
  }, [])
  useEffect(reload, [reload])

  if (selected) return <StudentDetail studentId={selected} onBack={() => { setSelected(null); reload() }} />

  return (
    <div className={styles.card}>
      <h2>Students ({students?.length ?? '…'})</h2>
      {error && <div className={styles.errorBox}>{error}</div>}
      {students && (
        <table>
          <thead><tr><th>Name</th><th>ID</th><th>Status</th><th>Last active</th><th /></tr></thead>
          <tbody>
            {students.map((s) => (
              <tr key={s.student_id}>
                <td>{s.display_name}</td>
                <td className={styles.muted}>{s.student_id}</td>
                <td><span className={`${styles.pill} ${s.status === 'active' ? styles.pillOk : styles.pillMuted}`}>{s.status}</span></td>
                <td>{s.last_active_at ? new Date(s.last_active_at).toLocaleString() : 'never'}</td>
                <td><button className={styles.linkBtn} onClick={() => setSelected(s.student_id)}>Open</button></td>
              </tr>
            ))}
          </tbody>
        </table>
      )}
    </div>
  )
}

function StudentDetail({ studentId, onBack }) {
  const [progress, setProgress] = useState(null)
  const [attempts, setAttempts] = useState(null)
  const [env, setEnv] = useState(null)
  const [events, setEvents] = useState(null)
  const [error, setError] = useState(null)
  const [busy, setBusy] = useState(false)

  const reload = useCallback(() => {
    adminApi.studentProgress(studentId).then(setProgress).catch(() => {})
    // Phase 4.1 §16 — studentAttempts is now paginated; this panel only ever shows the most
    // recent page (labeled "Recent attempts," not a full history browser — see
    // /api/admin/students/:id/attempts's own pagination for the underlying capability).
    adminApi.studentAttempts(studentId).then((r) => setAttempts(r.items)).catch(() => {})
    adminApi.studentEnvironment(studentId).then((rows) => setEnv(rows?.find((e) => e.status !== 'destroyed') || null)).catch(() => {})
  }, [studentId])
  useEffect(reload, [reload])

  const withBusy = (fn) => async () => {
    setBusy(true); setError(null)
    try { await fn(); reload() } catch (e) { setError(e.message) } finally { setBusy(false) }
  }

  const loadEvents = async () => {
    if (!env) return
    try { setEvents(await adminApi.environmentEvents(env.environment_id)) } catch (e) { setError(e.message) }
  }

  return (
    <>
      <button className={styles.linkBtn} onClick={onBack}>&larr; Back to students</button>
      <h2 style={{ margin: '1rem 0' }}>{studentId}</h2>
      {error && <div className={styles.errorBox}>{error}</div>}

      <div className={styles.card}>
        <h3>Environment</h3>
        {!env ? <p className={styles.muted}>No Lab provisioned.</p> : (
          <>
            <p>Status: <StatusPill status={env.status} /> — Lab host: {env.lab_host_id} — created {new Date(env.created_at).toLocaleString()}</p>
            {env.last_active_at && <p className={styles.muted}>Last active: {new Date(env.last_active_at).toLocaleString()}</p>}
          </>
        )}
        <div className={styles.formRow} style={{ marginTop: '0.75rem' }}>
          {!env && <button className={styles.btn} disabled={busy} onClick={withBusy(() => adminApi.provisionStudentLab(studentId))}>Provision Lab</button>}
          {env && <button className={styles.btnSecondary} disabled={busy} onClick={withBusy(() => adminApi.resetEnvironment(env.environment_id))}>Reset/Recreate</button>}
          {env && (
            <button className={styles.btnDanger} disabled={busy} onClick={withBusy(async () => {
              if (window.confirm('Destroy this Lab? Progress is not affected.')) await adminApi.destroyEnvironment(env.environment_id)
            })}>Destroy Lab</button>
          )}
          {env && <button className={styles.linkBtn} onClick={loadEvents}>View event history</button>}
        </div>
        {events && (
          <table style={{ marginTop: '0.75rem' }}>
            <thead><tr><th>Event</th><th>Actor</th><th>When</th></tr></thead>
            <tbody>
              {events.map((e) => <tr key={e.id}><td>{e.event_type}</td><td>{e.actor}</td><td>{new Date(e.created_at).toLocaleString()}</td></tr>)}
            </tbody>
          </table>
        )}
      </div>

      <div className={styles.card}>
        <h3>Curriculum progress</h3>
        {!progress ? <p className={styles.muted}>Loading…</p> : progress.stages.map((s) => (
          <div key={s.id} style={{ marginBottom: '0.5rem' }}>
            <strong>{s.name}</strong>
            <div className={styles.muted}>
              {s.scenarios.filter((sc) => sc.status === 'completed').length}/{s.scenarios.length} complete
            </div>
          </div>
        ))}
      </div>

      <div className={styles.card}>
        <h3>Recent attempts</h3>
        {!attempts ? <p className={styles.muted}>Loading…</p> : attempts.length === 0 ? <p className={styles.muted}>None yet.</p> : (
          <table>
            <thead><tr><th>Scenario</th><th>Result</th><th>Checks</th><th>When</th></tr></thead>
            <tbody>
              {attempts.map((a) => (
                <tr key={a.attempt_id}>
                  <td>{a.scenario_id}</td>
                  <td><span className={`${styles.pill} ${a.result === 'passed' ? styles.pillOk : styles.pillWarn}`}>{a.result}</span></td>
                  <td className={styles.muted}>{a.validation_count ?? '—'}</td>
                  <td>{new Date(a.created_at).toLocaleString()}</td>
                </tr>
              ))}
            </tbody>
          </table>
        )}
      </div>
    </>
  )
}