import { useState, useEffect } from 'react'
import { api, getCachedDisplay } from './api'
import LoginScreen from './LoginScreen'
import EntryScreen from './EntryScreen'
import SetPasswordScreen from './SetPasswordScreen'
import ForgotPasswordScreen from './ForgotPasswordScreen'
import StudentDashboard from './StudentDashboard'

// Top-level Platform Shell. Phase 5A: the credentialed LoginScreen is now the default entry
// point (was EntryScreen's pilot name-picker); an activation/reset link
// (?activate=<token> or ?reset=<token>) short-circuits straight to SetPasswordScreen before
// any session check, since neither flow requires an existing session. Session validity is
// still decided by the server (GET /api/session/whoami against the rn_session cookie), not by
// anything read from localStorage/sessionStorage.
export default function PlatformShell() {
  const [student, setStudent] = useState(null)
  const [checking, setChecking] = useState(true)
  const params = new URLSearchParams(window.location.search)
  const [view, setView] = useState(
    params.get('activate') ? 'activate' : params.get('reset') ? 'reset' : 'login'
  )
  const [resetToken, setResetToken] = useState(params.get('reset') || null)

  useEffect(() => {
    if (view === 'activate' || view === 'reset') { setChecking(false); return }
    const cached = getCachedDisplay()
    if (cached) setStudent(cached) // optimistic paint while we confirm with the server
    api.whoami()
      .then(({ student_id }) => {
        if (!cached || cached.student_id !== student_id) setStudent({ student_id, display_name: cached?.display_name || student_id })
      })
      .catch(() => setStudent(null))
      .finally(() => setChecking(false))
  }, [view])

  if (checking) return null

  if (view === 'activate') {
    return <SetPasswordScreen token={params.get('activate')} purpose="activation"
      onDone={(s) => { setStudent(s); setView('dashboard'); window.history.replaceState({}, '', '/') }}
      onCancel={() => { setView('login'); window.history.replaceState({}, '', '/') }} />
  }
  if (view === 'reset') {
    return <SetPasswordScreen token={resetToken} purpose="reset"
      onDone={() => { setView('login'); window.history.replaceState({}, '', '/') }}
      onCancel={() => { setView('login'); window.history.replaceState({}, '', '/') }} />
  }
  if (view === 'forgot') {
    return <ForgotPasswordScreen onCancel={() => setView('login')} onHaveToken={(t) => { setResetToken(t); setView('reset') }} />
  }
  if (view === 'pilot') {
    return <EntryScreen onLogin={(s) => { setStudent(s); setView('dashboard') }} />
  }
  if (!student) {
    return <LoginScreen onLogin={(s) => { setStudent(s); setView('dashboard') }}
      onShowPilotEntry={() => setView('pilot')} onShowForgotPassword={() => setView('forgot')} />
  }
  return <StudentDashboard student={student} onLogout={() => { setStudent(null); setView('login') }} />
}