import { useEffect, useState } from 'react'
import { Link, useParams, useSearchParams } from 'react-router-dom'
import {
  fetchTeacherDashboard,
  isTeacherDashboardApiEnabled,
  type TeacherDashboardPayload,
} from '../../api/teacherSession'
import { useSchoolYearOptions } from '../../hooks/useSchoolYearOptions'
import { TeacherShell } from './TeacherShell'
import { useTeacherResource } from './useTeacherResource'

type TrashRow = { id: number; subject?: string; created_at?: string }
type TrashPayload = { trashedMessages?: TrashRow[] }

type MsgRow = { id: number; sender_id?: string | number; subject?: string; created_at?: string }
type InboxPayload = { receivedMessages?: MsgRow[] }

type SentPayload = { sentMessages?: MsgRow[] }

type TeacherMessagePayload = { message?: Record<string, unknown>; thread?: unknown[] }

function appendSchoolYearParam(path: string, schoolYear: string): string {
  if (!schoolYear) return path
  const [base, hash = ''] = path.split('#', 2)
  const [pathname, query = ''] = base.split('?', 2)
  const params = new URLSearchParams(query)
  if (!params.get('school_year')) params.set('school_year', schoolYear)
  const next = `${pathname}?${params.toString()}`
  return hash ? `${next}#${hash}` : next
}

/** Every `/app/teacher/*` route so nothing is hidden behind the slim top nav alone. */
const TEACHER_PAGE_GROUPS = [
  {
    heading: 'Overview',
    links: [
      { label: 'Dashboard', to: '/app/teacher_dashboard' },
      { label: 'No classes (notice)', to: '/app/teacher/no-classes' },
      { label: 'Select semester', to: '/app/teacher/select-semester' },
    ],
  },
  {
    heading: 'Classes & attendance',
    links: [
      { label: 'Class list', to: '/app/teacher/class-view' },
      { label: 'Attendance', to: '/app/teacher/showupdate-attendance' },
      { label: 'Absence / vacation', to: '/app/teacher/absence-vacation' },
    ],
  },
  {
    heading: 'Grades & coursework',
    links: [
      { label: 'Scores', to: '/app/teacher/scores' },
      { label: 'Homework list', to: '/app/teacher/homework-list' },
      { label: 'Add homework', to: '/app/teacher/add-homework' },
      { label: 'Add quiz', to: '/app/teacher/add-quiz' },
      { label: 'Add quiz column', to: '/app/teacher/add-quiz-column-form' },
      { label: 'Add midterm exam', to: '/app/teacher/add-midterm-exam' },
      { label: 'Add final exam', to: '/app/teacher/add-final-exam' },
      { label: 'Add participation', to: '/app/teacher/add-participation' },
      { label: 'Add project', to: '/app/teacher/add-project' },
      { label: 'Teacher assignments', to: '/app/teacher/teacher-assignment' },
      { label: 'Exam drafts', to: '/app/teacher/exam-drafts' },
    ],
  },
  {
    heading: 'Class progress',
    links: [
      { label: 'Submit progress', to: '/app/teacher/class-progress-submit' },
      { label: 'Progress history', to: '/app/teacher/class-progress-history' },
      { label: 'View progress', to: '/app/teacher/class-progress-view' },
    ],
  },
  {
    heading: 'Competitions',
    links: [
      {
        label: 'Competition scores',
        to: '/app/teacher/competition-scores',
        hint: 'Score entry uses /app/teacher/competition-scores/:competitionId',
      },
    ],
  },
  {
    heading: 'Calendar',
    links: [{ label: 'Calendar', to: '/app/teacher/calendar' }],
  },
  {
    heading: 'Messages',
    links: [
      { label: 'Inbox', to: '/app/teacher/inbox' },
      { label: 'Sent', to: '/app/teacher/sent' },
      { label: 'Drafts', to: '/app/teacher/drafts' },
      { label: 'Trash', to: '/app/teacher/trash' },
      {
        label: 'Message thread',
        to: '/app/teacher/inbox',
        hint: '/app/teacher/messages/:messageId — open “View” from inbox.',
      },
    ],
  },
  {
    heading: 'Help',
    links: [
      { label: 'Contact us', to: '/app/teacher/teacher-contactus' },
      { label: 'Support', to: '/app/teacher/teacher-support' },
    ],
  },
] as const

/** `landing_page/teacher_dashboard` — optional `GET /api/v1/teacher/dashboard` (JWT) plus full route index. */
export function TeacherDashboardPage() {
  const apiEnabled = isTeacherDashboardApiEnabled()
  const [dash, setDash] = useState<TeacherDashboardPayload | null>(null)
  const [dashLoading, setDashLoading] = useState(apiEnabled)

  useEffect(() => {
    if (!apiEnabled) return

    let cancelled = false
    fetchTeacherDashboard()
      .then((d) => {
        if (!cancelled) setDash(d)
      })
      .catch(() => {
        if (!cancelled) setDash(null)
      })
      .finally(() => {
        if (!cancelled) setDashLoading(false)
      })
    return () => {
      cancelled = true
    }
  }, [apiEnabled])

  const termLine =
    dash?.school_year || dash?.semester
      ? [dash.school_year, dash.semester].filter(Boolean).join(' · ')
      : null

  const defaultSubtitle =
    'All teacher portal screens are listed below. The top bar shows shortcuts only.'

  return (
    <TeacherShell
      title="Teacher Dashboard"
      subtitle={defaultSubtitle}
      flash={dash?.welcome?.trim() ? String(dash.welcome) : undefined}
    >
      {dashLoading ? <p className="text-muted small mb-3">Loading dashboard…</p> : null}

      {termLine ? <p className="text-muted small mb-2">{termLine}</p> : null}

      {dash?.counts && Object.keys(dash.counts).length > 0 ? (
        <div className="row g-2 mb-4">
          {Object.entries(dash.counts).map(([k, v]) => (
            <div key={k} className="col-6 col-md-4 col-lg-2">
              <div className="border rounded p-2 text-center small">
                <div className="text-muted text-uppercase" style={{ fontSize: '0.7rem' }}>
                  {k.replace(/_/g, ' ')}
                </div>
                <div className="fw-semibold">{v != null && v !== '' ? String(v) : '—'}</div>
              </div>
            </div>
          ))}
        </div>
      ) : null}

      {dash?.announcements && dash.announcements.length > 0 ? (
        <div className="mb-4">
          {dash.announcements.map((a, i) => (
            <div key={i} className="alert alert-light border mb-2">
              {a.title ? <div className="fw-semibold">{a.title}</div> : null}
              {a.body ? <div className="small mt-1">{a.body}</div> : null}
            </div>
          ))}
        </div>
      ) : null}

      <p className="small text-muted mb-4">
        CI view browser:{' '}
        <Link to="/app/browse">/app/browse</Link> (registry links now map competition score views to this area).
      </p>
      {TEACHER_PAGE_GROUPS.map((group) => (
        <section key={group.heading} className="mb-4" id={`teacher-${group.heading.replace(/\s+/g, '-').toLowerCase()}`}>
          <h2 className="h6 text-uppercase text-muted mb-2">{group.heading}</h2>
          <div className="row g-2">
            {group.links.map((item) => (
              <div className="col-6 col-md-4 col-lg-3" key={`${item.to}-${item.label}`}>
                <Link className="btn btn-outline-primary w-100" to={item.to}>
                  {item.label}
                </Link>
                {'hint' in item && item.hint ? (
                  <p className="small text-muted mt-1 mb-0">{item.hint}</p>
                ) : null}
              </div>
            ))}
          </div>
        </section>
      ))}
    </TeacherShell>
  )
}

/** `teacher/no_classes.php` */
export function TeacherNoClassesPage() {
  const { data, loading, error } = useTeacherResource<{ message?: string }>('/no-classes')
  const msg = data?.message
  return (
    <TeacherShell title="Classes" loading={loading} error={error} flash={msg}>
      <p className="text-muted mb-0">If you believe this is an error, contact the school office.</p>
    </TeacherShell>
  )
}

/** `teacher/select_semester.php` */
export function TeacherSelectSemesterPage() {
  const [searchParams] = useSearchParams()
  const { data, loading, error } = useTeacherResource<{
    invalidChoice?: string
    fallPath?: string
    springPath?: string
  }>('/select-semester')
  const requestedSchoolYear = searchParams.get('school_year')?.trim() ?? ''
  const { selectedYear } = useSchoolYearOptions({
    preferredYear: requestedSchoolYear,
  })
  const activeSchoolYear = requestedSchoolYear || selectedYear

  const fallTo = appendSchoolYearParam(data?.fallPath ?? '/app/teacher/scores?semester=Fall', activeSchoolYear)
  const springTo = appendSchoolYearParam(data?.springPath ?? '/app/teacher/scores?semester=Spring', activeSchoolYear)

  return (
    <TeacherShell title="Choose a semester" loading={loading} error={error}>
      <div className="row justify-content-center">
        <div className="col-md-8 col-lg-6">
          <div className="card shadow-sm border-0">
            <div className="card-body text-center">
              <p className="text-muted mb-4">
                Before viewing scores, pick the semester you want to work with.
              </p>
              {data?.invalidChoice ? (
                <div className="alert alert-warning">
                  <strong>Note:</strong> &quot;{data.invalidChoice}&quot; is not a valid semester selection.
                </div>
              ) : null}
              <div className="d-flex flex-wrap justify-content-center gap-3">
                <Link to={fallTo} className="btn btn-primary btn-lg px-4">
                  Fall
                </Link>
                <Link to={springTo} className="btn btn-outline-primary btn-lg px-4">
                  Spring
                </Link>
              </div>
            </div>
          </div>
        </div>
      </div>
    </TeacherShell>
  )
}

/** `teacher/trash.php` */
export function TeacherTrashPage() {
  const { data, loading, error } = useTeacherResource<TrashPayload>('/trash')
  const rows = data?.trashedMessages ?? []
  return (
    <TeacherShell title="Trash" loading={loading} error={error}>
      {rows.length === 0 ? (
        <p>No messages found in trash.</p>
      ) : (
        <div className="table-responsive">
          <table className="table table-striped">
            <thead>
              <tr>
                <th>Subject</th>
                <th>Date</th>
                <th>Actions</th>
              </tr>
            </thead>
            <tbody>
              {rows.map((m) => (
                <tr key={m.id}>
                  <td>{m.subject ?? '—'}</td>
                  <td>{m.created_at ?? ''}</td>
                  <td>
                    <span className="text-muted small">Restore / delete via API when wired.</span>
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </TeacherShell>
  )
}

/** `teacher/inbox.php` */
export function TeacherInboxPage() {
  const { data, loading, error } = useTeacherResource<InboxPayload>('/inbox')
  const rows = data?.receivedMessages ?? []
  return (
    <TeacherShell title="Inbox" loading={loading} error={error}>
      {rows.length === 0 ? (
        <p>No messages found.</p>
      ) : (
        <div className="table-responsive">
          <table className="table table-striped">
            <thead>
              <tr>
                <th>From</th>
                <th>Subject</th>
                <th>Date</th>
                <th>Actions</th>
              </tr>
            </thead>
            <tbody>
              {rows.map((m) => (
                <tr key={m.id}>
                  <td>{String(m.sender_id ?? '')}</td>
                  <td>{m.subject ?? ''}</td>
                  <td>{m.created_at ?? ''}</td>
                  <td>
                    <Link to={`/app/teacher/messages/${m.id}`} className="me-2">
                      View
                    </Link>
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </TeacherShell>
  )
}

/** `teacher/sent.php` */
export function TeacherSentPage() {
  const { data, loading, error } = useTeacherResource<SentPayload>('/sent')
  const rows = data?.sentMessages ?? []
  return (
    <TeacherShell title="Sent" loading={loading} error={error}>
      {rows.length === 0 ? (
        <p>No sent messages.</p>
      ) : (
        <div className="table-responsive">
          <table className="table table-striped">
            <thead>
              <tr>
                <th>To</th>
                <th>Subject</th>
                <th>Date</th>
              </tr>
            </thead>
            <tbody>
              {rows.map((m) => (
                <tr key={m.id}>
                  <td>{String(m.sender_id ?? '')}</td>
                  <td>{m.subject ?? ''}</td>
                  <td>{m.created_at ?? ''}</td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      )}
    </TeacherShell>
  )
}

/** `teacher/teacher_message.php` — thread payload from `/api/v1/teacher/messages/:id`. */
export function TeacherMessagePage() {
  const { messageId } = useParams()
  const path = messageId ? `/messages/${messageId}` : '/message'
  const { data, loading, error } = useTeacherResource<TeacherMessagePayload>(path)
  return (
    <TeacherShell title="Message" loading={loading} error={error}>
      <pre className="small bg-light p-3 rounded overflow-auto" style={{ maxHeight: 420 }}>
        {data ? JSON.stringify(data, null, 2) : null}
      </pre>
    </TeacherShell>
  )
}