'use client'

import { useEffect, useState, useCallback } from 'react'
import {
  getAssignments, getContent, getModuleMedia, getQuiz, submitQuiz,
  startAssignment, generateCertificate, listCertificates, downloadCertificatePDF,
  getInteractiveManifest, completeAssignment,
} from '@/lib/sdk/training/api'
import type {
  TrainingAssignment, ModuleContent, TrainingMedia, QuizSubmitResponse,
  InteractiveVideoManifest,
} from '@/lib/sdk/training/types'
import { AssignmentsList } from './_components/AssignmentsList'
import { ContentView } from './_components/ContentView'
import { QuizView } from './_components/QuizView'
import { CertificatesView } from './_components/CertificatesView'

type Tab = 'assignments' | 'content' | 'quiz' | 'certificates'

interface QuizQuestionItem {
  id: string
  question: string
  options: string[]
  difficulty: string
}

const TABS: { key: Tab; label: string }[] = [
  { key: 'assignments', label: 'Meine Schulungen' },
  { key: 'content', label: 'Schulungsinhalt' },
  { key: 'quiz', label: 'Quiz' },
  { key: 'certificates', label: 'Zertifikate' },
]

export default function LearnerPage() {
  const [activeTab, setActiveTab] = useState<Tab>('assignments')
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)
  const [assignments, setAssignments] = useState<TrainingAssignment[]>([])
  const [selectedAssignment, setSelectedAssignment] = useState<TrainingAssignment | null>(null)
  const [content, setContent] = useState<ModuleContent | null>(null)
  const [media, setMedia] = useState<TrainingMedia[]>([])
  const [questions, setQuestions] = useState<QuizQuestionItem[]>([])
  const [answers, setAnswers] = useState<Record<string, number>>({})
  const [quizResult, setQuizResult] = useState<QuizSubmitResponse | null>(null)
  const [quizSubmitting, setQuizSubmitting] = useState(false)
  const [quizTimer, setQuizTimer] = useState(0)
  const [quizActive, setQuizActive] = useState(false)
  const [certificates, setCertificates] = useState<TrainingAssignment[]>([])
  const [certGenerating, setCertGenerating] = useState(false)
  const [interactiveManifest, setInteractiveManifest] = useState<InteractiveVideoManifest | null>(null)
  const [userId] = useState('00000000-0000-0000-0000-000000000001')

  const loadAssignments = useCallback(async () => {
    setLoading(true)
    try { const d = await getAssignments({ user_id: userId, limit: 100 }); setAssignments(d.assignments || []) }
    catch (e) { setError(e instanceof Error ? e.message : 'Fehler beim Laden') }
    finally { setLoading(false) }
  }, [userId])

  const loadCertificates = useCallback(async () => {
    try { const d = await listCertificates(); setCertificates(d.certificates || []) } catch { /* may not exist */ }
  }, [])

  useEffect(() => { loadAssignments(); loadCertificates() }, [loadAssignments, loadCertificates])
  useEffect(() => {
    if (!quizActive) return
    const interval = setInterval(() => setQuizTimer(t => t + 1), 1000)
    return () => clearInterval(interval)
  }, [quizActive])

  async function loadInteractiveManifest(moduleId: string, assignmentId: string) {
    try {
      const manifest = await getInteractiveManifest(moduleId, assignmentId)
      setInteractiveManifest(manifest?.checkpoints?.length > 0 ? manifest : null)
    } catch { setInteractiveManifest(null) }
  }

  async function handleStartAssignment(assignment: TrainingAssignment) {
    try {
      await startAssignment(assignment.id)
      setSelectedAssignment({ ...assignment, status: 'in_progress' })
      const [contentData, mediaData] = await Promise.all([
        getContent(assignment.module_id).catch(() => null),
        getModuleMedia(assignment.module_id).catch(() => ({ media: [] })),
      ])
      setContent(contentData); setMedia(mediaData.media || [])
      await loadInteractiveManifest(assignment.module_id, assignment.id)
      setActiveTab('content'); loadAssignments()
    } catch (e) { setError(e instanceof Error ? e.message : 'Fehler beim Starten') }
  }

  async function handleResumeContent(assignment: TrainingAssignment) {
    setSelectedAssignment(assignment)
    try {
      const [contentData, mediaData] = await Promise.all([
        getContent(assignment.module_id).catch(() => null),
        getModuleMedia(assignment.module_id).catch(() => ({ media: [] })),
      ])
      setContent(contentData); setMedia(mediaData.media || [])
      await loadInteractiveManifest(assignment.module_id, assignment.id)
      setActiveTab('content')
    } catch (e) { setError(e instanceof Error ? e.message : 'Fehler beim Laden') }
  }

  async function handleAllCheckpointsPassed() {
    if (!selectedAssignment) return
    try {
      await completeAssignment(selectedAssignment.id)
      setSelectedAssignment({ ...selectedAssignment, status: 'completed' })
      loadAssignments()
    } catch { /* already completed */ }
  }

  async function handleStartQuiz() {
    if (!selectedAssignment) return
    try {
      const data = await getQuiz(selectedAssignment.module_id)
      setQuestions(data.questions || []); setAnswers({}); setQuizResult(null)
      setQuizTimer(0); setQuizActive(true); setActiveTab('quiz')
    } catch (e) { setError(e instanceof Error ? e.message : 'Fehler beim Quiz-Laden') }
  }

  async function handleSubmitQuiz() {
    if (!selectedAssignment || questions.length === 0) return
    setQuizSubmitting(true); setQuizActive(false)
    try {
      const result = await submitQuiz(selectedAssignment.module_id, {
        assignment_id: selectedAssignment.id,
        answers: questions.map(q => ({ question_id: q.id, selected_index: answers[q.id] ?? -1 })),
        duration_seconds: quizTimer,
      })
      setQuizResult(result); loadAssignments()
    } catch (e) { setError(e instanceof Error ? e.message : 'Quiz-Abgabe fehlgeschlagen') }
    finally { setQuizSubmitting(false) }
  }

  async function handleGenerateCertificate(assignmentId: string) {
    setCertGenerating(true)
    try {
      const data = await generateCertificate(assignmentId)
      if (data.certificate_id) {
        const blob = await downloadCertificatePDF(data.certificate_id)
        const url = URL.createObjectURL(blob)
        const a = document.createElement('a'); a.href = url
        a.download = `zertifikat-${data.certificate_id.substring(0, 8)}.pdf`
        a.click(); URL.revokeObjectURL(url)
      }
      loadAssignments(); loadCertificates()
    } catch (e) { setError(e instanceof Error ? e.message : 'Zertifikat-Erstellung fehlgeschlagen') }
    finally { setCertGenerating(false) }
  }

  async function handleDownloadPDF(certId: string) {
    try {
      const blob = await downloadCertificatePDF(certId)
      const url = URL.createObjectURL(blob)
      const a = document.createElement('a'); a.href = url
      a.download = `zertifikat-${certId.substring(0, 8)}.pdf`
      a.click(); URL.revokeObjectURL(url)
    } catch (e) { setError(e instanceof Error ? e.message : 'PDF-Download fehlgeschlagen') }
  }

  return (
    <div className="max-w-7xl mx-auto p-6">
      <div className="mb-6">
        <h1 className="text-2xl font-bold text-gray-900">Learner Portal</h1>
        <p className="text-gray-500 mt-1">Absolvieren Sie Ihre Compliance-Schulungen</p>
      </div>

      {error && (
        <div className="mb-4 p-3 bg-red-50 border border-red-200 rounded-lg text-red-700 text-sm">
          {error}<button onClick={() => setError(null)} className="ml-2 text-red-500 hover:text-red-700">x</button>
        </div>
      )}

      <div className="border-b border-gray-200 mb-6">
        <div className="flex gap-6">
          {TABS.map(tab => (
            <button key={tab.key} onClick={() => setActiveTab(tab.key)}
              className={`pb-3 text-sm font-medium border-b-2 transition-colors ${activeTab === tab.key ? 'border-indigo-500 text-indigo-600' : 'border-transparent text-gray-500 hover:text-gray-700'}`}>
              {tab.label}
            </button>
          ))}
        </div>
      </div>

      {activeTab === 'assignments' && (
        <AssignmentsList
          assignments={assignments} loading={loading} certGenerating={certGenerating}
          onStart={handleStartAssignment} onResume={handleResumeContent}
          onGenerateCertificate={handleGenerateCertificate} onDownloadPDF={handleDownloadPDF}
        />
      )}
      {activeTab === 'content' && (
        <ContentView
          selectedAssignment={selectedAssignment} content={content} media={media}
          interactiveManifest={interactiveManifest} onStartQuiz={handleStartQuiz}
          onAllCheckpointsPassed={handleAllCheckpointsPassed}
        />
      )}
      {activeTab === 'quiz' && (
        <QuizView
          questions={questions} answers={answers} quizResult={quizResult}
          quizSubmitting={quizSubmitting} quizTimer={quizTimer} selectedAssignment={selectedAssignment}
          certGenerating={certGenerating}
          onAnswerChange={(qId, oi) => setAnswers(prev => ({ ...prev, [qId]: oi }))}
          onSubmitQuiz={handleSubmitQuiz} onRetryQuiz={handleStartQuiz}
          onGenerateCertificate={handleGenerateCertificate}
        />
      )}
      {activeTab === 'certificates' && (
        <CertificatesView certificates={certificates} onDownloadPDF={handleDownloadPDF} />
      )}
    </div>
  )
}