'use client'

import { useState, useCallback, useRef, useEffect } from 'react'
import { Language } from '../types'
import { PresenterState, SlideScript } from '../presenter/types'
import { PRESENTER_SCRIPT } from '../presenter/presenter-script'
import { SLIDE_ORDER } from './useSlideNavigation'

interface UsePresenterModeConfig {
  goToSlide: (index: number) => void
  currentSlide: number
  totalSlides: number
  language: Language
  ttsEnabled?: boolean
}

interface UsePresenterModeReturn {
  state: PresenterState
  currentParagraph: number
  start: () => void
  stop: () => void
  pause: () => void
  resume: () => void
  skipSlide: () => void
  prevSlide: () => void
  toggle: () => void
  displayText: string
  progress: number
  isSpeaking: boolean
  ttsAvailable: boolean
  ttsEnabled: boolean
  setTtsEnabled: (enabled: boolean) => void
}

// Client-side audio cache: text hash → blob URL
const audioCache = new Map<string, string>()

function cacheKey(text: string, lang: string): string {
  let hash = 0
  const str = text + '|' + lang
  for (let i = 0; i < str.length; i++) {
    hash = ((hash << 5) - hash + str.charCodeAt(i)) | 0
  }
  return 'tts_' + (hash >>> 0).toString(36)
}

// --- Slide audio plan: concatenates all paragraphs + transition into one text ---

interface AudioSegment {
  text: string
  startRatio: number  // 0..1 — where in the audio this segment starts
  isTransition: boolean
}

interface SlideAudioPlan {
  fullText: string
  segments: AudioSegment[]
}

function buildSlideAudioPlan(slideIdx: number, lang: Language): SlideAudioPlan | null {
  const slideId = SLIDE_ORDER[slideIdx]
  const script = PRESENTER_SCRIPT.find(s => s.slideId === slideId)
  if (!script || script.paragraphs.length === 0) return null

  const segments: AudioSegment[] = []
  let totalWords = 0
  const parts: string[] = []

  for (const para of script.paragraphs) {
    const text = lang === 'de' ? para.text_de : para.text_en
    segments.push({ text, startRatio: totalWords, isTransition: false })
    totalWords += text.split(/\s+/).length
    parts.push(text)
  }

  const hint = lang === 'de'
    ? (script.transition_hint_de || '')
    : (script.transition_hint_en || '')

  if (hint) {
    segments.push({ text: hint, startRatio: totalWords, isTransition: true })
    totalWords += hint.split(/\s+/).length
    parts.push(hint)
  }

  // Normalize ratios to 0..1
  if (totalWords > 0) {
    for (const s of segments) {
      s.startRatio /= totalWords
    }
  }

  return { fullText: parts.join(' '), segments }
}

async function fetchAudio(text: string, lang: string, signal?: AbortSignal): Promise<string | null> {
  const key = cacheKey(text, lang)
  const cached = audioCache.get(key)
  if (cached) return cached

  try {
    const res = await fetch('/api/presenter/tts', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ text, language: lang }),
      signal,
    })
    if (!res.ok) return null
    const blob = await res.blob()
    const url = URL.createObjectURL(blob)
    audioCache.set(key, url)
    return url
  } catch {
    return null
  }
}

export function usePresenterMode({
  goToSlide,
  currentSlide,
  totalSlides,
  language,
  ttsEnabled: initialTtsEnabled = true,
}: UsePresenterModeConfig): UsePresenterModeReturn {
  const [state, setState] = useState<PresenterState>('idle')
  const [currentParagraph, setCurrentParagraph] = useState(0)
  const [displayText, setDisplayText] = useState('')
  const [isSpeaking, setIsSpeaking] = useState(false)
  const [ttsEnabled, setTtsEnabled] = useState(initialTtsEnabled)
  const [ttsAvailable, setTtsAvailable] = useState(false)

  const stateRef = useRef<PresenterState>('idle')
  const slideIndexRef = useRef(currentSlide)
  const audioRef = useRef<HTMLAudioElement | null>(null)
  const abortRef = useRef<AbortController | null>(null)
  const audioUnlockedRef = useRef(false)
  const slideAdvancedRef = useRef(false)
  const timerRefs = useRef<NodeJS.Timeout[]>([])

  // Ref for playSlide — avoids stale closure in audio callbacks
  const playSlideRef = useRef<(slideIdx: number) => void>(() => {})

  // Unlock browser audio (must be called from user gesture)
  const unlockAudio = useCallback(() => {
    if (audioUnlockedRef.current) return
    try {
      const ctx = new (window.AudioContext || (window as any).webkitAudioContext)()
      const buffer = ctx.createBuffer(1, 1, 22050)
      const source = ctx.createBufferSource()
      source.buffer = buffer
      source.connect(ctx.destination)
      source.start(0)
      audioUnlockedRef.current = true
    } catch {}
  }, [])

  // Check TTS availability on mount
  useEffect(() => {
    fetch('/api/presenter/tts', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ text: 'Test', language: 'de' }),
      signal: AbortSignal.timeout(5000),
    })
      .then(res => setTtsAvailable(res.ok))
      .catch(() => setTtsAvailable(false))
  }, [])

  // Cancel all audio and timers
  const cancelAll = useCallback(() => {
    if (audioRef.current) {
      audioRef.current.pause()
      audioRef.current.onended = null
      audioRef.current.ontimeupdate = null
      audioRef.current.onerror = null
      audioRef.current = null
    }
    if (abortRef.current) {
      abortRef.current.abort()
      abortRef.current = null
    }
    for (const t of timerRefs.current) clearTimeout(t)
    timerRefs.current = []
    setIsSpeaking(false)
  }, [])

  // Keep refs in sync
  useEffect(() => { slideIndexRef.current = currentSlide }, [currentSlide])
  useEffect(() => { stateRef.current = state }, [state])

  // --- Core: play one slide's audio (all paragraphs concatenated) ---
  useEffect(() => {
    playSlideRef.current = async (slideIdx: number) => {
      if (stateRef.current !== 'presenting') return

      const plan = buildSlideAudioPlan(slideIdx, language)
      if (!plan) {
        // No script for this slide — skip to next
        if (slideIdx < totalSlides - 1) {
          goToSlide(slideIdx + 1)
          slideIndexRef.current = slideIdx + 1
          const t = setTimeout(() => playSlideRef.current(slideIdx + 1), 300)
          timerRefs.current.push(t)
        } else {
          setState('idle')
          stateRef.current = 'idle'
          setDisplayText('')
        }
        return
      }

      // Show first segment immediately
      setDisplayText(plan.segments[0]?.text || '')
      setCurrentParagraph(0)
      slideAdvancedRef.current = false

      // Pre-fetch next slide's audio in background
      if (slideIdx < totalSlides - 1) {
        const nextPlan = buildSlideAudioPlan(slideIdx + 1, language)
        if (nextPlan) fetchAudio(nextPlan.fullText, language).catch(() => {})
      }

      // --- Non-TTS path: word-count based timing ---
      if (!ttsAvailable || !ttsEnabled) {
        const words = plan.fullText.split(/\s+/).length
        const totalTime = Math.max(words * 130, 3000)

        for (const seg of plan.segments) {
          const t = setTimeout(() => {
            if (stateRef.current !== 'presenting') return
            setDisplayText(seg.text)
            if (seg.isTransition && slideIdx < totalSlides - 1 && !slideAdvancedRef.current) {
              slideAdvancedRef.current = true
              goToSlide(slideIdx + 1)
            }
          }, seg.startRatio * totalTime)
          timerRefs.current.push(t)
        }

        const t = setTimeout(() => {
          if (stateRef.current !== 'presenting') return
          const next = slideIdx + 1
          if (next < totalSlides) {
            if (!slideAdvancedRef.current) goToSlide(next)
            slideIndexRef.current = next
            playSlideRef.current(next)
          } else {
            setState('idle')
            stateRef.current = 'idle'
            setDisplayText('')
          }
        }, totalTime)
        timerRefs.current.push(t)
        return
      }

      // --- TTS path: fetch + play full-slide audio ---
      setIsSpeaking(true)
      const controller = new AbortController()
      abortRef.current = controller

      const blobUrl = await fetchAudio(plan.fullText, language, controller.signal)
      if (!blobUrl || controller.signal.aborted) {
        setIsSpeaking(false)
        return
      }
      if (stateRef.current !== 'presenting') {
        setIsSpeaking(false)
        return
      }

      const audio = new Audio(blobUrl)
      audioRef.current = audio

      // Sync subtitle text to playback position
      audio.ontimeupdate = () => {
        if (!audio.duration || stateRef.current !== 'presenting') return
        const ratio = audio.currentTime / audio.duration

        for (let i = plan.segments.length - 1; i >= 0; i--) {
          if (ratio >= plan.segments[i].startRatio) {
            setDisplayText(plan.segments[i].text)
            setCurrentParagraph(Math.min(i, plan.segments.length - 1))

            // Advance slide when transition phrase starts playing
            if (plan.segments[i].isTransition && !slideAdvancedRef.current && slideIdx < totalSlides - 1) {
              slideAdvancedRef.current = true
              goToSlide(slideIdx + 1)
            }
            break
          }
        }
      }

      // When audio finishes → immediately play next slide (pre-fetched)
      audio.onended = () => {
        setIsSpeaking(false)
        audioRef.current = null
        if (stateRef.current !== 'presenting') return

        const next = slideIdx + 1
        if (next < totalSlides) {
          if (!slideAdvancedRef.current) goToSlide(next)
          slideIndexRef.current = next
          playSlideRef.current(next)
        } else {
          setState('idle')
          stateRef.current = 'idle'
          setDisplayText('')
        }
      }

      audio.onerror = () => {
        setIsSpeaking(false)
        audioRef.current = null
        // Skip to next slide on error
        if (stateRef.current !== 'presenting') return
        const next = slideIdx + 1
        if (next < totalSlides) {
          goToSlide(next)
          slideIndexRef.current = next
          playSlideRef.current(next)
        }
      }

      try {
        await audio.play()
      } catch {
        setIsSpeaking(false)
      }
    }
  }, [language, totalSlides, goToSlide, ttsAvailable, ttsEnabled])

  const start = useCallback(() => {
    unlockAudio()
    cancelAll()
    setState('presenting')
    stateRef.current = 'presenting'
    playSlideRef.current(slideIndexRef.current)
  }, [unlockAudio, cancelAll])

  const stop = useCallback(() => {
    cancelAll()
    setState('idle')
    stateRef.current = 'idle'
    setDisplayText('')
    setCurrentParagraph(0)
  }, [cancelAll])

  // Pause: keep audio alive, just pause playback
  const pause = useCallback(() => {
    if (audioRef.current) {
      audioRef.current.pause()
    }
    for (const t of timerRefs.current) clearTimeout(t)
    timerRefs.current = []
    setState('paused')
    stateRef.current = 'paused'
    setIsSpeaking(false)
  }, [])

  // Resume: continue paused audio, or restart current slide
  const resume = useCallback(() => {
    setState('presenting')
    stateRef.current = 'presenting'

    if (audioRef.current && audioRef.current.paused && audioRef.current.currentTime > 0) {
      setIsSpeaking(true)
      audioRef.current.play().catch(() => {
        setIsSpeaking(false)
        playSlideRef.current(slideIndexRef.current)
      })
    } else {
      playSlideRef.current(slideIndexRef.current)
    }
  }, [])

  const skipSlide = useCallback(() => {
    cancelAll()
    const nextIdx = slideIndexRef.current + 1
    if (nextIdx < totalSlides) {
      goToSlide(nextIdx)
      slideIndexRef.current = nextIdx
      if (stateRef.current === 'presenting') {
        playSlideRef.current(nextIdx)
      }
    }
  }, [cancelAll, totalSlides, goToSlide])

  const prevSlide = useCallback(() => {
    cancelAll()
    const prevIdx = slideIndexRef.current - 1
    if (prevIdx >= 0) {
      goToSlide(prevIdx)
      slideIndexRef.current = prevIdx
      if (stateRef.current === 'presenting' || stateRef.current === 'paused') {
        setState('presenting')
        stateRef.current = 'presenting'
        playSlideRef.current(prevIdx)
      }
    }
  }, [cancelAll, goToSlide])

  const toggle = useCallback(() => {
    unlockAudio()
    if (stateRef.current === 'idle') {
      start()
    } else {
      stop()
    }
  }, [unlockAudio, start, stop])

  // Calculate overall progress
  const progress = (() => {
    if (state === 'idle') return 0
    const totalScripts = PRESENTER_SCRIPT.length
    const currentScriptIdx = PRESENTER_SCRIPT.findIndex(s => s.slideId === SLIDE_ORDER[currentSlide])
    if (currentScriptIdx < 0) return (currentSlide / totalSlides) * 100

    const script = PRESENTER_SCRIPT[currentScriptIdx]
    const slideProgress = script.paragraphs.length > 0
      ? currentParagraph / script.paragraphs.length
      : 0
    return ((currentScriptIdx + slideProgress) / totalScripts) * 100
  })()

  // Cleanup on unmount
  useEffect(() => {
    return () => { cancelAll() }
  }, [cancelAll])

  return {
    state,
    currentParagraph,
    start,
    stop,
    pause,
    resume,
    skipSlide,
    prevSlide,
    toggle,
    displayText,
    progress,
    isSpeaking,
    ttsAvailable,
    ttsEnabled,
    setTtsEnabled,
  }
}