'use client'

import { useCallback, useRef, useState } from 'react'

const KLAUSUR_API = '/klausur-api'

interface LlmChange {
  row_index: number
  field: 'english' | 'german' | 'example'
  old: string
  new: string
}

interface StepLlmReviewProps {
  sessionId: string | null
  onNext: () => void
}

interface ReviewMeta {
  total_entries: number
  to_review: number
  skipped: number
  model: string
}

interface StreamProgress {
  current: number
  total: number
}

const FIELD_LABELS: Record<string, string> = {
  english: 'EN',
  german: 'DE',
  example: 'Beispiel',
}

export function StepLlmReview({ sessionId, onNext }: StepLlmReviewProps) {
  const [status, setStatus] = useState<'idle' | 'running' | 'done' | 'error' | 'applied'>('idle')
  const [meta, setMeta] = useState<ReviewMeta | null>(null)
  const [changes, setChanges] = useState<LlmChange[]>([])
  const [progress, setProgress] = useState<StreamProgress | null>(null)
  const [batchLog, setBatchLog] = useState<string[]>([])
  const [totalDuration, setTotalDuration] = useState(0)
  const [error, setError] = useState('')
  const [accepted, setAccepted] = useState<Set<number>>(new Set())
  const [applying, setApplying] = useState(false)
  const tableEndRef = useRef<HTMLDivElement>(null)

  const runReview = useCallback(async () => {
    if (!sessionId) return
    setStatus('running')
    setError('')
    setChanges([])
    setBatchLog([])
    setProgress(null)
    setMeta(null)
    setTotalDuration(0)

    try {
      const res = await fetch(
        `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/llm-review?stream=true`,
        { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({}) },
      )

      if (!res.ok) {
        const data = await res.json().catch(() => ({}))
        throw new Error(data.detail || `HTTP ${res.status}`)
      }

      const reader = res.body!.getReader()
      const decoder = new TextDecoder()
      let buffer = ''
      let allChanges: LlmChange[] = []

      while (true) {
        const { done, value } = await reader.read()
        if (done) break
        buffer += decoder.decode(value, { stream: true })

        while (buffer.includes('\n\n')) {
          const idx = buffer.indexOf('\n\n')
          const chunk = buffer.slice(0, idx).trim()
          buffer = buffer.slice(idx + 2)

          if (!chunk.startsWith('data: ')) continue
          const dataStr = chunk.slice(6)

          let event: any
          try { event = JSON.parse(dataStr) } catch { continue }

          if (event.type === 'meta') {
            setMeta({
              total_entries: event.total_entries,
              to_review: event.to_review,
              skipped: event.skipped,
              model: event.model,
            })
            setBatchLog([`${event.total_entries} Eintraege, ${event.skipped} uebersprungen (Lautschrift), ${event.to_review} zu pruefen`])
          }

          if (event.type === 'batch') {
            const batchChanges: LlmChange[] = event.changes || []
            allChanges = [...allChanges, ...batchChanges]
            setChanges(allChanges)
            setProgress(event.progress)
            const rows = (event.entries_reviewed || []).map((r: number) => `R${r}`).join(', ')
            setBatchLog(prev => [...prev,
              `Batch ${event.batch_index + 1}: ${rows} — ${batchChanges.length} Korrektur${batchChanges.length !== 1 ? 'en' : ''} (${event.duration_ms}ms)`
            ])
            setTimeout(() => tableEndRef.current?.scrollIntoView({ behavior: 'smooth', block: 'nearest' }), 16)
          }

          if (event.type === 'complete') {
            setTotalDuration(event.duration_ms)
            setAccepted(new Set(allChanges.map((_, i) => i)))
            setStatus('done')
          }

          if (event.type === 'error') {
            throw new Error(event.detail || 'Unbekannter Fehler')
          }
        }
      }

      // If no complete event was received (e.g. 0 entries to review)
      if (allChanges.length === 0 && status !== 'done') {
        setStatus('done')
      }
    } catch (e: unknown) {
      const msg = e instanceof Error ? e.message : String(e)
      setError(msg)
      setStatus('error')
    }
  }, [sessionId])

  const toggleChange = (index: number) => {
    setAccepted(prev => {
      const next = new Set(prev)
      if (next.has(index)) next.delete(index)
      else next.add(index)
      return next
    })
  }

  const toggleAll = () => {
    if (accepted.size === changes.length) {
      setAccepted(new Set())
    } else {
      setAccepted(new Set(changes.map((_, i) => i)))
    }
  }

  const applyChanges = useCallback(async () => {
    if (!sessionId) return
    setApplying(true)
    try {
      const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/llm-review/apply`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ accepted_indices: Array.from(accepted) }),
      })
      if (!res.ok) {
        const data = await res.json().catch(() => ({}))
        throw new Error(data.detail || `HTTP ${res.status}`)
      }
      setStatus('applied')
    } catch (e: unknown) {
      setError(e instanceof Error ? e.message : String(e))
    } finally {
      setApplying(false)
    }
  }, [sessionId, accepted])

  if (!sessionId) {
    return <div className="text-center py-12 text-gray-400">Bitte zuerst eine Session auswaehlen.</div>
  }

  // --- Idle ---
  if (status === 'idle') {
    return (
      <div className="flex flex-col items-center justify-center py-12 text-center">
        <div className="text-5xl mb-4">🤖</div>
        <h3 className="text-lg font-medium text-gray-700 dark:text-gray-300 mb-2">
          Schritt 6: LLM-Korrektur
        </h3>
        <p className="text-gray-500 dark:text-gray-400 max-w-lg mb-2">
          Ein lokales Sprachmodell prueft die OCR-Ergebnisse auf typische Erkennungsfehler.
          Eintraege mit Lautschrift werden automatisch uebersprungen.
        </p>
        <p className="text-xs text-gray-400 dark:text-gray-500 mb-6">
          Modell: <span className="font-mono">qwen3:30b-a3b</span> via Ollama (lokal)
        </p>
        <button onClick={runReview}
          className="px-6 py-2.5 bg-teal-600 text-white rounded-lg hover:bg-teal-700 transition-colors font-medium">
          LLM-Korrektur starten
        </button>
      </div>
    )
  }

  // --- Running (with live progress) ---
  if (status === 'running') {
    const pct = progress ? Math.round((progress.current / progress.total) * 100) : 0

    return (
      <div className="space-y-4">
        <div className="flex items-center gap-3">
          <div className="animate-spin rounded-full h-5 w-5 border-b-2 border-teal-500" />
          <h3 className="text-base font-medium text-gray-700 dark:text-gray-300">
            LLM-Korrektur laeuft...
          </h3>
          {meta && (
            <span className="text-xs text-gray-400 font-mono">{meta.model}</span>
          )}
        </div>

        {/* Progress bar */}
        {progress && (
          <div className="space-y-1">
            <div className="flex justify-between text-xs text-gray-400">
              <span>{progress.current} / {progress.total} Eintraege geprueft</span>
              <span>{pct}%</span>
            </div>
            <div className="w-full bg-gray-200 dark:bg-gray-700 rounded-full h-2">
              <div className="bg-teal-500 h-2 rounded-full transition-all duration-500" style={{ width: `${pct}%` }} />
            </div>
          </div>
        )}

        {/* Live batch log */}
        <div className="bg-gray-50 dark:bg-gray-800/50 rounded-lg p-3 max-h-40 overflow-y-auto">
          {batchLog.map((line, i) => (
            <div key={i} className="text-xs text-gray-500 dark:text-gray-400 font-mono py-0.5">{line}</div>
          ))}
        </div>

        {/* Live changes appearing */}
        {changes.length > 0 && (
          <div className="border border-gray-200 dark:border-gray-700 rounded-lg overflow-hidden">
            <table className="w-full text-sm">
              <thead>
                <tr className="bg-gray-50 dark:bg-gray-800 border-b border-gray-200 dark:border-gray-700">
                  <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Zeile</th>
                  <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Feld</th>
                  <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Vorher</th>
                  <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Nachher</th>
                </tr>
              </thead>
              <tbody>
                {changes.map((change, idx) => (
                  <tr key={idx} className="border-b border-gray-100 dark:border-gray-700/50 bg-teal-50/50 dark:bg-teal-900/10">
                    <td className="px-3 py-1.5 text-gray-500 dark:text-gray-400 font-mono text-xs">R{change.row_index}</td>
                    <td className="px-3 py-1.5">
                      <span className="text-xs px-1.5 py-0.5 rounded bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-400">
                        {FIELD_LABELS[change.field] || change.field}
                      </span>
                    </td>
                    <td className="px-3 py-1.5"><span className="line-through text-red-500 dark:text-red-400">{change.old}</span></td>
                    <td className="px-3 py-1.5"><span className="text-green-600 dark:text-green-400 font-medium">{change.new}</span></td>
                  </tr>
                ))}
              </tbody>
            </table>
            <div ref={tableEndRef} />
          </div>
        )}
      </div>
    )
  }

  // --- Error ---
  if (status === 'error') {
    return (
      <div className="flex flex-col items-center justify-center py-12 text-center">
        <div className="text-5xl mb-4">⚠️</div>
        <h3 className="text-lg font-medium text-red-600 dark:text-red-400 mb-2">Fehler bei LLM-Korrektur</h3>
        <p className="text-sm text-gray-500 dark:text-gray-400 max-w-lg mb-4">{error}</p>
        <div className="flex gap-3">
          <button onClick={runReview}
            className="px-5 py-2 bg-teal-600 text-white rounded-lg hover:bg-teal-700 transition-colors text-sm">
            Erneut versuchen
          </button>
          <button onClick={onNext}
            className="px-5 py-2 bg-gray-200 dark:bg-gray-700 text-gray-700 dark:text-gray-300 rounded-lg hover:bg-gray-300 dark:hover:bg-gray-600 transition-colors text-sm">
            Ueberspringen →
          </button>
        </div>
      </div>
    )
  }

  // --- Applied ---
  if (status === 'applied') {
    return (
      <div className="flex flex-col items-center justify-center py-12 text-center">
        <div className="text-5xl mb-4">✅</div>
        <h3 className="text-lg font-medium text-gray-700 dark:text-gray-300 mb-2">Korrekturen uebernommen</h3>
        <p className="text-sm text-gray-500 dark:text-gray-400 mb-6">
          {accepted.size} von {changes.length} Korrekturen wurden angewendet.
        </p>
        <button onClick={onNext}
          className="px-6 py-2.5 bg-teal-600 text-white rounded-lg hover:bg-teal-700 transition-colors font-medium">
          Weiter →
        </button>
      </div>
    )
  }

  // --- Done: diff table with checkboxes ---
  if (changes.length === 0) {
    return (
      <div className="flex flex-col items-center justify-center py-12 text-center">
        <div className="text-5xl mb-4">👍</div>
        <h3 className="text-lg font-medium text-gray-700 dark:text-gray-300 mb-2">Keine Korrekturen noetig</h3>
        <p className="text-sm text-gray-500 dark:text-gray-400 mb-1">Das LLM hat keine OCR-Fehler gefunden.</p>
        {meta && (
          <p className="text-xs text-gray-400 dark:text-gray-500 mb-6">
            {meta.to_review} geprueft, {meta.skipped} uebersprungen · {totalDuration}ms · {meta.model}
          </p>
        )}
        <button onClick={onNext}
          className="px-6 py-2.5 bg-teal-600 text-white rounded-lg hover:bg-teal-700 transition-colors font-medium">
          Weiter →
        </button>
      </div>
    )
  }

  return (
    <div className="space-y-4">
      {/* Header */}
      <div className="flex items-center justify-between">
        <div>
          <h3 className="text-base font-medium text-gray-700 dark:text-gray-300">LLM-Korrekturvorschlaege</h3>
          <p className="text-xs text-gray-400 mt-0.5">
            {changes.length} Korrektur{changes.length !== 1 ? 'en' : ''} gefunden
            {meta && <> · {meta.skipped} uebersprungen (Lautschrift)</>}
            {' '}· {totalDuration}ms · {meta?.model}
          </p>
        </div>
        <button onClick={toggleAll}
          className="text-xs px-3 py-1.5 border border-gray-300 dark:border-gray-600 rounded-lg hover:bg-gray-50 dark:hover:bg-gray-700 transition-colors text-gray-600 dark:text-gray-400">
          {accepted.size === changes.length ? 'Keine' : 'Alle'} auswaehlen
        </button>
      </div>

      {/* Diff table */}
      <div className="border border-gray-200 dark:border-gray-700 rounded-lg overflow-hidden">
        <table className="w-full text-sm">
          <thead>
            <tr className="bg-gray-50 dark:bg-gray-800 border-b border-gray-200 dark:border-gray-700">
              <th className="w-10 px-3 py-2 text-center">
                <input type="checkbox" checked={accepted.size === changes.length} onChange={toggleAll}
                  className="rounded border-gray-300 dark:border-gray-600" />
              </th>
              <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Zeile</th>
              <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Feld</th>
              <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Vorher</th>
              <th className="px-3 py-2 text-left text-gray-500 dark:text-gray-400 font-medium">Nachher</th>
            </tr>
          </thead>
          <tbody>
            {changes.map((change, idx) => (
              <tr key={idx} className={`border-b border-gray-100 dark:border-gray-700/50 ${
                accepted.has(idx) ? 'bg-teal-50/50 dark:bg-teal-900/10' : 'bg-white dark:bg-gray-800/50'
              }`}>
                <td className="px-3 py-2 text-center">
                  <input type="checkbox" checked={accepted.has(idx)} onChange={() => toggleChange(idx)}
                    className="rounded border-gray-300 dark:border-gray-600" />
                </td>
                <td className="px-3 py-2 text-gray-500 dark:text-gray-400 font-mono text-xs">R{change.row_index}</td>
                <td className="px-3 py-2">
                  <span className="text-xs px-1.5 py-0.5 rounded bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-400">
                    {FIELD_LABELS[change.field] || change.field}
                  </span>
                </td>
                <td className="px-3 py-2"><span className="line-through text-red-500 dark:text-red-400">{change.old}</span></td>
                <td className="px-3 py-2"><span className="text-green-600 dark:text-green-400 font-medium">{change.new}</span></td>
              </tr>
            ))}
          </tbody>
        </table>
      </div>

      {/* Actions */}
      <div className="flex items-center justify-between pt-2">
        <p className="text-xs text-gray-400">{accepted.size} von {changes.length} ausgewaehlt</p>
        <div className="flex gap-3">
          <button onClick={onNext}
            className="px-4 py-2 text-sm border border-gray-300 dark:border-gray-600 rounded-lg hover:bg-gray-50 dark:hover:bg-gray-700 transition-colors text-gray-600 dark:text-gray-400">
            Alle ablehnen
          </button>
          <button onClick={applyChanges} disabled={applying || accepted.size === 0}
            className="px-5 py-2 text-sm bg-teal-600 text-white rounded-lg hover:bg-teal-700 disabled:opacity-50 disabled:cursor-not-allowed transition-colors font-medium">
            {applying ? 'Wird uebernommen...' : `${accepted.size} Korrektur${accepted.size !== 1 ? 'en' : ''} uebernehmen`}
          </button>
        </div>
      </div>
    </div>
  )
}