import React, { useState, useEffect } from 'react'
import { useAuth } from './auth/AuthContext'
import LoadingError from './LoadingError'
import './WordList.css'

const API_URL = '/api'

function WordList({ onNavigate, dictionaryId, isNewDictionary, refreshTrigger = 0 }) {
  const { authFetch } = useAuth()
  const [words, setWords] = useState([])
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState('')
  const [dictionary, setDictionary] = useState(null)
  const [dictionaryName, setDictionaryName] = useState('')
  const [originalDictionaryName, setOriginalDictionaryName] = useState('')
  const [isSavingName, setIsSavingName] = useState(false)
  const [selectedWord, setSelectedWord] = useState(null)
  // Normalize undefined to null for clarity: new dictionary if dictionaryId is null or undefined
  const [currentDictionaryId, setCurrentDictionaryId] = useState(dictionaryId ?? null)

  // isNewDict is computed from currentDictionaryId: new dictionary if currentDictionaryId == null
  const isNewDict = currentDictionaryId == null

  // Helper function to check if dictionary exists and is not new
  const hasValidDictionary = (dictId) => {
    return dictId !== undefined && dictId !== null
  }

  useEffect(() => {
    // Normalize undefined to null: if dictionaryId is undefined, treat it as null (new dictionary)
    const normalizedDictionaryId = dictionaryId ?? null
    setCurrentDictionaryId(normalizedDictionaryId)
    
    if (normalizedDictionaryId == null) {
      setLoading(false)
      setDictionary(null)
      setDictionaryName('')
      setOriginalDictionaryName('')
      setWords([])
    } else if (hasValidDictionary(normalizedDictionaryId)) {
      fetchDictionary(normalizedDictionaryId)
      fetchWords(normalizedDictionaryId)
    } else {
      setLoading(false)
      setWords([])
    }
  }, [dictionaryId, refreshTrigger])

  const fetchDictionary = async (dictId) => {
    try {
      const response = await authFetch(`${API_URL}/dictionaries`)
      if (!response.ok) {
        throw new Error('Ошибка при загрузке словарей')
      }
      const dictionaries = await response.json()
      const dict = dictionaries.find(d => d.id === dictId)
      if (dict) {
        setDictionary(dict)
        setDictionaryName(dict.name)
        setOriginalDictionaryName(dict.name)
      }
    } catch (err) {
      console.error('Error fetching dictionary:', err)
    }
  }

  const fetchWords = async (dictId) => {
    if (!hasValidDictionary(dictId)) {
      setWords([])
      setLoading(false)
      return
    }
    
    await fetchWordsForDictionary(dictId)
  }

  const fetchWordsForDictionary = async (dictId) => {
    try {
      setLoading(true)
      const url = `${API_URL}/words?dictionary_id=${dictId}`
      const response = await authFetch(url)
      if (!response.ok) {
        throw new Error('Ошибка при загрузке слов')
      }
      const data = await response.json()
      setWords(Array.isArray(data) ? data : [])
      setError('')
    } catch (err) {
      setError(err.message)
      setWords([])
    } finally {
      setLoading(false)
    }
  }

  const handleWordClick = (word) => {
    setSelectedWord(word)
  }

  const handleDeleteWord = async () => {
    if (!selectedWord) return
    
    if (!window.confirm('Вы уверены, что хотите удалить это слово?')) {
      return
    }

    try {
      const response = await authFetch(`${API_URL}/words/${selectedWord.id}`, {
        method: 'DELETE',
      })

      if (!response.ok) {
        throw new Error('Ошибка при удалении слова')
      }

      // Remove word from local state
      setWords(words.filter(word => word.id !== selectedWord.id))
      setSelectedWord(null)
    } catch (err) {
      setError(err.message)
    }
  }

  const handleResetProgress = async () => {
    if (!selectedWord) return
    
    if (!window.confirm('Вы уверены, что хотите сбросить прогресс этого слова?')) {
      return
    }

    try {
      const response = await authFetch(`${API_URL}/words/${selectedWord.id}/reset-progress`, {
        method: 'POST',
      })

      if (!response.ok) {
        throw new Error('Ошибка при сбросе прогресса')
      }

      // Update word in local state - reset progress fields
      setWords(words.map(word => 
        word.id === selectedWord.id 
          ? { ...word, success: 0, failure: 0, last_success_at: null, last_failure_at: null }
          : word
      ))
      setSelectedWord(null)
    } catch (err) {
      setError(err.message)
    }
  }

  const handleNameChange = (e) => {
    setDictionaryName(e.target.value)
  }

  const handleNameSave = async () => {
    if (!dictionaryName.trim()) {
      return
    }

    setIsSavingName(true)
    try {
      if (!hasValidDictionary(currentDictionaryId)) {
        // Create new dictionary
        const response = await authFetch(`${API_URL}/dictionaries`, {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
          },
          body: JSON.stringify({ name: dictionaryName.trim() }),
        })

        if (!response.ok) {
          throw new Error('Ошибка при создании словаря')
        }

        const newDict = await response.json()
        const newDictionaryId = newDict.id
        
        // Update local state
        setOriginalDictionaryName(newDict.name)
        setDictionaryName(newDict.name)
        setDictionary(newDict)
        setCurrentDictionaryId(newDictionaryId)
        
        // Reinitialize screen: fetch dictionary info and words for the new dictionary
        await fetchDictionary(newDictionaryId)
        await fetchWordsForDictionary(newDictionaryId)
        
        // Update navigation to use the new dictionary ID and name (replace history entry so back goes to dictionaries)
        onNavigate?.('words', { dictionaryId: newDictionaryId, dictionaryName: newDict.name }, { replace: true })
      } else if (hasValidDictionary(currentDictionaryId)) {
        // Update existing dictionary (rename)
        const response = await authFetch(`${API_URL}/dictionaries/${currentDictionaryId}`, {
          method: 'PUT',
          headers: {
            'Content-Type': 'application/json',
          },
          body: JSON.stringify({ name: dictionaryName.trim() }),
        })

        if (!response.ok) {
          throw new Error('Ошибка при обновлении словаря')
        }

        setOriginalDictionaryName(dictionaryName.trim())
        if (dictionary) {
          setDictionary({ ...dictionary, name: dictionaryName.trim() })
        }
      }
    } catch (err) {
      setError(err.message)
    } finally {
      setIsSavingName(false)
    }
  }

  // Show save button only if name is not empty and has changed
  const showSaveButton = dictionaryName.trim() !== '' && dictionaryName.trim() !== originalDictionaryName

  if (error && !loading) {
    return (
      <div className="word-list">
        <LoadingError onRetry={() => {
          if (hasValidDictionary(currentDictionaryId)) {
            fetchWordsForDictionary(currentDictionaryId)
          }
        }} />
      </div>
    )
  }

  return (
    <div className="word-list">
      <button
        onClick={() => window.history.back()}
        className="close-x-button"
        title="Закрыть"
      >
        ✕
      </button>
      {loading && (
        <div className="fixed inset-0 flex justify-center items-center">
          <div className="flex flex-col items-center">
            <div className="w-12 h-12 border-4 border-indigo-200 border-t-indigo-600 rounded-full animate-spin mb-4"></div>
            <div className="text-gray-600 font-medium">Загрузка...</div>
          </div>
        </div>
      )}
      
      {/* Dictionary name input */}
      <div className="dictionary-name-input-container">
        <input
          type="text"
          className="dictionary-name-input"
          value={dictionaryName}
          onChange={handleNameChange}
          placeholder="Введите название словаря"
        />
        {showSaveButton && (
          <button
            className="dictionary-name-save-button"
            onClick={handleNameSave}
            disabled={isSavingName}
            title="Сохранить название"
          >
            ✓
          </button>
        )}
      </div>

      {/* Show add button and words list only if dictionaryId exists and is not new */}
      {hasValidDictionary(currentDictionaryId) && (
        <>
          {(!words || words.length === 0) ? (
            <>
              <div className="empty-state">
                <p>Слов пока нет. Добавьте слова через экран "Добавить слова".</p>
              </div>
            </>
          ) : (
            <>
              <div className="words-grid">
                {words.map((word) => (
                  <div 
                    key={word.id} 
                    className="word-card"
                    onClick={() => handleWordClick(word)}
                  >
                    <div className="word-content">
                      <div className="word-header">
                        <h3 className="word-name">{word.name}</h3>
                      </div>
                      <div className="word-translation">{word.translation}</div>
                      {word.description && (
                        <div className="word-description">{word.description}</div>
                      )}
                    </div>
                    <div className="word-stats">
                      <span className="stat-success">{word.success || 0}</span>
                      <span className="stat-separator"> | </span>
                      <span className="stat-failure">{word.failure || 0}</span>
                    </div>
                  </div>
                ))}
              </div>
            </>
          )}
        </>
      )}

      {/* Модальное окно для действий со словом */}
      {selectedWord && (
        <div className="word-modal-overlay" onClick={() => setSelectedWord(null)}>
          <div className="word-modal" onClick={(e) => e.stopPropagation()}>
            <div className="word-modal-header">
              <h3>{selectedWord.name}</h3>
            </div>
            <div className="word-modal-actions">
              <button className="word-modal-reset" onClick={handleResetProgress}>
                Сбросить
              </button>
              <button className="word-modal-delete" onClick={handleDeleteWord}>
                Удалить
              </button>
            </div>
          </div>
        </div>
      )}
    </div>
  )
}

export default WordList

