import { NextRequest, NextResponse } from 'next/server'
import { z } from 'zod'
import { PrismaClient, ChatMessageRole } from '@prisma/client'
import { searchBibleHybrid, BibleVerse } from '@/lib/vector-search'
import { verifyToken } from '@/lib/auth'

const prisma = new PrismaClient()

export const runtime = 'nodejs'

const chatRequestSchema = z.object({
  message: z.string().min(1),
  conversationId: z.string().optional(),
  locale: z.string().optional().default('ro'),
  // Keep history for backward compatibility with frontend
  history: z.array(z.object({
    id: z.string(),
    role: z.enum(['user', 'assistant']),
    content: z.string(),
    timestamp: z.string()
  })).optional().default([])
})

export async function POST(request: NextRequest) {
  try {
    const body = await request.json()
    const { message, conversationId, locale, history } = chatRequestSchema.parse(body)

    // Try to get user from authentication (optional for backward compatibility)
    let userId: string | null = null
    const authHeader = request.headers.get('authorization')
    if (authHeader?.startsWith('Bearer ')) {
      try {
        const token = authHeader.substring(7)
        const payload = verifyToken(token)
        userId = payload.userId
      } catch (error) {
        // Continue without authentication for backward compatibility
        console.log('Chat without authentication')
      }
    }

    // Handle conversation logic
    let finalConversationId = conversationId
    let conversationHistory: any[] = []

    if (userId) {
      // User is authenticated - use conversation system
      if (conversationId) {
        // Load existing conversation
        const conversation = await prisma.chatConversation.findUnique({
          where: {
            id: conversationId,
            userId,
            isActive: true
          },
          include: {
            messages: {
              orderBy: { timestamp: 'desc' },
              take: 15, // Last 15 messages for context
              select: {
                role: true,
                content: true,
                timestamp: true
              }
            }
          }
        })

        if (conversation) {
          conversationHistory = conversation.messages
            .reverse() // Oldest first for context
            .map(msg => ({
              role: msg.role.toLowerCase(),
              content: msg.content,
              timestamp: msg.timestamp.toISOString()
            }))
        }
      } else {
        // Create new conversation
        const conversation = await prisma.chatConversation.create({
          data: {
            userId,
            title: generateConversationTitle(message),
            language: locale,
            lastMessageAt: new Date()
          }
        })
        finalConversationId = conversation.id
      }
    } else {
      // Anonymous user - use provided history for backward compatibility
      conversationHistory = history
    }

    // Generate AI response
    const aiResponse = await generateBiblicalResponse(message, locale, conversationHistory)

    // Save messages to database if user is authenticated
    if (userId && finalConversationId) {
      await prisma.$transaction([
        // Save user message
        prisma.chatMessage.create({
          data: {
            conversationId: finalConversationId,
            userId,
            role: ChatMessageRole.USER,
            content: message,
            timestamp: new Date()
          }
        }),
        // Save AI response
        prisma.chatMessage.create({
          data: {
            conversationId: finalConversationId,
            userId,
            role: ChatMessageRole.ASSISTANT,
            content: aiResponse,
            timestamp: new Date()
          }
        }),
        // Update conversation last message time
        prisma.chatConversation.update({
          where: { id: finalConversationId },
          data: { lastMessageAt: new Date() }
        })
      ])
    }

    return NextResponse.json({
      success: true,
      response: aiResponse,
      conversationId: finalConversationId
    })

  } catch (error) {
    console.error('Error in chat API:', error)

    if (error instanceof z.ZodError) {
      return NextResponse.json(
        {
          success: false,
          error: 'Invalid request format',
          details: error.errors
        },
        { status: 400 }
      )
    }

    return NextResponse.json(
      {
        success: false,
        error: 'Failed to process chat message'
      },
      { status: 500 }
    )
  }
}

async function generateBiblicalResponse(message: string, locale: string, history: any[]): Promise<string> {
  try {
    // Search for relevant Bible verses using vector search with language filtering
    const relevantVerses = await searchBibleHybrid(message, locale, 5)

    // Create context from relevant verses
    const versesContext = relevantVerses
      .map(verse => `${verse.ref}: "${verse.text_raw}"`)
      .join('\n\n')

    // Intelligent context selection for conversation history
    const conversationHistory = buildSmartContext(history, message, locale)

    // Create language-specific system prompts
    const systemPrompts = {
      ro: `Ești un asistent AI pentru întrebări biblice în limba română. Răspunde pe baza Scripturii, fiind respectuos și înțelept.

Instrucțiuni:
- Folosește versurile biblice relevante pentru a răspunde la întrebare
- Citează întotdeauna referințele biblice (ex: Ioan 3:16)
- Răspunde în română
- Fii empatic și încurajator
- Dacă nu ești sigur, încurajează studiul personal și rugăciunea

Versuri relevante pentru această întrebare:
${versesContext}

Conversația anterioară:
${conversationHistory}

Întrebarea curentă: ${message}`,

      en: `You are an AI assistant for biblical questions in English. Answer based on Scripture, being respectful and wise.

Instructions:
- Use the relevant Bible verses to answer the question
- Always cite biblical references (e.g., John 3:16)
- Respond in English
- Be empathetic and encouraging
- If unsure, encourage personal study and prayer

Relevant verses for this question:
${versesContext}

Previous conversation:
${conversationHistory}

Current question: ${message}`
    }

    const systemPrompt = systemPrompts[locale as keyof typeof systemPrompts] || systemPrompts.en

    // Call Azure OpenAI
    const response = await fetch(
      `${process.env.AZURE_OPENAI_ENDPOINT}/openai/deployments/${process.env.AZURE_OPENAI_DEPLOYMENT}/chat/completions?api-version=${process.env.AZURE_OPENAI_API_VERSION}`,
      {
        method: 'POST',
        headers: {
          'api-key': process.env.AZURE_OPENAI_KEY!,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          messages: [
            {
              role: 'system',
              content: systemPrompt
            },
            {
              role: 'user',
              content: message
            }
          ],
          max_tokens: 2000,
          temperature: 0.7,
          top_p: 0.9
        }),
      }
    )

    if (!response.ok) {
      throw new Error(`Azure OpenAI API error: ${response.status}`)
    }

    const data = await response.json()
    return data.choices[0].message.content

  } catch (error) {
    console.error('Error calling Azure OpenAI:', error)

    // Language-specific fallback responses
    const fallbackResponses = {
      ro: `Îmi pare rău, dar întâmpin o problemă tehnică în acest moment. Te încurajez să cercetezi acest subiect în Scripturi și să te rogi pentru înțelegere.

"Cercetați Scripturile, pentru că socotiți că în ele aveți viața veșnică, și tocmai ele mărturisesc despre Mine" (Ioan 5:39).

"Dacă vreunul dintre voi duce lipsă de înțelepciune, să ceară de la Dumnezeu, care dă tuturor cu dărnicie și fără mustrare, și i se va da" (Iacov 1:5).`,

      en: `Sorry, I'm experiencing a technical issue at the moment. I encourage you to research this topic in Scripture and pray for understanding.

"You study the Scriptures diligently because you think that in them you have eternal life. These are the very Scriptures that testify about me" (John 5:39).

"If any of you lacks wisdom, you should ask God, who gives generously to all without finding fault, and it will be given to you" (James 1:5).`
    }

    return fallbackResponses[locale as keyof typeof fallbackResponses] || fallbackResponses.en
  }
}

function generateConversationTitle(message: string): string {
  // Generate a title from the first message (max 50 characters)
  const title = message.length > 47
    ? message.substring(0, 47) + '...'
    : message

  return title
}

function buildSmartContext(history: any[], currentMessage: string, locale: string): string {
  if (history.length === 0) return ''

  const MAX_CONTEXT_TOKENS = 1500 // Reserve tokens for context
  const RECENT_MESSAGES_COUNT = 6 // Always include last 6 messages

  // Step 1: Always include the most recent messages for immediate context
  const recentMessages = history.slice(-RECENT_MESSAGES_COUNT)

  // Step 2: Calculate relevance scores for older messages
  const olderMessages = history.slice(0, -RECENT_MESSAGES_COUNT)
  const relevantOlderMessages = findRelevantMessages(olderMessages, currentMessage, locale)

  // Step 3: Combine recent + relevant older messages
  const selectedMessages = [...relevantOlderMessages, ...recentMessages]

  // Step 4: Apply token-based truncation if needed
  const optimizedContext = optimizeContextForTokens(selectedMessages, MAX_CONTEXT_TOKENS)

  // Step 5: Format for AI consumption
  return formatContextForAI(optimizedContext)
}

function findRelevantMessages(messages: any[], currentMessage: string, locale: string): any[] {
  if (messages.length === 0) return []

  // Score messages based on relevance to current question
  const scoredMessages = messages.map(msg => ({
    ...msg,
    relevanceScore: calculateMessageRelevance(msg, currentMessage, locale)
  }))

  // Sort by relevance and take top 3-5 most relevant older messages
  return scoredMessages
    .filter(msg => msg.relevanceScore > 0.3) // Only include somewhat relevant messages
    .sort((a, b) => b.relevanceScore - a.relevanceScore)
    .slice(0, 5) // Max 5 relevant older messages
}

function calculateMessageRelevance(message: any, currentMessage: string, locale: string): number {
  const msgContent = message.content.toLowerCase()
  const currentContent = currentMessage.toLowerCase()

  let score = 0

  // Keyword overlap scoring
  const currentWords = currentContent.split(/\s+/).filter(word => word.length > 3)
  const messageWords = msgContent.split(/\s+/)

  for (const word of currentWords) {
    if (messageWords.some(mWord => mWord.includes(word) || word.includes(mWord))) {
      score += 0.2
    }
  }

  // Biblical reference detection (higher relevance)
  const biblicalPatterns = locale === 'ro'
    ? [/\b(geneza|exod|levitic|numeri|deuteronom|iosua|judecători|rut|samuel|regi|cronici|ezra|neemia|estera|iov|psalmi|proverbe|ecclesiast|cântarea|isaia|ieremia|plângeri|ezechiel|daniel|osea|ioel|amos|obadia|iona|mica|naum|habacuc|țefania|hagai|zaharia|maleahi|matei|marcu|luca|ioan|faptele|romani|corinteni|galateni|efeseni|filipeni|coloseni|tesaloniceni|timotei|tit|filimon|evrei|iacov|petru|ioan|iuda|apocalipsa)\s*\d+/gi]
    : [/\b(genesis|exodus|leviticus|numbers|deuteronomy|joshua|judges|ruth|samuel|kings|chronicles|ezra|nehemiah|esther|job|psalm|proverbs|ecclesiastes|song|isaiah|jeremiah|lamentations|ezekiel|daniel|hosea|joel|amos|obadiah|jonah|micah|nahum|habakkuk|zephaniah|haggai|zechariah|malachi|matthew|mark|luke|john|acts|romans|corinthians|galatians|ephesians|philippians|colossians|thessalonians|timothy|titus|philemon|hebrews|james|peter|jude|revelation)\s*\d+/gi]

  if (biblicalPatterns.some(pattern => pattern.test(msgContent))) {
    score += 0.4
  }

  // Recent user questions get higher relevance
  if (message.role === 'user') {
    score += 0.1
  }

  // Time decay (older messages get slightly lower scores)
  const messageAge = Date.now() - new Date(message.timestamp).getTime()
  const hoursAge = messageAge / (1000 * 60 * 60)
  const timeDecay = Math.max(0.5, 1 - (hoursAge / 168)) // Decay over a week

  return Math.min(1.0, score * timeDecay)
}

function optimizeContextForTokens(messages: any[], maxTokens: number): any[] {
  // Rough token estimation (1 token ≈ 4 characters in English, 3 in Romanian)
  let currentTokens = 0
  const optimizedMessages = []

  // Start from most recent and work backwards
  for (let i = messages.length - 1; i >= 0; i--) {
    const message = messages[i]
    const estimatedTokens = Math.ceil(message.content.length / 3.5)

    if (currentTokens + estimatedTokens <= maxTokens) {
      optimizedMessages.unshift(message) // Add to beginning to maintain order
      currentTokens += estimatedTokens
    } else {
      // If this message would exceed limit, try to include a summary instead
      if (i > 0 && optimizedMessages.length < 3) {
        const summary = summarizeMessage(message)
        const summaryTokens = Math.ceil(summary.length / 3.5)
        if (currentTokens + summaryTokens <= maxTokens) {
          optimizedMessages.unshift({
            ...message,
            content: summary,
            isSummary: true
          })
          currentTokens += summaryTokens
        }
      }
      break
    }
  }

  return optimizedMessages
}

function summarizeMessage(message: any): string {
  const content = message.content
  if (content.length <= 100) return content

  // Extract key points and questions
  const sentences = content.split(/[.!?]+/).filter(s => s.trim().length > 10)
  if (sentences.length <= 2) return content

  // Keep first and last sentence, or most important parts
  const summary = sentences.length > 3
    ? `${sentences[0].trim()}... ${sentences[sentences.length - 1].trim()}`
    : sentences.slice(0, 2).join('. ').trim()

  return `[Summary] ${summary}`
}

function formatContextForAI(messages: any[]): string {
  if (messages.length === 0) return ''

  return messages.map(msg => {
    const prefix = msg.isSummary ? '[Summary] ' : ''
    return `${prefix}${msg.role}: ${msg.content}`
  }).join('\n')
}