import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import { paragraphRefactorService } from '@/lib/ai/services/paragraph-refactor.service'
import { getAISettings } from '@/app/actions/ai-settings'
import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'

export async function POST(request: NextRequest) {
  try {
    const session = await auth()

    if (!session?.user?.id) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    // Respect user's paragraphRefactor toggle (Assistant IA)
    const userSettings = await getAISettings(session.user.id)
    if (userSettings.paragraphRefactor === false) {
      return NextResponse.json({ error: 'Feature disabled' }, { status: 403 })
    }

    const { text, option, format, language } = await request.json()

    // Validation
    if (!text || typeof text !== 'string') {
      return NextResponse.json({ error: 'Text is required' }, { status: 400 })
    }

    // Map option to refactor mode
    const modeMap: Record<string, 'clarify' | 'shorten' | 'improveStyle' | 'fix_grammar' | 'translate' | 'explain'> = {
      'clarify': 'clarify',
      'shorten': 'shorten',
      'improve': 'improveStyle',
      'fix_grammar': 'fix_grammar',
      'translate': 'translate',
      'explain': 'explain'
    }

    const mode = modeMap[option]
    if (!mode) {
      return NextResponse.json(
        { error: 'Invalid option. Use: clarify, shorten, improve, fix_grammar, translate, or explain' },
        { status: 400 }
      )
    }

    // Validate word count
    const validation = paragraphRefactorService.validateWordCount(text)
    if (!validation.valid) {
      return NextResponse.json({
        error: validation.error,
        errorKey: validation.errorKey,
        params: validation.params,
      }, { status: 400 })
    }

    // Check quota
    try {
      await checkEntitlementOrThrow(session.user.id, 'reformulate')
    } catch (err) {
      if (err instanceof QuotaExceededError) {
        const isTierLocked = err.currentQuota === 0
        return NextResponse.json({
          error: isTierLocked ? 'feature_locked' : 'quota_exceeded',
          errorKey: isTierLocked ? 'ai.featureLocked' : 'ai.quotaExceeded',
          upgradeTier: err.upgradeTier,
          quotaExceeded: true,
        }, { status: 402 })
      }
      throw err
    }

    // Use the ParagraphRefactorService
    const result = await paragraphRefactorService.refactor(text, mode, format === 'html' ? 'html' : 'markdown', language)

    incrementUsageAsync(session.user.id, 'reformulate')

    return NextResponse.json({
      originalText: result.original,
      reformulatedText: result.refactored,
      option: option,
      language: result.language,
      wordCountChange: result.wordCountChange
    })
  } catch (error: any) {
    return NextResponse.json(
      { error: error.message || 'Failed to reformulate text' },
      { status: 500 }
    )
  }
}