import { NextRequest, NextResponse } from 'next/server'

export async function POST(request: NextRequest) {
  try {
    const { latex, filename } = await request.json()

    if (!latex) {
      return NextResponse.json(
        { error: 'LaTeX content is required' },
        { status: 400 }
      )
    }

    console.log('📄 Compiling LaTeX to PDF...')
    console.log(`   Content length: ${latex.length} characters`)

    // Try LaTeX compilation API with better error handling
    try {
      const compileResponse = await fetch('https://texlive.net/cgi-bin/latexcgi', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded',
        },
        body: new URLSearchParams({
          filecontents: latex,
          filename: 'document.tex',
          engine: 'pdflatex',
          return: 'pdf'
        }),
        signal: AbortSignal.timeout(60000)
      })

      // Check if response is actually a PDF
      const contentType = compileResponse.headers.get('content-type')
      
      if (compileResponse.ok && contentType?.includes('pdf')) {
        const pdfBuffer = Buffer.from(await compileResponse.arrayBuffer())
        console.log(`✅ LaTeX compiled successfully! PDF size: ${pdfBuffer.byteLength} bytes`)

        const response = new NextResponse(pdfBuffer)
        response.headers.set('Content-Type', 'application/pdf')
        response.headers.set('Content-Disposition', `attachment; filename="${filename || 'document.pdf'}"`)

        return response
      } else {
        // API returned error or HTML
        const errorText = await compileResponse.text()
        console.error('❌ LaTeX compilation failed:', errorText.substring(0, 200))
        
        return NextResponse.json(
          { 
            error: 'LaTeX compilation service unavailable',
            details: 'The external LaTeX compiler is currently unavailable.',
            message: 'LaTeX compilation services are temporarily unavailable. Your .tex file has been saved - you can download and compile it locally.'
          },
          { status: 503 }
        )
      }
    } catch (fetchError) {
      console.error('❌ API fetch error:', fetchError)
      return NextResponse.json(
        { 
          error: 'LaTeX compilation service unavailable',
          details: 'Could not reach LaTeX compilation service',
          message: 'LaTeX compilation services are temporarily unavailable. Your .tex file has been saved - you can download and compile it locally.'
        },
        { status: 503 }
      )
    }

  } catch (error) {
    console.error('❌ Error compiling LaTeX:', error)
    console.error('   Error type:', error instanceof Error ? error.constructor.name : typeof error)
    console.error('   Error message:', error instanceof Error ? error.message : String(error))
    
    return NextResponse.json(
      { 
        error: 'Failed to compile LaTeX',
        details: error instanceof Error ? error.message : String(error),
        message: 'Network error or compilation timeout. Please try again.'
      },
      { status: 500 }
    )
  }
}