import { NextRequest, NextResponse } from 'next/server'
import { readFile } from 'fs/promises'
import { existsSync } from 'fs'
import { join } from 'path'
import { getManualsThumbnailsRoot } from '@/lib/manuals-paths'

// API routes are not supported in static export (GHL hosting)
// Thumbnails are now served as static files from /thumbnails/
export const dynamic = 'force-static'

/**
 * API route to serve thumbnail images for PDF manuals
 * This allows serving files from outside the public folder
 * 
 * Usage: /api/thumbnails/BevMax/manual.jpg
 * NOTE: This route is disabled for static export. Use /thumbnails/ paths instead.
 */

// Required for static export - returns empty array to skip this route
export async function generateStaticParams(): Promise<Array<{ path: string[] }>> {
  return []
}

export async function GET(
  request: NextRequest,
  { params }: { params: Promise<{ path: string[] }> }
) {
  try {
    const { path: pathArray } = await params
    
    // Decode URL-encoded path segments - handle multiple encodings
    const decodedPath = pathArray.map(segment => {
      try {
        // Try decoding multiple times in case of double encoding
        let decoded = segment
        while (decoded !== decodeURIComponent(decoded)) {
          decoded = decodeURIComponent(decoded)
        }
        return decoded
      } catch {
        // If decoding fails, use original
        return segment
      }
    })
    const filePath = decodedPath.join('/')
    
    // Security: Prevent directory traversal
    if (filePath.includes('..') || filePath.startsWith('/')) {
      return new NextResponse('Invalid path', { status: 400 })
    }
    
    // Construct full path to thumbnail
    const thumbnailsDir = getManualsThumbnailsRoot()
    const fullPath = join(thumbnailsDir, filePath)
    
    // Normalize paths to handle both forward and backward slashes
    const normalizedFullPath = fullPath.replace(/\\/g, '/')
    const normalizedThumbnailsDir = thumbnailsDir.replace(/\\/g, '/')
    
    // Verify file exists and is within thumbnails directory
    let fileToRead = normalizedFullPath
    if (!existsSync(normalizedFullPath)) {
      // Try with original path in case of encoding issues
      if (existsSync(fullPath)) {
        fileToRead = fullPath
      } else {
        // Try with different path separators
        const altPath = fullPath.replace(/\//g, '\\')
        if (existsSync(altPath)) {
          fileToRead = altPath
        } else {
          // Thumbnail doesn't exist - return 404 (this is expected for manuals without thumbnails)
          return new NextResponse('Thumbnail not found', { status: 404 })
        }
      }
    }
    
    // Verify the file is within the thumbnails directory (security check)
    const resolvedPath = fileToRead.replace(/\\/g, '/')
    if (!resolvedPath.startsWith(normalizedThumbnailsDir.replace(/\\/g, '/'))) {
      console.error(`Security violation: Path outside thumbnails directory: ${resolvedPath}`)
      return new NextResponse('Invalid path', { status: 400 })
    }
    
    // Only allow image files (jpg, jpeg, png)
    const lowerPath = filePath.toLowerCase()
    if (!lowerPath.endsWith('.jpg') && !lowerPath.endsWith('.jpeg') && !lowerPath.endsWith('.png')) {
      return new NextResponse('Invalid file type', { status: 400 })
    }
    
    // Read and serve the file
    const fileBuffer = await readFile(fileToRead)
    
    // Get filename for Content-Disposition header
    const filename = decodedPath[decodedPath.length - 1]
    
    // Determine content type
    const contentType = lowerPath.endsWith('.png') 
      ? 'image/png' 
      : 'image/jpeg'
    
    return new NextResponse(fileBuffer, {
      headers: {
        'Content-Type': contentType,
        'Content-Disposition': `inline; filename="${encodeURIComponent(filename)}"`,
        'Cache-Control': 'public, max-age=31536000, immutable',
        'X-Content-Type-Options': 'nosniff',
      },
    })
  } catch (error) {
    console.error('Error serving thumbnail:', error)
    if (error instanceof Error) {
      console.error('Error details:', error.message, error.stack)
    }
    return new NextResponse('Internal server error', { status: 500 })
  }
}