import { NextRequest, NextResponse } from 'next/server'
import { readFile, stat } from 'fs/promises'
import path from 'path'
import { auth } from '@/auth'
import { canAccessUploadedNoteImage } from '@/lib/upload-access'

const UPLOAD_DIR = path.join(process.cwd(), 'data', 'uploads')

const MIME_MAP: Record<string, string> = {
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.png': 'image/png',
  '.gif': 'image/gif',
  '.webp': 'image/webp',
}

export async function GET(
  _req: NextRequest,
  { params }: { params: Promise<{ path: string[] }> }
) {
  const session = await auth()
  const { path: segments } = await params

  // Only serve from uploads/notes/ (flat or userId/file)
  if (!segments.length || segments[0] !== 'notes') {
    return new NextResponse('Not found', { status: 404 })
  }

  // Reject path traversal
  if (segments.some((s) => s === '..' || s.includes('\0'))) {
    return new NextResponse('Forbidden', { status: 403 })
  }

  const filename = segments[segments.length - 1]
  // Never serve meta sidecars as images
  if (filename.endsWith('.meta.json')) {
    return new NextResponse('Not found', { status: 404 })
  }

  const allowed = await canAccessUploadedNoteImage(segments, session?.user?.id)
  if (!allowed) {
    return new NextResponse(session?.user?.id ? 'Forbidden' : 'Unauthorized', {
      status: session?.user?.id ? 403 : 401,
      headers: {
        // Do not let browsers / CDNs cache a denial (would stick a broken image)
        'Cache-Control': 'no-store',
      },
    })
  }

  const ext = path.extname(filename).toLowerCase()
  const contentType = MIME_MAP[ext]
  if (!contentType) {
    return new NextResponse('Unsupported file type', { status: 400 })
  }

  const safePath = path.join(UPLOAD_DIR, ...segments)
  if (!safePath.startsWith(UPLOAD_DIR + path.sep) && safePath !== UPLOAD_DIR) {
    return new NextResponse('Forbidden', { status: 403 })
  }

  try {
    const fileStats = await stat(safePath)
    if (!fileStats.isFile()) {
      return new NextResponse('Not found', { status: 404 })
    }

    const buffer = await readFile(safePath)

    return new NextResponse(buffer, {
      headers: {
        'Content-Type': contentType,
        // private: only for authenticated session fetches; still long cache after auth ok
        'Cache-Control': 'private, max-age=31536000, immutable',
        'Content-Length': String(buffer.length),
      },
    })
  } catch {
    return new NextResponse('Not found', { status: 404 })
  }
}