import { createServerClient, type CookieOptions } from '@supabase/ssr'
import { cookies } from 'next/headers'
import { NextResponse } from 'next/server'

export interface AuthResult {
  authenticated: true
  userId: string
  email: string | undefined
}

interface AuthError {
  authenticated: false
  response: NextResponse
}

/**
 * Verify that the incoming request belongs to an authenticated Supabase user.
 *
 * Usage in any API route:
 * ```ts
 * const auth = await requireAuth()
 * if (!auth.authenticated) return auth.response
 * // auth.userId is available
 * ```
 *
 * Works with both cookie-based sessions (browser) and
 * Authorization: Bearer <token> header (API clients).
 */
export async function requireAuth(request?: Request): Promise<AuthResult | AuthError> {
  try {
    const cookieStore = await cookies()

    const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL
    const supabaseAnonKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY
    if (!supabaseUrl || !supabaseAnonKey) {
      return {
        authenticated: false as const,
        response: NextResponse.json(
          { error: 'Sunucu yapılandırma hatası' },
          { status: 500 }
        ),
      }
    }

    const supabase = createServerClient(
      supabaseUrl,
      supabaseAnonKey,
      {
        cookies: {
          getAll() {
            return cookieStore.getAll()
          },
          setAll(cookiesToSet: { name: string; value: string; options: CookieOptions }[]) {
            try {
              cookiesToSet.forEach(({ name, value, options }) =>
                cookieStore.set(name, value, options)
              )
            } catch {
              // Cannot set cookies in read-only context
            }
          },
        },
      }
    )

    // Try cookie-based auth first
    const { data: { user }, error } = await supabase.auth.getUser()

    if (user && !error) {
      return { authenticated: true, userId: user.id, email: user.email }
    }

    // Fallback: try Authorization header (for API clients)
    if (request) {
      const authHeader = request.headers.get('authorization')
      if (authHeader?.startsWith('Bearer ')) {
        const token = authHeader.slice(7)
        const { data: { user: tokenUser }, error: tokenError } =
          await supabase.auth.getUser(token)
        if (tokenUser && !tokenError) {
          return { authenticated: true, userId: tokenUser.id, email: tokenUser.email }
        }
      }
    }

    return {
      authenticated: false,
      response: NextResponse.json(
        { error: 'Kimlik doğrulama gerekli. Lütfen giriş yapın.' },
        { status: 401 }
      ),
    }
  } catch {
    return {
      authenticated: false,
      response: NextResponse.json(
        { error: 'Kimlik doğrulama hatası' },
        { status: 401 }
      ),
    }
  }
}