import crypto from 'crypto'

/**
 * At-rest encryption for Shopify custom-app client id/secret.
 *
 * AES-256-GCM with a dedicated env key, mirroring the WooCommerce credential
 * store (extensions/general/woocommerce/lib/credentials.ts) and the
 * Skatteverket token store: 12-byte IV, 16-byte auth tag, layout
 * iv|tag|ciphertext, base64url encoded. The key is deployment-wide (not
 * per-tenant); what makes rows useless off-server is that
 * SHOPIFY_CREDENTIALS_ENCRYPTION_KEY never leaves the environment.
 */

const ALGORITHM = 'aes-256-gcm'

/** Whether the integration is configured on this deployment. */
export function isShopifyConfigured(): boolean {
  return Boolean(process.env.SHOPIFY_CREDENTIALS_ENCRYPTION_KEY)
}

function getEncryptionKey(): Buffer {
  const key = process.env.SHOPIFY_CREDENTIALS_ENCRYPTION_KEY
  if (!key) throw new Error('SHOPIFY_CREDENTIALS_ENCRYPTION_KEY is required')
  return crypto.createHash('sha256').update(key).digest()
}

export function encryptCredential(plaintext: string): string {
  const key = getEncryptionKey()
  const iv = crypto.randomBytes(12)
  const cipher = crypto.createCipheriv(ALGORITHM, key, iv)
  const encrypted = Buffer.concat([cipher.update(plaintext, 'utf8'), cipher.final()])
  const tag = cipher.getAuthTag()
  return Buffer.concat([iv, tag, encrypted]).toString('base64url')
}

export function decryptCredential(ciphertext: string): string {
  const key = getEncryptionKey()
  const combined = Buffer.from(ciphertext, 'base64url')
  const iv = combined.subarray(0, 12)
  const tag = combined.subarray(12, 28)
  const encrypted = combined.subarray(28)
  const decipher = crypto.createDecipheriv(ALGORITHM, key, iv)
  decipher.setAuthTag(tag)
  return Buffer.concat([decipher.update(encrypted), decipher.final()]).toString('utf8')
}

/** Decrypted API credentials for an active connection. */
export function credentialsOf(connection: {
  shop_domain: string
  client_id_encrypted: string | null
  client_secret_encrypted: string | null
}): { shopDomain: string; clientId: string; clientSecret: string } {
  if (!connection.client_id_encrypted || !connection.client_secret_encrypted) {
    throw new Error('Connection has no stored credentials')
  }
  return {
    shopDomain: connection.shop_domain,
    clientId: decryptCredential(connection.client_id_encrypted),
    clientSecret: decryptCredential(connection.client_secret_encrypted),
  }
}