-- Additive: User.role for admin access control + AuditLog for sensitive admin actions.
-- Non-destructive: existing users default to role `user`; no rows deleted.

ALTER TABLE `users`
  ADD COLUMN `role` ENUM('user', 'admin') NOT NULL DEFAULT 'user';

CREATE INDEX `idx_users_role` ON `users`(`role`);

CREATE TABLE `audit_logs` (
  `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
  `actorUserId` BIGINT UNSIGNED NULL,
  `action` VARCHAR(64) NOT NULL,
  `targetUserId` BIGINT UNSIGNED NULL,
  `targetType` VARCHAR(64) NULL,
  `targetId` VARCHAR(191) NULL,
  `metadata` JSON NULL,
  `ipAddress` VARCHAR(64) NULL,
  `userAgent` VARCHAR(512) NULL,
  `createdAt` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),

  PRIMARY KEY (`id`),
  INDEX `idx_audit_logs_actor_created`(`actorUserId`, `createdAt`),
  INDEX `idx_audit_logs_action_created`(`action`, `createdAt`),
  INDEX `idx_audit_logs_target_created`(`targetUserId`, `createdAt`),

  CONSTRAINT `audit_logs_actorUserId_fkey`
    FOREIGN KEY (`actorUserId`) REFERENCES `users`(`id`)
    ON DELETE SET NULL ON UPDATE CASCADE,
  CONSTRAINT `audit_logs_targetUserId_fkey`
    FOREIGN KEY (`targetUserId`) REFERENCES `users`(`id`)
    ON DELETE SET NULL ON UPDATE CASCADE
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;