CREATE TABLE IF NOT EXISTS `user_credits` (
    `id`         BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    `user_id`    BIGINT UNSIGNED NOT NULL UNIQUE,
    `balance`    INT UNSIGNED    NOT NULL DEFAULT 10,
    `total_used` INT UNSIGNED    NOT NULL DEFAULT 0,
    `updated_at` DATETIME        NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    PRIMARY KEY (`id`),
    INDEX `idx_user_credits_user_id` (`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

CREATE TABLE IF NOT EXISTS `credit_transactions` (
    `id`          BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    `user_id`     BIGINT UNSIGNED NOT NULL,
    `amount`      INT             NOT NULL COMMENT 'Negative = debit, positive = credit',
    `type`        ENUM('debit','credit','refund','bonus') NOT NULL,
    `description` VARCHAR(255)    NOT NULL,
    `created_at`  DATETIME        NOT NULL DEFAULT CURRENT_TIMESTAMP,
    PRIMARY KEY (`id`),
    INDEX `idx_credit_tx_user_id` (`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;