-- 课时核对表 Excel 流水账 — 扩展字段 + 月度快照 + 上课记录
-- 与现有 students / courses / student_accounts 集成，非独立库

-- ---------- students 扩展 ----------
ALTER TABLE `students`
    ADD COLUMN `display_name` VARCHAR(50) NULL COMMENT '括号外正式姓名' AFTER `name`,
    ADD COLUMN `nickname` VARCHAR(50) NULL COMMENT '括号内小名' AFTER `display_name`;

-- ---------- courses 扩展 ----------
ALTER TABLE `courses`
    ADD COLUMN `course_code` VARCHAR(20) NULL COMMENT 'scratch/python/c++/wedo' AFTER `name`,
    ADD UNIQUE INDEX `uk_courses_code` (`course_code`);

-- ---------- student_accounts（学员课程账户）扩展 ----------
ALTER TABLE `student_accounts`
    ADD COLUMN `unit_price` DECIMAL(10,4) DEFAULT 0 COMMENT '当前单价' AFTER `cumulative_start_date`,
    ADD COLUMN `account_status` VARCHAR(20) DEFAULT 'active' COMMENT 'active/graduated' AFTER `unit_price`;

-- ---------- monthly_snapshots（月度快照，核心表）----------
CREATE TABLE IF NOT EXISTS `monthly_snapshots` (
    `id` INT NOT NULL AUTO_INCREMENT,
    `account_id` INT NOT NULL,
    `year` SMALLINT NOT NULL,
    `month` SMALLINT NOT NULL,
    `seq_no` INT NULL,
    `prev_lessons` DECIMAL(10,2) NULL,
    `prev_gift_lessons` DECIMAL(10,2) NULL,
    `prev_total_lessons` DECIMAL(10,2) NULL,
    `prev_balance` DECIMAL(12,2) NULL,
    `new_signup_amount` DECIMAL(12,2) NULL,
    `new_signup_lessons` DECIMAL(10,2) NULL,
    `new_signup_gift_lessons` DECIMAL(10,2) NULL,
    `renewal_amount` DECIMAL(12,2) NULL,
    `renewal_lessons` DECIMAL(10,2) NULL,
    `renewal_gift_lessons` DECIMAL(10,2) NULL,
    `consumed_lessons` DECIMAL(10,2) NULL,
    `consumed_amount` DECIMAL(12,2) NULL,
    `refund_lessons` DECIMAL(10,2) NULL,
    `account_fee` DECIMAL(12,2) NULL,
    `refund_gift_lessons` DECIMAL(10,2) NULL,
    `refund_amount` DECIMAL(12,2) NULL,
    `end_lessons` DECIMAL(10,2) NULL,
    `end_gift_lessons` DECIMAL(10,2) NULL,
    `end_total_lessons` DECIMAL(10,2) NULL,
    `end_balance` DECIMAL(12,2) NULL,
    `unit_price` DECIMAL(10,4) NULL,
    `notes` TEXT NULL,
    `source_file` VARCHAR(200) NULL,
    `created_at` DATETIME DEFAULT CURRENT_TIMESTAMP,
    PRIMARY KEY (`id`),
    UNIQUE KEY `uq_snapshot_account_month` (`account_id`, `year`, `month`),
    KEY `idx_snapshot_period` (`year`, `month`),
    KEY `idx_snapshot_account` (`account_id`),
    CONSTRAINT `fk_snapshot_account` FOREIGN KEY (`account_id`) REFERENCES `student_accounts` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='课时核对表月度快照';

-- ---------- class_records（上课记录）----------
CREATE TABLE IF NOT EXISTS `class_records` (
    `id` INT NOT NULL AUTO_INCREMENT,
    `account_id` INT NOT NULL,
    `year` SMALLINT NOT NULL,
    `month` SMALLINT NOT NULL,
    `class_date` DATE NOT NULL,
    `lessons_consumed` DECIMAL(10,2) DEFAULT 2,
    `raw_text` VARCHAR(50) NULL,
    `created_at` DATETIME DEFAULT CURRENT_TIMESTAMP,
    PRIMARY KEY (`id`),
    UNIQUE KEY `uq_class_record_day` (`account_id`, `year`, `month`, `class_date`, `lessons_consumed`),
    KEY `idx_class_record_account` (`account_id`),
    KEY `idx_class_record_date` (`class_date`),
    CONSTRAINT `fk_class_record_account` FOREIGN KEY (`account_id`) REFERENCES `student_accounts` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='Excel上课情况解析记录';

-- 初始化课程类型（可按机构调整显示名）
INSERT IGNORE INTO `courses` (`name`, `course_code`, `level`, `type`, `status`) VALUES
    ('Scratch', 'scratch', 'scratch', '编程', 1),
    ('Python', 'python', 'python', '编程', 1),
    ('C++', 'c++', 'c++', '编程', 1),
    ('WeDo', 'wedo', 'wedo', '编程', 1);