SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- P3: FAQ分类树增强（最多三级）

CREATE TABLE IF NOT EXISTS tb_faq_category
(
    id            bigint UNSIGNED NOT NULL COMMENT '主键',
    collection_id bigint UNSIGNED NOT NULL COMMENT '知识库ID',
    parent_id     bigint UNSIGNED NOT NULL DEFAULT 0 COMMENT '父分类ID，0表示根',
    ancestors     varchar(512) NOT NULL DEFAULT '0' COMMENT '祖先路径(逗号分隔)',
    level_no      tinyint UNSIGNED NOT NULL DEFAULT 1 COMMENT '层级(1-3)',
    category_name varchar(64) NOT NULL COMMENT '分类名称',
    sort_no       int NOT NULL DEFAULT 0 COMMENT '排序',
    is_default    tinyint(1) NOT NULL DEFAULT 0 COMMENT '是否默认分类',
    status        int NOT NULL DEFAULT 0 COMMENT '数据状态',
    created       datetime NULL COMMENT '创建时间',
    created_by    bigint UNSIGNED NULL COMMENT '创建人',
    modified      datetime NULL COMMENT '更新时间',
    modified_by   bigint UNSIGNED NULL COMMENT '更新人',
    PRIMARY KEY (id),
    INDEX idx_faq_category_collection_parent_sort (collection_id, parent_id, sort_no),
    INDEX idx_faq_category_collection_level (collection_id, level_no),
    INDEX idx_faq_category_collection_status (collection_id, status)
) ENGINE = InnoDB DEFAULT CHARSET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci COMMENT ='FAQ分类';

-- 兼容低版本 MySQL：不使用 ADD COLUMN / ADD INDEX IF NOT EXISTS
SET @faq_item_category_col_exists := (
    SELECT COUNT(1)
    FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA = DATABASE()
      AND TABLE_NAME = 'tb_faq_item'
      AND COLUMN_NAME = 'category_id'
);

SET @faq_item_add_category_col_sql := IF(
        @faq_item_category_col_exists = 0,
        'ALTER TABLE tb_faq_item ADD COLUMN category_id bigint UNSIGNED NULL DEFAULT NULL COMMENT ''FAQ分类ID'' AFTER collection_id',
        'DO 0'
                                   );
PREPARE stmt_add_faq_item_category_col FROM @faq_item_add_category_col_sql;
EXECUTE stmt_add_faq_item_category_col;
DEALLOCATE PREPARE stmt_add_faq_item_category_col;

SET @faq_item_category_idx_exists := (
    SELECT COUNT(1)
    FROM information_schema.STATISTICS
    WHERE TABLE_SCHEMA = DATABASE()
      AND TABLE_NAME = 'tb_faq_item'
      AND INDEX_NAME = 'idx_faq_collection_category_order'
);

SET @faq_item_add_category_idx_sql := IF(
        @faq_item_category_idx_exists = 0,
        'ALTER TABLE tb_faq_item ADD INDEX idx_faq_collection_category_order (collection_id, category_id, order_no)',
        'DO 0'
                                   );
PREPARE stmt_add_faq_item_category_idx FROM @faq_item_add_category_idx_sql;
EXECUTE stmt_add_faq_item_category_idx;
DEALLOCATE PREPARE stmt_add_faq_item_category_idx;

SET FOREIGN_KEY_CHECKS = 1;