-- =============================================
-- 优惠券业务基础表（最小集，用于优惠券效果分析）
-- 说明：
-- - 基于项目规格文档 pages/mall/mall.md 第4节“优惠券系统”抽象而来。
-- - 仅创建 Analytics 所需的最小字段集合，兼容后续完整业务表替换。
-- - 可安全重复执行（IF NOT EXISTS + 列存在性检查）。
-- - 依赖：merchants、orders 表已存在（由 01_create_tables.sql 提供）。
-- =============================================

-- 1) 优惠券模板表（coupon_templates）
CREATE TABLE IF NOT EXISTS public.coupon_templates (
  id           uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  name         text NOT NULL,
  description  text,
  coupon_type  integer NOT NULL,         -- 1..8：满减/折扣/免运费/新人/会员/品类/商家/限时（见 mall.md）
  discount_type integer NOT NULL,        -- 满减 / 折扣 / 免运费 等类型枚举
  discount_value numeric(10,2) NOT NULL, -- 金额或折扣值
  min_order_amount numeric(10,2) DEFAULT 0,
  max_discount_amount numeric(10,2),
  total_quantity integer,
  per_user_limit integer DEFAULT 1,
  usage_limit integer DEFAULT 1,
  merchant_id uuid,
  category_ids jsonb,
  product_ids jsonb,
  user_type_limit integer,
  start_time timestamptz NOT NULL,
  end_time   timestamptz NOT NULL,
  status     integer DEFAULT 1,
  created_at timestamptz DEFAULT now()
);

DO $$
BEGIN
  -- 若缺少 merchant_id 外键且 merchants 表存在，则补充外键
  IF EXISTS (
    SELECT 1 FROM information_schema.tables
    WHERE table_schema = 'public' AND table_name = 'merchants'
  ) THEN
    IF NOT EXISTS (
      SELECT 1
      FROM   pg_constraint c
      JOIN   pg_class t ON t.oid = c.conrelid
      JOIN   pg_namespace n ON n.oid = t.relnamespace
      WHERE  n.nspname = 'public'
      AND    t.relname = 'coupon_templates'
      AND    c.conname = 'coupon_templates_merchant_id_fkey'
    ) THEN
      ALTER TABLE public.coupon_templates
        ADD CONSTRAINT coupon_templates_merchant_id_fkey
        FOREIGN KEY (merchant_id) REFERENCES public.merchants(id) ON DELETE SET NULL;
    END IF;
  END IF;
END;
$$;

COMMENT ON TABLE  public.coupon_templates IS '优惠券模板表（业务权威表，来自 mall.md）';
COMMENT ON COLUMN public.coupon_templates.coupon_type IS '券类型：1..8（满减/折扣/免运费/新人/会员/品类/商家/限时）';


-- 2) 用户优惠券表（user_coupons）
CREATE TABLE IF NOT EXISTS public.user_coupons (
  id           uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id      uuid,
  template_id  uuid REFERENCES public.coupon_templates(id) ON DELETE CASCADE,
  coupon_code  varchar(50) UNIQUE NOT NULL,
  status       integer DEFAULT 1,        -- 1 未使用，2 已使用，3 已过期 等（与 mall.md 对齐）
  used_at      timestamptz,
  order_id     uuid,
  received_at  timestamptz DEFAULT now(),
  expire_at    timestamptz NOT NULL
);

DO $$
BEGIN
  -- 若 users 表存在则补 user_id 外键（保证幂等）
  IF EXISTS (
    SELECT 1 FROM information_schema.tables
    WHERE table_schema = 'public' AND table_name = 'users'
  ) THEN
    IF NOT EXISTS (
      SELECT 1
      FROM   pg_constraint c
      JOIN   pg_class t ON t.oid = c.conrelid
      JOIN   pg_namespace n ON n.oid = t.relnamespace
      WHERE  n.nspname = 'public'
      AND    t.relname = 'user_coupons'
      AND    c.conname = 'user_coupons_user_id_fkey'
    ) THEN
      ALTER TABLE public.user_coupons
        ADD CONSTRAINT user_coupons_user_id_fkey
        FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE;
    END IF;
  END IF;

  -- 若 orders 表存在则补 order_id 外键
  IF EXISTS (
    SELECT 1 FROM information_schema.tables
    WHERE table_schema = 'public' AND table_name = 'orders'
  ) THEN
    IF NOT EXISTS (
      SELECT 1
      FROM   pg_constraint c
      JOIN   pg_class t ON t.oid = c.conrelid
      JOIN   pg_namespace n ON n.oid = t.relnamespace
      WHERE  n.nspname = 'public'
      AND    t.relname = 'user_coupons'
      AND    c.conname = 'user_coupons_order_id_fkey'
    ) THEN
      ALTER TABLE public.user_coupons
        ADD CONSTRAINT user_coupons_order_id_fkey
        FOREIGN KEY (order_id) REFERENCES public.orders(id) ON DELETE SET NULL;
    END IF;
  END IF;

  -- 分析增强字段：发放渠道 obtain_channel
  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'user_coupons' AND column_name = 'obtain_channel'
  ) THEN
    ALTER TABLE public.user_coupons ADD COLUMN obtain_channel text;
  END IF;

  -- 分析增强字段：冗余 merchant_id，便于按商家过滤
  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'user_coupons' AND column_name = 'merchant_id'
  ) THEN
    ALTER TABLE public.user_coupons ADD COLUMN merchant_id uuid;
  END IF;
END;
$$;

COMMENT ON TABLE  public.user_coupons IS '用户优惠券表（领取/使用/到期信息）';
COMMENT ON COLUMN public.user_coupons.obtain_channel IS '发放渠道：manual/auto/campaign/invite/cs/points 等';


-- 3) 优惠券使用记录表（coupon_usage_logs）
CREATE TABLE IF NOT EXISTS public.coupon_usage_logs (
  id            uuid PRIMARY KEY DEFAULT gen_random_uuid(),
  user_coupon_id uuid REFERENCES public.user_coupons(id) ON DELETE CASCADE,
  order_id      uuid NOT NULL,
  discount_amount numeric(10,2) NOT NULL,
  used_at       timestamptz DEFAULT now()
);

DO $$
BEGIN
  -- 若 orders 表存在则补 order_id 外键
  IF EXISTS (
    SELECT 1 FROM information_schema.tables
    WHERE table_schema = 'public' AND table_name = 'orders'
  ) THEN
    IF NOT EXISTS (
      SELECT 1
      FROM   pg_constraint c
      JOIN   pg_class t ON t.oid = c.conrelid
      JOIN   pg_namespace n ON n.oid = t.relnamespace
      WHERE  n.nspname = 'public'
      AND    t.relname = 'coupon_usage_logs'
      AND    c.conname = 'coupon_usage_logs_order_id_fkey'
    ) THEN
      ALTER TABLE public.coupon_usage_logs
        ADD CONSTRAINT coupon_usage_logs_order_id_fkey
        FOREIGN KEY (order_id) REFERENCES public.orders(id) ON DELETE CASCADE;
    END IF;
  END IF;

  -- 分析增强字段：冗余 user_id / template_id / merchant_id / order_amount / created_at
  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'coupon_usage_logs' AND column_name = 'user_id'
  ) THEN
    ALTER TABLE public.coupon_usage_logs ADD COLUMN user_id uuid;
  END IF;

  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'coupon_usage_logs' AND column_name = 'template_id'
  ) THEN
    ALTER TABLE public.coupon_usage_logs ADD COLUMN template_id uuid;
  END IF;

  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'coupon_usage_logs' AND column_name = 'merchant_id'
  ) THEN
    ALTER TABLE public.coupon_usage_logs ADD COLUMN merchant_id uuid;
  END IF;

  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'coupon_usage_logs' AND column_name = 'order_amount'
  ) THEN
    ALTER TABLE public.coupon_usage_logs ADD COLUMN order_amount numeric(10,2);
  END IF;

  IF NOT EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'public' AND table_name = 'coupon_usage_logs' AND column_name = 'created_at'
  ) THEN
    ALTER TABLE public.coupon_usage_logs ADD COLUMN created_at timestamptz DEFAULT now();
  END IF;
END;
$$;

COMMENT ON TABLE  public.coupon_usage_logs IS '优惠券使用记录表（单次核销流水，用于 GMV / ROI 分析）';


-- 4) 索引（幂等）
CREATE INDEX IF NOT EXISTS idx_coupon_templates_merchant_id ON public.coupon_templates(merchant_id);
CREATE INDEX IF NOT EXISTS idx_user_coupons_user_id        ON public.user_coupons(user_id);
CREATE INDEX IF NOT EXISTS idx_user_coupons_template_id    ON public.user_coupons(template_id);
CREATE INDEX IF NOT EXISTS idx_user_coupons_status         ON public.user_coupons(status);
CREATE INDEX IF NOT EXISTS idx_user_coupons_received_at    ON public.user_coupons(received_at);
CREATE INDEX IF NOT EXISTS idx_user_coupons_expire_at      ON public.user_coupons(expire_at);
CREATE INDEX IF NOT EXISTS idx_coupon_usage_logs_order_id  ON public.coupon_usage_logs(order_id);
CREATE INDEX IF NOT EXISTS idx_coupon_usage_logs_used_at   ON public.coupon_usage_logs(used_at);


-- 完成
SELECT 'coupon tables ensured' AS message;