-- Shop coupons: a shop-owned template plus a customer-owned snapshot taken at
-- claim time. The snapshot copies terms and window so editing or disabling a
-- template cannot change a coupon a customer already holds.
--
-- `orders` gains the realized discount and the coupon it redeemed. Both tables
-- reference each other; ON DELETE SET NULL keeps either side deletable.

CREATE TYPE coupon_status AS ENUM ('claimed', 'redeemed', 'expired');

CREATE TABLE coupon_templates (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    shop_id UUID NOT NULL REFERENCES shops (id) ON DELETE CASCADE,
    title JSONB NOT NULL,
    amount_minor BIGINT NOT NULL CHECK (amount_minor > 0),
    threshold_minor BIGINT NOT NULL CHECK (threshold_minor >= 0),
    currency CHAR(3) NOT NULL REFERENCES currencies (code),
    stock INT NOT NULL CHECK (stock >= 0),
    enabled BOOLEAN NOT NULL DEFAULT TRUE,
    starts_at TIMESTAMPTZ NOT NULL,
    ends_at TIMESTAMPTZ NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT coupon_templates_window CHECK (ends_at >= starts_at)
);

CREATE INDEX coupon_templates_shop_idx ON coupon_templates (shop_id);

CREATE TABLE coupons (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users (id) ON DELETE CASCADE,
    -- Nullable so deleting a template keeps the snapshots customers already hold.
    template_id UUID REFERENCES coupon_templates (id) ON DELETE SET NULL,
    shop_id UUID NOT NULL REFERENCES shops (id) ON DELETE CASCADE,
    title JSONB NOT NULL,
    amount_minor BIGINT NOT NULL CHECK (amount_minor > 0),
    threshold_minor BIGINT NOT NULL CHECK (threshold_minor >= 0),
    currency CHAR(3) NOT NULL REFERENCES currencies (code),
    starts_at TIMESTAMPTZ NOT NULL,
    ends_at TIMESTAMPTZ NOT NULL,
    status coupon_status NOT NULL DEFAULT 'claimed',
    order_id UUID REFERENCES orders (id) ON DELETE SET NULL,
    claimed_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    redeemed_at TIMESTAMPTZ
);

-- One claim per customer per template.
CREATE UNIQUE INDEX coupons_user_template_idx ON coupons (user_id, template_id);
CREATE INDEX coupons_user_idx ON coupons (user_id, status);

ALTER TABLE orders ADD COLUMN coupon_id UUID REFERENCES coupons (id) ON DELETE SET NULL;
ALTER TABLE orders ADD COLUMN discount_minor BIGINT NOT NULL DEFAULT 0 CHECK (discount_minor >= 0);