-- Group buying: a shop-owned timed activity on one SKU, concrete group
-- instances with a lifecycle, and one paid membership row per paid order.
--
-- The activity column names are a contract: the archived flash-sales guard
-- queries `group_buying_activities` by `sku_id`, `enabled`, `starts_at`, and
-- `ends_at` to reject a SKU that is in both activities at once.

CREATE TYPE collective_group_status AS ENUM ('open', 'successful', 'expired', 'cancelled');

CREATE TABLE group_buying_activities (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    shop_id UUID NOT NULL REFERENCES shops (id) ON DELETE CASCADE,
    sku_id UUID NOT NULL REFERENCES skus (id) ON DELETE CASCADE,
    name JSONB NOT NULL,
    description JSONB,
    image TEXT,
    group_price_minor BIGINT NOT NULL CHECK (group_price_minor > 0),
    currency CHAR(3) NOT NULL REFERENCES currencies (code),
    required_members INT NOT NULL CHECK (required_members >= 2),
    starts_at TIMESTAMPTZ NOT NULL,
    ends_at TIMESTAMPTZ NOT NULL,
    group_lifetime_hours INT NOT NULL CHECK (group_lifetime_hours > 0),
    enabled BOOLEAN NOT NULL DEFAULT TRUE,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT group_buying_activities_window CHECK (ends_at >= starts_at)
);

CREATE INDEX group_buying_activities_shop_idx ON group_buying_activities (shop_id);
CREATE INDEX group_buying_activities_sku_idx ON group_buying_activities (sku_id);

CREATE TABLE collective_groups (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    activity_id UUID NOT NULL REFERENCES group_buying_activities (id) ON DELETE CASCADE,
    -- The pending order that opened the group; it may be cancelled later.
    leader_order_id UUID REFERENCES orders (id) ON DELETE SET NULL,
    paid_member_count INT NOT NULL DEFAULT 0 CHECK (paid_member_count >= 0),
    status collective_group_status NOT NULL DEFAULT 'open',
    expires_at TIMESTAMPTZ NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX collective_groups_activity_idx ON collective_groups (activity_id, status);

CREATE TABLE collective_group_members (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    group_id UUID NOT NULL REFERENCES collective_groups (id) ON DELETE CASCADE,
    order_id UUID NOT NULL REFERENCES orders (id) ON DELETE CASCADE,
    user_id UUID NOT NULL REFERENCES users (id) ON DELETE CASCADE,
    joined_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

-- One paid seat per order, and one membership per customer per group.
CREATE UNIQUE INDEX collective_group_members_order_idx ON collective_group_members (order_id);
CREATE UNIQUE INDEX collective_group_members_user_idx
    ON collective_group_members (group_id, user_id);
CREATE INDEX collective_group_members_group_idx ON collective_group_members (group_id);

-- Group identity snapshotted on the order at checkout.
ALTER TABLE orders
    ADD COLUMN group_activity_id UUID REFERENCES group_buying_activities (id) ON DELETE SET NULL;
ALTER TABLE orders
    ADD COLUMN group_id UUID REFERENCES collective_groups (id) ON DELETE SET NULL;

CREATE INDEX idx_orders_group ON orders (group_id);