-- One-time charges that are included once, on the first generated invoice.
CREATE TABLE IF NOT EXISTS sag_subscription_first_invoice_items (
    id BIGSERIAL PRIMARY KEY,
    subscription_id BIGINT NOT NULL REFERENCES sag_subscriptions(id) ON DELETE CASCADE,
    line_no INTEGER NOT NULL,
    product_id BIGINT REFERENCES products(id) ON DELETE SET NULL,
    description TEXT NOT NULL,
    quantity NUMERIC(14,4) NOT NULL DEFAULT 1 CHECK (quantity > 0),
    unit_price NUMERIC(14,2) NOT NULL DEFAULT 0 CHECK (unit_price >= 0),
    line_total NUMERIC(14,2) NOT NULL DEFAULT 0,
    billed_at TIMESTAMPTZ,
    billing_run_id BIGINT REFERENCES subscription_billing_runs(id) ON DELETE SET NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
    UNIQUE (subscription_id, line_no)
);

CREATE INDEX IF NOT EXISTS idx_subscription_first_invoice_unbilled
    ON sag_subscription_first_invoice_items(subscription_id)
    WHERE billed_at IS NULL;