-- Credit card billing period configuration per account
ALTER TABLE accounts
    ADD COLUMN IF NOT EXISTS closing_day   INTEGER CHECK (closing_day BETWEEN 1 AND 28),
    ADD COLUMN IF NOT EXISTS due_day       INTEGER CHECK (due_day BETWEEN 1 AND 28);

-- Materialized bill metadata (calculated from transactions)
-- One row per (account, billing period start date)
CREATE TABLE IF NOT EXISTS credit_bills (
    id              SERIAL PRIMARY KEY,
    account_id      INTEGER NOT NULL REFERENCES accounts(id) ON DELETE CASCADE,
    period_start    DATE    NOT NULL,
    period_end      DATE    NOT NULL,
    due_date        DATE    NOT NULL,
    paid            BOOLEAN NOT NULL DEFAULT FALSE,
    paid_at         TIMESTAMP WITH TIME ZONE,
    payment_account_id INTEGER REFERENCES accounts(id) ON DELETE SET NULL,
    created_at      TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
    UNIQUE(account_id, period_start)
);