CREATE OR REPLACE FUNCTION create_debit
  (
    purchase_id INT,
    amount INT,
    started_at TIMESTAMP,
    finished_at TIMESTAMP,
    bonus_card_id INT,
    created_at TIMESTAMP
  )
RETURNS VOID AS
$body$
DECLARE
  debit_id INT;
  balance INT;
BEGIN
  insert into "debits"
    (
      "purchase_id",
      "amount",
      "created_at",
      "started_at",
      "finished_at"
    )
  VALUES
    (
      purchase_id,
      amount,
      created_at,
      started_at,
      finished_at
    )
  RETURNING "id" INTO debit_id;

  IF NOW() != started_at
  THEN
    SELECT a.balance INTO balance FROM accounts a WHERE a.card_id = bonus_card_id ORDER BY a.created_at DESC LIMIT 1;

    IF balance IS NULL
    THEN balance = 0;
    END IF;

    INSERT INTO accounts
      (
        "card_id",
        "debit_amount",
        "debit_id",
        "created_at",
        "balance"
      )
    VALUES
      (
        bonus_card_id,
        amount,
        debit_id,
        NOW(),
        balance + amount
      );
  END IF;
END
$body$
LANGUAGE 'plpgsql';

DROP FUNCTION create_debit;