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--
-- This file is part of TALER
-- Copyright (C) 2014--2023 Taler Systems SA
--
-- TALER is free software; you can redistribute it and/or modify it under the
-- terms of the GNU General Public License as published by the Free Software
-- Foundation; either version 3, or (at your option) any later version.
--
-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-- A PARTICULAR PURPOSE. See the GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License along with
-- TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
--
CREATE OR REPLACE FUNCTION exchange_do_refund(
IN in_amount_with_fee taler_amount,
IN in_amount taler_amount,
IN in_deposit_fee taler_amount,
IN in_h_contract_terms BYTEA,
IN in_rtransaction_id INT8,
IN in_deposit_shard INT8,
IN in_known_coin_id INT8,
IN in_coin_pub BYTEA,
IN in_merchant_pub BYTEA,
IN in_merchant_sig BYTEA,
OUT out_not_found BOOLEAN,
OUT out_refund_ok BOOLEAN,
OUT out_gone BOOLEAN,
OUT out_conflict BOOLEAN)
LANGUAGE plpgsql
AS $$
DECLARE
bdsi INT8; -- ID of deposit being refunded
DECLARE
tmp_val INT8; -- total amount refunded
DECLARE
tmp_frac INT8; -- total amount refunded, large fraction to deal with overflows!
DECLARE
tmp taler_amount; -- total amount refunded, normalized
DECLARE
deposit taler_amount; -- amount that was originally deposited
BEGIN
-- Shards: SELECT deposits (coin_pub, shard, h_contract_terms, merchant_pub)
-- INSERT refunds (by coin_pub, rtransaction_id) ON CONFLICT DO NOTHING
-- SELECT refunds (by coin_pub)
-- UPDATE known_coins (by coin_pub)
SELECT
bdep.batch_deposit_serial_id
,(cdep.amount_with_fee).val
,(cdep.amount_with_fee).frac
,bdep.done
INTO
bdsi
,deposit.val
,deposit.frac
,out_gone
FROM batch_deposits bdep
JOIN coin_deposits cdep
USING (batch_deposit_serial_id)
WHERE cdep.coin_pub=in_coin_pub
AND shard=in_deposit_shard
AND merchant_pub=in_merchant_pub
AND h_contract_terms=in_h_contract_terms;
IF NOT FOUND
THEN
-- No matching deposit found!
out_refund_ok=FALSE;
out_conflict=FALSE;
out_not_found=TRUE;
out_gone=FALSE;
RETURN;
END IF;
INSERT INTO refunds
(batch_deposit_serial_id
,coin_pub
,merchant_sig
,rtransaction_id
,amount_with_fee
)
VALUES
(bdsi
,in_coin_pub
,in_merchant_sig
,in_rtransaction_id
,in_amount_with_fee
)
ON CONFLICT DO NOTHING;
IF NOT FOUND
THEN
-- Idempotency check: see if an identical record exists.
-- Note that by checking 'coin_sig', we implicitly check
-- identity over everything that the signature covers.
-- We do select over merchant_pub and h_contract_terms
-- primarily here to maximally use the existing index.
PERFORM
FROM exchange.refunds
WHERE coin_pub=in_coin_pub
AND batch_deposit_serial_id=bdsi
AND rtransaction_id=in_rtransaction_id
AND amount_with_fee=in_amount_with_fee;
IF NOT FOUND
THEN
-- Deposit exists, but have conflicting refund.
out_refund_ok=FALSE;
out_conflict=TRUE;
out_not_found=FALSE;
RETURN;
END IF;
-- Idempotent request known, return success.
out_refund_ok=TRUE;
out_conflict=FALSE;
out_not_found=FALSE;
out_gone=FALSE;
RETURN;
END IF;
IF out_gone
THEN
-- money already sent to the merchant. Tough luck.
out_refund_ok=FALSE;
out_conflict=FALSE;
out_not_found=FALSE;
RETURN;
END IF;
-- Check refund balance invariant.
SELECT
SUM((refs.amount_with_fee).val) -- overflow here is not plausible
,SUM(CAST((refs.amount_with_fee).frac AS INT8)) -- compute using 64 bits
INTO
tmp_val
,tmp_frac
FROM refunds refs
WHERE coin_pub=in_coin_pub
AND batch_deposit_serial_id=bdsi;
IF tmp_val IS NULL
THEN
RAISE NOTICE 'failed to sum up existing refunds';
out_refund_ok=FALSE;
out_conflict=FALSE;
out_not_found=FALSE;
RETURN;
END IF;
-- Normalize result before continuing
tmp.val = tmp_val + tmp_frac / 100000000;
tmp.frac = tmp_frac % 100000000;
-- Actually check if the deposits are sufficient for the refund. Verbosely. ;-)
IF (tmp.val < deposit.val)
THEN
out_refund_ok=TRUE;
ELSE
IF (tmp.val = deposit.val) AND (tmp.frac <= deposit.frac)
THEN
out_refund_ok=TRUE;
ELSE
out_refund_ok=FALSE;
END IF;
END IF;
IF (tmp.val = deposit.val) AND (tmp.frac = deposit.frac)
THEN
-- Refunds have reached the full value of the original
-- deposit. Also refund the deposit fee.
in_amount.frac = in_amount.frac + in_deposit_fee.frac;
in_amount.val = in_amount.val + in_deposit_fee.val;
-- Normalize result before continuing
in_amount.val = in_amount.val + in_amount.frac / 100000000;
in_amount.frac = in_amount.frac % 100000000;
END IF;
-- Update balance of the coin.
UPDATE known_coins kc
SET
remaining.frac=(kc.remaining).frac+in_amount.frac
- CASE
WHEN (kc.remaining).frac+in_amount.frac >= 100000000
THEN 100000000
ELSE 0
END,
remaining.val=(kc.remaining).val+in_amount.val
+ CASE
WHEN (kc.remaining).frac+in_amount.frac >= 100000000
THEN 1
ELSE 0
END
WHERE coin_pub=in_coin_pub;
out_conflict=FALSE;
out_not_found=FALSE;
END $$;
COMMENT ON FUNCTION exchange_do_refund(taler_amount, taler_amount, taler_amount, BYTEA, INT8, INT8, INT8, BYTEA, BYTEA, BYTEA)
IS 'Executes a refund operation, checking that the corresponding deposit was sufficient to cover the refunded amount';
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