exchange/src/exchangedb/exchange_do_melt.sql

--
-- This file is part of TALER
-- Copyright (C) 2014--2022 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_melt(
  IN in_cs_rms BYTEA,
  IN in_amount_with_fee_val INT8,
  IN in_amount_with_fee_frac INT4,
  IN in_rc BYTEA,
  IN in_old_coin_pub BYTEA,
  IN in_old_coin_sig BYTEA,
  IN in_known_coin_id INT8, -- not used, but that's OK
  IN in_noreveal_index INT4,
  IN in_zombie_required BOOLEAN,
  OUT out_balance_ok BOOLEAN,
  OUT out_zombie_bad BOOLEAN,
  OUT out_noreveal_index INT4)
LANGUAGE plpgsql
AS $$
DECLARE
  denom_max INT8;
BEGIN
-- Shards: INSERT refresh_commitments (by rc)
-- (rare:) SELECT refresh_commitments (by old_coin_pub) -- crosses shards!
-- (rare:) SEELCT refresh_revealed_coins (by melt_serial_id)
-- (rare:) PERFORM recoup_refresh (by rrc_serial) -- crosses shards!
--         UPDATE known_coins (by coin_pub)

INSERT INTO exchange.refresh_commitments
  (rc
  ,old_coin_pub
  ,old_coin_sig
  ,amount_with_fee_val
  ,amount_with_fee_frac
  ,noreveal_index
  )
  VALUES
  (in_rc
  ,in_old_coin_pub
  ,in_old_coin_sig
  ,in_amount_with_fee_val
  ,in_amount_with_fee_frac
  ,in_noreveal_index)
  ON CONFLICT DO NOTHING;

IF NOT FOUND
THEN
  -- Idempotency check: see if an identical record exists.
  out_noreveal_index=-1;
  SELECT
     noreveal_index
    INTO
     out_noreveal_index
    FROM exchange.refresh_commitments
   WHERE rc=in_rc;
  out_balance_ok=FOUND;
  out_zombie_bad=FALSE; -- zombie is OK
  RETURN;
END IF;


IF in_zombie_required
THEN
  -- Check if this coin was part of a refresh
  -- operation that was subsequently involved
  -- in a recoup operation.  We begin by all
  -- refresh operations our coin was involved
  -- with, then find all associated reveal
  -- operations, and then see if any of these
  -- reveal operations was involved in a recoup.
  PERFORM
    FROM exchange.recoup_refresh
   WHERE rrc_serial IN
    (SELECT rrc_serial
       FROM exchange.refresh_revealed_coins
      WHERE melt_serial_id IN
      (SELECT melt_serial_id
         FROM exchange.refresh_commitments
        WHERE old_coin_pub=in_old_coin_pub));
  IF NOT FOUND
  THEN
    out_zombie_bad=TRUE;
    out_balance_ok=FALSE;
    RETURN;
  END IF;
END IF;

out_zombie_bad=FALSE; -- zombie is OK


-- Check and update balance of the coin.
UPDATE known_coins
  SET
    remaining_frac=remaining_frac-in_amount_with_fee_frac
       + CASE
         WHEN remaining_frac < in_amount_with_fee_frac
         THEN 100000000
         ELSE 0
         END,
    remaining_val=remaining_val-in_amount_with_fee_val
       - CASE
         WHEN remaining_frac < in_amount_with_fee_frac
         THEN 1
         ELSE 0
         END
  WHERE coin_pub=in_old_coin_pub
    AND ( (remaining_val > in_amount_with_fee_val) OR
          ( (remaining_frac >= in_amount_with_fee_frac) AND
            (remaining_val >= in_amount_with_fee_val) ) );

IF NOT FOUND
THEN
  -- Insufficient balance.
  out_noreveal_index=-1;
  out_balance_ok=FALSE;
  RETURN;
END IF;



-- Special actions needed for a CS melt?
IF NOT NULL in_cs_rms
THEN
  -- Get maximum denominations serial value in
  -- existence, this will determine how long the
  -- nonce will be locked.
  SELECT
      denominations_serial
    INTO
      denom_max
    FROM exchange.denominations
      ORDER BY denominations_serial DESC
      LIMIT 1;

  -- Cache CS signature to prevent replays in the future
  -- (and check if cached signature exists at the same time).
  INSERT INTO exchange.cs_nonce_locks
    (nonce
    ,max_denomination_serial
    ,op_hash)
  VALUES
    (cs_rms
    ,denom_serial
    ,in_rc)
  ON CONFLICT DO NOTHING;

  IF NOT FOUND
  THEN
    -- Record exists, make sure it is the same
    SELECT 1
      FROM exchange.cs_nonce_locks
     WHERE nonce=cs_rms
       AND op_hash=in_rc;

    IF NOT FOUND
    THEN
       -- Nonce reuse detected
       out_balance_ok=FALSE;
       out_zombie_bad=FALSE;
       out_noreveal_index=42; -- FIXME: return error message more nicely!
       ASSERT false, 'nonce reuse attempted by client';
    END IF;
  END IF;
END IF;

-- Everything fine, return success!
out_balance_ok=TRUE;
out_noreveal_index=in_noreveal_index;

END $$;