CREATE OR REPLACE FUNCTION exchange_do_withdraw(
  IN amount_val INT8,
  IN amount_frac INT4,
  IN h_denom_pub BYTEA,
  IN rpub BYTEA,
  IN reserve_sig BYTEA,
  IN h_coin_envelope BYTEA,
  IN denom_sig BYTEA,
  IN now INT8,
  IN min_reserve_gc INT8,
  OUT reserve_found BOOLEAN,
  OUT balance_ok BOOLEAN,
  OUT kycok BOOLEAN,
  OUT ruuid INT8,
  OUT account_uuid INT8)
LANGUAGE plpgsql
AS $$
DECLARE
  reserve_gc INT8;
DECLARE
  denom_serial INT8;
DECLARE
  reserve_val INT8;
DECLARE
  reserve_frac INT4;
BEGIN


SELECT denominations_serial INTO denom_serial
  FROM denominations
 WHERE denom_pub_hash=h_denom_pub;

IF NOT FOUND
THEN
  -- denomination unknown, should be impossible!
  reserve_found=FALSE;
  balance_ok=FALSE;
  kycok=FALSE;
  ruuid=0;
  account_uuid=0;
  ASSERT false, 'denomination unknown';
  RETURN;
END IF;


UPDATE reserves SET
   gc_date=GREATEST(gc_date, min_reserve_gc)
  ,current_balance_val=current_balance_val - amount_val
     - CASE WHEN (current_balance_frac < amount_frac)
         THEN 1
         ELSE 0
       END
  ,current_balance_frac=current_balance_frac - amount_frac
     + CASE WHEN (current_balance_frac < amount_frac)
         THEN 100000000
         ELSE 0
       END
 WHERE reserves.reserve_pub=rpub
   AND ( (current_balance_val > amount_val) OR
         ( (current_balance_val = amount_val) AND
           (current_balance_frac >= amount_frac) ) );

balance_ok=FOUND;

-- Obtain KYC status based on the last wire transfer into
-- this reserve. FIXME: likely not adequate for reserves that got P2P transfers!
SELECT
   kyc_ok
  ,wire_source_serial_id
  ,reserve_uuid
  INTO
   kycok
  ,account_uuid
  ,ruuid
  FROM reserves 
  JOIN reserves_in USING (reserve_uuid)
  JOIN wire_targets ON (wire_source_serial_id = wire_target_serial_id)
 WHERE reserves.reserve_pub=rpub
 LIMIT 1; -- limit 1 should not be required (without p2p transfers)

IF NOT FOUND
THEN
  -- reserve unknown
  reserve_found=FALSE;
  balance_ok=FALSE;
  kycok=FALSE;
  account_uuid=0;
  RETURN;
END IF;

reserve_found=TRUE;


-- We optimistically insert, and then on conflict declare
-- the query successful due to idempotency.
INSERT INTO reserves_out
  (h_blind_ev
  ,denominations_serial
  ,denom_sig
  ,reserve_uuid
  ,reserve_sig
  ,execution_date
  ,amount_with_fee_val
  ,amount_with_fee_frac)
VALUES
  (h_coin_envelope
  ,denom_serial
  ,denom_sig
  ,ruuid
  ,reserve_sig
  ,now
  ,amount_val
  ,amount_frac)
ON CONFLICT DO NOTHING;

IF NOT FOUND
THEN
  -- idempotent query, all constraints must be satisfied
  balance_ok=TRUE;
  -- rollback any potential balance update we may have made
  ROLLBACK;
  START TRANSACTION ISOLATION LEVEL SERIALIZABLE;
  RETURN;
END IF;

END $$;

COMMENT ON FUNCTION exchange_do_withdraw(INT8, INT4, BYTEA, BYTEA, BYTEA, BYTEA, BYTEA, INT8, INT8)
  IS 'Checks whether the reserve has sufficient balance for a withdraw operation (or the request is repeated and was previously approved) and if so updates the database with the result';