#9: stored function for sell transaction

brmbar3/brmbar/Currency.py

@@ -40,18 +40,20 @@ class Currency:
         """ Return tuple ($buy, $sell) of rates of $self in relation to $other (brmbar.Currency):
         $buy is the price of $self in means of $other when buying it (into brmbar)
         $sell is the price of $self in means of $other when selling it (from brmbar) """
-
+        # buy rate
-        res = self.db.execute_and_fetch("SELECT rate, rate_dir FROM exchange_rates WHERE target = %s AND source = %s AND valid_since <= NOW() ORDER BY valid_since DESC LIMIT 1", [self.id, other.id])
+        res = self.db.execute_and_fetch("SELECT public.find_buy_rate(%s, %s)",[self.id, other.id])
         if res is None:
+            raise NameError("Something fishy in find_buy_rate.");
+        buy = res[0]
+        if buy < 0:
             raise NameError("Currency.rate(): Unknown conversion " + other.name() + " to " + self.name())
-        buy_rate, buy_rate_dir = res
+        # sell rate
-        buy = buy_rate if buy_rate_dir == "target_to_source" else 1/buy_rate
+        res = self.db.execute_and_fetch("SELECT public.find_sell_rate(%s, %s)",[self.id, other.id])
-
-        res = self.db.execute_and_fetch("SELECT rate, rate_dir FROM exchange_rates WHERE target = %s AND source = %s AND valid_since <= NOW() ORDER BY valid_since DESC LIMIT 1", [other.id, self.id])
         if res is None:
+            raise NameError("Something fishy in find_sell_rate.");
+        sell = res[0]
+        if sell < 0:
             raise NameError("Currency.rate(): Unknown conversion " + self.name() + " to " + other.name())
-        sell_rate, sell_rate_dir = res
-        sell = sell_rate if sell_rate_dir == "source_to_target" else 1/sell_rate
 
         return (buy, sell)
 

brmbar3/brmbar/Shop.py

@@ -25,18 +25,25 @@ class Shop:
             deficit = Account.load(db, name = "BrmBar Deficit"))
 
     def sell(self, item, user, amount = 1):
-        # Sale: Currency conversion from item currency to shop currency
+        # Call the stored procedure for the sale
-        (buy, sell) = item.currency.rates(self.currency)
+        cost = self.db.execute_and_fetch(
-        cost = amount * sell
+            "SELECT public.sell_item(%s, %s, %s, %s, %s)",
-        profit = amount * (sell - buy)
+            [item.id, amount, user.id, self.currency.id, f"BrmBar sale of {amount}x {item.name} to {user.name}"]
+        )[0]#[0]
 
-        transaction = self._transaction(responsible = user, description = "BrmBar sale of {}x {} to {}".format(amount, item.name, user.name))
-        item.credit(transaction, amount, user.name)
-        user.debit(transaction, cost, item.name) # debit (increase) on a _debt_ account
-        self.profits.debit(transaction, profit, "Margin on " + item.name)
         self.db.commit()
-
         return cost
+        # Sale: Currency conversion from item currency to shop currency
+        #(buy, sell) = item.currency.rates(self.currency)
+        #cost = amount * sell
+        #profit = amount * (sell - buy)
+
+        #transaction = self._transaction(responsible = user, description = "BrmBar sale of {}x {} to {}".format(amount, item.name, user.name))
+        #item.credit(transaction, amount, user.name)
+        #user.debit(transaction, cost, item.name) # debit (increase) on a _debt_ account
+        #self.profits.debit(transaction, profit, "Margin on " + item.name)
+        #self.db.commit()
+        #return cost
 
     def sell_for_cash(self, item, amount = 1):
         # Sale: Currency conversion from item currency to shop currency

brmbar3/schema/0009-shop-sell.sql

@@ -0,0 +1,149 @@
+--
+-- 0009-shop-sell.sql
+--
+-- #9 - stored function for sell transaction
+--
+-- ISC License
+--
+-- Copyright 2023-2025 Brmlab, z.s.
+-- TMA <tma+hs@jikos.cz>
+--
+-- Permission to use, copy, modify, and/or distribute this software
+-- for any purpose with or without fee is hereby granted, provided
+-- that the above copyright notice and this permission notice appear
+-- in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+-- WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+-- WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+-- AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+-- CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+-- OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+-- NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+--
+
+-- To require fully-qualified names
+SELECT pg_catalog.set_config('search_path', '', false);
+
+DO $upgrade_block$
+BEGIN
+
+IF brmbar_privileged.has_exact_schema_version(8) THEN
+
+-- return negative number on rate not found
+CREATE OR REPLACE FUNCTION public.find_buy_rate(
+	IN i_item_id public.accounts.id%TYPE;
+	IN i_other_id public.accounts.id%TYPE;
+) RETURNS NUMERIC
+LANGUAGE plpgsql
+AS $$
+DECLARE
+	v_rate public.exchange_rates.rate%TYPE;
+	v_rate_dir public.exchange_rates.rate_dir%TYPE;
+BEGIN
+        SELECT rate INTO STRICT v_rate, rate_dir INTO STRICT v_rate_dir FROM public.exchange_rates WHERE target = i_item_id AND source = i_other_id AND valid_since <= NOW() ORDER BY valid_since DESC LIMIT 1;
+	IF v_rate_dir = 'target_to_source'::public.exchange_rate_direction THEN
+		RETURN v_rate;
+	ELSE
+		RETURN 1/v_rate;
+	END IF;
+EXCEPTION
+	WHEN NO_DATA_FOUND THEN
+		RETURN -1;
+END;
+$$
+
+
+-- return negative number on rate not found
+CREATE OR REPLACE FUNCTION public.find_sell_rate(
+	IN i_item_id public.accounts.id%TYPE;
+	IN i_other_id public.accounts.id%TYPE;
+) RETURNS NUMERIC
+LANGUAGE plpgsql
+AS $$
+DECLARE
+	v_rate public.exchange_rates.rate%TYPE;
+	v_rate_dir public.exchange_rates.rate_dir%TYPE;
+BEGIN
+        SELECT rate INTO STRICT v_rate, rate_dir INTO STRICT v_rate_dir FROM public.exchange_rates WHERE target = i_other_id AND source = i_item_id AND valid_since <= NOW() ORDER BY valid_since DESC LIMIT 1;
+	IF v_rate_dir = 'source_to_target'::public.exchange_rate_direction THEN
+		RETURN v_rate;
+	ELSE
+		RETURN 1/v_rate;
+	END IF;
+EXCEPTION
+	WHEN NO_DATA_FOUND THEN
+		RETURN -1;
+END;
+$$
+
+CREATE OR REPLACE FUNCTION public.create_transaction(
+	i_responsible_id public.accounts.id%TYPE,
+	i_description public.transactions.description%TYPE
+) RETURNS public.transactions.id%TYPE AS $$
+DECLARE
+	new_transaction_id public.transactions%TYPE;
+BEGIN
+	-- Create a new transaction
+	INSERT INTO transactions (responsible, description)
+	VALUES (i_responsible_id, i_description)
+	RETURNING id INTO new_transaction_id;
+	-- Return the new transaction ID
+	RETURN new_transaction_id;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION public.sell_item(
+	i_item_id public.accounts.id%TYPE,
+	i_amount INTEGER,
+	i_user_id public.accounts.id%TYPE,
+	i_target_currency_id public.currencies.id%TYPE,
+	i_description TEXT
+) RETURNS NUMERIC
+LANGUAGE plpgsql
+AS $$
+DECLARE
+	v_buy_rate NUMERIC;
+	v_sell_rate NUMERIC;
+	v_cost NUMERIC;
+	v_profit NUMERIC;
+	v_transaction_id public.transactions.id%TYPE;
+BEGIN
+	-- Get the buy and sell rates from the stored functions
+	v_buy_rate := find_buy_rate(i_item_id, i_target_currency_id);
+	v_sell_rate := find_sell_rate(i_item_id, i_target_currency_id);
+
+	-- Calculate cost and profit
+	v_cost := i_amount * v_sell_rate;
+	v_profit := i_amount * (v_sell_rate - v_buy_rate);
+
+	-- Create a new transaction
+	v_transaction_id := create_transaction(i_user_id, i_description);
+
+	-- the item (decrease stock)
+	INSERT INTO transaction_splits (transaction, side, account, amount, memo)
+	VALUES (i_transaction_id, 'credit', i_item_id, i_amount,
+	(SELECT "name" FROM public.accounts WHERE id = i_user_id));
+
+	-- the user
+	INSERT INTO transaction_splits (transaction, side, account, amount, memo)
+	VALUES (i_transaction_id, 'debit', i_user_id, v_cost,
+	(SELECT "name" FROM public.accounts WHERE id = i_item_id));
+
+	-- the profit
+	INSERT INTO transaction_splits (transaction, side, account, amount, memo)
+	VALUES (i_transaction_id, 'debit', (SELECT account_id FROM accounts WHERE name = 'BrmBar Profits'), v_profit, (SELECT 'Margin on ' || "name" FROM public.accounts WHERE id = i_item_id));
+
+	-- Return the cost
+	RETURN v_cost;
+END;
+$$;
+
+PERFORM brmbar_privileged.upgrade_schema_version_to(9);
+END IF;
+
+END;
+$upgrade_block$;
+
+-- vim: set ft=plsql :