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77 lines
3.6 KiB
Python
77 lines
3.6 KiB
Python
# vim: set fileencoding=utf8
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class Currency:
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""" Currency
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Each account has a currency (1 Kč, 1 Club Maté, ...), pairs of
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currencies have (asymmetric) exchange rates. """
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def __init__(self, db, id, name):
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self.db = db
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self.id = id
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self.name = name
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@classmethod
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def default(cls, db):
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""" Default wallet currency """
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return cls.load(db, name = "Kč")
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@classmethod
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def load(cls, db, id = None, name = None):
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""" Constructor for existing currency """
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if id is not None:
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name = db.execute_and_fetch("SELECT name FROM currencies WHERE id = %s", [id])
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name = name[0]
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elif name is not None:
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id = db.execute_and_fetch("SELECT id FROM currencies WHERE name = %s", [name])
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id = id[0]
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else:
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raise NameError("Currency.load(): Specify either id or name")
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return cls(db, name = name, id = id)
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@classmethod
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def create(cls, db, name):
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""" Constructor for new currency """
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# id = db.execute_and_fetch("INSERT INTO currencies (name) VALUES (%s) RETURNING id", [name])
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id = db.execute_and_fetch("SELECT public.create_currency(%s)", [name])
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# id = id[0]
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return cls(db, name = name, id = id)
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def rates(self, other):
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""" Return tuple ($buy, $sell) of rates of $self in relation to $other (brmbar.Currency):
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$buy is the price of $self in means of $other when buying it (into brmbar)
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$sell is the price of $self in means of $other when selling it (from brmbar) """
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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])
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if res is None:
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raise NameError("Currency.rate(): Unknown conversion " + other.name() + " to " + self.name())
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buy_rate, buy_rate_dir = res
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buy = buy_rate if buy_rate_dir == "target_to_source" else 1/buy_rate
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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])
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if res is None:
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raise NameError("Currency.rate(): Unknown conversion " + self.name() + " to " + other.name())
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sell_rate, sell_rate_dir = res
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sell = sell_rate if sell_rate_dir == "source_to_target" else 1/sell_rate
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return (buy, sell)
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def convert(self, amount, target):
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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", [target.id, self.id])
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if res is None:
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raise NameError("Currency.convert(): Unknown conversion " + self.name() + " to " + target.name())
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rate, rate_dir = res
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if rate_dir == "source_to_target":
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resamount = amount * rate
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else:
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resamount = amount / rate
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return resamount
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def str(self, amount):
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return "{:.2f} {}".format(amount, self.name)
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def update_sell_rate(self, target, rate):
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# self.db.execute("INSERT INTO exchange_rates (source, target, rate, rate_dir) VALUES (%s, %s, %s, %s)", [self.id, target.id, rate, "source_to_target"])
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self.db.execute("SELECT update_currency_sell_rate(%s, %s, %s)",
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[self.id, target.id, rate])
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def update_buy_rate(self, source, rate):
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self.db.execute("INSERT INTO exchange_rates (source, target, rate, rate_dir) VALUES (%s, %s, %s, %s)", [source.id, self.id, rate, "target_to_source"])
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