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account.rs
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account.rs
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use asset::*;
use rate::*;
use std::collections::HashMap;
use std::ops;
#[derive(Debug, PartialEq, Eq, PartialOrd, Hash, Clone, Copy)]
pub struct Quantity(pub i32);
#[derive(Debug, Clone)]
pub struct Account(pub HashMap<Asset, Quantity>);
pub enum Tranx {
Approved(Account, Account),
Denied(HashMap<Asset, Quantity>),
}
impl Account {
pub fn quantity(&self, asset: &Asset) -> Quantity {
match self.0.get(asset) {
Some(quantity) => quantity.clone(),
None => Quantity(0),
}
}
pub fn exchange(rate: &Rate, quantity: Quantity, buyer: &Account, seller: &Account) -> Tranx {
let credit = &Account(rate.credit.clone()) * quantity;
let debit = &Account(rate.debit.clone()) * quantity;
let (buyer, seller) = (&(buyer - &debit) + &credit, &(seller - &credit) + &debit);
let mut success = true;
let mut deficit = hashmap![];
{
let Account(buyer) = &buyer;
let Account(debit) = debit;
for asset in debit.keys() {
match buyer.get(asset) {
Some(Quantity(quantity)) if *quantity < 0 => {
success = false;
deficit.insert(asset.clone(), Quantity(*quantity));
}
_ => (),
}
}
}
if success {
Tranx::Approved(buyer, seller)
} else {
Tranx::Denied(deficit)
}
}
pub fn map(&self) -> &HashMap<Asset, Quantity> {
let Account(map) = self;
map
}
fn prime(&mut self, rhs: &Account) {
let Account(lhs) = self;
let Account(rhs) = rhs;
for rhs_key in rhs.keys() {
if !lhs.contains_key(rhs_key) {
lhs.insert(rhs_key.clone(), Quantity(0));
}
}
}
fn op<F>(lhs: &Account, rhs: &Account, op: F) -> Account
where
F: Fn(&Quantity, &Quantity) -> Quantity,
{
let mut acc = hashmap![];
let mut lhs = lhs.clone();
let mut rhs = rhs.clone();
lhs.prime(&rhs);
rhs.prime(&lhs);
let Account(lhs) = lhs;
let Account(rhs) = rhs;
for key in lhs.keys() {
let lhs_quantity = lhs.get(key).unwrap();
let rhs_quantity = rhs.get(key).unwrap();
let quantity = op(lhs_quantity, rhs_quantity);
acc.insert(key.clone(), quantity.clone());
}
Account(acc)
}
}
impl PartialEq for Account {
fn eq(&self, rhs: &Account) -> bool {
let mut lhs = self.clone();
let mut rhs = rhs.clone();
lhs.prime(&rhs);
rhs.prime(&lhs);
let Account(lhs) = lhs;
let Account(rhs) = rhs;
lhs == rhs
}
}
impl<'a, 'b> ops::Add<&'a Account> for &'b Account {
type Output = Account;
fn add(self, rhs: &Account) -> Account {
Account::op(self, rhs, |Quantity(lq), Quantity(rq)| Quantity(lq + rq))
}
}
impl<'a, 'b> ops::Sub<&'a Account> for &'b Account {
type Output = Account;
fn sub(self, rhs: &Account) -> Account {
Account::op(self, rhs, |Quantity(lq), Quantity(rq)| Quantity(lq - rq))
}
}
impl<'a> ops::Mul<Quantity> for &'a Account {
type Output = Account;
fn mul(self, rhs: Quantity) -> Account {
let Account(lhs) = self;
let keys = lhs.keys();
let mut lhs = lhs.clone();
let Quantity(rhs_quantity) = rhs;
for key in keys {
let q = lhs.entry(key.clone()).or_insert(Quantity(0));
let Quantity(lhs_quantity) = *q;
*q = Quantity(lhs_quantity * rhs_quantity);
}
Account(lhs)
}
}