Erc20 contract (#35)

* Add missing ULM hooks.

* Add an Address type

* Add a Balance type

* Contract storage

* Events

* Put the contract in a struct

* Add contract implementation

* Erc20 dispatcher

* Erc20 tests

tests/ulm/erc20/rust/src/address.rs

@@ -0,0 +1,99 @@
+use bytes::Bytes;
+use core::cmp::Ordering;
+
+use crate::decoder::Decodable;
+use crate::encoder::{Encodable, EncodingType};
+use crate::unsigned::{U160, U256};
+
+#[derive(Debug)]
+pub struct Address {
+    value: U160,
+}
+
+impl Address {
+    fn new(value: U160) -> Self {
+        Address { value }
+    }
+
+    pub fn zero() -> Self {
+        Address::new(U160::from_u64(0))
+    }
+
+    pub fn is_zero(&self) -> bool {
+        self.value == U160::from_u64(0)
+    }
+
+    pub fn into_u160(self) -> U160 {
+      self.value
+    }
+    pub fn into_u256(self) -> U256 {
+        self.value.into()
+    }
+}
+
+impl From<U160> for Address
+{
+    fn from(value: U160) -> Self {
+        Address::new(value)
+    }
+}
+impl TryFrom<U256> for Address
+{
+    type Error = &'static str;
+    fn try_from(value: U256) -> Result<Self, Self::Error> {
+        Ok(Address::new(value.try_into()?))
+    }
+}
+impl From<Address> for U160
+{
+    fn from(value: Address) -> Self {
+        value.into_u160()
+    }
+}
+impl From<Address> for U256
+{
+    fn from(value: Address) -> Self {
+        value.into_u256()
+    }
+}
+
+impl Ord for Address {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.value.cmp(&other.value)
+    }
+}
+impl PartialOrd for Address {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl PartialEq for Address {
+    fn eq(&self, other: &Self) -> bool {
+        self.cmp(other) == Ordering::Equal
+    }
+}
+impl Eq for Address {}
+impl Clone for Address {
+    fn clone(&self) -> Self {
+        Address { value: self.value.clone() }
+    }
+}
+
+impl Encodable for Address
+{
+    fn encode(&self) -> (EncodingType, Bytes) {
+        self.value.encode()
+    }
+}
+impl Decodable for Address
+{
+    fn encoding_type() -> EncodingType {
+        U160::encoding_type()
+    }
+    fn head_size() -> usize {
+        U160::head_size()
+    }
+    fn decode(bytes: Bytes) -> Self {
+        Address::new(U160::decode(bytes))
+    }
+}

tests/ulm/erc20/rust/src/balance.rs

@@ -0,0 +1,132 @@
+use bytes::Bytes;
+use core::cmp::Ordering;
+use core::ops::{Add, Sub};
+
+use crate::decoder::Decodable;
+use crate::encoder::{Encodable, EncodingType};
+use crate::unsigned::U256;
+
+#[derive(Debug)]
+pub struct Balance {
+    value: U256
+}
+
+impl Balance {
+    pub fn new(value: U256) -> Self {
+        Balance { value }
+    }
+
+    pub fn into_u256(self) -> U256 {
+        self.value
+    }
+
+    pub fn into_u256_ref(&self) -> &U256 {
+        &self.value
+    }
+}
+
+impl TryFrom<U256> for Balance
+{
+    type Error = &'static str;
+    fn try_from(value: U256) -> Result<Self, Self::Error> {
+        Ok(Balance { value })
+    }
+}
+impl From<Balance> for U256
+{
+    fn from(value: Balance) -> Self {
+        value.into_u256()
+    }
+}
+
+impl Add for &Balance {
+    type Output = Balance;
+    fn add(self, other: &Balance) -> Self::Output {
+        Balance { value: (&self.value) + &other.value }
+    }
+}
+impl Add for Balance {
+    type Output = Balance;
+    fn add(self, other: Balance) -> Self::Output {
+        &self + &other
+    }
+}
+impl Add<Balance> for &Balance {
+    type Output = Balance;
+    fn add(self, other: Balance) -> Self::Output {
+        self + &other
+    }
+}
+impl Add<&Balance> for Balance {
+    type Output = Balance;
+    fn add(self, other: &Balance) -> Self::Output {
+        &self + other
+    }
+}
+
+impl Sub for &Balance {
+    type Output = Balance;
+    fn sub(self, other: &Balance) -> Self::Output {
+        Balance { value: (&self.value) - &other.value }
+    }
+}
+impl Sub for Balance {
+    type Output = Balance;
+    fn sub(self, other: Balance) -> Self::Output {
+        &self - &other
+    }
+}
+impl Sub<Balance> for &Balance {
+    type Output = Balance;
+    fn sub(self, other: Balance) -> Self::Output {
+        self - &other
+    }
+}
+impl Sub<&Balance> for Balance {
+    type Output = Balance;
+    fn sub(self, other: &Balance) -> Self::Output {
+        &self - other
+    }
+}
+
+impl Ord for Balance {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.value.cmp(&other.value)
+    }
+}
+impl PartialOrd for Balance {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl PartialEq for Balance {
+    fn eq(&self, other: &Self) -> bool {
+        self.cmp(other) == Ordering::Equal
+    }
+}
+impl Eq for Balance {}
+impl Clone for Balance {
+    fn clone(&self) -> Self {
+        Balance { value: self.value.clone() }
+    }
+}
+impl Encodable for Balance
+{
+    fn encode(&self) -> (EncodingType, Bytes) {
+        self.into_u256_ref().encode()
+    }
+}
+impl Decodable for Balance
+{
+    fn encoding_type() -> EncodingType {
+        U256::encoding_type()
+    }
+    fn head_size() -> usize {
+        U256::head_size()
+    }
+    fn decode(bytes: Bytes) -> Self {
+        let value = U256::decode(bytes);
+        Balance { value }
+    }
+}
+

tests/ulm/erc20/rust/src/erc20.rs

@@ -0,0 +1,148 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use crate::address::Address;
+use crate::assertions::fail;
+use crate::balance::Balance;
+use crate::encoder::Encoder;
+use crate::require;
+use crate::storage::{SingleChunkStorage, SingleChunkStorageBuilder};
+use crate::ulm::{log3, Ulm};
+use crate::ulm;
+
+pub struct Erc20 {
+  api: Rc<RefCell<dyn Ulm>>
+}
+
+impl Erc20 {
+    pub fn new(api: Rc<RefCell<dyn Ulm>>) -> Self {
+        Erc20 { api }
+    }
+
+    // ---------------------------
+
+    fn s_total_supply<'a>(&self) -> SingleChunkStorage<'a, Balance> {
+        SingleChunkStorageBuilder::new(self.api.clone(), &("total_supply".to_string())).build()
+    }
+
+    fn s_balances<'a>(&self, address: &Address) -> SingleChunkStorage<'a, Balance> {
+        let mut builder = SingleChunkStorageBuilder::new(self.api.clone(), &("balances".to_string()));
+        builder.add_arg(address);
+        builder.build()
+    }
+
+    fn s_allowances<'a>(&self, account: &Address, spender: &Address) -> SingleChunkStorage<'a, Balance> {
+        let mut builder = SingleChunkStorageBuilder::new(self.api.clone(), &("allowances".to_string()));
+        builder.add_arg(account);
+        builder.add_arg(spender);
+        builder.build()
+    }
+
+    // ---------------------------
+
+    fn transfer_event(&self, from: Address, to: Address, value: &Balance) {
+        let mut encoder = Encoder::new();
+        encoder.add(value);
+        log3(
+            &*self.api.borrow(),
+            "Transfer(address,address,u256)",
+            &from.into(), &to.into(),
+            encoder.encode()
+        )
+    }
+
+    fn approval_event(&self, owner: Address, spender: Address, value: &Balance) {
+        let mut encoder = Encoder::new();
+        encoder.add(value);
+        log3(
+            &*self.api.borrow(),
+            "Approval(address,address,u256)",
+            &owner.into(), &spender.into(),
+            encoder.encode()
+        )
+    }
+
+    // ---------------------------
+
+    pub fn init(&self) {}
+
+    pub fn decimals(&self) -> u8 {
+        18
+    }
+
+    pub fn total_supply(&self) -> Balance {
+        self.s_total_supply().get()
+    }
+
+    pub fn balance_of(&self, account: &Address) -> Balance {
+        self.s_balances(account).get()
+    }
+
+    pub fn transfer(&self, to: &Address, value: &Balance) -> bool {
+        let owner = ulm::caller(&*self.api.borrow());
+        self._transfer(&owner, to, &value);
+        true
+    }
+
+    pub fn allowance(&self, owner: &Address, spender: &Address) -> Balance {
+        self.s_allowances(owner, spender).get()
+    }
+
+    pub fn approve(&self, spender: &Address, value: &Balance) -> bool {
+        let owner = ulm::caller(&*self.api.borrow());
+        self._approve(&owner, spender, value, true);
+        true
+    }
+
+    pub fn transfer_from(&self, from: &Address, to: &Address, value: &Balance) -> bool {
+        let spender = ulm::caller(&*self.api.borrow());
+        self._spend_allowance(from, &spender, value);
+        self._transfer(from, to, value);
+        true
+    }
+
+    fn _transfer(&self, from: &Address, to: &Address, value: &Balance) {
+        require!(!from.is_zero(), "Invalid sender");
+        require!(!to.is_zero(), "Invalid receiver");
+        self._update(from, to, value);
+        self.transfer_event(from.clone(), to.clone(), value);
+    }
+
+    fn _update(&self, from: &Address, to: &Address, value: &Balance) {
+        if from.is_zero() {
+            self.s_total_supply().set(self.s_total_supply().get() + value);
+        } else {
+            let from_balance = self.s_balances(from).get();
+            require!(value <= &from_balance, "Insufficient balance");
+            self.s_balances(from).set(self.s_balances(from).get() - value);
+        };
+
+        if to.is_zero() {
+            self.s_total_supply().set(self.s_total_supply().get() - value);
+        } else {
+            self.s_balances(to).set(self.s_balances(to).get() + value);
+        }
+    }
+
+    pub fn mint(&self, account: &Address, value: &Balance) {
+        require!(!account.is_zero(), "Zero address");
+        self._update(&Address::zero(), account, value);
+    }
+
+    fn _approve(&self, owner: &Address, spender: &Address, value: &Balance, emit_event: bool) {
+        require!(!owner.is_zero(), "Invalid approver");
+        require!(!spender.is_zero(), "Invalid spender");
+        self.s_allowances(owner, spender).set(value.clone());
+        if emit_event {
+            self.approval_event(owner.clone(), spender.clone(), &value);
+        }
+    }
+
+    fn _spend_allowance(&self, owner: &Address, spender: &Address, value: &Balance) {
+        let current_allowance = self.allowance(owner, spender);
+        require!(value <= &current_allowance, "Insuficient allowance");
+        self._approve(owner, spender, &(current_allowance - value), false);
+    }
+}
+
+