Here's an example implementation of a BEP20 token smart contract with buy & sell functions, developer fee, charity fee, and auto liquidity function in Rust using the ink! framework:
use ink_lang::contract;
contract! {
#![env = ink_env::Environment]
// Define the BEP20 token contract
struct MyBEP20 {
// The total supply of the token
total_supply: balance::Balance,
// The balance of each account
balances: ink_storage::collections::HashMap<AccountId, balance::Balance>,
// The allowance for each account to transfer a certain amount of tokens
allowances: ink_storage::collections::HashMap<(AccountId, AccountId), balance::Balance>,
// The developer fee percentage
developer_fee_percent: u32,
// The charity fee percentage
charity_fee_percent: u32,
// The auto liquidity fee percentage
auto_liquidity_fee_percent: u32,
// The liquidity pool balance
liquidity_pool_balance: balance::Balance,
// The address of the charity beneficiary
charity_beneficiary: AccountId,
// The address of the developer
developer: AccountId,
}
impl MyBEP20 {
// The constructor function to initialize the token contract
#[ink(constructor)]
pub fn new(initial_supply: balance::Balance, developer_fee_percent: u32, charity_fee_percent: u32, auto_liquidity_fee_percent: u32, charity_beneficiary: AccountId, developer: AccountId) -> Self {
let mut balances = ink_storage::collections::HashMap::new();
balances.insert(Self::env().caller(), initial_supply);
Self {
total_supply: initial_supply,
balances,
allowances: ink_storage::collections::HashMap::new(),
developer_fee_percent,
charity_fee_percent,
auto_liquidity_fee_percent,
liquidity_pool_balance: 0,
charity_beneficiary,
developer,
}
}
// The buy function to purchase tokens
#[ink(message, payable)]
pub fn buy(&mut self) -> bool {
// Calculate the amount of tokens to be purchased
let tokens_to_purchase = self.calculate_tokens_to_purchase();
// Validate the purchase amount
let purchase_amount = self.calculate_purchase_amount(tokens_to_purchase);
if Self::env().transferred_balance() != purchase_amount {
return false;
}
// Transfer the purchase amount to the token contract
self.env().extension().transfer_from(
Self::env().caller(),
Self::env().account_id(),
purchase_amount,
).unwrap();
// Update the balances
self.balances.insert(Self::env().caller(), self.balance_of(Self::env().caller()) + tokens_to_purchase);
self.balances.insert(Self::env().account_id(), self.balance_of(Self::env().account_id()) - tokens_to_purchase);
// Distribute the fees
self.distribute_fees(tokens_to_purchase);
// Emit the event
self.env().emit_event(Buy {
buyer: Self::env().caller(),
tokens: tokens_to_purchase,
price: purchase_amount,
});
true
}
// The sell function to sell tokens
#[ink(message)]
pub fn sell(&mut self, tokens: balance::Balance) -> bool {
// Validate the sell amount
if tokens > self.balance_of(Self::env().caller()) {
return false;
}
// Calculate the sell amount
let sell_amount = self.calculate_sell_amount(tokens);
// Transfer the sell amount to the caller
self.env().extension().transfer(
Self::env().caller(),
sell_amount,
).unwrap();
// Update the balances
self.balances.insert(Self::env().caller(), self.balance_of(Self::env().caller()) - tokens);
self.balances.insert(Self::env().account_id(), self.balance_of(Self::env().account_id()) + tokens);
// Emit the event
self.env().emit_event(Sell {
seller: Self::env().caller(),
tokens,
price: sell_amount,
});
true
}
// The transfer function to transfer tokens
#[ink(message)]
pub fn transfer(&mut self, to: AccountId, tokens: balance::Balance) -> bool {
// Validate the transfer amount
if tokens > self.balance_of(Self::env().caller()) {
return false;
}
// Update the balances
self.balances.insert(Self::env().caller(), self.balance_of(Self::env().caller()) - tokens);
self.balances.insert(to, self.balance_of(to) + tokens);
// Emit the event
self.env().emit_event(Transfer {
from: Self::env().caller(),
to,
tokens,
});
true
}
// The approve function to set the allowance for another account to transfer tokens on your behalf
#[ink(message)]
pub fn approve(&mut self, spender: AccountId, tokens: balance::Balance) -> bool {
// Set the allowance
self.allowances.insert((Self::env().caller(), spender), tokens);
// Emit the event
self.env().emit_event(Approval {
owner: Self::env().caller(),
spender,
tokens,
});
true
}
// The transfer from function to transfer tokens on behalf of another account
#[ink(message)]
pub fn transfer_from(&mut self, from: AccountId, to: AccountId, tokens: balance::Balance) -> bool {
// Validate the transfer amount and allowance
if tokens > self.allowance_of((from, Self::env().caller())) || tokens > self.balance_of(from) {
return false;
}
// Update the balances
self.balances.insert(from, self.balance_of(from) - tokens);
self.balances.insert(to, self.balance_of(to) + tokens);
// Update the allowance
self.allowances.insert((from, Self::env().caller()), self.allowance_of((from, Self::env().caller())) - tokens);
// Emit the event
self.env().emit_event(Transfer {
from,
to,
tokens,
});
true
}
// The balance of function to get the balance of an account
#[ink(message)]
pub fn balance_of(&self, account: AccountId) -> balance::Balance {
*self.balances.get(&account).unwrap_or(&0)
}
// The allowance of function to get the allowance of an account to transfer tokens on behalf of another account
#[ink(message)]
pub fn allowance_of(&self, accounts: (AccountId, AccountId)) -> balance::Balance {
*self.allowances.get(&accounts).unwrap_or(&0)
}
// The total supply of function to get the total supply of the token
#[ink(message)]
pub fn total_supply(&self) -> balance::Balance {
self.total_supply
}
// The calculate tokens to purchase function to calculate the amount of tokens to be purchased
fn calculate_tokens_to_purchase(&self) -> balance::Balance {
let purchase_amount = Self::env().transferred_balance();
let total_fees = self.calculate_total_fees(purchase_amount);
let purchase_amount_after_fees = purchase_amount - total_fees;
let token_price = self.calculate_token_price(self.total_supply + self.liquidity_pool_balance, self.total_supply, purchase_amount_after_fees);
let tokens_to_purchase = purchase_amount_after_fees / token_price;
tokens_to_purchase
}
// The calculate purchase amount function to calculate the purchase amount
fn calculate_purchase_amount(&self, tokens_to_purchase: balance::Balance) -> balance::Balance {
let token_price = self.calculate_token_price(self.total_supply + self.liquidity_pool_balance, self.total_supply, tokens_to_purchase);
let purchase_amount_after_fees = token_price * tokens_to_purchase;
let total_fees = self.calculate_total_fees(purchase_amount_after_fees);
let purchase_amount = purchase_amount_after_fees + total_fees;
purchase_amount
}
// The calculate sell amount function to calculate the sell amount
fn calculate_sell_amount(&self, tokens: balance::Balance) -> balance::Balance {
let token_price = self.calculate_token_price(self.total_supply + self.liquidity_pool_balance, self.total_supply, tokens);
let sell_amount_before_fees = token_price * tokens;
let total_fees = self.calculate_total_fees(sell_amount_before_fees);
let sell_amount = sell_amount_before_fees - total_fees;
sell_amount
}
// The calculate token price function to calculate the token price
fn calculate_token_price(&self, total_tokens: balance::Balance, tokens: balance::Balance, amount: balance::Balance) -> balance::Balance {
amount * total_tokens / (tokens * 100 - self.calculate_total_fees(100 * tokens))
}
// The calculate total fees function to calculate the total fees
fn calculate_total_fees(&self, amount: balance::Balance) -> balance::Balance {
let total_fee_percent = self.developer_fee_percent + self.charity_fee_percent + self.auto_liquidity_fee_percent;
amount * total_fee_percent / 100
}
// The distribute fees function to distribute the fees
fn distribute_fees(&mut self, tokens_to_purchase: balance::Balance) {
// Calculate the fees
let developer_fee = tokens_to_purchase * self.developer_fee_percent / 100;
let charity_fee = tokens_to_purchase * self.charity_fee_percent / 100;
let auto_liquidity_fee = tokens_to_purchase * self.auto_liquidity_fee_percent / 100;
// Transfer the developer fee to the developer
self.env().extension().transfer(
self.developer,
developer_fee,
).unwrap();
// Transfer the charity fee to the charity beneficiary
self.env().extension().transfer(
self.charity_beneficiary,
charity_fee,
).unwrap();
// Add the auto liquidity fee to the liquidity pool balance
self.liquidity_pool_balance += auto_liquidity_fee;
}
}
// Define the events
#[ink(event)]
pub struct Buy {
#[ink(topic)]
buyer: AccountId,
#[ink(topic)]
tokens: balance::Balance,
#[ink(topic)]
price: balance::Balance,
}
#[ink(event)]
pub struct Sell {
#[ink(topic)]
seller: AccountId,
#[ink(topic)]
tokens: balance::Balance,
#[ink(topic)]
price: balance::Balance,
}
#[ink(event)]
pub struct Transfer {
#[ink(topic)]
from: AccountId,
#[ink(topic)]
to: AccountId,
#[ink(topic)]
tokens: balance::Balance,
}
#[ink(event)]
pub struct Approval {
#[ink(topic)]
owner: AccountId,
#[ink(topic)]
spender: AccountId,
#[ink(topic)]
tokens: balance::Balance,
}
}
In addition to the standard BEP20 token functions, this smart contract also has the following features:
Note that this is just an example implementation and should not be used in production without proper auditing and testing.