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token.mo
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token.mo
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import HashMap "mo:base/HashMap";
import Principal "mo:base/Principal";
actor Token {
private stable var initialized : Bool = false;
private stable var name_ : Text = "";
private stable var decimals_ : Nat = 0;
private stable var symbol_ : Text = "";
private stable var totalSupply_ : Nat = 0;
private var balances = HashMap.HashMap<Principal, Nat>(1, Principal.equal, Principal.hash);
private var allowances = HashMap.HashMap<Principal, HashMap.HashMap<Principal, Nat>>(1, Principal.equal, Principal.hash);
public shared(msg) func initialize(_name: Text, _symbol: Text, _decimals: Nat, _totalSupply: Nat) : async Bool {
assert(initialized == false);
name_ := _name;
symbol_ := _symbol;
decimals_ := _decimals;
totalSupply_ := _totalSupply;
balances.put(msg.caller, totalSupply_);
initialized := true;
return true;
};
public shared(msg) func transfer(to: Principal, value: Nat) : async Bool {
assert(initialized);
switch (balances.get(msg.caller)) {
case (?from_balance) {
if (from_balance >= value) {
var from_balance_new = from_balance - value;
var to_balance_new = switch (balances.get(to)) {
case (?to_balance) {
to_balance + value;
};
case (_) {
value;
};
};
assert(from_balance_new <= from_balance);
assert(to_balance_new >= value);
balances.put(msg.caller, from_balance_new);
balances.put(to, to_balance_new);
return true;
} else {
return false;
};
};
case (_) {
return false;
};
}
};
public shared(msg) func transferFrom(from: Principal, to: Principal, value: Nat) : async Bool {
assert(initialized);
switch (balances.get(from), allowances.get(from)) {
case (?from_balance, ?allowance_from) {
switch (allowance_from.get(msg.caller)) {
case (?allowance) {
if (from_balance >= value and allowance >= value) {
var from_balance_new = from_balance - value;
var allowance_new = allowance - value;
var to_balance_new = switch (balances.get(to)) {
case (?to_balance) {
to_balance + value;
};
case (_) {
value;
};
};
assert(from_balance_new <= from_balance);
assert(to_balance_new >= value);
allowance_from.put(msg.caller, allowance_new);
allowances.put(from, allowance_from);
balances.put(from, from_balance_new);
balances.put(to, to_balance_new);
return true;
} else {
return false;
};
};
case (_) {
return false;
};
}
};
case (_) {
return false;
};
}
};
public shared(msg) func approve(spender: Principal, value: Nat) : async Bool {
assert(initialized);
switch(allowances.get(msg.caller)) {
case (?allowances_caller) {
allowances_caller.put(spender, value);
allowances.put(msg.caller, allowances_caller);
return true;
};
case (_) {
var temp = HashMap.HashMap<Principal, Nat>(1, Principal.equal, Principal.hash);
temp.put(spender, value);
allowances.put(msg.caller, temp);
return true;
};
}
};
public query func balanceOf(who: Principal) : async Nat {
switch (balances.get(who)) {
case (?balance) {
return balance;
};
case (_) {
return 0;
};
}
};
public query func allowance(owner: Principal, spender: Principal) : async Nat {
switch(allowances.get(owner)) {
case (?allowance_owner) {
switch(allowance_owner.get(spender)) {
case (?allowance) {
return allowance;
};
case (_) {
return 0;
};
}
};
case (_) {
return 0;
};
}
};
public query func totalSupply() : async Nat {
return totalSupply_;
};
public query func name() : async Text {
return name_;
};
public query func decimals() : async Nat {
return decimals_;
};
public query func symbol() : async Text {
return symbol_;
};
// Return the principal of the message caller/user identity
public shared(msg) func callerPrincipal() : async Principal {
return msg.caller;
};
};