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if amount =/= 0tz then failwith ("This contract do not accept token amount");

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// Allowed roles, you can add a new annotation right here, for example 'Dev' or 'Moderator'
type role is Admin | User | NoRole

type action is
  | MakeAdmin of (address)
  | MakeUser of (address)
  | RemoveRole of (address)

type store is record
  users: big_map(address, role);

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type action is AddOwner of (address)

// An unordered collections of owner accounts 
type store is record
  owners: set(address);
end  

type return is list(operation) * store

// Function that checks if an account is an owner

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// This is an implementation of the FA1.2 specification in PascaLIGO

type amountNat is nat;

type account is record
    balance : amountNat;
    allowances: map(address, amountNat);
end

type action is

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function depositImp(var store: store): return is
  block {
    if amount = 0mutez
      then failwith("No tez transferred!");
      else skip;

    // Setting the deposit to the sender
    store := updateDeposit(amount, store);

    // TODO: try to get the decimals property from the token contract

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function tokenProxy (const action : tokenAction; const store : store): operation is
  block {
    const tokenContract: contract (tokenAction) =
      case (Tezos.get_contract_opt (store.token.contractAddress) : option (contract (tokenAction))) of
        Some (contractAction) -> contractAction
      | None -> (failwith ("Contract not found.") : contract (tokenAction))
      end;
    const proxyOperation : operation = Tezos.transaction (action, 0mutez, tokenContract);
  } with proxyOperation;

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function transfer (const addressFrom : address; const addressTo : address; const value : nat; var store : store) : return is
  block {
    if addressFrom = addressTo then skip;
    else block {
      case isAllowed(addressFrom, addressTo, value, store) of 
      | False -> block {
          failwith ("NotEnoughAllowance");
        }
      | True -> skip
      end;

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function approve (const addressSpender : address; const value : nat; var store : store) : return is
  block {
    // If sender is the spender approving is not necessary
    if sender = addressSpender then skip;
    else block {
        const senderAccount: account = getAccount(sender, store.accounts);
        var allowed: nat :=  getAllowance(addressSpender, senderAccount.allowances); 

        // Changing allowance value from non-zero value to a non-zero value is forbidden to prevent the corresponding attack vector.
        if allowed =/= 0n then failwith("UnsafeAllowanceChange");

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function mint (const value : nat ; var store : store) : return is
 block {
  // Fail if is not an owner
  if not isOwner(sender, store) then failwith("You must be an owner of the contract to mint tokens");
  else block {
    var ownerAccount: account := record 
        balance = 0n;
        allowances = (map end : map(address, nat));
    end;
    case store.accounts[sender] of

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type account is record
  balance: nat;
  allowances: map(address, nat);
end

type store is record
  owners: set(address);
  decimals: nat; // Added this property used in the erc20 ethereum specification
  symbol: string; // Added this property used in the erc20 ethereum specification
  name: string; // Added this property used in the erc20 ethereum specification