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core.rs
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core.rs
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use near_sdk::ext_contract;
use near_sdk::json_types::U128;
use near_sdk::AccountId;
use near_sdk::PromiseOrValue;
/// The core methods for a basic fungible token. Extension standards may be
/// added in addition to this trait.
///
/// # Examples
///
/// ```
/// use near_sdk::{near, PanicOnDefault, AccountId, PromiseOrValue};
/// use near_sdk::collections::LazyOption;
/// use near_sdk::json_types::U128;
/// use near_contract_standards::fungible_token::{FungibleToken, FungibleTokenCore};
/// use near_contract_standards::fungible_token::metadata::FungibleTokenMetadata;
///
/// #[near(contract_state)]
/// #[derive(PanicOnDefault)]
/// pub struct Contract {
/// token: FungibleToken,
/// metadata: LazyOption<FungibleTokenMetadata>,
/// }
///
/// #[near]
/// impl FungibleTokenCore for Contract {
/// #[payable]
/// fn ft_transfer(&mut self, receiver_id: AccountId, amount: U128, memo: Option<String>) {
/// self.token.ft_transfer(receiver_id, amount, memo)
/// }
///
/// #[payable]
/// fn ft_transfer_call(
/// &mut self,
/// receiver_id: AccountId,
/// amount: U128,
/// memo: Option<String>,
/// msg: String,
/// ) -> PromiseOrValue<U128> {
/// self.token.ft_transfer_call(receiver_id, amount, memo, msg)
/// }
///
/// fn ft_total_supply(&self) -> U128 {
/// self.token.ft_total_supply()
/// }
///
/// fn ft_balance_of(&self, account_id: AccountId) -> U128 {
/// self.token.ft_balance_of(account_id)
/// }
/// }
/// ```
///
#[ext_contract(ext_ft_core)]
pub trait FungibleTokenCore {
/// Transfers positive `amount` of tokens from the `env::predecessor_account_id` to `receiver_id`.
/// Both accounts must be registered with the contract for transfer to succeed. (See [NEP-145](https://github.com/near/NEPs/discussions/145))
/// This method must to be able to accept attached deposits, and must not panic on attached deposit.
/// Exactly 1 yoctoNEAR must be attached.
/// See [the Security section](https://github.com/near/NEPs/issues/141#user-content-security) of the standard.
///
/// Arguments:
/// - `receiver_id` - the account ID of the receiver.
/// - `amount` - the amount of tokens to transfer. Must be a positive number in decimal string representation.
/// - `memo` - an optional string field in a free form to associate a memo with this transfer.
fn ft_transfer(&mut self, receiver_id: AccountId, amount: U128, memo: Option<String>);
/// Transfers positive `amount` of tokens from the `env::predecessor_account_id` to `receiver_id` account. Then
/// calls `ft_on_transfer` method on `receiver_id` contract and attaches a callback to resolve this transfer.
/// `ft_on_transfer` method must return the amount of tokens unused by the receiver contract, the remaining tokens
/// must be refunded to the `predecessor_account_id` at the resolve transfer callback.
///
/// Token contract must pass all the remaining unused gas to the `ft_on_transfer` call.
///
/// Malicious or invalid behavior by the receiver's contract:
/// - If the receiver contract promise fails or returns invalid value, the full transfer amount must be refunded.
/// - If the receiver contract overspent the tokens, and the `receiver_id` balance is lower than the required refund
/// amount, the remaining balance must be refunded. See [the Security section](https://github.com/near/NEPs/issues/141#user-content-security) of the standard.
///
/// Both accounts must be registered with the contract for transfer to succeed. (See #145)
/// This method must to be able to accept attached deposits, and must not panic on attached deposit. Exactly 1 yoctoNEAR must be attached. See [the Security
/// section](https://github.com/near/NEPs/issues/141#user-content-security) of the standard.
///
/// Arguments:
/// - `receiver_id` - the account ID of the receiver contract. This contract will be called.
/// - `amount` - the amount of tokens to transfer. Must be a positive number in a decimal string representation.
/// - `memo` - an optional string field in a free form to associate a memo with this transfer.
/// - `msg` - a string message that will be passed to `ft_on_transfer` contract call.
///
/// Returns a promise which will result in the amount of tokens withdrawn from sender's account.
fn ft_transfer_call(
&mut self,
receiver_id: AccountId,
amount: U128,
memo: Option<String>,
msg: String,
) -> PromiseOrValue<U128>;
/// Returns the total supply of the token in a decimal string representation.
fn ft_total_supply(&self) -> U128;
/// Returns the balance of the account. If the account doesn't exist must returns `"0"`.
fn ft_balance_of(&self, account_id: AccountId) -> U128;
}