Interface example: RGB20

In the following code block, we report a portion of Rust code taken from the RGB20 Interface.

// ...
fn rgb20() -> Iface {
    let types = StandardTypes::with(rgb20_stl());

    Iface {
        version: VerNo::V1,
        name: tn!("RGB20"),
        global_state: tiny_bmap! {
            fname!("spec") => GlobalIface::required(types.get("RGBContract.DivisibleAssetSpec")),
            fname!("data") => GlobalIface::required(types.get("RGBContract.ContractData")),
            fname!("created") => GlobalIface::required(types.get("RGBContract.Timestamp")),
            fname!("issuedSupply") => GlobalIface::one_or_many(types.get("RGBContract.Amount")),
            fname!("burnedSupply") => GlobalIface::none_or_many(types.get("RGBContract.Amount")),
            fname!("replacedSupply") => GlobalIface::none_or_many(types.get("RGBContract.Amount")),
        },
        assignments: tiny_bmap! {
            fname!("inflationAllowance") => AssignIface::public(OwnedIface::Amount, Req::NoneOrMore),
            fname!("updateRight") => AssignIface::public(OwnedIface::Rights, Req::Optional),
            fname!("burnEpoch") => AssignIface::public(OwnedIface::Rights, Req::Optional),
            fname!("burnRight") => AssignIface::public(OwnedIface::Rights, Req::NoneOrMore),
            fname!("assetOwner") => AssignIface::private(OwnedIface::Amount, Req::NoneOrMore),
        },
        valencies: none!(),
        genesis: GenesisIface {
            metadata: Some(types.get("RGBContract.IssueMeta")),
            global: tiny_bmap! {
                fname!("spec") => ArgSpec::required(),
                fname!("data") => ArgSpec::required(),
                fname!("created") => ArgSpec::required(),
                fname!("issuedSupply") => ArgSpec::required(),
            },
            assignments: tiny_bmap! {
                fname!("assetOwner") => ArgSpec::many(),
                fname!("inflationAllowance") => ArgSpec::many(),
                fname!("updateRight") => ArgSpec::optional(),
                fname!("burnEpoch") => ArgSpec::optional(),
            },
            valencies: none!(),
            errors: tiny_bset! {
                SUPPLY_MISMATCH,
                INVALID_PROOF,
                INSUFFICIENT_RESERVES
            },
        },
        transitions: tiny_bmap! {
            tn!("Transfer") => TransitionIface {
                optional: false,
                metadata: None,
                globals: none!(),
                inputs: tiny_bmap! {
                    fname!("previous") => ArgSpec::from_non_empty("assetOwner"),
                },
                assignments: tiny_bmap! {
                    fname!("beneficiary") => ArgSpec::from_non_empty("assetOwner"),
                },
                valencies: none!(),
                errors: tiny_bset! {
                    NON_EQUAL_AMOUNTS
                },
                default_assignment: Some(fname!("beneficiary")),
            },
            tn!("Issue") => TransitionIface {
                optional: true,
                metadata: Some(types.get("RGBContract.IssueMeta")),
                globals: tiny_bmap! {
                    fname!("issuedSupply") => ArgSpec::required(),
                },
                inputs: tiny_bmap! {
                    fname!("used") => ArgSpec::from_non_empty("inflationAllowance"),
                },
                assignments: tiny_bmap! {
                    fname!("beneficiary") => ArgSpec::from_many("assetOwner"),
                    fname!("future") => ArgSpec::from_many("inflationAllowance"),
                },
                valencies: none!(),
                errors: tiny_bset! {
                    SUPPLY_MISMATCH,
                    INVALID_PROOF,
                    ISSUE_EXCEEDS_ALLOWANCE,
                    INSUFFICIENT_RESERVES
                },
                default_assignment: Some(fname!("beneficiary")),
            },
            tn!("OpenEpoch") => TransitionIface {
                optional: true,
                metadata: None,
                globals: none!(),
                inputs: tiny_bmap! {
                    fname!("used") => ArgSpec::from_required("burnEpoch"),
                },
                assignments: tiny_bmap! {
                    fname!("next") => ArgSpec::from_optional("burnEpoch"),
                    fname!("burnRight") => ArgSpec::required()
                },
                valencies: none!(),
                errors: none!(),
                default_assignment: Some(fname!("burnRight")),
            },
            tn!("Burn") => TransitionIface {
                optional: true,
                metadata: Some(types.get("RGBContract.BurnMeta")),
                globals: tiny_bmap! {
                    fname!("burnedSupply") => ArgSpec::required(),
                },
                inputs: tiny_bmap! {
                    fname!("used") => ArgSpec::from_required("burnRight"),
                },
                assignments: tiny_bmap! {
                    fname!("future") => ArgSpec::from_optional("burnRight"),
                },
                valencies: none!(),
                errors: tiny_bset! {
                    SUPPLY_MISMATCH,
                    INVALID_PROOF,
                    INSUFFICIENT_COVERAGE
                },
                default_assignment: None,
            },
            tn!("Replace") => TransitionIface {
                optional: true,
                metadata: Some(types.get("RGBContract.BurnMeta")),
                globals: tiny_bmap! {
                    fname!("replacedSupply") => ArgSpec::required(),
                },
                inputs: tiny_bmap! {
                    fname!("used") => ArgSpec::from_required("burnRight"),
                },
                assignments: tiny_bmap! {
                    fname!("beneficiary") => ArgSpec::from_many("assetOwner"),
                    fname!("future") => ArgSpec::from_optional("burnRight"),
                },
                valencies: none!(),
                errors: tiny_bset! {
                    NON_EQUAL_AMOUNTS,
                    SUPPLY_MISMATCH,
                    INVALID_PROOF,
                    INSUFFICIENT_COVERAGE
                },
                default_assignment: Some(fname!("beneficiary")),
            },
            tn!("Rename") => TransitionIface {
                optional: true,
                metadata: None,
                globals: tiny_bmap! {
                    fname!("new") => ArgSpec::from_required("spec"),
                },
                inputs: tiny_bmap! {
                    fname!("used") => ArgSpec::from_required("updateRight"),
                },
                assignments: tiny_bmap! {
                    fname!("future") => ArgSpec::from_optional("updateRight"),
                },
                valencies: none!(),
                errors: none!(),
                default_assignment: Some(fname!("future")),
            },
        },
        extensions: none!(),
        error_type: types.get("RGB20.Error"),
        default_operation: Some(tn!("Transfer")),
        type_system: types.type_system(),
    }
}

From the code above, we can observe that the interface has a rather similar structure to that of Schema. However, the key difference lies in the different type definitions, which in the interface's code are expressed in terms of strings through fname!() or tn!() macros, while in Schema are defined through primitive strict data types.

Moreover, we can observe that in addition to the related endpoint encoded in the NIA Schema, we find several additional state data such as:

• burnEpoch

• issuedSupply

• burnedSupply

• replacedSupply

Additional endpoints for Contract Operations Transition:

• Issue

• Burn

• Replace

• Rename

Declaration for Errors in the Contract State or Transitions:

• SUPPLY_MISMATCH

• INVALID_PROOF

• ISSUE_EXCEEDS_ALLOWANCE

• INSUFFICIENT_RESERVES

The Interface Implementation which will be described in the next section is responsible for the selection and mapping of the suitable endpoints declared in the Interface with the the data structure and operation present in the Schema.