Writing simple contract

Firstly, using cargo to create a new project: cargo new rgb20-token, and enter it: cd rgb20-token. Then create a directory to store the contract file. You may name it whatever you like, here we set it to examples: mkdir examples. See source codes at RGB20 Contract.

Here is the complete project file tree:

➜  rgb20-token git:(main) ✗ tree .
.
├── Cargo.lock
├── Cargo.toml
├── contracts
└── src
    └── main.rs

3 directories, 3 files

Secondly, we add some libs in Cargo.toml file:

[package]
name = "rgb20-token"
version = "0.1.0"
edition = "2021"
resolver = "2"

[dependencies]
amplify = "4.6.0"
ascii-armor = "0.2.0"
strict_encoding = "2.7.0-beta.1"
strict_types = "2.7.0-beta.1"
aluvm = { version = "0.11.0-beta.4", features = ["log"] }
bp-core = "0.11.0-beta.4"
rgb-std = { version = "0.11.0-beta.4", features = ["serde", "fs"] }
serde = "1.0"
serde_json = "1.0"
sha2 = "0.10.8"
rgb-schemata = "0.11.0-beta.4"
hex = "0.4.3"

[dev-dependencies]
chrono = "0.4.31"
serde_yaml = "0.9.27"

[features]
all = []

[patch.crates-io]
commit_verify = { git = "https://github.com/LNP-BP/client_side_validation", branch = "master" }
bp-consensus = { git = "https://github.com/BP-WG/bp-core", branch = "master" }
bp-dbc = { git = "https://github.com/BP-WG/bp-core", branch = "master" }
bp-seals = { git = "https://github.com/BP-WG/bp-core", branch = "master" }
bp-core = { git = "https://github.com/BP-WG/bp-core", branch = "master" }
rgb-core = { git = "https://github.com/RGB-WG/rgb-core", branch = "master" }
rgb-std = { git = "https://github.com/RGB-WG/rgb-std", branch = "master" }
rgb-schemata = { git = "https://github.com/RGB-WG/rgb-schemata", branch = "master" }

Then, in src/main.rs, write following codes:

use std::convert::Infallible;
use std::fs;

use amplify::hex::FromHex;
use armor::AsciiArmor;
use bp::dbc::Method;
use bp::{Outpoint, Txid};
use rgb_schemata::NonInflatableAsset;
use rgbstd::containers::FileContent;
use rgbstd::interface::{FilterIncludeAll, FungibleAllocation, IfaceClass, IssuerClass, Rgb20};
use rgbstd::invoice::Precision;
use rgbstd::persistence::{Inventory, Stock};
use rgbstd::resolvers::ResolveHeight;
use rgbstd::validation::{ResolveWitness, WitnessResolverError};
use rgbstd::{WitnessAnchor, WitnessId, XAnchor, XPubWitness};
use strict_encoding::StrictDumb;

struct DumbResolver;

impl ResolveWitness for DumbResolver {
    fn resolve_pub_witness(&self, _: WitnessId) -> Result<XPubWitness, WitnessResolverError> {
        Ok(XPubWitness::strict_dumb())
    }
}

impl ResolveHeight for DumbResolver {
    type Error = Infallible;
    fn resolve_anchor(&mut self, _: &XAnchor) -> Result<WitnessAnchor, Self::Error> {
        Ok(WitnessAnchor::strict_dumb())
    }
}

#[rustfmt::skip]
fn main() {
    let beneficiary_txid =
        Txid::from_hex("d6afd1233f2c3a7228ae2f07d64b2091db0d66f2e8ef169cf01217617f51b8fb").unwrap();
    let beneficiary = Outpoint::new(beneficiary_txid, 1);

    let contract = NonInflatableAsset::testnet("TEST", "Test asset", None, Precision::CentiMicro)
        .expect("invalid contract data")
        .allocate(Method::TapretFirst, beneficiary, 100_000_000_000_u64.into())
        .expect("invalid allocations")
        .issue_contract()
        .expect("invalid contract data");

    let contract_id = contract.contract_id();

    eprintln!("{contract}");
    contract.save_file("examples/rgb20-simplest.rgb").expect("unable to save contract");
    fs::write("examples/rgb20-simplest.rgba", contract.to_ascii_armored_string()).expect("unable to save contract");

    // Let's create some stock - an in-memory stash and inventory around it:
    let mut stock = Stock::default();
    stock.import_iface(Rgb20::iface()).unwrap();
    stock.import_schema(NonInflatableAsset::schema()).unwrap();
    stock.import_iface_impl(NonInflatableAsset::issue_impl()).unwrap();

    stock.import_contract(contract, &mut DumbResolver).unwrap();

    // Reading contract state through the interface from the stock:
    let contract = stock.contract_iface_id(contract_id, Rgb20::iface().iface_id()).unwrap();
    let contract = Rgb20::from(contract);
    let allocations = contract.fungible("assetOwner", &FilterIncludeAll).unwrap();
    eprintln!("\nThe issued contract data:");
    eprintln!("{}", serde_json::to_string(&contract.spec()).unwrap());

    for FungibleAllocation  { seal, state, witness, .. } in allocations {
        eprintln!("amount={state}, owner={seal}, witness={witness}");
    }
    eprintln!("totalSupply={}", contract.total_supply());
    eprintln!("created={}", contract.created().to_local().unwrap());
}

Save it, and execute cargo run, after that, contract file would save in examples directory. You can specify your own token name, decimal, description, beneficiary and supply by modifing corresponding variable's value, as well as contracts saving fold.

Now, you can import the contract with rgb import command: rgb import examples/rgb20-simplest.rgb.