Chapter 6: BSV20-V2

1. Introduction:

The BSV20V2.tsx file contains a React component named BSV20v2. This component is designed to facilitate the inscription of BSV20 - V2 using the BSV20Mint class from the scrypt-ord library. Let's break down the key features of this component.

2. Contract:

Every BSV20-V2 contract needs to inherits the BSV20V2 base class.

The BSV20-v2 protocol issues all tokens upon deployment. We implement any token distribution logic through the public methods of the contract. The mint method implements a simple logic, where anyone can mint some tokens locked in the contract.

class BSV20Mint extends BSV20V2 {
    @prop(true)
    supply: bigint

    @prop()
    lim: bigint

    constructor(
        id: ByteString,
        sym: ByteString,
        max: bigint,
        dec: bigint,
        lim: bigint
    ) {
        super(id, sym, max, dec)
        this.init(...arguments)

        this.supply = max
        this.lim = lim
    }

    @method()
    public mint(dest: Addr, amount: bigint) {
        // Check mint amount doesn't exceed maximum.
        assert(amount <= this.lim, 'mint amount exceeds maximum')
        assert(amount > 0n, 'mint amount should > 0')

        this.supply -= amount
        assert(this.supply >= 0n, 'all supply mint out')
        let outputs = toByteString('')

        if (this.supply > 0n) {
            outputs += this.buildStateOutputFT(this.supply)
        }

        // Build FT P2PKH output to dest paying specified amount of tokens.
        outputs += BSV20V2.buildTransferOutput(dest, this.id, amount)

        // Build change output.
        outputs += this.buildChangeOutput()

        assert(hash256(outputs) === this.ctx.hashOutputs, 'hashOutputs mismatch')
    }

}

3. Front-end Component Breakdown:

scrypt-ord Libraries: Imports classes and utility functions related to BSV20v2, such as BSV20V2P2PKH for token instantiation and isBSV20v2 for checking if a given string is a valid BSV20v2 token.

Scrypt Libraries: Imports functionality for handling addresses, signing transactions, and converting values to byte strings from the scrypt-ts library.

React Router: Imports Navigate from react-router-dom for programmatic navigation.

Function Component: Declares a functional React component named BSV20v2 that takes props as its parameter.

State Variables: Uses the useState hook to declare state variables like _symbol, _amount, _decimal, _icon, and _result.

Return Statement: Returns JSX content wrapped in a Material-UI Container component.

State Variables: Declare state variables using useState for symbol, amount, decimal, and icon. Initial values are set to undefined.

Event Handlers: Define event handlers (symbolOnChange, amountOnChange, iconOnChange, decimalOnChange) to update state variables based on user input.

Valid Input Function: Defines a function validInput that checks if required input fields are defined, enabling or disabling the Mint It! button accordingly.

4. Inscribe:

Artifact: Imports the contract artifact from public/bsv20Mint_release_desc.json and load it with BSV20Mint.loadArtifact(artifact);

Deploy: Defines a function deploy to handle the deploying logic. The deploy function deploys a BSV20-v2 FT by calling instance.deployToken().

Minting: Defines a function mint to handle the minting logic.

1. Get latest contract instance by fromUTXO and connect a signer
2. Bind a transaction builder to call the contract by bindTxBuilder
3. Call contract public function mint to mint token.

Put it to the test

1. Call loadArtifact before we new a contract instance.
2. Call mint method of the instance to inscribe BSV-20 v2 tokens.

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Complete code at Github