mint.cash

pragma cashscript ^0.10.0;

// Multi-threaded minting smart contract

// Contract holds the next NFT nummber to mint as state in the commitment field of the minting NFT
// Contract consists of a mintNFT and a payout function

// Opcode count: 84 (max 201)
// Bytesize: 163 (max 520)

contract Mint(
    int mintPrice,
    int increment,
    bytes20 pkhPayout,
    int maximumCount
) {
    function mintNFT() {
        // require minting contract to be at input index zero
        require(this.activeInputIndex == 0);

        // Read nftNumber from contract commitment
        bytes commitment = tx.inputs[0].nftCommitment;
        int nftNumber = int(commitment);
        
        // Check if minting is still allowed
        require(nftNumber <= maximumCount);

        // Limit the max number of outputs to 3
        require(tx.outputs.length <= 3);
            
        // Output#0 preserves the NFT minting contract with a minting nft holding the new state and increased BCH value
        require(tx.outputs[0].lockingBytecode == tx.inputs[0].lockingBytecode);
        require(tx.outputs[0].tokenCategory == tx.inputs[0].tokenCategory);
        int nextNftNumber = nftNumber + increment;
        require(tx.outputs[0].nftCommitment == bytes(nextNftNumber));
        require(tx.outputs[0].value == tx.inputs[0].value + mintPrice);

        // Output#1 for the minted NFT
        require(tx.outputs[1].value == 1000);
        require(tx.outputs[1].nftCommitment == bytes(nftNumber));
        // Strip capability to get the tokenId for an immutable NFT
        bytes tokenId = tx.inputs[0].tokenCategory.split(32)[0];
        require(tx.outputs[1].tokenCategory == tokenId);

        // Allow for BCH change output
        if(tx.outputs.length == 3){
            // Output#2 BCH change output for minter
            require(tx.outputs[2].tokenCategory == 0x);
        }
    }
    function payout(sig sigPayout, pubkey pkPayout) {
        // Check the signature & public key against pkhPayout
        require(hash160(pkPayout) == pkhPayout);
        require(checkSig(sigPayout, pkPayout));
        
        // require minting contract to be at input index zero
        require(tx.inputs.length == 1);

        // Read count from contract commitment
        bytes commitment = tx.inputs[0].nftCommitment;
        int nftNumber = int(commitment);

        // Check if minting is still ongoing
        if(nftNumber <= maximumCount){
            // Limit the number of outputs to 2
            require(tx.outputs.length == 2);
                
            // Output#0 preserves the NFT minting contract with same minting nft
            require(tx.outputs[0].lockingBytecode == tx.inputs[0].lockingBytecode);
            require(tx.outputs[0].tokenCategory == tx.inputs[0].tokenCategory);
            require(tx.outputs[0].nftCommitment == tx.inputs[0].nftCommitment);

            // Output#1 payout output
            require(tx.outputs[1].tokenCategory == 0x);
        } else {
            // Output#0 payout output
            require(tx.outputs.length == 1);

            // Burns minting NFT
            require(tx.outputs[0].tokenCategory == 0x);
        }
    }
}