f_cancel.cash

pragma cashscript ^0.10.0;

contract CashStarterCancel() {
  //////////////////////////////////////////////////////////////////////////////////////////
 ///////////////////////////////    Cancel Camapaign   ////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////
// Creator removes minting capability from an active campaignNFT.
// Prevents pledge(), fail(), cancel() from being called on the campaign.
// Still allows refund() and claim() to be called on the campaign.
//
// Callable at any time, but only by the creator of the campaign.
// If no pledges exist on the campaign then cancel() will burn the campignNFT.
// If pledges do exist on the campaign then after cancel() only sats from pledges will
// remain on it.
// Creator can still claim() after the campaign has been cancel()'d if enough BCH is still pledged.
// After the last pledge refund()'s, or the campaign is claim()'d, the campaignNFT will be burned.
// ___________________________________________________________________________________
//inputs: 
//  0   masterNFT       [NFT]       (from CashStarterCancel contract)
//  1   campaignNFT     [NFT]       (from CashStarter contract)
//  2   userUTXO        [BCH]       (from user)
//outputs:                                                      
//  0   masterNFT       [NFT]       (to CashStarterCancel contract)   | O |   0   masterNFT   [NFT]     (to CashStarterCancel contract)    
//  1   campaignNFT     [NFT]       (to CashStarter contract)         | R |   1   userUTXO    [BCH]     (to user)
//  2   userUTXO        [BCH]       (to user)                         |   |
//////////////////////////////////////////////////////////////////////////////////////////
    function cancel() {
        require(this.activeInputIndex == 0);                                                    // this contracts utxo must be input 0
        require(tx.inputs.length == 3);                                                         // exactly three inputs
        require(tx.outputs.length <= 3);                                                        // three or less outputs
        require(tx.inputs[1].tokenCategory == 0x64c9ea104e07d9099bc3cdcb2a0035286773790c40dbcb0ae67068b1b8453748 + 0x02); //input1 must be an active campaignNFT (minting)
        require(tx.inputs[2].tokenCategory == 0x);                                                                        //input2 must have no tokens

        bytes20 payoutAddress = bytes20(tx.inputs[1].nftCommitment.split(26)[0].split(6)[1]);   // get campaigns payoutAddress from commitment
        require(tx.inputs[2].lockingBytecode == new LockingBytecodeP2PKH(payoutAddress));       // check that userUTXO is from that payoutAddress (proves creator is calling cancel())

        bytes masterID = tx.inputs[0].nftCommitment.split(35)[1];                               // get ID from input0 (masterNFT)
        require(masterID == 0xFFFFFFFFFF);                                                      // must be a masterNFT

        bytes campaignID = tx.inputs[1].nftCommitment.split(35)[1];                             // get ID from input1 (campaignNFT)
        require(campaignID != 0xFFFFFFFFFF);                                                    // prevent using a masterNFT

        require(tx.outputs[0].lockingBytecode == tx.inputs[0].lockingBytecode);                 // recreate masterNFT to CashStarterCancel contract
        require(tx.outputs[0].tokenCategory == tx.inputs[0].tokenCategory);                     // carry forward categoryID + capability
        require(tx.outputs[0].tokenAmount == tx.inputs[0].tokenAmount);                         // carry forward token balance
        require(tx.outputs[0].nftCommitment == tx.inputs[0].nftCommitment);                     // carry forward commitment
        require(tx.outputs[0].value == tx.inputs[0].value);                                     // carry forward satoshis

        if (tx.inputs[1].value == 1000) {                                                       // if nobody has pleged to this campaign
            require(tx.outputs[1].lockingBytecode == tx.inputs[2].lockingBytecode);                 // userUTXO must be sent back to users address
            require(tx.outputs[1].tokenCategory == 0x);                                             // userUTXO must not have tokens
            require(tx.outputs[1].value == tx.inputs[2].value);                                     // userUTXO retains BCH value

            require(tx.outputs.length == 2);                                                        // implicit burn the campaignNFT (consumes campignNFT 1000sats for miner fee)

        } else {                                                                                // else pledges have been made
            require(tx.outputs[1].lockingBytecode == tx.inputs[1].lockingBytecode);                 // recreate campaignNFT to CashStarter contract
            require(tx.outputs[1].tokenCategory == tx.inputs[1].tokenCategory.split(32)[0] + 0x01); // set campaignNFT's categoryID to mutable
            require(tx.outputs[1].tokenAmount == tx.inputs[1].tokenAmount);                         // carry forward campaignNFT tokenAmount
            require(tx.outputs[1].nftCommitment == tx.inputs[1].nftCommitment);                     // carry forward campaignNFT commitment
            require(tx.outputs[1].value == tx.inputs[1].value - 1000);                              // remove initial 1000sats from campaignNFT for miner fee. only pledge sats remain

            require(tx.outputs[2].lockingBytecode == tx.inputs[2].lockingBytecode);                 // userUTXO must be sent back to users address
            require(tx.outputs[2].tokenCategory == 0x);                                             // userUTXO must not have tokens
            require(tx.outputs[2].value == tx.inputs[2].value);                                     // userUTXO retains BCH value
        }
    }
}