# All files / src/tx/applyTx checkSpendCond.js

87.5% Statements 84/96
61.54% Branches 16/26
90% Functions 18/20
87.5% Lines 84/96

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     /**
     * Copyright (c) 2018-present, Leap DAO (leapdao.org)
     *
     * This source code is licensed under the Mozilla Public License Version 2.0
     * found in the LICENSE file in the root directory of this source tree.
     */

    const { Type, Output } = require('leap-core');
    const Transaction = require('ethereumjs-tx');
    const VM = require('ethereumjs-vm');
    const utils = require('ethereumjs-util');
    const { BigInt, add, divide, subtract, lessThan } = require('jsbi-utils');
    const isEqual = require('lodash/isEqual');
    const { checkInsAndOuts, groupValuesByColor } = require('./utils');
    const getColors = require('../../api/methods/getColors');
    const { NFT_COLOR_BASE } = require('../../api/methods/constants');

    const { Account } = VM.deps;

    // commpiled https://github.com/leapdao/spending-conditions/blob/master/contracts/ERC20Min.sol
    const erc20Code = Buffer.from(
      ' ',
      'hex'
    );

    const REACTOR_ADDR = Buffer.from(
      '0000000000000000000000000000000000000001',
      'hex'
    );

    const MINT_FUNCSIG = Buffer.from(
      '40c10f19000000000000000000000000',
      'hex'
    );

    function setAccount(account, address, stateManager) {
      return new Promise((resolve, reject) => {
        stateManager.putAccount(address, account, (err) => {
          Iif (err) {
            return reject(err);
          }
          return resolve();
        });
      });
    }

    function setAccountCode(code, address, stateManager) {
      return new Promise((resolve, reject) => {
        stateManager.putContractCode(address, code, (err) => {
          Iif (err) {
            return reject(err);
          }
          return resolve();
        });
      });
    }

    // runs a transaction through the vm
    function runTx(vm, raw) {
      // create a new transaction out of the js object
      const tx = new Transaction(raw);

      Object.defineProperty(tx, 'from', {
        // instead of tx.sign(Buffer.from(secretKey, 'hex'))
        // eslint-disable-next-line object-shorthand
        get() {
          return REACTOR_ADDR;
        },
      });

      return new Promise((resolve, reject) => {
        // run the tx \o/
        vm.runTx({ tx }, (err, results) => {
          Iif (err) {
            return reject(err);
          }
          Iif (results.vm.exceptionError) {
            return reject(results.vm.exceptionError);
          }
          return resolve(results);
        });
      });
    }

    const addColors = (map, colors, colorBase = 0) => {
      colors.forEach((color, i) => {
        map[i + colorBase] = Buffer.from(color.replace('0x', ''), 'hex');
      });
    };

    module.exports = async (state, tx, bridgeState, nodeConfig = {}) => {
      Iif (tx.type !== Type.SPEND_COND) {
        throw new Error('Spending Condition tx expected');
      }
      if (nodeConfig.network && nodeConfig.network.noSpendingConditions) {
        throw new Error('Spending Conditions are not supported on this network');
      }

      // check that script hashes to address
      checkInsAndOuts(
        tx,
        state,
        bridgeState,
        ({ address }, i) =>
          address === `0x${utils.ripemd160(tx.inputs[i].script).toString('hex')}`
      );

      const colorMap = {};
      addColors(colorMap, await getColors(bridgeState, false), 0);
      addColors(colorMap, await getColors(bridgeState, true), NFT_COLOR_BASE);

      // TODO make inputMap
      // convenience mapping from inputs to the previous outputs
      const inputMap = {};
      for (let i = 0; i < tx.inputs.length; i += 1) {
        inputMap[tx.inputs[i].prevout.getUtxoId()] =
          state.unspent[tx.inputs[i].prevout.hex()];
      }

      // creating a new VM instance
      const vm = new VM({ hardfork: 'petersburg' });
      // creating the reactor account with some wei
      const reactorAccount = new Account();
      reactorAccount.balance = '0xf00000000000000001';
      await setAccount(reactorAccount, REACTOR_ADDR, vm.stateManager);

      // deploying colors and mint tokens
      let results;
      let nonceCounter = 0;

      const sigHashBuf = tx.sigHashBuf();
      const insValues = Object.values(inputMap).reduce(groupValuesByColor, {});
      const outsValues = tx.outputs.reduce(groupValuesByColor, {});
      // eslint-disable-next-line  guard-for-in
      for (const color in insValues) {
        // eslint-disable-next-line no-await-in-loop
        await setAccountCode(erc20Code, colorMap[color], vm.stateManager); // eslint-disable-line no-await-in-loop

        // minting amount of output to address of condition
        const amountHex = utils.setLengthLeft(
          utils.toBuffer(`0x${BigInt(outsValues[color]).toString(16)}`),
          32
        );
        // eslint-disable-next-line no-await-in-loop
        await runTx(vm, {
          nonce: nonceCounter,
          gasLimit: '0xffffffffffff',
          to: colorMap[color],
          data: Buffer.concat([MINT_FUNCSIG, sigHashBuf, amountHex]),
        });
        nonceCounter += 1;
      }

      // deploying conditions
      tx.inputs.forEach(async input => {
        // TODO: what if there are multiple condition scripts in one tx?
        await setAccountCode(input.script, sigHashBuf, vm.stateManager);
      });

      // need to commit to trie, needs a checkpoint first 🤪
      await new Promise((resolve) => {
        vm.stateManager.checkpoint(() => {
          vm.stateManager.commit(() => {
            resolve();
          });
        });
      });

      const logOuts = [];
      const colorGasSums = {};
      // running conditions with msgData
      for (let i = 0; i < tx.inputs.length; i += 1) {
        // eslint-disable-next-line no-await-in-loop
        results = await runTx(vm, {
          nonce: nonceCounter,
          gasLimit: 6000000, // TODO: set gas Limit to (inputs - outputs) / gasPrice
          to: sigHashBuf, // the plasma address is replaced with sighash, to prevent replay attacks
          data: tx.inputs[i].msgData,
        });
        nonceCounter += 1;

        const out = inputMap[tx.inputs[i].prevout.getUtxoId()];

        Iif (colorGasSums[out.color]) {
          colorGasSums[out.color] = add(
            colorGasSums[out.color],
            BigInt(results.gasUsed)
          );
        } else {
          colorGasSums[out.color] = BigInt(results.gasUsed);
        }

        // itterate through all transfer events and sum them up per color
        results.vm.logs.forEach(log => {
          Eif (log[0].equals(colorMap[out.color])) {
            const transferAmount = BigInt(`0x${log[2].toString('hex')}`, 16);
            let toAddr = log[1][2].slice(12, 32);
            // replace injected sigHash with plasma address
            if (toAddr.equals(sigHashBuf)) {
              toAddr = utils.ripemd160(tx.inputs[i].script);
            }
            logOuts.push(new Output(transferAmount, `0x${toAddr.toString('hex')}`, out.color));
          }
        });
      }

      // eslint-disable-next-line  guard-for-in
      for (const color in insValues) {
        const gasPrice = divide(
          subtract(insValues[color], outsValues[color]),
          colorGasSums[color]
        );
        const minGasPrice = BigInt(
          bridgeState.minGasPrices[bridgeState.minGasPrices.length - 1]
        );
        Iif (lessThan(gasPrice, minGasPrice)) {
          return Promise.reject(
            new Error(
              `tx gasPrice ${gasPrice.toString()} less than minGasPRice: ${minGasPrice.toString()}`
            )
          );
        }
      }
      // TODO: compact logOuts
      Iif (!isEqual(tx.outputs, logOuts)) {
        const txOuts = tx.outputs
          .map(output => JSON.stringify(output.toJSON()))
          .join(',');
        const logs = logOuts
          .map(output => JSON.stringify(output.toJSON()))
          .join(',');
        return Promise.reject(
          new Error(
            `outputs do not match computation results. \n outputs ${txOuts} \n calculated: ${logs}`
          )
        );
      }
      return Promise.resolve();
    };