FundBalancing

FundBalancer.js

const FundData = require('./FundData');
class FundBalancer {
  constructor(){
    this.state = { data: [] }
  };

  insert({ owner, current, expected }){
    const fd = new FundData({ owner, current, expected });
    this.data().push(fd);
  }

  data(){
    return this.state.data;
  }

  transferables(){
    return this.data().sort(FundData.compare);
  }

  static isEquilibrium(transferables){
    for(let t of transferables){
      if(t.hasTransferable()){ return false; }
    }
    return true;
  }

  transferActions(){
    const transferables = this.transferables();
    const actions = [];
    while(!FundBalancer.isEquilibrium(transferables)){
      let source = transferables.shift();
      let destination = transferables.pop();
      let transferValue = Math.min(source.transferValue(), destination.transferValue())
      let action = { source: source.owner(), destination: destination.owner(), transferValue }
      let sourceAfter = source.afterAction(action);
      let destinationAfter = destination.afterAction(action);
      actions.push(action);
      transferables.push(sourceAfter);
      transferables.push(destinationAfter);
      transferables.sort(FundData.compare);
    };
    return { actions, transferables};
  }

}

module.exports = FundBalancer;

FundData.js

class FundData {

  static compare(fd1, fd2){
    return fd2.transferable() - fd1.transferable();
  }

  constructor({ owner, current, expected, buffer = 0 }){
    this.props = { owner, current, expected, buffer };
  }

  current(){
    return this.props.current;
  }

  expected(){
    return this.props.expected;
  }

  owner(){
    return this.props.owner;
  }

  buffer(){
    return this.props.buffer;
  }

  hasTransferable(){
    return this.transferable() > this.buffer();
  }

  transferable(){
    return this.props.current - this.props.expected;
  }

  transferValue(){
    return Math.abs(this.transferable());
  }

  afterAction(action){
    if(this.owner() === action.source){
      const amount = this.current() - action.transferValue;
      return new FundData({ owner: this.owner(), current: amount, expected: this.expected() });
    } else if(this.owner() === action.destination){
      const amount = this.current() + action.transferValue;
      return new FundData({ owner: this.owner(), current: amount, expected: this.expected() });
    };
  }
}

module.exports = FundData;