foo.js

const { __, pick, compose, curry, concat, map, reduce, cond,
    T, divide, multiply, add, subtract, lift, view, lensProp, lensPath, over,
    prop, props, identity, findLast, keys, sort, split, apply } = require("ramda");
const Either = require('data.either');
const SCORECAST_CONVERSIONS = {
    '1': '1/2000',
    '1.001': '1/1000',
    '1.002': '1/400',
    '1.003': '1/300',
    '1.004': '1/250',
    '1.005': '1/200',
    '1.007': '1/150',
    '1.008': '1/125',
    '1.01': '1/100',
    '1.012': '1/80',
    '1.015': '1/66',
    '1.017': '1/60',
    '1.02': '1/50',
    '1.025': '1/40',
    '1.03': '1/33',
    '1.033': '1/30',
    '1.036': '1/28',
    '1.04': '1/25',
    '1.046': '1/22',
    '1.05': '1/20',
    '1.053': '1/19',
    '1.056': '1/18',
    '1.062': '1/16',
    '1.067': '1/15',
    '1.071': '1/14',
    '1.077': '1/13',
    '1.083': '1/12',
    '1.091': '1/11',
    '1.1': '1/10',
    '1.111': '1/9',
    '1.118': '2/17',
    '1.125': '1/8',
    '1.133': '2/15',
    '1.143': '1/7',
    '1.154': '2/13',
    '1.167': '1/6',
    '1.182': '2/11',
    '1.2': '1/5',
    '1.222': '2/9',
    '1.25': '1/4',
    '1.286': '2/7',
    '1.3': '30/100',
    '1.333': '1/3',
    '1.35': '7/20',
    '1.364': '4/11',
    '1.4': '2/5',
    '1.444': '4/9',
    '1.45': '9/20',
    '1.471': '40/85',
    '1.5': '1/2',
    '1.533': '8/15',
    '1.571': '4/7',
    '1.6': '3/5',
    '1.615': '8/13',
    '1.625': '5/8',
    '1.667': '4/6',
    '1.7': '7/10',
    '1.727': '8/11',
    '1.8': '4/5',
    '1.833': '5/6',
    '1.9': '9/10',
    '1.909': '10/11',
    '1.952': '20/21',
    '2': '1/1',
    '2.05': '21/20',
    '2.1': '11/10',
    '2.2': '6/5',
    '2.25': '5/4',
    '2.3': '13/10',
    '2.375': '11/8',
    '2.4': '7/5',
    '2.5': '6/4',
    '2.6': '8/5',
    '2.625': '13/8',
    '2.7': '17/10',
    '2.75': '7/4',
    '2.8': '9/5',
    '2.875': '15/8',
    '2.9': '19/10',
    '3': '2/1',
    '3.1': '21/10',
    '3.125': '85/40',
    '3.2': '11/5',
    '3.25': '9/4',
    '3.3': '23/10',
    '3.375': '95/40',
    '3.4': '12/5',
    '3.5': '5/2',
    '3.6': '13/5',
    '3.75': '11/4',
    '3.8': '14/5',
    '4': '3/1',
    '4.2': '16/5',
    '4.333': '100/30',
    '4.5': '7/2',
    '4.6': '18/5',
    '5': '4/1',
    '5.5': '9/2',
    '6': '5/1',
    '6.5': '11/2',
    '7': '6/1',
    '7.5': '13/2',
    '8': '7/1',
    '8.5': '15/2',
    '9': '8/1',
    '9.5': '17/2',
    '10': '9/1',
    '11': '10/1',
    '12': '11/1',
    '13': '12/1',
    '14': '13/1',
    '15': '14/1',
    '16': '15/1',
    '17': '16/1',
    '18': '17/1',
    '19': '18/1',
    '20': '19/1',
    '21': '20/1',
    '23': '22/1',
    '26': '25/1',
    '29': '28/1',
    '31': '30/1',
    '34': '33/1',
    '36': '35/1',
    '41': '40/1',
    '46': '45/1',
    '51': '50/1',
    '56': '55/1',
    '61': '60/1',
    '67': '66/1',
    '71': '70/1',
    '76': '75/1',
    '81': '80/1',
    '86': '85/1',
    '91': '90/1',
    '96': '95/1',
    '101': '100/1',
    '106': '105/1',
    '111': '110/1',
    '116': '115/1',
    '121': '120/1',
    '126': '125/1',
    '131': '130/1',
    '136': '135/1',
    '141': '140/1',
    '146': '145/1',
    '151': '150/1',
    '156': '155/1',
    '161': '160/1',
    '166': '165/1',
    '171': '170/1',
    '176': '175/1',
    '181': '180/1',
    '186': '185/1',
    '191': '190/1',
    '196': '195/1',
    '201': '200/1',
    '211': '210/1',
    '221': '220/1',
    '231': '230/1',
    '241': '240/1',
    '251': '250/1',
    '261': '260/1',
    '271': '270/1',
    '281': '280/1',
    '291': '290/1',
    '301': '300/1',
    '326': '325/1',
    '351': '350/1',
    '376': '375/1',
    '401': '400/1',
    '426': '425/1',
    '451': '450/1',
    '476': '475/1',
    '501': '500/1',
    '551': '550/1',
    '601': '600/1',
    '651': '650/1',
    '701': '700/1',
    '751': '750/1',
    '801': '800/1',
    '851': '850/1',
    '901': '900/1',
    '951': '950/1',
    '1001': '1000/1',
    '1101': '1100/1',
    '1201': '1200/1',
    '1251': '1250/1',
    '1501': '1500/1',
    '1601': '1600/1',
    '1701': '1700/1',
    '1801': '1800/1',
    '1901': '1900/1',
    '2001': '2000/1',
    '2501': '2500/1',
    '3001': '3000/1',
    '4001': '4000/1',
    '5001': '5000/1',
    '6001': '6000/1',
    '7001': '7000/1',
    '8001': '8000/1',
    '9001': '9000/1',
    '10001': '10000/1'
};
const buildOrderedKeys = compose(sort(subtract), map((p) => parseFloat(p)),keys);
const ORDERED_KEYS = buildOrderedKeys(SCORECAST_CONVERSIONS);
const scorer = {
    price: {
        num: 5,
        den: 1
    },
    type: "home"
}

const correctScore = {
    score: {
        home: 1,
        away: 0
    },
    price: {
        num: 13,
        den: 2
    },
    type: "home"
}

/**
 * Check if the selection is actually possible
 */
const validateSelectedOutcomes = (scorer, correctScore) => correctScore.score[scorer.type] > 0 ?
    Either.Right( [scorer, correctScore] ) :
    Either.Left("Invalid selection");

/**
 * Work out what the price is based on type of the outcomes and overall score
 */
const isDraw = ([scorer, correctScore]) => correctScore.type === "draw";
const scorerAndTeamMatch = ([ scorer, correctScore ]) => scorer.type === correctScore.type;
const calculatePriceWithScaleFactor = (factor) => compose(reduce(multiply, factor), map(prop('price')))
const calculateTruePrice = cond(
    [
        [isDraw, calculatePriceWithScaleFactor(0.8)],
        [scorerAndTeamMatch, calculatePriceWithScaleFactor(0.6)],
        [T, calculatePriceWithScaleFactor(1.25)]
    ]
);

/**
 * Convert the outcomes' prices to decimals and scale appropriately
 */
const convertToDecimal = over(lensProp('price'), compose(add(1), apply(divide), props([ 'num', 'den' ])));
const buildPrice = compose(calculateTruePrice, map(convertToDecimal));

/**
 * Take the true price and identify the nearest neighbour from the original price map
 */
const pickNearestPriceFromMap = (keys, map) => (decimalPrice) => prop(findLast((p) => parseFloat(p) < decimalPrice, keys), map)
const findNearestPrice = pickNearestPriceFromMap(ORDERED_KEYS, SCORECAST_CONVERSIONS);

/**
 * Convert a string representation of a price to a Price object
 */
const toPriceObject = compose(([num, den]) => ({num,den}), split('/'))

const getPrice = compose(toPriceObject, findNearestPrice, buildPrice)
const app = compose(map(getPrice), validateSelectedOutcomes)

// Price should be 25/1
console.log('---');
console.log(app(scorer, correctScore));
console.log('---');