Create Player Probabilities

createPlayerProbabilitiesFn.ts

type ExpectedProbabilitiesFn = (playerARating: number, playerBRating: number) =>
    [
        playerAProbability: number,
        playerBProbability: number,
        ratingADifference: number,
        ratingBDifference: number
    ]

function createPlayerProbabilitiesFn(exponentBase: number, exponentDenominator: number): ExpectedProbabilitiesFn {
    const expectedPlayerProbabilityFn = createBaseExpectedPlayerProbabilityFn(exponentBase, exponentDenominator)

    const expectedPlayerProbability: ExpectedProbabilitiesFn = (playerARating, playerBRating) => {
        const ratingADifference = playerBRating - playerARating
        const ratingBDifference = playerARating - playerBRating

        const playerAProbability = expectedPlayerProbabilityFn(ratingADifference)
        const playerBProbability = expectedPlayerProbabilityFn(ratingBDifference)

        return [
            playerAProbability,
            playerBProbability,
            ratingADifference,
            ratingBDifference,
        ]
    }

    return expectedPlayerProbability
}