28 lines
995 B
TypeScript
28 lines
995 B
TypeScript
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import { groupBy, mapValues, sum, sumBy } from 'lodash'
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import { Txn } from './txn'
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// Returns a map of charity ids to the amount of M$ matched
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export function quadraticMatches(
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allCharityTxns: Txn[],
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matchingPool: number
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): Record<string, number> {
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// For each charity, group the donations by each individual donor
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const donationsByCharity = groupBy(allCharityTxns, 'toId')
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const donationsByDonors = mapValues(donationsByCharity, (txns) =>
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groupBy(txns, 'fromId')
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)
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// Weight for each charity = [sum of sqrt(individual donor)] ^ 2
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const weights = mapValues(donationsByDonors, (byDonor) => {
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const sumByDonor = Object.values(byDonor).map((txns) =>
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sumBy(txns, 'amount')
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)
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const sumOfRoots = sumBy(sumByDonor, Math.sqrt)
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return sumOfRoots ** 2
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})
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// Then distribute the matching pool based on the individual weights
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const totalWeight = sum(Object.values(weights))
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return mapValues(weights, (weight) => matchingPool * (weight / totalWeight))
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}
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