\n\n \n\n# PoolTogether Draw Calculator JS\n\n[](https://github.com/pooltogether/draw-calculators-js/actions/workflows/main.yml)\n[](https://badge.fury.io/js/@chanceprotocol%2Fdraw-calculator-js)\n[](https://definitelytyped.org)\n\nThis library includes a stateless Typescript model of the Solidity DrawCalculator. It is intended to be uses as a tool to easily check if a User has won a prize for a particular draw. This could also be calculated on-chain through the `DrawCalculator::calculate()` view function but this library is much faster.\n\n# Setup\n\nThis project is available as an NPM package:\n\n```bash\n$ yarn add @chanceprotocol/draw-calculator-js\n```\n\n# How to use\n\nTo create a claim or calculate winnings for an address:\n\n1. Run `yarn add @chanceprotocol/draw-calculator-js` in your project to install the package.\n1. Import the desired functions and types: `import {drawCalculator, Draw, PrizeDistribution, DrawResults, filterResultsByValue, generatePicks, prepareClaims } from \"@chanceprotocol/draw-calculator-js\"`\n\nStarting with a particular `drawId` and `userAddress`, fetch the Draw information from the DrawBuffer contract:\n\n```js\nconst drawBuffer: Contract = new ethers.Contract(address, drawBufferAbi, signerOrProvider);\nconst drawId: number = await drawBuffer.getNewestDraw(); // can go back cardinality in time (8 draws)\nconst draw: Draw = await drawBuffer.functions.getDraw(drawId); // read-only rpc call\n```\n\nNext fetch the PrizeDistribution for the `drawId` from the PrizeDistributionBuffer contract:\n\n```javascript\n// get PrizeDistribution from the DrawCalculatorHistory contract for a particular drawId\nconst PrizeDistributionBufferContract: Contract = new ethers.Contract(\n address,\n prizeDistributionAbi,\n signerOrProvider,\n);\nconst prizeDistribution = await PrizeDistributionBufferContract.functions.getPrizeDistribution(\n drawId,\n); // read-only rpc call\n```\n\nNext, get the users balance using the convenient `getNormalizedBalancesForDrawIds(address _user, uint32[] calldata _drawIds)` view method\non the DrawCalculator contract which returns an array of balances for drawIds:\nW\n\n```js\nconst drawCalculator: Contract = new ethers.Contract(address, drawCalculatorAbi, signerOrProvider);\nconst balances = await drawCalculator.functions.getNormalizedBalancesForDrawIds(userAddress, [\n drawId,\n]); // read-only rpc call\n```\n\nRun this `draw-calculator-js` library locally to see the user has any prizes to claim:\n\n```js\nconst exampleUser: User = {\n address: userAddress // user address we want to calculate for\n normalizedBalances: balances\n}\n\nlet results: DrawResults = batchCalculateDrawResults([prizeDistribution], [draw], exampleUser)\n```\n\nThe `results.totalValue` field should indicate the total amount of prize available for `userAddress` for the `drawId`.\n\nThese results may then need to be filtered by value, since the user can only claim `prizeDistribution.maxPicksPerUser` number of prizes per draw.\n\n```js\nresults = filterResultsByValue(results, prizeDistribution.maxPicksPerUser);\n```\n\nFinally, to claim a prize, forward these `DrawResults` to `prepareClaims(user: User, drawResult: DrawResults[])` to generate the data for the on-chain PrizeDistributor `claim()` call:\n\n```js\nconst claim: Claim = prepareClaims(user, [results]);\n```\n\nThe on-chain call to `PrizeDistributor::claim(address _user, uint32[] calldata _drawIds, bytes calldata _data)` can then be populated and called with this data:\n\n```js\nconst PrizeDistributorContract = new ethers.Contract(\n address,\n PrizeDistributorAbi,\n signerOrProvider,\n);\nawait PrizeDistributorContract.functions.claim(\n claim.userAddress,\n claim.drawIds,\n claim.encodedWinningPickIndices,\n); //write rpc call\n```\n\nCongratulations you have now claimed a prize!\n\n# API Guide\n\ntodo.\n\n# Types\n\nA full breakdown of the types can be found [here](./src/types.ts)\n\n# Testing\n\nUnit tests can be run using:\n\n```bash\n$ yarn test\n```\n\n# Development\n\nFork/clone this repo. Create a pull request with the changes you would like to make. Unit tests must be passing.\n","readmeFilename":"README.md"}
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