Ballot Encoder

Provides encoding and decoding services for completed ballots.

Dev Install

To use within VS Code:

pnpm install

Pubishing New NPM Version

1. Update the version and create a git tag: npm version [major|minor|patch]
2. Push branch for PR review. Once approved…
3. Generate the JavaScript files from TypeScript: pnpm prepare (or pnpx tsc)
4. Publish current version: npm publish --access=public

Optionally, deprecate a previous version. For example: npm deprecate -f '@votingworks/[email protected]' "Poor translations"

Example

import {
  CompletedBallot,
  decodeBallot,
  electionSample as election,
  encodeBallot,
  getContests,
  vote,
} from '@votingworks/ballot-encoder'

const ballotStyle = election.ballotStyles[0]
const precinct = election.precincts[0]
const ballotId = 'abcde'
const contests = getContests({ ballotStyle, election })
const votes = vote(contests, {
  'judicial-robert-demergue': 'yes',
  'judicial-elmer-hull': 'yes',
  'question-a': 'yes',
  'question-b': 'no',
  'question-c': 'yes',
  'proposition-1': 'yes',
  'measure-101': 'no',
  '102': 'yes',
})
const ballot: CompletedBallot = {
  ballotId,
  ballotStyle,
  precinct,
  votes,
}

console.log(encodeBallot(ballot))
/*
Uint8Array [
  86, 88,  1,  2,  49,  50,  2,
  50, 51,  0, 15, 254, 208, 86,
  22, 38, 54, 70,  80
]
*/

console.log(decodeBallot(election, encodeBallot(ballot)).ballot.votes)
/*
{
  '102': 'yes',
  'judicial-robert-demergue': 'yes',
  'judicial-elmer-hull': 'yes',
  'question-a': 'yes',
  'question-b': 'no',
  'question-c': 'yes',
  'proposition-1': 'yes',
  'measure-101': 'no'
}
*/

Usage

To encode a ballot, simply pass an election and a completed ballot object to encodeBallot. You'll get back a buffer that may be stored or transmitted and later passed to decodeBallot with the same election data given to encodeBallot.

There are multiple encoder versions and by default the latest will be used when encoding. To specify the version, pass the EncoderVersion as the second parameter to encodeBallot:

import { encodeBallot, EncoderVersion } from '@votingworks/ballot-encoder'

const encodedBallot = encodeBallot(ballot, EncoderVersion.v1)

When decoding, you may pass an EncoderVersion or you may allow decodeBallot to detect the encoder version:

import { decodeBallot, EncoderVersion } from '@votingworks/ballot-encoder'

// automatically detect version
const result = decodeBallot(election, encodedBallot)
console.log('Ballot version:', result.version)
console.log('Ballot:', result.ballot)

// specify version
const result = decodeBallot(election, encodedBallot, EncoderVersion.v0)
console.log('Ballot version:', result.version)
console.log('Ballot:', result.ballot)

If you only want to detect the version, you can simply use detect:

import { detect } from '@votingworks/ballot-encoder'

const version = detect(encodedBallot)
console.log('Ballot version:', version)

Publish

This project uses the Angular Commit Message Format convention. How to publish a new version:

1. Determine what the appropriate version bump is (i.e. patch, minor, or major). Let's assume this is stored in the environment variable BUMP.
2. Create a branch for publishing the new version.
3. Bump the version: npm version $BUMP.
4. Publish the package to NPM: pnpm publish:npm.
5. Push the branch and the new tag: git push -u origin HEAD && git push --tags.
6. Create a pull request for your newly pushed branch. Note that this pull request should only have the version bump commit, nothing else.
7. Get the pull request approved and merged.