labeler.ts

import { danger } from "danger"

interface ApiError {
  action: string
  opts: object
  error: any
}

export const logApiError = ({ action, opts, error }: ApiError) => {
  const msg = `Could not run ${action} with options ${JSON.stringify(
    opts
  )}\n Error was ${error}\nSet env var DEBUG=octokit:rest* for extended logging info.`
  console.warn(msg)
}

const questionWords: Set<string> = new Set([
  "how",
  "who",
  "what",
  "where",
  "when",
  "why",
  "will",
  "which",
])

const documentationWords: Set<string> = new Set([
  "documentation",
  "document",
  "docs",
  "doc",
  "readme",
  "changelog",
  "tutorial",
])

const endsWith = (character: string, sentence: string): boolean =>
  sentence.slice(-1) === character

const matchKeyword = (
  keywords: Set<string>,
  sentence: string,
  firstOnly: boolean = false
): boolean => {
  /*
   * We need to turn the title into a parseable array of words. To do this, we:
   * 1. Remove any character that’s not a letter or space
   * 2. Split the sentence on spaces to create an array of words, and
   * 3. Get the first word if `firstOnly` is `true`, or else the whole array
   */
  const words = sentence
    .replace(/\W /g, " ")
    .split(" ")
    .slice(0, firstOnly ? 1 : Infinity) as string[]

  // Check if any of the words matches our set of keywords.
  return words.some((word: string) => keywords.has(word.toLowerCase()))
}

export const labeler = async () => {
  const gh = danger.github as any
  const repo = gh.repository
  const issue = gh.issue
  const title = issue.title
  const currentLabels = danger.github.issue.labels.map(i => i.name)

  let labels: Set<string> = new Set(currentLabels)

  if (endsWith("?", title) || matchKeyword(questionWords, title, true)) {
    labels.add("type: question or discussion")
  }

  if (matchKeyword(documentationWords, title)) {
    labels.add("type: documentation")
  }

  if (labels.size > 0) {
    const opts = {
      owner: repo.owner.login,
      repo: repo.name,
      number: issue.number,
      labels: Array.from(labels),
    }

    try {
      await danger.github.api.issues.addLabels(opts)
    } catch (error) {
      logApiError({ action: `issues.addLabel`, opts, error })
    }
  }
}

export default async () => {
  await labeler()
}