// @ts-check

import fs from 'fs/promises'

import { promisify } from 'util'

import { exec as execOrig } from 'child_process'

const exec = promisify(execOrig)

/**

* Gets git repository information from the environment

* @returns {Promise<{branchName: string, remoteUrl: string, commitSha: string}>}

*/

export async function getGitInfo() {

let eventData = {}

try {

eventData =

JSON.parse(

await fs.readFile(process.env.GITHUB_EVENT_PATH || '', 'utf8')

)['pull_request'] || {}

} catch (_) {}

const branchName =

eventData?.head?.ref ||

process.env.GITHUB_REF_NAME ||

(await exec('git rev-parse --abbrev-ref HEAD')).stdout.trim()

const remoteUrl =

eventData?.head?.repo?.full_name ||

process.env.GITHUB_REPOSITORY ||

(await exec('git remote get-url origin')).stdout.trim()

const commitSha =

eventData?.head?.sha ||

process.env.GITHUB_SHA ||

(await exec('git rev-parse HEAD')).stdout.trim()

return { branchName, remoteUrl, commitSha }

}

/**

* Determines the appropriate git diff revision based on the environment

* @returns {Promise<string>} The git revision to diff against

*/

export async function getDiffRevision() {

if (process.env.GITHUB_ACTIONS === 'true') {

const eventName = process.env.GITHUB_EVENT_NAME

switch (eventName) {

// GH Actions for `pull_request` run on the merge commit by default so HEAD~1:

// 1. includes all changes in the PR

// e.g. in

// A-B-C-main - F

// \ /

// D-E-branch

// GH actions for `branch` runs on F, so a diff for HEAD~1 includes the diff of D and E combined

// 2. Includes all changes of the commit for pushes (assuming the push event is from a squash merge)

case 'pull_request':

case 'push':

return 'HEAD~1'

default:

throw new Error(`Unsupported GITHUB_EVENT_NAME: ${eventName}`)

}

} else {

try {

await exec('git remote set-branches --add origin canary')

await exec('git fetch origin canary --depth=20')

} catch (err) {

const remoteInfo = await exec('git remote -v')

console.error(remoteInfo.stdout)

console.error(remoteInfo.stderr)

console.error(`Failed to fetch origin/canary`, err)

}

// TODO: We should diff against the merge base with origin/canary not directly against origin/canary.

// A --- B ---- origin/canary

// \

// \-- C ---- HEAD

// `git diff origin/canary` includes B and C

// But we should only include C.

return 'origin/canary'

}

}