const fs = require('fs')
const proc = require('child_process')

const skipChangelogInfix = '[no-changelog]'
const changelogPath = process.argv[2]
const baseRef = process.argv[3]

/// Runs the git command with the provided arguments.
function runGit(args) {
  const result = proc.spawnSync('git', args)
  if (result.error) {
    console.log('Cannot access git', result.error)
    process.exit(1)
  }
  return result
}

/** Checks if the changelog file was changed in any commits that are part of the
 * PR.
 */
function wasChangelogModified() {
  const diffArgs = ['--no-pager', 'diff', '--exit-code', baseRef, '--', changelogPath]

  const result = runGit(diffArgs)
  const exitCode = result.status
  console.log(result.stdout.toString('utf-8'))
  const noDifference = exitCode == 0
  return !noDifference
}

/// Checks if any commit has overridden the changelog check.
function isChangelogSkipped() {
  const logArgs = ['--no-pager', 'log', 'HEAD~3...HEAD', '--pretty=oneline']
  const result = runGit(logArgs)

  const output = result.stdout.toString('utf-8')
  const containsSkipCommit = output.indexOf(skipChangelogInfix) >= 0
  return containsSkipCommit
}

if (wasChangelogModified()) {
  console.log('Changelog was changed')
  process.exit(0)
} else {
  console.log('No changes to the changelog')
  if (isChangelogSkipped()) {
    console.log(
      'But one of the commits within the PR includes ' +
        skipChangelogInfix +
        ', so the check is skipped.',
    )
    process.exit(0)
  } else {
    process.exit(1)
  }
}