index.js

const core = require('@actions/core');
const github = require('@actions/github')

async function run() {
  try {
    const owner = core.getInput('owner', { required: true })
    const repo = core.getInput('repo', { required: true })
    const pr_number = core.getInput('pr_number', { required: true })
    const token = core.getInput('token', { required: true })

    const octokit = new github.getOctokit(token)

    const { data: changedFiles } = await octokit.rest.pulls.listFiles({
      owner,
      repo,
      pull_number: pr_number
    })

    let diffData = {
      addition: 0,
      deletions: 0,
      changes: 0
    }

    diffData = changedFiles.reduce((acc, file) => {
      acc.additions += file.additions;
      acc.deletions += file.deletions;
      acc.changes += file.changes;
      return acc;
    }, diffData);

    await octokit.rest.issues.createComment({
      owner,
      repo,
      issue_number: pr_number,
      body: `
        Pull request ${pr_number} has been updated with: \n
        - ${diffData.changes} changes\n
        - ${diffData.addition} additions\n
        - ${diffData.deletions} deletions\n
      `
    })


    for (const file of changedFiles) {
      const fileExtension = file.filename.split('.').pop();
      let label = '';
      switch (fileExtension) {
        case 'md':
          label = 'markdown';
          break;
        case 'js':
          label = 'javascript'
          break;
        case 'yml':
          label = 'yaml'
          break;

        default:
          label = 'noextension'
          break;
      }

      await octokit.rest.issues.addLabel({
        owner,
        repo,
        issue_number: pr_number,
        labels: [label]
      })
    }
  } catch (error) {
    core.setFailed(error.message);
  }
}

run();