mention_users_on_filechange.yml

name: Mention Users on Specific File Change in PR

on:
  pull_request:

jobs:
  mention-users:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repo
        uses: actions/checkout@v2

      - name: Read configuration and mention users
        uses: actions/github-script@v6
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const fs = require('fs');
            
            // Read the configuration file
            const configPath = '.github/notify-users-config.json';
            const configFile = fs.readFileSync(configPath, 'utf8');
            const config = JSON.parse(configFile);
            
            // Extract PR number
            const prNumber = context.issue.number;
            
            // Async function to handle API calls and logic
            async function run() {
              // Fetch list of files changed in the PR
              const listFilesResponse = await github.rest.pulls.listFiles({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: prNumber,
              });
              const changedFiles = listFilesResponse.data.map(file => file.filename);
              
              // Fetch all comments from the PR
              const commentsResponse = await github.rest.issues.listComments({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: prNumber,
              });
              const comments = commentsResponse.data.map(comment => comment.body);
              
              // Combine all comments into a single string to search for user mentions
              const commentsText = comments.join(" ");
              
              let message = "Changes have been detected in:";
              let hasMentionedFiles = false;
              let mentionedUsers = new Set();
              
              // Check if the PR contains changes to the files or folders specified in the configuration
              for (const item of config.files_to_watch) {
                const isFolder = item.path.endsWith('/');
                for (const changedFile of changedFiles) {
                  if (isFolder ? changedFile.startsWith(item.path) : changedFile === item.path) {
                    // Filter out users who have already been mentioned
                    const usersToMention = item.users.filter(user => !commentsText.includes(user));
                    
                    if (usersToMention.length > 0) {
                      // Add users to the set of mentioned users to avoid duplicates
                      usersToMention.forEach(user => mentionedUsers.add(user));
                      if (!hasMentionedFiles) {
                        // First time adding to the message, change the flag
                        hasMentionedFiles = true;
                      }
                      message += `\n- \`${item.path}\` (Pinging ${usersToMention.join(', ')} for review).`;
                    }
                  }
                }
              }
              
              // Post the comment on the PR if there are any files or folders to mention
              if (hasMentionedFiles) {
                await github.rest.issues.createComment({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  issue_number: prNumber,
                  body: message
                });
              } else {
                console.log("No configured files or folders were changed in this PR, or users have already been mentioned.");
              }
            }
            
            // Execute the async function
            run().catch(err => core.setFailed(`Unhandled error: ${err}`));