pr-title-labeler.yml

name: PR Labeller

on:
  pull_request:
    types: [opened, edited]

jobs:
  label-pr:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4.2.2

      - name: Update PR labels and title
        uses: actions/github-script@v7.0.1
        with:
          script: |
            const prBody = context.payload.pull_request.body;
            const shouldHaveLabels = new Set();

            const labelMappings = {
              'Bug fix': 'Bug',
              'New feature': 'Feature',
              'UI/UX improvement': 'UI/UX',
              'Weather data processing': 'Data Processing',
              'Optimisation': 'Optimisation',
              'Security': 'Security',
              'Documentation update': 'Documentation',
              'Chore': 'Chore'
            };

            const titlePrefixMappings = {
              'Bug': 'fix',
              'Feature': 'feat',
              'UI/UX': 'ui',
              'Data Processing': 'data',
              'Optimisation': 'perf',
              'Security': 'security',
              'Documentation': 'docs',
              'Chore': 'chore'
            };

            const validPrefixes = Object.values(titlePrefixMappings);
           
            // Determine which labels should be present
            for (const [text, label] of Object.entries(labelMappings)) {
              if (prBody && prBody.includes(`- [x] ${text}`)) {
                shouldHaveLabels.add(label);
              }
            }
        
            // Get current labels
            const currentLabels = await github.rest.issues.listLabelsOnIssue({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.payload.pull_request.number,
            });
            
            const currentLabelNames = new Set(currentLabels.data.map(l => l.name));
            const allMappedLabels = new Set(Object.values(labelMappings));
            
            // Remove labels that shouldn't be there
            const labelsToRemove = [...currentLabelNames].filter(label => 
              allMappedLabels.has(label) && !shouldHaveLabels.has(label)
            );
            
            for (const label of labelsToRemove) {
              await github.rest.issues.removeLabel({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.payload.pull_request.number,
                name: label
              });
            }
            
            // Add missing labels
            const labelsToAdd = [...shouldHaveLabels].filter(label => 
              !currentLabelNames.has(label)
            );
            
            if (labelsToAdd.length > 0) {
              await github.rest.issues.addLabels({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.payload.pull_request.number,
                labels: labelsToAdd
              });
            }

            // Update PR title with prefix
            const selectedLabel = [...shouldHaveLabels][0];
            if (selectedLabel) {
              const prefix = titlePrefixMappings[selectedLabel].toLowerCase();
              let currentTitle = context.payload.pull_request.title;
              
              // Check if current title has any prefix (including non-standard ones)
              const prefixMatch = currentTitle.match(/^([a-zA-Z]+):\s*(.*)/);
              
              if (prefixMatch) {
                const titleContent = prefixMatch[2];
                // Only update if current prefix is not the correct one
                const currentPrefix = prefixMatch[1].toLowerCase();
                if (!validPrefixes.includes(currentPrefix) || currentPrefix !== prefix) {
                  const newTitle = `${prefix}: ${titleContent}`;
                  
                  await github.rest.pulls.update({
                    owner: context.repo.owner,
                    repo: context.repo.repo,
                    pull_number: context.payload.pull_request.number,
                    title: newTitle
                  });
                }
              } else {
                // No prefix exists, add new one
                const newTitle = `${prefix}: ${currentTitle}`;
                
                await github.rest.pulls.update({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  pull_number: context.payload.pull_request.number,
                  title: newTitle
                });
              }
            }