name: Label PR merge conflicts

on:
  pull_request:
    types: [opened, synchronize, reopened, ready_for_review]

jobs:
  label-conflict:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
      contents: read
    steps:
      - name: Get PR data and label conflicts
        uses: actions/github-script@v7
        with:
          script: |
            const pr = context.payload.pull_request;
            const prNumber = pr.number;
            const repo = context.repo;

            // Fetch PR details to get mergeable_state
            const { data: prData } = await github.rest.pulls.get({
              ...repo,
              pull_number: prNumber
            });

            const mergeableState = prData.mergeable_state; // clean, dirty, blocked, unstable
            const hasConflict = mergeableState === 'dirty';

            const labelName = 'merge-conflict';

            // Get current labels
            const { data: labels } = await github.rest.issues.listLabelsOnIssue({
              ...repo,
              issue_number: prNumber
            });
            const hasLabel = labels.some(l => l.name === labelName);

            if (hasConflict && !hasLabel) {
              console.log(`PR #${prNumber} has merge conflicts. Adding label '${labelName}'.`);
              await github.rest.issues.addLabels({
                ...repo,
                issue_number: prNumber,
                labels: [labelName]
              });
            } else if (!hasConflict && hasLabel) {
              console.log(`PR #${prNumber} no longer has merge conflicts. Removing label '${labelName}'.`);
              await github.rest.issues.removeLabel({
                ...repo,
                issue_number: prNumber,
                name: labelName
              });
            } else {
              console.log(`PR #${prNumber}: conflict=${hasConflict}, label=${hasLabel}. No change needed.`);
            }