# Backfill PR labels on all open PRs.
#
# Manual-only workflow that applies the same labels as pr_labeler.yml
# (size, file, title, contributor classification) to existing open PRs.
# Reuses shared logic from .github/scripts/pr-labeler.js.

name: "🏷️ PR Labeler Backfill"

on:
  workflow_dispatch:
    inputs:
      max_items:
        description: "Maximum number of open PRs to process"
        default: "100"
        type: string

permissions:
  contents: read

jobs:
  backfill:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write
      issues: write

    steps:
      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6

      - name: Generate GitHub App token
        id: app-token
        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3
        with:
          app-id: ${{ secrets.ORG_MEMBERSHIP_APP_ID }}
          private-key: ${{ secrets.ORG_MEMBERSHIP_APP_PRIVATE_KEY }}

      - name: Backfill labels on open PRs
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          github-token: ${{ steps.app-token.outputs.token }}
          script: |
            const { owner, repo } = context.repo;
            const rawMax = '${{ inputs.max_items }}';
            const maxItems = parseInt(rawMax, 10);
            if (isNaN(maxItems) || maxItems <= 0) {
              core.setFailed(`Invalid max_items: "${rawMax}" — must be a positive integer`);
              return;
            }

            const { h } = require('./.github/scripts/pr-labeler.js').loadAndInit(github, owner, repo, core);

            for (const name of [...h.sizeLabels, ...h.tierLabels]) {
              await h.ensureLabel(name);
            }

            const contributorCache = new Map();
            const fileRules = h.buildFileRules();

            const prs = await github.paginate(github.rest.pulls.list, {
              owner, repo, state: 'open', per_page: 100,
            });

            let processed = 0;
            let failures = 0;
            for (const pr of prs) {
              if (processed >= maxItems) break;
              try {
                const author = pr.user.login;
                const info = await h.getContributorInfo(contributorCache, author, pr.user.type);
                const labels = new Set();

                labels.add(info.isExternal ? 'external' : 'internal');
                if (info.isExternal && info.mergedCount != null && info.mergedCount >= h.trustedThreshold) {
                  labels.add('trusted-contributor');
                } else if (info.isExternal && info.mergedCount === 0) {
                  labels.add('new-contributor');
                }

                // Size + file labels
                const files = await github.paginate(github.rest.pulls.listFiles, {
                  owner, repo, pull_number: pr.number, per_page: 100,
                });
                const { sizeLabel } = h.computeSize(files);
                labels.add(sizeLabel);

                for (const label of h.matchFileLabels(files, fileRules)) {
                  labels.add(label);
                }

                // Title labels
                const { labels: titleLabels } = h.matchTitleLabels(pr.title ?? '');
                for (const tl of titleLabels) labels.add(tl);

                // Ensure all labels exist before batch add
                for (const name of labels) {
                  await h.ensureLabel(name);
                }

                // Remove stale managed labels
                const currentLabels = (await github.paginate(
                  github.rest.issues.listLabelsOnIssue,
                  { owner, repo, issue_number: pr.number, per_page: 100 },
                )).map(l => l.name ?? '');

                const managed = [...h.sizeLabels, ...h.tierLabels, ...h.allTypeLabels];
                for (const name of currentLabels) {
                  if (managed.includes(name) && !labels.has(name)) {
                    try {
                      await github.rest.issues.removeLabel({
                        owner, repo, issue_number: pr.number, name,
                      });
                    } catch (e) {
                      if (e.status !== 404) throw e;
                    }
                  }
                }

                await github.rest.issues.addLabels({
                  owner, repo, issue_number: pr.number, labels: [...labels],
                });
                console.log(`PR #${pr.number} (${author}): ${[...labels].join(', ')}`);
                processed++;
              } catch (e) {
                failures++;
                core.warning(`Failed to process PR #${pr.number}: ${e.message}`);
              }
            }

            console.log(`\nBackfill complete. Processed ${processed} PRs, ${failures} failures. ${contributorCache.size} unique authors.`);
