name: Output API Diff

on:
  issue_comment:
    types: [created]

permissions: {}

concurrency:
  group: api-diff-${{ github.event.issue.number }}
  cancel-in-progress: true

jobs:
  api-diff:
    name: Output API Diff
    if: >-
      github.event.issue.pull_request
      && contains(github.event.comment.body, '/api-diff')
      && contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.comment.author_association)
    runs-on: ubuntu-latest

    permissions:
      contents: read
      pull-requests: write

    steps:
      - name: Check maintainer permission
        uses: actions/github-script@v7
        with:
          script: |
            const { data: permLevel } = await github.rest.repos.getCollaboratorPermissionLevel({
              owner: context.repo.owner,
              repo: context.repo.repo,
              username: context.payload.comment.user.login,
            });
            const allowed = ['admin', 'maintain', 'write'];
            if (!allowed.includes(permLevel.permission)) {
              core.setFailed(`User @${context.payload.comment.user.login} does not have write access.`);
            }

      - name: Add reaction to acknowledge command
        uses: actions/github-script@v7
        with:
          script: |
            await github.rest.reactions.createForIssueComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              comment_id: context.payload.comment.id,
              content: 'eyes',
            });

      - name: Get PR branch info
        id: pr
        uses: actions/github-script@v7
        with:
          script: |
            const { data: pr } = await github.rest.pulls.get({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.issue.number,
            });
            if (pr.head.repo.full_name !== `${context.repo.owner}/${context.repo.repo}`) {
              core.setFailed('Cannot run /api-diff on fork PRs — would execute untrusted code.');
              return;
            }
            core.setOutput('ref', pr.head.ref);
            core.setOutput('sha', pr.head.sha);

      - name: Checkout PR branch
        uses: actions/checkout@v4
        with:
          ref: ${{ steps.pr.outputs.sha }}
          submodules: recursive

      - name: Setup .NET
        uses: actions/setup-dotnet@v4
        with:
          global-json-file: global.json

      - name: Run OutputApiDiff
        run: dotnet run --project ./nukebuild/_build.csproj -- OutputApiDiff

      - name: Post API diff as PR comment
        if: always() && steps.pr.outcome == 'success'
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const path = require('path');

            const diffDir = path.join(process.env.GITHUB_WORKSPACE, 'artifacts', 'api-diff', 'markdown');
            const mergedPath = path.join(diffDir, '_diff.md');

            let body;
            if (fs.existsSync(mergedPath)) {
              let diff = fs.readFileSync(mergedPath, 'utf8').trim();
              if (!diff || diff.toLowerCase().includes('no changes')) {
                body = '### API Diff\n\n✅ No public API changes detected in this PR.';
              } else {
                const MAX_COMMENT_LENGTH = 60000; // GitHub comment limit is 65536
                const header = '### API Diff\n\n';
                const footer = '\n\n---\n_Generated by `/api-diff` command._';
                const budget = MAX_COMMENT_LENGTH - header.length - footer.length;

                if (diff.length > budget) {
                  diff = diff.substring(0, budget) + '\n\n> ⚠️ Output truncated. See the [full workflow run](' +
                    `${process.env.GITHUB_SERVER_URL}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}` +
                    ') for complete diff.';
                }

                body = header + diff + footer;
              }
            } else {
              body = '### API Diff\n\n⚠️ No diff output was produced. Check the [workflow run](' +
                `${process.env.GITHUB_SERVER_URL}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}` +
                ') for details.';
            }

            // Collapse into <details> if large
            if (body.length > 2000) {
              const inner = body;
              body = '<details>\n<summary>📋 API Diff (click to expand)</summary>\n\n' + inner + '\n\n</details>';
            }

            // Update existing bot comment or create a new one
            const marker = '<!-- api-diff-bot -->';
            body = marker + '\n' + body;

            const { data: comments } = await github.rest.issues.listComments({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              per_page: 100,
            });
            const existing = comments.find(c => c.body?.includes(marker));

            if (existing) {
              await github.rest.issues.updateComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                comment_id: existing.id,
                body,
              });
            } else {
              await github.rest.issues.createComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.issue.number,
                body,
              });
            }

      - name: Add success reaction
        if: success()
        uses: actions/github-script@v7
        with:
          script: |
            await github.rest.reactions.createForIssueComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              comment_id: context.payload.comment.id,
              content: 'rocket',
            });

      - name: Report failure
        if: failure()
        uses: actions/github-script@v7
        with:
          script: |
            await github.rest.reactions.createForIssueComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              comment_id: context.payload.comment.id,
              content: '-1',
            });
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: `❌ \`/api-diff\` failed. [See logs](${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}).`,
            });