name: Performance Benchmarks

on:
    push:
        branches: [main]
    workflow_dispatch:

concurrency:
    group: bench-${{ github.event.pull_request.number || github.sha }}
    cancel-in-progress: true

permissions:
    contents: read
    pull-requests: write

env:
    CARGO_TERM_COLOR: always

jobs:
    benchmarks:
        name: Criterion Benchmarks
        runs-on: blacksmith-2vcpu-ubuntu-2404
        timeout-minutes: 30
        steps:
            - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
            - uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable
              with:
                  toolchain: 1.92.0
            - uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2

            - name: Run benchmarks
              run: cargo bench --locked 2>&1 | tee benchmark_output.txt

            - name: Upload benchmark results
              if: always()
              uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
              with:
                  name: benchmark-results
                  path: |
                      target/criterion/
                      benchmark_output.txt
                  retention-days: 30

            - name: Post benchmark summary on PR
              if: github.event_name == 'pull_request'
              uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
              with:
                  script: |
                      const fs = require('fs');
                      const output = fs.readFileSync('benchmark_output.txt', 'utf8');

                      // Extract Criterion result lines
                      const lines = output.split('\n').filter(l =>
                        l.includes('time:') || l.includes('change:') || l.includes('Performance')
                      );

                      if (lines.length === 0) {
                        core.info('No benchmark results to post.');
                        return;
                      }

                      const body = [
                        '## 📊 Benchmark Results',
                        '',
                        '```',
                        lines.join('\n'),
                        '```',
                        '',
                        '<details><summary>Full output</summary>',
                        '',
                        '```',
                        output.substring(0, 60000),
                        '```',
                        '</details>',
                      ].join('\n');

                      // Find and update or create comment
                      const { data: comments } = await github.rest.issues.listComments({
                        owner: context.repo.owner,
                        repo: context.repo.repo,
                        issue_number: context.payload.pull_request.number,
                      });

                      const marker = '## 📊 Benchmark Results';
                      const existing = comments.find(c => c.body && c.body.startsWith(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.payload.pull_request.number,
                          body,
                        });
                      }