name: Merge-Checker

on:
  pull_request:
    branches: ["**"]
    paths-ignore:
        - 'unit-tests/timing-results/**'

jobs:
  Benchmarking:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout source code
        uses: actions/checkout@v3
        with:
          persist-credentials: true
          fetch-depth: 0

      - name: Install dependencies (CMake + Ninja + build tools)
        run: |
          sudo apt-get update
          sudo apt-get install -y cmake ninja-build build-essential time git

      - name: Configure project with CMake
        run: cmake -G Ninja -S . -B build/

      - name: Build with Ninja
        run: ninja -C build/

      - name: Run matrix-timing-tests
        run: |
          mkdir -p unit-tests/timing-results
          if [ -x build/unit-tests/matrix-timing-tests ]; then
            echo "Running matrix-timing-tests with timing"
            /usr/bin/time -v build/unit-tests/matrix-timing-tests -d yes &> unit-tests/timing-results/matrix-timing-tests.txt
            cat unit-tests/timing-results/matrix-timing-tests.txt
          else
            echo "matrix-timing-tests executable not found or not executable"
            exit 1
          fi

      - name: Compare timing results
        id: check_diff
        run: |
          git show origin/${{ github.event.pull_request.head.ref }}:unit-tests/timing-results/matrix-timing-tests.txt > old.txt || echo "" > old.txt
          cp unit-tests/timing-results/matrix-timing-tests.txt new.txt

          echo "Comparing timing results for changes ≥ 0.1s (ignoring 'Timing Tests' lines)..."

          changed=0

          awk -v changed_ref=/tmp/timings_changed.flag '
            BEGIN {
              change_threshold = 0.1
            }
            FILENAME == "old.txt" && /^[0-9]+\.[0-9]+ s: / {
              label = substr($0, index($0, ":") + 2)
              if (label != "Timing Tests") {
                label_times[label] = $1
              }
            }
            FILENAME == "new.txt" && /^[0-9]+\.[0-9]+ s: / {
              new_time = $1
              label = substr($0, index($0, ":") + 2)
              if (label == "Timing Tests") next

              old_time = label_times[label]
              delta = new_time - old_time
              if (delta < 0) delta = -delta

              if (old_time != "" && delta >= change_threshold) {
                printf "⚠️  %.3f s → %.3f s: %s (Δ=%.3f s)\n", old_time, new_time, label, delta
                system("touch " changed_ref)
              } else if (old_time == "") {
                printf "🆕 New timing entry: %.3f s: %s\n", new_time, label
                system("touch " changed_ref)
              }
            }
            END {
              if (!system("test -f " changed_ref)) {
                exit 0
              } else {
                print "✅ Timings haven’t changed significantly (Δ < 0.1s)."
                exit 0
              }
            }
          ' old.txt new.txt

          if [ -f /tmp/timings_changed.flag ]; then
            echo "timings_changed=true" >> $GITHUB_OUTPUT
          else
            echo "timings_changed=false" >> $GITHUB_OUTPUT
          fi

      - name: Leave PR comment with timing updates
        if: steps.check_diff.outputs.timings_changed == 'true'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          echo "Preparing PR comment with new timing results..."

          COMMENT_BODY=$(echo -e "### ⏱ Timing Results Changed\n\n" \
            "The benchmark detected significant timing changes (≥ 0.1s).\n\n" \
            "**Please review and commit the updated timing results** to:\n\`\`\`\nunit-tests/timing-results/matrix-timing-tests.txt\n\`\`\`\n\n" \
            "Latest result:\n\`\`\`\n$(cat unit-tests/timing-results/matrix-timing-tests.txt)\n\`\`\`\n\n" \
            "<!-- timing-bot-comment -->")

          PR_NUMBER="${{ github.event.pull_request.number }}"

          # Look for an existing bot comment
          COMMENT_ID=$(gh api repos/${{ github.repository }}/issues/${PR_NUMBER}/comments \
            --jq '.[] | select(.body | contains("<!-- timing-bot-comment -->")) | .id')

          if [ -z "$COMMENT_ID" ]; then
            echo "Creating new PR comment"
            gh api repos/${{ github.repository }}/issues/${PR_NUMBER}/comments \
              -f body="$COMMENT_BODY"
          else
            echo "Updating existing PR comment"
            gh api repos/${{ github.repository }}/issues/comments/${COMMENT_ID} \
              -X PATCH -F body="$COMMENT_BODY"
          fi