ci.yml

name: CI

on:
  push:
    branches: [main, master]
    paths:
      - 'src/**/*.cpp'
      - 'include/**/*.h'
      - 'test/**/*.cpp'
      - 'CMakeLists.txt'
  pull_request:
    branches: [main, master, develop]
    paths:
      - 'src/**/*.cpp'
      - 'include/**/*.h'
      - 'test/**/*.cpp'
      - 'CMakeLists.txt'

# Cancel redundant workflows
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

jobs:
  detect-changes:
    name: Detect Changes
    runs-on: ubuntu-latest
    outputs:
      problems: ${{ steps.detect.outputs.problems }}
      problem_count: ${{ steps.detect.outputs.problem_count }}
      is_full_build: ${{ steps.strategy.outputs.is_full_build }}
      build_type: ${{ steps.strategy.outputs.build_type }}

    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Restore file timestamps
        uses: chetan/git-restore-mtime-action@v2

      - name: Detect changed problems
        id: detect
        run: |
          CHANGED_PROBLEMS=$(python3 script/ci/detect_changed_problems.py origin/main)
          PROBLEM_COUNT=$(echo "$CHANGED_PROBLEMS" | tr ';' '\n' | grep -c '^' || true)
          
          echo "problems=$CHANGED_PROBLEMS" >> $GITHUB_OUTPUT
          echo "problem_count=$PROBLEM_COUNT" >> $GITHUB_OUTPUT
          echo "Detected $PROBLEM_COUNT changed problem(s)"

      - name: Determine build strategy
        id: strategy
        run: |
          IS_PR="${{ github.event_name == 'pull_request' }}"
          PROBLEM_COUNT="${{ steps.detect.outputs.problem_count }}"
          
          if [ "$IS_PR" == "true" ]; then
            # PR: Use incremental build if <= 10 problems
            if [ "$PROBLEM_COUNT" -gt 10 ]; then
              echo "is_full_build=true" >> $GITHUB_OUTPUT
              echo "build_type=full" >> $GITHUB_OUTPUT
              echo "PR with many changes ($PROBLEM_COUNT), using full build"
            elif [ "$PROBLEM_COUNT" -eq 0 ]; then
              # Check if core files changed
              CORE_CHANGES=$(git diff --name-only origin/main HEAD | grep -E "(CMakeLists\.txt|include/leetcode/(core|solution)\.h|src/leetcode/utils/)" || true)
              if [ -n "$CORE_CHANGES" ]; then
                echo "is_full_build=true" >> $GITHUB_OUTPUT
                echo "build_type=full" >> $GITHUB_OUTPUT
                echo "Core files changed, using full build"
              else
                echo "is_full_build=false" >> $GITHUB_OUTPUT
                echo "build_type=skip" >> $GITHUB_OUTPUT
                echo "No relevant changes, skipping build"
              fi
            else
              echo "is_full_build=false" >> $GITHUB_OUTPUT
              echo "build_type=incremental" >> $GITHUB_OUTPUT
              echo "PR with $PROBLEM_COUNT problem(s), using incremental build"
            fi
          else
            # Push to main: Always full build
            echo "is_full_build=true" >> $GITHUB_OUTPUT
            echo "build_type=full" >> $GITHUB_OUTPUT
            echo "Push to main, using full build"
          fi

  build-incremental:
    name: Incremental Build
    runs-on: ubuntu-latest
    needs: detect-changes
    if: ${{ needs.detect-changes.outputs.build_type == 'incremental' }}

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Restore file timestamps
        uses: chetan/git-restore-mtime-action@v2

      - name: Install dependencies
        run: |
          sudo apt-get update
          sudo apt-get install -y cmake build-essential ccache ninja-build python3 gcc g++

      - name: Setup ccache
        uses: hendrikmuhs/ccache-action@v1.2
        with:
          # Use problem list in key for incremental builds
          # This allows separate caches for different PRs but share within same problems
          key: ${{ runner.os }}-gcc-incremental-${{ hashFiles('CMakeLists.txt') }}-${{ needs.detect-changes.outputs.problems }}
          restore-keys: |
            ${{ runner.os }}-gcc-incremental-${{ hashFiles('CMakeLists.txt') }}-
            ${{ runner.os }}-gcc-incremental-
            ${{ runner.os }}-gcc-full-
            ${{ runner.os }}-gcc-
          max-size: 500M

      - name: Setup ccache symlinks
        run: |
          sudo mkdir -p /usr/local/lib/ccache
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/gcc
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/g++
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/cc
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/c++
          echo "/usr/local/lib/ccache" >> $GITHUB_PATH
          ccache --set-config=sloppiness=pch_defines,time_macros,include_file_mtime,include_file_ctime
          ccache -s

      - name: Build changed problems
        run: |
          PROBLEMS="${{ needs.detect-changes.outputs.problems }}"
          echo "Building problems: $PROBLEMS"
          
          mkdir -p build && cd build
          cmake .. -G Ninja \
            -DCMAKE_BUILD_TYPE=Release \
            -DCMAKE_C_COMPILER=/usr/local/lib/ccache/gcc \
            -DCMAKE_CXX_COMPILER=/usr/local/lib/ccache/g++ \
            -DLEETCODE_MULTI_PROBLEMS="$PROBLEMS"
          cmake --build . -j
          ccache -s

      - name: Run tests
        working-directory: build
        run: ./bin/multi_problem_test

  build-full:
    name: Full Build
    runs-on: ubuntu-latest
    needs: detect-changes
    if: ${{ needs.detect-changes.outputs.build_type == 'full' }}

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Restore file timestamps
        uses: chetan/git-restore-mtime-action@v2

      - name: Install dependencies
        run: |
          sudo apt-get update
          sudo apt-get install -y cmake build-essential ccache ninja-build python3 gcc g++

      - name: Setup ccache
        uses: hendrikmuhs/ccache-action@v1.2
        with:
          # Full build cache - most comprehensive, used as fallback for all builds
          key: ${{ runner.os }}-gcc-full-${{ hashFiles('CMakeLists.txt', 'src/leetcode/utils/*.cpp', 'include/leetcode/*.h') }}
          restore-keys: |
            ${{ runner.os }}-gcc-full-
            ${{ runner.os }}-gcc-
          max-size: 500M

      - name: Setup ccache symlinks
        run: |
          # Create ccache symlinks to intercept all compiler calls (including FetchContent)
          sudo mkdir -p /usr/local/lib/ccache
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/gcc
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/g++
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/cc
          sudo ln -sf $(which ccache) /usr/local/lib/ccache/c++
          echo "/usr/local/lib/ccache" >> $GITHUB_PATH
          ccache --set-config=sloppiness=pch_defines,time_macros,include_file_mtime,include_file_ctime
          ccache -s

      - name: Build project
        run: |
          mkdir -p build && cd build
          cmake .. -G Ninja \
            -DCMAKE_BUILD_TYPE=Release \
            -DCMAKE_C_COMPILER=/usr/local/lib/ccache/gcc \
            -DCMAKE_CXX_COMPILER=/usr/local/lib/ccache/g++
          cmake --build . -j
          ccache -s

      - name: Run all tests
        working-directory: build
        run: ctest --output-on-failure