name: Free runner disk space
description: |
  Reclaims disk space on GitHub-hosted Ubuntu runners by removing
  pre-installed toolchains we do not use (Android SDK, GHC/Haskell,
  CodeQL bundle), Docker images, and swap. Also relocates the
  NuGet package cache to /mnt (which has ~75 GB free vs ~14 GB
  on /). No-op on non-Linux runners.

runs:
  using: composite
  steps:
    - name: Free disk space (Linux only)
      if: runner.os == 'Linux'
      shell: bash
      run: |
        set -euo pipefail
        echo "::group::Disk usage before cleanup"
        df -h /
        echo "::endgroup::"

        # Remove pre-installed toolchains we never use on this repo's
        # dotnet/python jobs. These reclaim ~25-30 GB on ubuntu-latest.
        sudo rm -rf \
          /usr/local/lib/android \
          /usr/share/dotnet/sdk/NuGetFallbackFolder \
          /opt/ghc \
          /usr/local/.ghcup \
          /opt/hostedtoolcache/CodeQL \
          /opt/hostedtoolcache/PyPy \
          /opt/hostedtoolcache/Ruby \
          /opt/hostedtoolcache/go \
          /usr/local/share/boost \
          /usr/local/share/powershell \
          /usr/local/share/chromium \
          /usr/local/share/vcpkg \
          /usr/local/lib/heroku \
          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/PyPy" \
          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/Ruby" \
          "${AGENT_TOOLSDIRECTORY:-/opt/hostedtoolcache}/go" || true

        # Drop docker images shipped on the runner; jobs that need
        # docker pull what they need fresh.
        if command -v docker >/dev/null 2>&1; then
          sudo docker image prune --all --force >/dev/null 2>&1 || true
        fi

        # Disable swap to free its backing file.
        sudo swapoff -a || true
        sudo rm -f /mnt/swapfile /swapfile || true

        echo "::group::Disk usage after cleanup"
        df -h /
        echo "::endgroup::"

    - name: Relocate NuGet package cache to /mnt (Linux only)
      if: runner.os == 'Linux'
      shell: bash
      run: |
        set -euo pipefail
        sudo mkdir -p /mnt/nuget
        sudo chown -R "$USER":"$USER" /mnt/nuget
        echo "NUGET_PACKAGES=/mnt/nuget" >> "$GITHUB_ENV"
        echo "Relocated NuGet package cache to /mnt/nuget"
        df -h /mnt || true