name: libghostty-vt
description: Build or restore libghostty-vt and point pkg-config at it.

# libghostty-vt is the C library go-libghostty links against, and the
# conformance module needs it to build at all. Three jobs across two workflows
# need the same thing, so it lives here once rather than being copied into each
# of them and drifting.

runs:
  using: composite
  steps:
    # The library has to be built from the go-libghostty commit the module
    # already depends on. That commit's CMakeLists pins the ghostty revision it
    # fetches, and a different revision exports a different set of symbols than
    # these bindings call, so a mismatch fails at link time with undefined
    # symbols. Reading the commit out of go.mod is what keeps the two in step:
    # bumping the dependency moves the build with it, and there is no second
    # place to remember to update.
    - name: Resolve the go-libghostty pin
      id: pin
      shell: bash
      run: |
        mod=internal/conformance/go.mod

        # Exactly one line may mention the module. A replace directive, in
        # either spelling, adds another, and picking one silently builds a
        # revision the module does not use.
        matches=$(grep -c 'go\.mitchellh\.com/libghostty' "$mod" || true)
        if [ "$matches" -ne 1 ]; then
          echo "::error::expected one go.mitchellh.com/libghostty line in $mod, found $matches"
          exit 1
        fi
        version=$(awk '$1 == "go.mitchellh.com/libghostty" { print $2 }' "$mod")

        # A pseudo-version ends in the twelve-digit commit it was built from,
        # and that commit is the ref. Anything else is a tag, already a ref.
        rev=${version%+incompatible}
        if [[ $rev =~ -([0-9a-f]{12})$ ]]; then
          rev=${BASH_REMATCH[1]}
        fi
        echo "rev=$rev" >> "$GITHUB_OUTPUT"

    - uses: mlugg/setup-zig@v2
      with:
        version: "0.16.0"

    # Building from source takes a couple of minutes, so cache the result. The
    # key carries the pin, so the build happens again exactly when the
    # dependency moves and not otherwise.
    #
    # The cpu suffix is in the key so entries cached before the build below
    # pinned a baseline CPU are not reused. Those were tuned for whichever
    # runner produced them, and crash on a runner that lacks the instructions.
    - name: Cache libghostty-vt
      id: cache
      uses: actions/cache@v6
      with:
        path: ${{ github.workspace }}/.cache/libghostty-vt
        key: libghostty-vt-${{ steps.pin.outputs.rev }}-${{ runner.os }}-${{ runner.arch }}-cpu-baseline

    - name: Build libghostty-vt
      if: steps.cache.outputs.cache-hit != 'true'
      shell: bash
      run: |
        git clone https://github.com/mitchellh/go-libghostty /tmp/go-libghostty
        git -C /tmp/go-libghostty checkout --detach "${{ steps.pin.outputs.rev }}"
        # Zig builds for the host CPU unless told otherwise, so the library
        # picks up whatever instructions the runner that built it happened to
        # support. Every runner then shares that binary through the cache, and
        # one without those instructions dies on the first call into it. A
        # baseline CPU is what makes the artifact portable enough to cache.
        cmake -B /tmp/go-libghostty/build -S /tmp/go-libghostty \
          -DCMAKE_BUILD_TYPE=Release \
          -DGHOSTTY_ZIG_BUILD_FLAGS=-Dcpu=baseline
        cmake --build /tmp/go-libghostty/build
        mkdir -p .cache
        cp -r /tmp/go-libghostty/build/_deps/ghostty-src/zig-out .cache/libghostty-vt

    # The .pc file records the absolute path it was built at. Rewrite it to
    # point at this workspace so a restored cache resolves correctly, then put
    # it on PKG_CONFIG_PATH for every step that follows.
    - name: Configure pkg-config
      shell: bash
      run: |
        prefix="${{ github.workspace }}/.cache/libghostty-vt"
        sed -i "s|^prefix=.*|prefix=$prefix|" "$prefix/share/pkgconfig/libghostty-vt-static.pc"
        echo "PKG_CONFIG_PATH=$prefix/share/pkgconfig" >> "$GITHUB_ENV"