name: Build a Python version
description: >
  Install python-build's system dependencies for the current runner's OS, build
  and check the requested version.
inputs:
  python-version:
    description: A version as accepted by `pyenv install`.
    required: true
runs:
  using: composite
  steps:
    - shell: bash
      run: |
        #envvars
        export PYENV_ROOT="$GITHUB_WORKSPACE"
        echo "PYENV_ROOT=$PYENV_ROOT" >> $GITHUB_ENV
        echo "$PYENV_ROOT/shims:$PYENV_ROOT/bin" >> $GITHUB_PATH
    # The two OSes differ only in this step.
    - if: runner.os == 'macOS'
      shell: bash
      run: |
        #prerequisites
        brew install openssl readline sqlite3 xz tcl-tk@8 libb2 zstd
    - if: runner.os == 'Linux'
      shell: bash
      run: |
        #prerequisites
        pyenv install-prerequisites
    - shell: bash
      run: |
        #build
        pyenv --debug install ${{ inputs.python-version }} && rc=$? || rc=$?
        if [[ $rc -ne 0 ]]; then echo config.log:; cat "${TMPDIR:-/tmp}"/python-build*/*/config.log; false; fi
        pyenv global ${{ inputs.python-version }}
        pyenv rehash
    - shell: bash
      run: |
        #print version
        python --version
        python -m pip --version
    - shell: python  # Prove that actual Python == expected Python
      env:
        EXPECTED_PYTHON: ${{ inputs.python-version }}
      run: import os, sys ; assert sys.version.startswith(os.getenv("EXPECTED_PYTHON"))