action.yml

name: "IfChange (slnc)"
description: Enforce LINT.IfChange/ThenChange directives in pull requests
branding:
  icon: check-circle
  color: green

# LINT.IfChange("inputs")
inputs:
  version:
    description: "Release tag to install (e.g. v1.0.0). Empty means latest."
    required: false
    default: ""
  args:
    description: "Extra arguments passed to ifchange"
    required: false
    default: ""
  diff:
    description: "Path to a pre-built diff file. If empty, the action generates one."
    required: false
    default: ""
  token:
    description: "GitHub token for downloading release assets"
    required: false
    default: ${{ github.token }}
# LINT.ThenChange([
#   "README.md#action",
#   "examples/README.md#action",
#   "examples/workflows/ifchange.yml",
#   ".github/workflows/ci.yml",
# ])

runs:
  using: composite
  steps:
    - name: Check for existing binary
      id: check
      shell: bash
      run: |
        if command -v ifchange &>/dev/null; then
          echo "found=true" >> "$GITHUB_OUTPUT"
          echo "ifchange already on PATH: $(which ifchange)"
        else
          echo "found=false" >> "$GITHUB_OUTPUT"
        fi

    - name: Detect platform
      if: steps.check.outputs.found == 'false'
      id: platform
      shell: bash
      env:
        RUNNER_OS_ARCH: ${{ runner.os }}-${{ runner.arch }}
      run: |
        case "$RUNNER_OS_ARCH" in
          Linux-X64)   target="x86_64-unknown-linux-gnu" ; ext="tar.gz" ;;
          Linux-ARM64)  target="aarch64-unknown-linux-gnu" ; ext="tar.gz" ;;
          macOS-ARM64)  target="aarch64-apple-darwin" ; ext="tar.gz" ;;
          macOS-X64)    target="x86_64-apple-darwin" ; ext="tar.gz" ;;
          Windows-X64)  target="x86_64-pc-windows-msvc" ; ext="zip" ;;
          *) echo "::error::Unsupported platform: $RUNNER_OS_ARCH" ; exit 1 ;;
        esac
        echo "target=$target" >> "$GITHUB_OUTPUT"
        echo "ext=$ext" >> "$GITHUB_OUTPUT"

    - name: Resolve version
      if: steps.check.outputs.found == 'false'
      id: version
      shell: bash
      env:
        GH_TOKEN: ${{ inputs.token }}
        INPUT_VERSION: ${{ inputs.version }}
        ACTION_REPO: ${{ github.action_repository || github.repository }}
      run: |
        if [[ -n "$INPUT_VERSION" ]]; then
          echo "tag=$INPUT_VERSION" >> "$GITHUB_OUTPUT"
        else
          tag="$(gh api "/repos/$ACTION_REPO/releases/latest" --jq .tag_name)"
          echo "tag=$tag" >> "$GITHUB_OUTPUT"
        fi

    - name: Download and install binary
      if: steps.check.outputs.found == 'false'
      shell: bash
      env:
        GH_TOKEN: ${{ inputs.token }}
        ACTION_REPO: ${{ github.action_repository || github.repository }}
        VERSION: ${{ steps.version.outputs.tag }}
        TARGET: ${{ steps.platform.outputs.target }}
        EXT: ${{ steps.platform.outputs.ext }}
        RUNNER_TEMP: ${{ runner.temp }}
      run: |
        set -euo pipefail
        version="$VERSION"
        target="$TARGET"
        ext="$EXT"
        archive="ifchange-${version}-${target}.${ext}"

        gh release download "$version" \
          --repo "$ACTION_REPO" \
          --pattern "$archive" \
          --dir "$RUNNER_TEMP"

        cd "$RUNNER_TEMP"
        if [[ "$ext" == "tar.gz" ]]; then
          tar -xzf "$archive"
        else
          unzip -o "$archive"
        fi
        chmod +x ifchange* 2>/dev/null || true
        mkdir -p "$HOME/.local/bin"
        mv ifchange* "$HOME/.local/bin/"
        echo "$HOME/.local/bin" >> "$GITHUB_PATH"

    - name: Build diff
      if: ${{ inputs.diff == '' }}
      id: diff
      shell: bash
      env:
        RUNNER_TEMP: ${{ runner.temp }}
        EVENT_NAME: ${{ github.event_name }}
        BASE_REF: ${{ github.base_ref }}
        EVENT_BEFORE: ${{ github.event.before }}
        EVENT_SHA: ${{ github.sha }}
      run: |
        set -euo pipefail
        diff_file="${RUNNER_TEMP}/changes.diff"

        if [[ "$EVENT_NAME" == "pull_request" ]]; then
          git fetch origin "$BASE_REF" --depth=1 2>/dev/null || true
          git diff --merge-base "origin/$BASE_REF" HEAD > "$diff_file"
        else
          git diff "$EVENT_BEFORE" "$EVENT_SHA" > "$diff_file"
        fi
        echo "path=$diff_file" >> "$GITHUB_OUTPUT"

    - name: Run ifchange
      shell: bash
      env:
        INPUT_ARGS: ${{ inputs.args }}
        DIFF_FILE: ${{ inputs.diff || steps.diff.outputs.path }}
      run: |
        set -euo pipefail
        diff_file="$DIFF_FILE"
        args=()
        if [[ -n "$INPUT_ARGS" ]]; then
          # Split on shell whitespace without evaluating metacharacters.
          read -r -a args <<< "$INPUT_ARGS"
        fi
        ifchange "${args[@]}" "$diff_file"