name: 'Docker Build Platform'
description: 'Builds and pushes a single-platform Docker image by digest.'
runs:
  using: 'composite'
  steps:
    - name: Prepare platform pair
      id: prepare
      shell: bash
      run: |
        platform="${{ inputs.platform }}"
        echo "platform_pair=${platform//\//-}" >> $GITHUB_OUTPUT

    - name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v3

    - name: Log in to GHCR
      uses: docker/login-action@v3
      with:
        registry: ghcr.io
        username: ${{ inputs.ghcr_username }}
        password: ${{ inputs.ghcr_token }}

    - name: Build and push by digest
      id: build
      uses: docker/build-push-action@v6
      env:
        BUILDKIT_PROGRESS: plain
      with:
        context: ${{ inputs.context }}
        file: ${{ inputs.file }}
        platforms: ${{ inputs.platform }}
        outputs: type=image,"name=${{ inputs.image_name }}",push-by-digest=true,name-canonical=true,push=true
        cache-from: type=gha,scope=build-${{ steps.prepare.outputs.platform_pair }}
        cache-to: type=gha,mode=max,scope=build-${{ steps.prepare.outputs.platform_pair }}

    - name: Export digest
      shell: bash
      run: |
        mkdir -p "${{ runner.temp }}/digests"
        digest="${{ steps.build.outputs.digest }}"
        touch "${{ runner.temp }}/digests/${digest#sha256:}"

    - name: Upload digest
      uses: actions/upload-artifact@v7
      with:
        name: digests-${{ steps.prepare.outputs.platform_pair }}
        path: ${{ runner.temp }}/digests/*
        if-no-files-found: error
        retention-days: 1

inputs:
  ghcr_username:
    required: true
    description: 'GHCR username'
  ghcr_token:
    required: true
    description: 'GHCR token'
  context:
    required: true
    description: 'Build context'
  file:
    required: true
    description: 'Dockerfile path'
  platform:
    required: true
    description: 'Target platform (e.g. linux/amd64)'
  image_name:
    required: true
    description: 'Image name without tag (e.g. ghcr.io/gameyfin/gameyfin)'