entrypoint.sh

#!/bin/bash

set -e

if ! command -v curl &>/dev/null; then
  echo "Installing curl..."
  sudo apt update -y && sudo apt install -y curl
fi

if ! command -v nixpacks &>/dev/null; then
  echo "Installing Nixpacks..."
  curl -sSL https://nixpacks.com/install.sh | bash
fi

BUILD_CMD="nixpacks build $INPUT_CONTEXT"

# Incorporate provided input parameters from actions.yml into the Nixpacks build command
if [ -n "${INPUT_TAGS}" ]; then
  read -ra TAGS <<<"$(echo "$INPUT_TAGS" | tr ',\n' ' ')"
fi

if [ -n "${INPUT_LABELS}" ]; then
  read -ra LABELS <<<"$(echo "$INPUT_LABELS" | tr ',\n' ' ')"
fi

# TODO add the description label as well? Does this add any value?

for label in "${LABELS[@]}"; do
  BUILD_CMD="$BUILD_CMD --label $label"
done

if [ -n "${INPUT_PKGS}" ]; then
  read -ra PKGS_ARR <<<"$(echo "$INPUT_PKGS" | tr ',\n' ' ')"
  BUILD_CMD="$BUILD_CMD --pkgs '${PKGS_ARR[*]}'"
fi

if [ -n "${INPUT_APT}" ]; then
  read -ra APT_ARR <<<"$(echo "$INPUT_APT" | tr ',\n' ' ')"
  BUILD_CMD="$BUILD_CMD --apt '${APT_ARR[*]}'"
fi

# Include environment variables in the build command
if [ -n "${INPUT_ENV}" ]; then
  IFS=',' read -ra ENVS <<<"$INPUT_ENV"
  for env_var in "${ENVS[@]}"; do
    BUILD_CMD="$BUILD_CMD --env $env_var"
  done
fi

if [ -n "${INPUT_PLATFORMS}" ]; then
  read -ra PLATFORMS <<<"$(echo "$INPUT_PLATFORMS" | tr ',\n' ' ')"
fi

if [ "${#PLATFORMS[@]}" -gt 1 ] && [ "$INPUT_PUSH" != "true" ]; then
  echo "Multi-platform builds *must* be pushed to a registry. Please set 'push: true' in your action configuration or do a single architecture build."
  exit 1
fi

function build_and_push() {
  local build_cmd=$BUILD_CMD

  if [ -n "$PLATFORMS" ]; then
    build_cmd="$build_cmd --platform $PLATFORMS"
  fi

  for tag in "${TAGS[@]}"; do
    build_cmd="$build_cmd --tag $tag"
  done

  echo "Executing Nixpacks build command:"
  echo "$build_cmd"

  eval "$build_cmd"

  # Conditionally push the images based on the 'push' input
  if [[ "$INPUT_PUSH" == "true" ]]; then
    for tag in "${TAGS[@]}"; do
      echo "Pushing Docker image: $tag"
      docker push "$tag"
    done
  else
    echo "Skipping Docker image push."
  fi
}

function build_and_push_multiple_architectures() {
  echo "Building for multiple architectures: ${PLATFORMS[*]}"

  local manifest_list=()

  for platform in "${PLATFORMS[@]}"; do
    local build_cmd=$BUILD_CMD
    # Replace '/' with '-'
    local normalized_platform=${platform//\//-}
    local architecture_image_name=${GHCR_IMAGE_NAME}:$normalized_platform

    build_cmd="$build_cmd --platform $platform"
    build_cmd="$build_cmd --tag $architecture_image_name"

    echo "Executing Nixpacks build command for $platform:"
    echo "$build_cmd"

    eval "$build_cmd"

    manifest_list+=("$architecture_image_name")
  done

  echo "All architectures built. Pushing images..."
  for architecture_image_name in "${manifest_list[@]}"; do
    # if we don't push the images the multi-architecture manifest will not be created
    # best practice here seems to be to push `base:platform` images to the registry
    # when they are overwritten by the next architecture build, the previous manifest
    # will reference the sha of the image instead of the tag
    docker push "$architecture_image_name"
  done

  echo "Constructing manifest and pushing to registry..."

  # now, with all architectures built locally, we can construct a manifest and push to the registry
  for tag in "${TAGS[@]}"; do
    local manifest_creation="docker manifest create $tag ${manifest_list[@]}"
    echo "Creating manifest: $manifest_creation"
    eval "$manifest_creation"

    docker manifest push "$tag"
  done
}

if [ "${#PLATFORMS[@]}" -gt 1 ]; then
  build_and_push_multiple_architectures
else
  build_and_push
fi

echo "Nixpacks Build & Push completed successfully."