slipway

defmodule Mix.Tasks.Slipway.Gen.Docker do
  @moduledoc "Creates a template docker file"
  @shortdoc "Generates a template docker file"

  use Mix.Task

  @impl Mix.Task
  def run(_) do
    name = Mix.Project.get()
    app = Mix.Project.config[:app]
    elixir_version = Mix.Project.config[:elixir] |> String.replace("~> ", "")

    if name == nil do
      Mix.shell().error("No mix.exs found, must be run in an Elixir project")
    else
      Mix.Generator.create_file("Dockerfile", contents(app, elixir_version))
      Mix.shell().info(
      """
      You need to run the following to build the docker image:
      docker build -t elixir-#{app} .

      Then eithr

      docker run --rm elixir-#{app}

      or

      docker run -it --rm elixir-#{app}
      """)
    end
  end

  defp contents(app_name, elixir_version) do
    """
    #===========
    #Build Stage
    #===========
    FROM bitwalker/alpine-elixir:#{elixir_version} as build

    ARG BUILD_ENV=prod
    ARG BUILD_REL=#{app_name}

    #Copy the source folder into the Docker image
    COPY . .

    ENV MIX_ENV=${BUILD_ENV}

    #Install dependencies and build Release
    RUN mix local.hex --force && \
        mix local.rebar --force && \
        mix deps.get && \
        mix compile && \
        mix release --path /export

    # #================
    # #Deployment Stage
    # #================
    FROM pentacent/alpine-erlang-base:latest

    ARG BUILD_REL=#{app_name}

    RUN apk add --no-cache openssl ncurses-libs libstdc++

    #Copy release file from the previous stage
    COPY --from=build /export/ .

    #Set environment variables and expose port
    EXPOSE 4000
    ENV REPLACE_OS_VARS=true \
        PORT=4000

    ENV RELEASE_DISTRIBUTION="name"

    # This value should be overriden at runtime
    ENV RELEASE_IP="127.0.0.1"

    # This will be the basename of our node
    ENV RELEASE_NAME="${BUILD_REL}"

    # This will be the full nodename
    ENV RELEASE_NODE="${RELEASE_NAME}@${RELEASE_IP}"

    # If empty, the default cookie generated by `mix release` will be used
    # OVERRIDE IT!!
    ENV RELEASE_COOKIE=""

    # #Change user
    USER default

    #Set default entrypoint and command
    ENTRYPOINT ["bin/#{app_name}", "start"]
    CMD ["foreground"]
    """
  end
end