# Extend rake with file-like Docker tasks
#
require 'rake'
require 'docker'

module Rake
  module DSL
    def dockerimage(*args, &block)
      Lux::DockerImageTask.define_task(*args, &block)
    end
    def container(*args, &block)
      Lux::DockerContainerTask.define_task(*args, &block)
    end
  end
end

module Lux
  class DockerImageTask < Rake::FileTask
    # This task checks to see if the image is present in the local Docker Server
    # If present it returns the creation date as the timestamp, if not then it
    # returns Rake::Early. This allows dependencies to execute correctly
    # The action block should build the container.
    #
    def initialize(task_name, app)
      super(task_name, app)
      @imagename = @name
      @imagename += ':latest' unless @imagename.index(':')
      @image = Docker::Image.all.select{|i| i.info['RepoTags'].include? @imagename}.first
    end

    def needed?
      ! @image || out_of_date?(timestamp) || @application.options.build_all
    end

    def timestamp
      if @image = Docker::Image.all.select{|i| i.info['RepoTags'].include? @imagename}.first
        Time.at(@image.info['Created'])
      else
        Rake::EARLY
      end
    end
  end

  class DockerContainerTask < Rake::FileTask
    # This task checks whether a named container is running from a given image.
    # The name of the task is <container-name>@<image-name>
    # The container name must match /?[a-zA-Z0-9_-]+
    #
    # If a container is already running for this image, the creation time
    # is checked against the current image modification date.
    # If the container is not running or out-of-date it is restarted.
    #
    def initialize(task_name, app)
      super(task_name, app)
      @containername, sep, @imagename = task_name.partition('@')
      raise "Task #{task_name} must be name@image" if @containername.empty? or @imagename.empty?
      @container = Docker::Container.get(@containername) rescue nil
      @imagename += ':latest' unless @imagename.index(':')
      @image = Docker::Image.all.select{|i| i.info['RepoTags'].include? @imagename}.first
    end

    def needed?
      not @container or
      @container.info["Image"] != @image.id or
      not @container.info["State"]["Running"] or
      out_of_date?(timestamp) or
      @application.options.build_all
    end

    # Before the task actions are done, remove the container
    def execute(args)
      destroy_container("it is out-of-date") { out_of_date?(timestamp) }
      destroy_container("it uses the wrong image") { @container.info["Image"] != @image.id }
      destroy_container("it is not running") { not @container.info["State"]["Running"] }
      destroy_container("it exists!") { @container }
      super args
    end

    # Destroy the container if the block yields true
    def destroy_container msg, &block
      return if !@container or (block_given? and not yield)
      application.trace "** Prepare #{name} (destroying container: #{msg})" if application.options.trace
      return if application.options.dryrun
      # It may be hard to kill this container, try but if something goes wrong
      # then print a message and proceed with the action block. The start command
      # in there will fail in a more user-friendly way.
      begin
        @container.stop # @container.kill(signal: 'SIGTERM') better?
        @container.wait(10)
        @container.delete
      rescue Exception => e
        puts "Exception destroying container: #{e.to_s}"
      end
      @container = nil
    end

    def timestamp
      if @container = Docker::Container.get(@containername) rescue nil
        Time.iso8601(@container.info['Created'])
      else
        Rake::EARLY
      end
    end
  end

end