require 'pathname'

class DeploySpec
  Error = Class.new(StandardError)

  class << self
    def load(json)
      new(JSON.parse(json)) if json.present?
    end

    def dump(spec)
      JSON.dump(spec.cacheable.config) if spec
    end

    def bundle_path
      Rails.root.join('data/bundler')
    end
  end

  def initialize(config)
    @config = config
  end

  delegate :bundle_path, to: :class

  def cacheable
    self
  end

  def config(*keys)
    keys.flatten.reduce(@config) { |h, k| h[k] if h.respond_to?(:[]) }
  end

  def supports_fetch_deployed_revision?
    fetch_deployed_revision_steps.present?
  end

  def supports_rollback?
    rollback_steps.present?
  end

  def machine_env
    config('machine', 'environment') || {}
  end

  def directory
    config('machine', 'directory')
  end

  def dependencies_steps
    config('dependencies', 'override') || discover_dependencies_steps || []
  end
  alias_method :dependencies_steps!, :dependencies_steps

  def deploy_steps
    config('deploy', 'override') || discover_deploy_steps
  end

  def deploy_steps!
    deploy_steps || cant_detect!(:deploy)
  end

  def rollback_steps
    config('rollback', 'override') || discover_rollback_steps
  end

  def rollback_steps!
    rollback_steps || cant_detect!(:rollback)
  end

  def fetch_deployed_revision_steps
    config('fetch') || discover_fetch_deployed_revision_steps
  end

  def fetch_deployed_revision_steps!
    fetch_deployed_revision_steps || cant_detect!(:fetch)
  end

  def task_definitions
    (config('tasks') || {}).map { |name, definition| TaskDefinition.new(name, coerce_task_definition(definition)) }
  end

  def find_task_definition(id)
    TaskDefinition.new(id, coerce_task_definition(config('tasks', id)) || task_not_found!(id))
  end

  def review_checklist
    config('review', 'checklist') || discover_review_checklist || []
  end

  def review_monitoring
    config('review', 'monitoring') || []
  end

  private

  def coerce_task_definition(config)
    config
  end

  def discover_review_checklist
  end

  def discover_dependencies_steps
  end

  def discover_deploy_steps
  end

  def discover_rollback_steps
  end

  def discover_fetch_deployed_revision_steps
  end

  def task_not_found!(id)
    raise TaskDefinition::NotFound.new("No definition for task #{id.inspect}")
  end

  def cant_detect!(type)
    raise DeploySpec::Error.new(I18n.t("deploy_spec.hint.#{type}"))
  end
end