require 'lib/string_helper'
require 'db/mongo/models/stack_template/stack_template_factory'

module Devops
  module StackTemplatePresets
    class Base

      def id
        StringHelper.underscore_class(self.class)
      end

      def to_hash
        {id: id, template_preset_body: template_preset_body}
      end

      def build_template_from_preset(provider, stack_template_id, template_attrs)
        stack_template_attrs = {
          'id' => stack_template_id,
          'provider' => provider,
          'template_body' => serialize(actual_template_hash(template_attrs))
        }
        template_model = Model::StackTemplateFactory.create(provider, stack_template_attrs)
      end

      def template_preset_body
        @template_preset_body ||= begin
          file_name = File.join("lib/stack_template_presets/#{id}.#{template_file_extension}")
          File.read(file_name)
        end
      end


      private

      def template_preset_hash
        unserialize(template_preset_body)
      end

      def actual_template_hash(template_attrs)
        actual = template_preset_hash.dup
        template_attrs.each do |key, value|
          path = param_attrs_pathes_in_preset[key.to_s]
          next unless path
          insert_value_at(actual, value, path)
        end
        actual
      end

      # returns hash with keys lists. Better to show an example:
      # Imagine tha t template is the following:
      # {
      #   template: {
      #     users_count: %users_count%
      #   }
      # }
      #
      # So param_attrs_pathes_in_preset will be
      # {users_count: [:template, :users_count]}
      def param_attrs_pathes_in_preset
        {}
      end

      # given hash = {t: {a: nil}}, value = 1, path = [:t, :a] returns
      # {t: {a: 1}}
      def insert_value_at(hash, value, path)
        current = hash
        path.each_with_index do |key, i|
          if i == path.size - 1
            current[key] = value
          else
            current = current[key]
          end
        end
        hash
      end

      # some templates may be YAML files
      def template_file_extension
        serialization_strategy.to_s
      end

      # some templates may be YAML files
      def serialize(hash)
        case serialization_strategy
        when :json
          hash.to_json
        else
          raise
        end
      end

      def unserialize(text)
        case serialization_strategy
        when :json
          JSON.parse(text)
        else
          raise
        end
      end

      def serialization_strategy
        :json
      end

    end
  end
end