module Ecoportal
  module API
    module Common
      class BaseModel
        class UnlinkedModel < Exception
          def initialize (msg = "Something went wrong when linking the document.")
            super(msg)
          end
        end

        extend BaseClass

        class << self
          def passthrough(*methods, to: :doc)
            methods.each do |method|
              method = method.to_s
              define_method method do
                send(to)[method]
              end
              define_method "#{method}=" do |value|
                send(to)[method] = value
              end
            end
          end

          def embeds_one(method, key: method, nullable: false, klass:)
            method = method.to_s.freeze
            var    = "@#{method}".freeze
            key    = key.to_s.freeze
            define_method(method) do
              return instance_variable_get(var) if instance_variable_defined?(var)
              doc[key] ||= {} unless nullable
              return instance_variable_set(var, nil) unless doc[key]

              self.class.resolve_class(klass).new(
                doc[key], parent: self, key: key
              ).tap {|obj| instance_variable_set(var, obj)}
            end
          end

        end

        attr_reader :_parent, :_key

        def initialize(doc = {}, parent: self, key: nil)
          @_parent = parent
          @_key    = key
          if !_parent || !_key
            @doc          = doc
            @original_doc = JSON.parse(@doc.to_json)
            @initial_doc  = JSON.parse(@doc.to_json)
          end
        end

        def doc
          raise UnlinkedModel.new  unless linked?
          return @doc if is_root?
          _parent.doc.dig(*[_key].flatten)
        end

        def original_doc
          raise UnlinkedModel.new  unless linked?
          return @original_doc if is_root?
          _parent.original_doc.dig(*[_key].flatten)
        end

        def initial_doc
          raise UnlinkedModel.new  unless linked?
          return @initial_doc if is_root?
          _parent.initial_doc.dig(*[_key].flatten)
        end

        def as_json
          doc
        end

        def to_json(*args)
          doc.to_json(*args)
        end

        def as_update(ref = :last)
          new_doc = as_json
          ref_doc = ref == :total ? initial_doc : original_doc
          Common::HashDiff.diff(new_doc, ref_doc)
        end

        def dirty?
          as_update != {}
        end

        def consolidate!
          raise UnlinkedModel.new  unless linked?
          new_doc = JSON.parse(doc.to_json)
          if is_root?
            @original_doc = new_doc
          else
            dig_set(_parent.original_doc, [_key].flatten, new_doc)
          end
        end

        def reset!
          raise UnlinkedModel.new  unless linked?
          new_doc = JSON.parse(original_doc.to_json)
          if is_root?
            @doc = new_doc
          else
            dig_set(_parent.doc, [_key].flatten, new_doc)
          end
        end

        def pretty_print
          puts JSON.pretty_generate(as_json)
          self
        end

        protected

        def is_root?
          _parent == self && !!defined?(@doc)
        end

        def linked?
          is_root? || !!_parent.doc.dig(*[_key].flatten)
        end

        private

        def dig_set(obj, keys, value)
          if keys.length == 1
            obj[keys.first] = value
          else
            dig_set(obj[keys.first], keys.slice(1..-1), value)
          end
        end

      end
    end
  end
end