module Eco
  module API
    module Common
      module People

        # @attr_reader direct_attrs [Array<String>] only those internal attributes present in the person entry that do **not** have an internal/external name mapping.
        class PersonEntryAttributeMapper
          @@cached_warnings = {}

          attr_reader :aliased_attrs, :direct_attrs

          # Helper class tied to `PersonEntry` that allows to track which attributes of a person entry are present
          # and how they should be mapped between internal and external names if applicable.
          # This class is meant to help in providing a common interface to access entries of source data that come in different formats.
          # @note
          #   - if `data` is a `Person` object, its behaviour is `serialise`.
          #   - if `data` is **not** a `Person` object, it does a `parse`.
          #   - currently **in rework**, so there may be subtle differences that make it temporarily unstable (yet it is reliable).
          # @param data [Hash, Ecoportal::API::V1::Person] `Person` object to be serialized or hashed entry to be parsed (note: `CSV::Row` is accepted).
          # @param person_parser [Common::People::PersonParser]  parser/serializer of person attributes (it contains a set of attribute parsers).
          # @param attr_map [Eco::Data::Mapper] mapper to translate attribute names from _external_ to _internal_ names and _vice versa_.
          # @param logger [Common::Session::Logger, ::Logger] object to manage logs.
          def initialize(data, person_parser:, attr_map:, logger: ::Logger.new(IO::NULL))
            raise "Constructor needs a PersonParser. Given: #{parser}" if !person_parser.is_a?(Eco::API::Common::People::PersonParser)
            raise "Expecting Mapper object. Given: #{attr_map}" if attr_map && !attr_map.is_a?(Eco::Data::Mapper)

            @source         = data
            @person_parser  = person_parser
            @attr_map       = attr_map
            @logger         = logger

            if parsing?
              @external_entry   = data
            else  # SERIALIZING
              @person          = data
            end
          end

          # @return [Array<String>] only those internal attributes present in the person entry that have an internal/external name mapping.
          def aliased_attrs
            return @aliased_attrs unless !@aliased_attrs
            if parsing?
              init_attr_trackers
            else
              @aliased_attrs = @attr_map.list(:internal)
            end
            @aliased_attrs
          end

          # @return [Array<String>] all the internally named attributes that the person entry has.
          def internal_attrs(data = nil)
            return @internal_attrs unless data || !@internal_attrs
            if parsing?
              init_attr_trackers unless @internal_attrs
              if data
                return data.keys & @person_parser.all_model_attrs
              end
            else
              @internal_attrs = @person_parser.all_model_attrs
            end
            @internal_attrs
          end


          # @return [Array<String>] all the attrs that are present in the person entry.
          def all_model_attrs(data = nil)
            core_attrs(data) | account_attrs(data) | details_attrs(data)
          end

          # @return [Array<String>] core attributes that are present in the person entry.
          def core_attrs(data = nil)
            return @core_attrs unless data || !@core_attrs
            @person_parser.target_attrs_core(internal_attrs(data)).tap do |core_attrs|
              @core_attrs ||= core_attrs
            end
          end

          # @return [Array<String>] schema details attributes that are present in the person entry.
          def details_attrs(data = nil)
            return @details_attrs unless data || !@details_attrs
            @person_parser.target_attrs_details(internal_attrs(data)).tap do |details_attrs|
              @details_attrs ||= details_attrs
            end
          end

          # @return [Array<String>] account attributes that are present in the person entry.
          def account_attrs(data = nil)
            return @account_attrs unless data || !@account_attrs
            @person_parser.target_attrs_account(internal_attrs(data)).tap do |account_attrs|
              @account_attrs ||= account_attrs
            end
          end

          # To know if currently the object is in parse or serialize mode.
          # @return [Boolean] returns `true` if we are **parsing**, `false` otherwise.
          def parsing?
            !@source.is_a?(Ecoportal::API::V1::Person)
          end

          # To know if currently the object is in parse or serialize mode.
          # @return [Boolean] returns `true` if we are **serializing**, `false` otherwise.
          def serializing?
            !parsing?
          end

          # If there **no** `mapper` defined for the object, it mirrors `value`.
          # If there is a `mapper` defined for the object:
          #  1. if the `value` exists as external, translates it into an internal one.
          #  2. if it doesn't exist, returns `nil`.
          # @note
          #  1. the **scope of attributes** is based on all the attributes recognized by the person parser.
          #  2. the attributes recognized by the person parser are those of of the `Person` model (where details attributes depend on the `schema`).
          # @param value [String, Array<String>] value(s) to be translated into internal names.
          # @return [String, nil, Array<String] the internal name(s) of `value`.
          def to_internal(value)
            # TODO: check PersonEntry#to_internal and #to_external in init_attr_trackers
            # => when attr_map is avoided, it doesn't work as it should
            return value if !@attr_map
            attr = value
            case value
            when Array
              return value.map do |v|
                to_internal(v)
              end.compact
            when String
              case
              when @attr_map.external?(value)
                attr = @attr_map.to_internal(value)
              when @attr_map.external?(value.strip)
                unless cached_warning("external", "spaces", value)
                  logger.warn("The external person field name '#{value}' contains additional spaces in the reference file")
                end
                attr = @attr_map.to_internal(value.strip)
              when @attr_map.internal?(value) || @attr_map.internal?(value.strip) || @attr_map.internal?(value.strip.downcase)
                unless cached_warning("external", "reversed", value)
                  logger.warn("The mapper [external, internal] attribute names may be declared reversedly for EXTERNAL attribute: '#{value}'")
                end
              end
            end

            return nil unless @person_parser.all_model_attrs.include?(attr)
          end

          # Serializing helper also used to do a reverse mapping when parsing:
          #  - as there could be _internal attributes_ that shared _external attributes_,
          #  - when parsing, you use this helper to recognize the source _external attribute_ of each _internal_ one.
          # If there **no** `mapper` defined for the object, it mirrors `value`.
          # If there is a `mapper` defined for the object:
          #  1. if the `value` exists as _internal-, translates it into an _external_ one.
          #  2. if it doesn't exist, returns `nil`.
          # @note
          #  1. the **scope of attributes** is based on all the attributes defined in the current entry.
          #  2. the attributes recognized by the person parser are those of of the `Person` model (where details attributes depend on the `schema`).
          # @param value [String, Array<String>] value(s) to be translated or aliased into external ones.
          # @return [String, nil, Array<String] the external name(s) of `value`.
          def to_external(value)
            return value if !@attr_map
            attr = value
            case value
            when Array
              return value.map do |v|
                to_external(v)
              end.compact
            when String
              case
              when @attr_map.internal?(value)
                attr = @attr_map.to_external(value)
              when @attr_map.internal?(value.strip)
                unless cached_warning("internal", "spaces", value)
                  logger.warn("The internal person field name '#{value}' contains additional spaces in the reference file")
                end
                attr = @attr_map.to_external(value.strip)
              when @attr_map.external?(value) || @attr_map.external?(value.strip) || @attr_map.external?(value.strip.downcase)
                unless cached_warning("internal", "reversed", value)
                  logger.warn("The mapper [external, internal] attribute names may be declared reversedly for INTERNAL attribute: '#{value}'")
                end
              end
            end

            return nil unless !@external_entry || attributes(@external_entry).include?(attr)
            attr
          end

          private

          # when parsing:
          def init_attr_trackers
            # (def) all internal attributes we can expect
            def_all_attrs     = @person_parser.all_model_attrs
            # (def) internal attrs with no aliasing nor parser definition (expected to be direct)
            def_unlinked      = @person_parser.undefined_model_attrs.select { |attr| !to_external(attr) }
            # (def) those with parser or alias:
            def_linked        = def_all_attrs - def_unlinked
            # (data) data attributes (actual attributes of the entry)
            data_attrs        = attributes(@external_entry)
            # (data) attributes of the data that come directly as internal attribute names
            data_direct_attrs = data_attrs & def_all_attrs

            # (def) configured  as alised (internal <-> external attributes)
            def_int_aliased   = def_all_attrs.select  { |attr| to_external(attr) }
            def_ext_alias     = def_int_aliased.map   { |attr| to_external(attr) }

            # (data) virtual attrs (external alias of non native internal attr in data):
            data_vi_ext_alias = data_attrs.select do |attr|
              !def_ext_alias.include?(attr) && @attr_map&.external?(attr)
            end
            # (data) virtual internal attrs (the internal names of those virtual attrs)
            data_vi_int_aliased = data_vi_ext_alias.map do |attr|
              # to_internal(attr) can't be used here, becauase virtual fields would get filtered out,
              # as they are not recognized by @parser.all_model_attrs.include?(attr)
              @attr_map.to_internal(attr)
            end.compact

            # (data) attrs that could come aliased in the current data
            # => modify aliased based on those that came directly as internal attrs in the entry
            data_def_int_aliased = def_int_aliased - data_direct_attrs
            data_def_ext_alias   = data_def_int_aliased.map { |attr| to_external(attr) }
            # (data) actual attrs of the data that come aliased
            data_ext_alias       = data_def_ext_alias & data_attrs

            # (data) all internal attributes that could come aliased, with given the entry
            @aliased_attrs       = data_def_int_aliased + data_vi_int_aliased
            # (data) all those ext attrs present that will require aliasing
            #data_ext_alias_all   = data_def_ext_alias   + data_vi_ext_alias
            data_ext_alias_all   = data_ext_alias       + data_vi_ext_alias

            # those that are direct external to internal:
            data_ext_direct      = data_attrs - data_ext_alias_all

            # (data) attributes that do not require aliasing
            # to avoid collisions between internal names:
            #@direct_attrs        = data_ext_direct - def_linked
            @direct_attrs        = data_ext_direct
            @internal_attrs      = @aliased_attrs | @direct_attrs
          end

          def attributes(value)
            case value
            when CSV::Row
              value&.headers
            when Hash
              value&.keys
            when PersonEntry
              @person_parser.target_attrs_core
            else
              []
            end
          end

          # LOGGER
          def logger
            @logger || ::Logger.new(IO::NULL)
          end

          def cached_warning(*args)
            unless exists = !!@@cached_warnings.dig(*args)
              args.reduce(@@cached_warnings) do |cache, level|
                cache[level] = {} if !cache.key?(level)
                cache[level]
              end
            end
            exists
          end

          def fatal(msg)
            logger.fatal(msg)
            raise msg
          end

        end
      end
    end
  end
end