require_relative 'value_extractor'
require_relative 'must_support_metadata_extractor_us_core_3'
require_relative 'must_support_metadata_extractor_us_core_4'
require_relative 'must_support_metadata_extractor_us_core_5'
require_relative 'must_support_metadata_extractor_us_core_6'
require_relative 'must_support_metadata_extractor_us_core_7'

module USCoreTestKit
  class Generator
    class MustSupportMetadataExtractor
      attr_accessor :profile_elements, :profile, :resource, :ig_resources

      def initialize(profile_elements, profile, resource, ig_resources)
        self.profile_elements = profile_elements
        self.profile = profile
        self.resource = resource
        self.ig_resources = ig_resources
      end

      def must_supports
        @must_supports = {
          extensions: must_support_extensions,
          slices: must_support_slices,
          elements: must_support_elements
        }

        handle_special_cases

        @must_supports
      end

      def is_uscdi_requirement_element?(element)
        element.extension.any? do |extension|
          extension.url == 'http://hl7.org/fhir/us/core/StructureDefinition/uscdi-requirement' &&
          extension.valueBoolean
        end && !element.mustSupport
      end

      def all_must_support_elements
        profile_elements.select { |element| (element.mustSupport || is_uscdi_requirement_element?(element))}
      end

      def must_support_extension_elements
        all_must_support_elements.select { |element| element.path.end_with? 'extension' }
      end

      def must_support_extensions
        must_support_extension_elements.map do |element|
          {
            id: element.id,
            path: element.path.gsub("#{resource}.", ''),
            url: element.type.first.profile.first
          }.tap do |metadata|
            if is_uscdi_requirement_element?(element)
              metadata[:uscdi_only] = true
            end
          end
        end
      end

      def must_support_slice_elements
        all_must_support_elements.select { |element| !element.path.end_with?('extension') && element.sliceName.present? }
      end

      def sliced_element(slice)
        profile_elements.find { |element| element.id == slice.path || element.id == slice.id.sub(":#{slice.sliceName}", '') }
      end

      def discriminators(slice)
        slice.slicing.discriminator
      end

      def must_support_pattern_slice_elements
        must_support_slice_elements.select do |element|
          discriminators(sliced_element(element)).first.type == 'pattern'
        end
      end

      def pattern_slices
        must_support_pattern_slice_elements.map do |current_element|
          {
            slice_id: current_element.id,
            slice_name: current_element.sliceName,
            path: current_element.path.gsub("#{resource}.", '')
          }.tap do |metadata|
            discriminator = discriminators(sliced_element(current_element)).first
            discriminator_path = discriminator.path
            discriminator_path = '' if discriminator_path == '$this'
            pattern_element =
              if discriminator_path.present?
                profile_elements.find { |element| element.id == "#{current_element.id}.#{discriminator_path}" }
              else
                current_element
              end
            metadata[:discriminator] =
              if pattern_element.patternCodeableConcept.present?
                {
                  type: 'patternCodeableConcept',
                  path: discriminator_path,
                  code: pattern_element.patternCodeableConcept.coding.first.code,
                  system: pattern_element.patternCodeableConcept.coding.first.system
                }
              elsif pattern_element.patternCoding.present?
                {
                  type: 'patternCoding',
                  path: discriminator_path,
                  code: pattern_element.patternCoding.code,
                  system: pattern_element.patternCoding.system
                }
              elsif pattern_element.patternIdentifier.present?
                {
                  type: 'patternIdentifier',
                  path: discriminator_path,
                  system: pattern_element.patternIdentifier.system
                }
              elsif pattern_element.binding&.strength == 'required' &&
                    pattern_element.binding&.valueSet.present?

                value_extractor = ValueExactor.new(ig_resources, resource, profile_elements)

                values = value_extractor.codings_from_value_set_binding(pattern_element).presence ||
                         value_extractor.values_from_resource_metadata([metadata[:path]]).presence || []

                {
                  type: 'requiredBinding',
                  path: discriminator_path,
                  values: values
                }
              else
                raise StandardError, 'Unsupported discriminator pattern type'
              end

            if is_uscdi_requirement_element?(current_element)
              metadata[:uscdi_only] = true
            end
          end
        end
      end

      def must_support_type_slice_elements
        must_support_slice_elements.select do |element|
          discriminators(sliced_element(element)).first.type == 'type'
        end
      end

      def type_slices
        must_support_type_slice_elements.map do |current_element|
          discriminator = discriminators(sliced_element(current_element)).first
          type_path = discriminator.path
          type_path = '' if type_path == '$this'
          type_element =
            if type_path.present?
              elements.find { |element| element.id == "#{current_element.id}.#{type_path}" }
            else
              current_element
            end

          type_code = type_element.type.first.code

          {
            slice_id: current_element.id,
            slice_name: current_element.sliceName,
            path: current_element.path.gsub("#{resource}.", ''),
            discriminator: {
              type: 'type',
              code: type_code.upcase_first
            }
          }.tap do |metadata|
            if is_uscdi_requirement_element?(current_element)
              metadata[:uscdi_only] = true
            end
          end
        end
      end

      def must_support_value_slice_elements
        must_support_slice_elements.select do |element|
          discriminators(sliced_element(element)).first.type == 'value'
        end
      end

      def value_slices
        must_support_value_slice_elements.map do |current_element|
          {
            slice_id: current_element.id,
            slice_name: current_element.sliceName,
            path: current_element.path.gsub("#{resource}.", ''),
            discriminator: {
              type: 'value'
            }
          }.tap do |metadata|
            metadata[:discriminator][:values] = discriminators(sliced_element(current_element)).map do |discriminator|
              fixed_element = profile_elements.find do |element|
                element.id.starts_with?(current_element.id) &&
                  element.path == "#{current_element.path}.#{discriminator.path}"
              end

              {
                path: discriminator.path,
                value: fixed_element.fixedUri || fixed_element.fixedCode
              }
            end

            if is_uscdi_requirement_element?(current_element)
              metadata[:uscdi_only] = true
            end
          end
        end
      end

      def must_support_slices
        pattern_slices + type_slices + value_slices
      end

      def plain_must_support_elements
        plain_must_supports = all_must_support_elements - must_support_extension_elements - must_support_slice_elements
      end

      def element_part_of_slice_discrimination?(element)
        must_support_slice_elements.any? { |ms_slice| element.id.include?(ms_slice.id) }
      end


      def handle_fixed_values(metadata, element)
        if element.fixedUri.present?
          metadata[:fixed_value] = element.fixedUri
        elsif element.patternCodeableConcept.present? && !element_part_of_slice_discrimination?(element)
          metadata[:fixed_value] = element.patternCodeableConcept.coding.first.code
          metadata[:path] += '.coding.code'
        elsif element.fixedCode.present?
          metadata[:fixed_value] = element.fixedCode
        elsif element.patternIdentifier.present? && !element_part_of_slice_discrimination?(element)
          metadata[:fixed_value] = element.patternIdentifier.system
          metadata[:path] += '.system'
        end
      end

      def type_must_support_extension?(extensions)
        extensions&.any? do |extension|
          extension.url == 'http://hl7.org/fhir/StructureDefinition/elementdefinition-type-must-support' &&
          extension.valueBoolean
        end
      end

      def save_type_code?(type)
        'Reference' == type.code
      end

      def get_type_must_support_metadata(current_metadata, current_element)
        current_element.type.map do |type|
          if type_must_support_extension?(type.extension)
            metadata =
            {
              path: "#{current_metadata[:path].delete_suffix('[x]')}#{type.code.upcase_first}",
              original_path: current_metadata[:path]
            }
            metadata[:types] = [type.code] if save_type_code?(type)
            handle_type_must_support_target_profiles(type, metadata) if type.code == 'Reference'

            metadata
          end
        end.compact
      end

      def handle_type_must_support_target_profiles(type, metadata)
        # US Core 3.1.1 profiles do not have US Core target profiles.
        # Vital Sign proifles from FHIR R4 (version 4.0.1) do not have US Core target profiles either.
        return if ['3.1.1', '4.0.1'].include?(profile.version)

        target_profiles = []

        if type.targetProfile&.length == 1
          target_profiles << type.targetProfile.first
        else
          type.source_hash['_targetProfile']&.each_with_index do |hash, index|
            if hash.present?
              element = FHIR::Element.new(hash)
              target_profiles << type.targetProfile[index] if type_must_support_extension?(element.extension)
            end
          end
        end

        # remove target_profile for FHIR Base resource type.
        target_profiles.delete_if { |reference| reference.start_with?('http://hl7.org/fhir/StructureDefinition')}
        metadata[:target_profiles] = target_profiles if target_profiles.present?
      end

      def handle_choice_type_in_sliced_element(current_metadata, must_support_elements_metadata)
        choice_element_metadata = must_support_elements_metadata.find do |metadata|
          metadata[:original_path].present? &&
          current_metadata[:path].include?( metadata[:original_path] )
        end

        if choice_element_metadata.present?
          current_metadata[:original_path] = current_metadata[:path]
          current_metadata[:path] = current_metadata[:path].sub(choice_element_metadata[:original_path], choice_element_metadata[:path])
        end
      end

      def must_support_elements
        plain_must_support_elements.each_with_object([]) do |current_element, must_support_elements_metadata|
          {
            path: current_element.id.gsub("#{resource}.", '')
          }.tap do |current_metadata|
            if is_uscdi_requirement_element?(current_element)
              current_metadata[:uscdi_only] = true
            end

            type_must_support_metadata = get_type_must_support_metadata(current_metadata, current_element)

            if type_must_support_metadata.any?
              must_support_elements_metadata.concat(type_must_support_metadata)
            else
              handle_choice_type_in_sliced_element(current_metadata, must_support_elements_metadata)

              supported_types = current_element.type.select { |type| save_type_code?(type) }.map { |type| type.code }
              current_metadata[:types] = supported_types if supported_types.present?

              handle_type_must_support_target_profiles(current_element.type.first, current_metadata) if current_element.type.first&.code == 'Reference'

              handle_fixed_values(current_metadata, current_element)

              must_support_elements_metadata.delete_if do |metadata|
                metadata[:path] == current_metadata[:path] && metadata[:fixed_value].blank?
              end

              must_support_elements_metadata << current_metadata
            end
          end
        end.uniq
      end

      #### SPECIAL CASE ####

      def handle_special_cases
        remove_vital_sign_component
        remove_blood_pressure_value_data_absent_reason
        remove_observation_data_absent_reason

        case profile.version
        when '3.1.1'
          MustSupportMetadataExtractorUsCore3.new(profile, @must_supports).handle_special_cases
        when '4.0.0'
          MustSupportMetadataExtractorUsCore4.new(profile, @must_supports).handle_special_cases
        when '5.0.1'
          MustSupportMetadataExtractorUsCore5.new(profile, @must_supports).handle_special_cases
        when '6.1.0'
          MustSupportMetadataExtractorUsCore6.new(profile, @must_supports).handle_special_cases
        when '7.0.0'
          MustSupportMetadataExtractorUsCore7.new(profile, @must_supports).handle_special_cases
        end
      end

      def is_vital_sign?
        [
          'http://hl7.org/fhir/StructureDefinition/vitalsigns',
          'http://hl7.org/fhir/us/core/StructureDefinition/us-core-vital-signs'
        ].include?(profile.baseDefinition)
      end

      def is_blood_pressure?
        ['bp', 'us-core-blood-pressure', 'us-core-average-blood-pressure'].include?(profile.id)
      end

      # Exclude Observation.component from vital sign profiles except observation-bp and observation-pulse-ox
      def remove_vital_sign_component
        return if is_blood_pressure? || profile.name == 'USCorePulseOximetryProfile'

        if is_vital_sign?
          @must_supports[:elements].delete_if do |element|
            element[:path].start_with?('component')
          end
        end
      end

      # Exclude Observation.value[x] from observation-bp
      def remove_blood_pressure_value_data_absent_reason
        return unless is_blood_pressure?

        pattern = /component(:[^.]+)?\.dataAbsentReason/

        @must_supports[:elements].delete_if do |element|
          element[:path].start_with?('value[x]') ||
          element[:original_path]&.start_with?('value[x]') ||
          element[:path] == ('dataAbsentReason') ||
          (
            pattern.match?(element[:path]) && ['3.1.1', '4.0.0'].include?(ig_resources.ig.version)
          )
        end

        @must_supports[:slices].delete_if do |slice|
          slice[:path].start_with?('value[x]')
        end
      end

      # ONC and US Core 4.0.0 both clarified that health IT developers that always provide HL7 FHIR "observation" values
      # are not required to demonstrate Health IT Module support for "dataAbsentReason" elements.
      # Remove MS check for dataAbsentReason and component.dataAbsentReason from vital sign profiles and observation lab profile
      # Smoking status profile does not have MS on dataAbsentReason. It is safe to use profile.type == 'Observation'
      # Since US Core 5.0.1, Blood Pressure profile restores component.dataAbsentReason as MustSupport.
      def remove_observation_data_absent_reason
        return if is_blood_pressure?

        pattern = /(component(:[^.]+)?\.)?dataAbsentReason/

        if profile.type == 'Observation'
          @must_supports[:elements].delete_if do |element|
            pattern.match?(element[:path])
          end
        end
      end
    end
  end
end