refactor(export): expose new interface on type de champ and use it in champs

app/models/champ.rb

@@ -109,24 +109,29 @@ class Champ < ApplicationRecord
     [to_s]
   end
 
-  def to_s
-    value.present? ? value.to_s : ''
-  end
-
-  def for_export(path = :value)
-    path == :value ? value.presence : nil
-  end
-
-  def for_api
+  def valid_value
+    return unless valid_champ_value?
     value
   end
 
+  def to_s
+    TypeDeChamp.champ_value(type_champ, self)
+  end
+
+  def for_api
+    TypeDeChamp.champ_value_for_api(type_champ, self, 1)
+  end
+
   def for_api_v2
-    to_s
+    TypeDeChamp.champ_value_for_api(type_champ, self, 2)
+  end
+
+  def for_export(path = :value)
+    TypeDeChamp.champ_value_for_export(type_champ, self, path)
   end
 
   def for_tag(path = :value)
-    path == :value && value.present? ? value.to_s : ''
+    TypeDeChamp.champ_value_for_tag(type_champ, self, path)
   end
 
   def main_value_name

app/models/concerns/dossier_champs_concern.rb

@@ -25,7 +25,7 @@ module DossierChampsConcern
     types_de_champ.flat_map do |type_de_champ|
       champ = champ_for_export(type_de_champ, row_id)
       type_de_champ.libelles_for_export.map do |(libelle, path)|
-        [libelle, champ&.for_export(path)]
+        [libelle, TypeDeChamp.champ_value_for_export(type_de_champ.type_champ, champ, path)]
       end
     end
   end

app/models/type_de_champ.rb

@@ -250,7 +250,7 @@ class TypeDeChamp < ApplicationRecord
   def params_for_champ
     {
       private: private?,
-      type: "Champs::#{type_champ.classify}Champ",
+      type: self.class.type_champ_to_champ_class_name(type_champ),
       stable_id:,
       stream: 'main'
     }
@@ -463,10 +463,6 @@ class TypeDeChamp < ApplicationRecord
     !private?
   end
 
-  def self.type_champ_to_class_name(type_champ)
-    "TypesDeChamp::#{type_champ.classify}TypeDeChamp"
-  end
-
   def filename_for_attachement(attachment_sym)
     attachment = send(attachment_sym)
     if attachment.attached?
@@ -687,6 +683,56 @@ class TypeDeChamp < ApplicationRecord
     end
   end
 
+  class << self
+    def champ_value(type_champ, champ)
+      dynamic_type_class = type_champ_to_class_name(type_champ).constantize
+      # special case for linked drop down champ – it's blank implementation is not what you think
+      if champ.blank? && (type_champ != TypeDeChamp.type_champs.fetch(:linked_drop_down_list) || champ.nil? || champ.value.blank?)
+        dynamic_type_class.champ_default_value
+      else
+        dynamic_type_class.champ_value(champ)
+      end
+    end
+
+    def champ_value_for_api(type_champ, champ, version = 2)
+      dynamic_type_class = type_champ_to_class_name(type_champ).constantize
+      # special case for linked drop down champ – it's blank implementation is not what you think
+      if champ.blank? && (type_champ != TypeDeChamp.type_champs.fetch(:linked_drop_down_list) || champ.nil? || champ.value.blank?)
+        dynamic_type_class.champ_default_api_value(version)
+      else
+        dynamic_type_class.champ_value_for_api(champ, version)
+      end
+    end
+
+    def champ_value_for_export(type_champ, champ, path = :value)
+      dynamic_type_class = type_champ_to_class_name(type_champ).constantize
+      # special case for linked drop down champ – it's blank implementation is not what you think
+      if champ.blank? && (type_champ != TypeDeChamp.type_champs.fetch(:linked_drop_down_list) || champ.nil? || champ.value.blank?)
+        dynamic_type_class.champ_default_export_value(path)
+      else
+        dynamic_type_class.champ_value_for_export(champ, path)
+      end
+    end
+
+    def champ_value_for_tag(type_champ, champ, path = :value)
+      dynamic_type_class = type_champ_to_class_name(type_champ).constantize
+      # special case for linked drop down champ – it's blank implementation is not what you think
+      if champ.blank? && (type_champ != TypeDeChamp.type_champs.fetch(:linked_drop_down_list) || champ.nil? || champ.value.blank?)
+        ''
+      else
+        dynamic_type_class.champ_value_for_tag(champ, path)
+      end
+    end
+
+    def type_champ_to_champ_class_name(type_champ)
+      "Champs::#{type_champ.classify}Champ"
+    end
+
+    def type_champ_to_class_name(type_champ)
+      "TypesDeChamp::#{type_champ.classify}TypeDeChamp"
+    end
+  end
+
   private
 
   DEFAULT_EMPTY = ['']

app/models/types_de_champ/type_de_champ_base.rb

@@ -56,6 +56,46 @@ class TypesDeChamp::TypeDeChampBase
     human_value
   end
 
+  class << self
+    def champ_value(champ)
+      champ.value.present? ? champ.value.to_s : champ_default_value
+    end
+
+    def champ_value_for_api(champ, version = 2)
+      case version
+      when 2
+        champ_value(champ)
+      else
+        champ.valid_value.presence || champ_default_api_value(version)
+      end
+    end
+
+    def champ_value_for_export(champ, path = :value)
+      path == :value ? champ.valid_value.presence : champ_default_export_value(path)
+    end
+
+    def champ_value_for_tag(champ, path = :value)
+      path == :value ? champ_value(champ) : nil
+    end
+
+    def champ_default_value
+      ''
+    end
+
+    def champ_default_export_value(path = :value)
+      nil
+    end
+
+    def champ_default_api_value(version = 2)
+      case version
+      when 2
+        ''
+      else
+        nil
+      end
+    end
+  end
+
   private
 
   def paths