chore: Enhance contact merge action for identified users (#4886)

- Discard conflicting keys 
- Do not merge if there is already an identified contact

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/actions/contact_identify_action.rb

@@ -1,7 +1,16 @@
+# retain_original_contact_name: false / true
+# In case of setUser we want to update the name of the identified contact,
+# which is the default behaviour
+#
+# But, In case of contact merge during prechat form contact update.
+# We don't want to update the name of the identified original contact.
+
 class ContactIdentifyAction
-  pattr_initialize [:contact!, :params!]
+  pattr_initialize [:contact!, :params!, { retain_original_contact_name: false }]
 
   def perform
+    @attributes_to_update = [:identifier, :name, :email, :phone_number]
+
     ActiveRecord::Base.transaction do
       merge_if_existing_identified_contact
       merge_if_existing_email_contact
@@ -18,49 +27,88 @@ class ContactIdentifyAction
   end
 
   def merge_if_existing_identified_contact
-    @contact = merge_contact(existing_identified_contact, @contact) if merge_contacts?(existing_identified_contact, @contact)
+    return unless merge_contacts?(existing_identified_contact, :identifier)
+
+    process_contact_merge(existing_identified_contact)
   end
 
   def merge_if_existing_email_contact
-    @contact = merge_contact(existing_email_contact, @contact) if merge_contacts?(existing_email_contact, @contact)
+    return unless merge_contacts?(existing_email_contact, :email)
+
+    process_contact_merge(existing_email_contact)
   end
 
   def merge_if_existing_phone_number_contact
-    @contact = merge_contact(existing_phone_number_contact, @contact) if merge_contacts?(existing_phone_number_contact, @contact)
+    return unless merge_contacts?(existing_phone_number_contact, :phone_number)
+    return unless mergable_phone_contact?
+
+    process_contact_merge(existing_phone_number_contact)
+  end
+
+  def process_contact_merge(mergee_contact)
+    @contact = merge_contact(mergee_contact, @contact)
+    @attributes_to_update.delete(:name) if retain_original_contact_name
   end
 
   def existing_identified_contact
     return if params[:identifier].blank?
 
-    @existing_identified_contact ||= Contact.where(account_id: account.id).find_by(identifier: params[:identifier])
+    @existing_identified_contact ||= account.contacts.find_by(identifier: params[:identifier])
   end
 
   def existing_email_contact
     return if params[:email].blank?
 
-    @existing_email_contact ||= Contact.where(account_id: account.id).find_by(email: params[:email])
+    @existing_email_contact ||= account.contacts.find_by(email: params[:email])
   end
 
   def existing_phone_number_contact
     return if params[:phone_number].blank?
 
-    @existing_phone_number_contact ||= Contact.where(account_id: account.id).find_by(phone_number: params[:phone_number])
+    @existing_phone_number_contact ||= account.contacts.find_by(phone_number: params[:phone_number])
   end
 
-  def merge_contacts?(existing_contact, _contact)
-    existing_contact && existing_contact.id != @contact.id
+  def merge_contacts?(existing_contact, key)
+    return if existing_contact.blank?
+
+    return true if params[:identifier].blank?
+
+    # we want to prevent merging contacts with different identifiers
+    if existing_contact.identifier.present? && existing_contact.identifier != params[:identifier]
+      # we will remove attribute from update list
+      @attributes_to_update.delete(key)
+      return false
+    end
+
+    true
+  end
+
+  # case: contact 1: email: 1@test.com, phone: 123456789
+  # params: email: 2@test.com, phone: 123456789
+  # we don't want to overwrite 1@test.com since email parameter takes higer priority
+  def mergable_phone_contact?
+    return true if params[:email].blank?
+
+    if existing_phone_number_contact.email.present? && existing_phone_number_contact.email != params[:email]
+      @attributes_to_update.delete(:phone_number)
+      return false
+    end
+    true
   end
 
   def update_contact
+    params_to_update = params.slice(*@attributes_to_update).reject do |_k, v|
+      v.blank?
+    end.merge({ custom_attributes: custom_attributes, additional_attributes: additional_attributes })
     # blank identifier or email will throw unique index error
     # TODO: replace reject { |_k, v| v.blank? } with compact_blank when rails is upgraded
-    @contact.update!(params.slice(:name, :email, :identifier, :phone_number).reject do |_k, v|
-                       v.blank?
-                     end.merge({ custom_attributes: custom_attributes, additional_attributes: additional_attributes }))
+    @contact.update!(params_to_update)
     ContactAvatarJob.perform_later(@contact, params[:avatar_url]) if params[:avatar_url].present?
   end
 
   def merge_contact(base_contact, merge_contact)
+    return base_contact if base_contact.id == merge_contact.id
+
     ContactMergeAction.new(
       account: account,
       base_contact: base_contact,
@@ -69,14 +117,14 @@ class ContactIdentifyAction
   end
 
   def custom_attributes
-    params[:custom_attributes] ? @contact.custom_attributes.deep_merge(params[:custom_attributes].stringify_keys) : @contact.custom_attributes
+    return @contact.custom_attributes if params[:custom_attributes].blank?
+
+    (@contact.custom_attributes || {}).deep_merge(params[:custom_attributes].stringify_keys)
   end
 
   def additional_attributes
-    if params[:additional_attributes]
-      @contact.additional_attributes.deep_merge(params[:additional_attributes].stringify_keys)
-    else
-      @contact.additional_attributes
-    end
+    return @contact.additional_attributes if params[:additional_attributes].blank?
+
+    (@contact.additional_attributes || {}).deep_merge(params[:additional_attributes].stringify_keys)
   end
 end