Added logic for conflict resolution

* Conflict is detected when attempting to save a new GridCharacter
* New `resolve` method executes the replacement
* Template to render a decision on the frontend

app/controllers/api/v1/grid_characters_controller.rb

@@ -1,7 +1,7 @@
 class Api::V1::GridCharactersController < Api::V1::ApiController
     def create
         party = Party.find(character_params[:party_id])
-        canonical_character = Character.find(character_params[:character_id])
+        incoming_character = Character.find(character_params[:character_id])
 
         if current_user
             if party.user != current_user
@@ -9,13 +9,67 @@ class Api::V1::GridCharactersController < Api::V1::ApiController
             end
         end
 
-        if GridCharacter.where(party_id: party.id, position: character_params[:position]).exists?
-            @character = GridCharacter.where(party_id: party.id, position: character_params[:position]).limit(1)[0]
-            @character.character_id = canonical_character.id
-        else
-            @character = GridCharacter.create!(character_params.merge(party_id: party.id, character_id: canonical_character.id))
-        end
+        current_characters = party.characters.map { |c| 
+            Character.find(c.character.id).character_id 
+        }.flatten
 
+        # Check all character ids on incoming character against current characters
+        conflict_ids = (current_characters & incoming_character.character_id)
+        
+        if conflict_ids.length > 0
+            # Find conflicting character ids in party characters
+            conflict_characters = party.characters.filter { |c|
+                c if (conflict_ids & c.character.character_id).length > 0 
+            }.flatten
+
+            # Render a template with the conflicting and incoming characters,
+            # as well as the selected position, so the user can be presented with
+            # a decision.
+
+            # Up to 3 characters can be removed at the same time
+            @conflict_characters = conflict_characters
+            @incoming_character  = incoming_character
+            @incoming_position   = character_params[:position]
+
+            render :conflict, status: :ok
+        else
+            # Replace the grid character in the position if it is already filled
+            if GridCharacter.where(party_id: party.id, position: character_params[:position]).exists?
+                @character = GridCharacter.where(party_id: party.id, position: character_params[:position]).limit(1)[0]
+                @character.character_id = incoming_character.id
+
+            # Otherwise, create a new grid character
+            else
+                @character = GridCharacter.create!(character_params.merge(party_id: party.id, character_id: incoming_character.id))
+            end
+
+            render :show, status: :created if @character.save!
+        end
+    end
+
+    def resolve
+        incoming = Character.find(resolve_params[:incoming])
+        conflicting = resolve_params[:conflicting].map { |id| GridCharacter.find(id) }
+        party = conflicting.first.party
+
+        # Destroy each conflicting character
+        conflicting.each { |character| GridCharacter.destroy(character.id) }
+
+        # Destroy the character at the desired position if it exists
+        existing_character = GridCharacter.where(party: party.id, position: resolve_params[:position]).first
+        GridCharacter.destroy(existing_character.id) unless !existing_character
+
+        if (incoming.special)
+            uncap_level = 3
+            uncap_level = 5 if incoming.ulb 
+            uncap_level = 4 if incoming.flb
+        else
+            uncap_level = 4
+            uncap_level = 6 if incoming.ulb 
+            uncap_level = 5 if incoming.flb
+        end
+        
+        @character = GridCharacter.create!(party_id: party.id, character_id: incoming.id, position: resolve_params[:position], uncap_level: uncap_level)
         render :show, status: :created if @character.save!
     end
 
@@ -39,6 +93,10 @@ class Api::V1::GridCharactersController < Api::V1::ApiController
 
     # Specify whitelisted properties that can be modified.
     def character_params
-        params.require(:character).permit(:id, :party_id, :character_id, :position, :uncap_level)
+        params.require(:character).permit(:id, :party_id, :character_id, :position, :uncap_level, :conflicting, :incoming)
     end
-end
+
+    def resolve_params
+        params.require(:resolve).permit(:position, :incoming, :conflicting => [])
+    end
+end

app/views/api/v1/grid_characters/conflict.json.rabl

@@ -0,0 +1,14 @@
+object false
+
+node :conflicts do
+  partial('grid_characters/base', :object => @conflict_characters)
+end
+
+node :incoming do
+  partial('characters/base', :object => @incoming_character)
+end
+
+node :position do
+  @incoming_position
+end
+