add mutation for deleting Conversations

fixes VICE-871
flag=react_inbox

test plan:
  - create a conversation with messages between two users
  - as a user not in the conversation
    - navigate to /graphiql
    - add a new mutation
    - use the deleteConversation to attempt to delete
      all messages from the conversation
      - this should fail due to insufficient permissions
  - as a user in the conversation
    - navigate to /graphiql
    - attempt to delete a conversation that doesn't exist
      - this should fail to unfound Conversation
    - attempt to delete a conversation that does exist
      - this should succeed

qa risk: low

Change-Id: Iea7a02fa9e22e0ebd122dd4bab6e52f91bc3004d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/254756
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Caleb Guanzon <cguanzon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Caleb Guanzon <cguanzon@instructure.com>

app/graphql/audit_log_field_extension.rb

@@ -140,6 +140,7 @@ class AuditLogFieldExtension < GraphQL::Schema::FieldExtension
       next if mutation == Mutations::UpdateNotificationPreferences
       next if mutation == Mutations::CreateConversation
       next if mutation == Mutations::DeleteConversationMessage
+      next if mutation == Mutations::DeleteConversation
 
       logger = Logger.new(mutation, context, arguments)
 

app/graphql/mutations/delete_conversation.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+#
+# Copyright (C) 2020 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+class Mutations::DeleteConversation < Mutations::BaseMutation
+  graphql_name "DeleteConversation"
+
+  # input arguments
+  argument :id, ID, required: true, prepare: GraphQLHelpers.relay_or_legacy_id_prepare_func('Conversation')
+
+  field :conversation_id, ID, null: false
+
+  def resolve(input:)
+    conversation = Conversation.find_by(id: input[:id])
+    raise GraphQL::ExecutionError, "Unable to find Conversation" if conversation.nil?
+
+    participant_record = current_user.all_conversations.find_by(conversation_id: conversation.id)
+    raise GraphQL::ExecutionError, "insufficient permissions" if participant_record.nil?
+
+    participant_record.remove_messages(:all)
+    {conversation_id: conversation.id}
+
+  rescue ActiveRecord::RecordInvalid => invalid
+    errors_for(invalid.record)
+  end
+end

app/graphql/types/mutation_type.rb

@@ -69,6 +69,7 @@ class Types::MutationType < Types::ApplicationObjectType
   field :create_module, mutation: Mutations::CreateModule
   field :update_notification_preferences, mutation: Mutations::UpdateNotificationPreferences
   field :delete_conversation_message, mutation: Mutations::DeleteConversationMessage
+  field :delete_conversation, mutation: Mutations::DeleteConversation
 
   # TODO: Remove the in active development string from here once this is more
   #       finalized.

spec/graphql/mutations/delete_conversation_spec.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+#
+# Copyright (C) 2020 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+require "spec_helper"
+require_relative "../graphql_spec_helper"
+
+describe Mutations::DeleteConversation do
+  before :once do
+    @sender = user_model
+    @conversation = conversation(@sender, user_model).conversation
+  end
+
+  def execute_with_input(delete_input, user_executing: @sender)
+    mutation_command = <<~GQL
+      mutation {
+        deleteConversation(input: {
+          #{delete_input}
+        }) {
+          conversationId
+          errors {
+            attribute
+            message
+          }
+        }
+      }
+    GQL
+    context = {current_user: user_executing, request: ActionDispatch::TestRequest.create}
+    CanvasSchema.execute(mutation_command, context: context)
+  end
+
+  it "removes all messages from the participant's view" do
+    query = <<~QUERY
+      id: #{@conversation.id}
+    QUERY
+    expect(@sender.all_conversations.find_by(conversation: @conversation).messages.length).to eq 1
+    result = execute_with_input(query)
+    expect(result.dig('errors')).to be_nil
+    expect(result.dig('data', 'deleteConversation', 'errors')).to be_nil
+    expect(result.dig('data', 'deleteConversation', 'conversationId')).to eq @conversation.id.to_s
+    expect(@sender.all_conversations.find_by(conversation: @conversation).messages.length).to eq 0
+  end
+
+  context "errors" do
+    def expect_error(result, message)
+      errors = result.dig('errors') || result.dig('data', 'deleteConversation', 'errors')
+      expect(errors).not_to be_nil
+      expect(errors[0]['message']).to match(/#{message}/)
+    end
+
+    it "fails if the conversation doesn't exist" do
+      query = <<~QUERY
+        id: #{Conversation.maximum(:id).next}
+      QUERY
+      result = execute_with_input(query)
+      expect_error(result, 'Unable to find Conversation')
+    end
+
+    it "fails if the requesting user is not a participant" do
+      query = <<~QUERY
+        id: #{@conversation.id}
+      QUERY
+      result = execute_with_input(query, user_executing: user_model)
+      expect_error(result, 'insufficient permissions')
+    end
+  end
+end