From 6db042dc72eaf86b35f337d184cb63feb5055fa4 Mon Sep 17 00:00:00 2001
From: Mohit Alonja <monty16597@users.noreply.github.com>
Date: Tue, 10 Aug 2021 11:41:50 +0530
Subject: [PATCH] Added DisassociateTransitGatewayRouteTable API (#4154)

---
 moto/ec2/models.py                            | 23 ++++++++++++++++++
 .../responses/transit_gateway_attachments.py  | 24 +++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index 6008ed24c..08bf22da9 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -6240,6 +6240,10 @@ class TransitGatewayRouteTableBackend(object):
             "transitGatewayAttachmentId": transit_gateway_attachment_id,
         }
 
+    def unset_route_table_association(self, tgw_rt_id):
+        tgw_rt = self.transit_gateways_route_tables[tgw_rt_id]
+        tgw_rt.route_table_association = {}
+
     def set_route_table_propagation(
         self, transit_gateway_attachment_id, transit_gateway_route_table_id
     ):
@@ -6256,6 +6260,10 @@ class TransitGatewayRouteTableBackend(object):
             "transitGatewayAttachmentId": transit_gateway_attachment_id,
         }
 
+    def unset_route_table_propagation(self, tgw_rt_id):
+        tgw_rt = self.transit_gateways_route_tables[tgw_rt_id]
+        tgw_rt.route_table_propagation = {}
+
     def disable_route_table_propagation(self, transit_gateway_route_table_id):
         self.transit_gateways_route_tables[
             transit_gateway_route_table_id
@@ -6538,6 +6546,9 @@ class TransitGatewayAttachmentBackend(object):
             "transitGatewayRouteTableId": transit_gateway_route_table_id,
         }
 
+    def unset_attachment_association(self, tgw_attach_id):
+        self.transit_gateway_attachments.get(tgw_attach_id).association = {}
+
     def set_attachment_propagation(
         self, transit_gateway_attachment_id=None, transit_gateway_route_table_id=None
     ):
@@ -6546,6 +6557,9 @@ class TransitGatewayAttachmentBackend(object):
             "transitGatewayRouteTableId": transit_gateway_route_table_id,
         }
 
+    def unset_attachment_propagation(self, tgw_attach_id):
+        self.transit_gateway_attachments.get(tgw_attach_id).propagation = {}
+
     def disable_attachment_propagation(self, transit_gateway_attachment_id=None):
         self.transit_gateway_attachments[transit_gateway_attachment_id].propagation[
             "state"
@@ -6715,6 +6729,15 @@ class TransitGatewayRelationsBackend(object):
 
         return transit_gateway_propagation
 
+    def disassociate_transit_gateway_route_table(self, tgw_attach_id, tgw_rt_id):
+        tgw_association = self.transit_gateway_associations.pop(tgw_attach_id)
+        tgw_association.state == "disassociated"
+
+        self.unset_route_table_association(tgw_rt_id)
+        self.unset_attachment_association(tgw_attach_id)
+
+        return tgw_association
+
 
 class NatGateway(CloudFormationModel):
     def __init__(self, backend, subnet_id, allocation_id, tags=[]):
diff --git a/moto/ec2/responses/transit_gateway_attachments.py b/moto/ec2/responses/transit_gateway_attachments.py
index 0b877c8c9..4edef0617 100644
--- a/moto/ec2/responses/transit_gateway_attachments.py
+++ b/moto/ec2/responses/transit_gateway_attachments.py
@@ -88,6 +88,17 @@ class TransitGatewayAttachment(BaseResponse):
         template = self.response_template(TRANSIT_GATEWAY_ASSOCIATION)
         return template.render(transit_gateway_association=transit_gateway_association)
 
+    def disassociate_transit_gateway_route_table(self,):
+        tgw_attach_id = self._get_param("TransitGatewayAttachmentId")
+        tgw_rt_id = self._get_param("TransitGatewayRouteTableId")
+
+        tgw_association = self.ec2_backend.disassociate_transit_gateway_route_table(
+            tgw_attach_id, tgw_rt_id
+        )
+        tgw_association.state == "disassociated"
+        template = self.response_template(TRANSIT_GATEWAY_DISASSOCIATION)
+        return template.render(tgw_association=tgw_association)
+
     def enable_transit_gateway_route_table_propagation(self):
         transit_gateway_attachment_id = self._get_param("TransitGatewayAttachmentId")
         transit_gateway_route_table_id = self._get_param("TransitGatewayRouteTableId")
@@ -351,6 +362,19 @@ TRANSIT_GATEWAY_ASSOCIATION = """<AssociateTransitGatewayRouteTableResponse xmln
 """
 
 
+TRANSIT_GATEWAY_DISASSOCIATION = """<DisassociateTransitGatewayRouteTableResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
+    <requestId>86a597cf-93ec-44a3-9559-4641863642a5</requestId>
+    <association>
+        <resourceId>{{ tgw_association.resource_id }}</resourceId>
+        <resourceType>{{ tgw_association.resource_type }}</resourceType>
+        <state>{{ tgw_association.state }}</state>
+        <transitGatewayAttachmentId>{{ tgw_association.transit_gateway_attachment_id }}</transitGatewayAttachmentId>
+        <transitGatewayRouteTableId>{{ tgw_association.transit_gateway_route_table_id }}</transitGatewayRouteTableId>
+    </association>
+</DisassociateTransitGatewayRouteTableResponse>
+"""
+
+
 TRANSIT_GATEWAY_PROPAGATION = """<EnableTransitGatewayRouteTablePropagationResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
     <requestId>c78427d4-e498-46ae-bc14-32841b16bff4</requestId>
     <propagation>