Fix remove integration with multiple consumers

Currently removing an integration with an offer removes
the remote offer. This does not take into consideration
of any other consumers integrated with the offer.
This leads to other consumers getting relation-broken
which is not expected.

Check for number of consumers during delete integration
for an offer. Remove RemoteOffer only when the current
integration is the only consumer to the offer. Otherwise
use DestroyIntegration that removes only the integration
between the calling comsumer and the offer without affecting
the relation between other consumers and offer.

Fixes: #308

internal/juju/offers.go

@@ -50,11 +50,12 @@ type ReadOfferInput struct {
 }
 
 type ReadOfferResponse struct {
-	ApplicationName string
-	Endpoint        string
-	ModelName       string
-	Name            string
-	OfferURL        string
+	ApplicationName  string
+	Endpoint         string
+	ModelName        string
+	Name             string
+	OfferURL         string
+	ConnectionsCount int
 }
 
 type DestroyOfferInput struct {
@@ -173,6 +174,7 @@ func (c offersClient) ReadOffer(input *ReadOfferInput) (*ReadOfferResponse, erro
 	response.ApplicationName = result.ApplicationName
 	response.OfferURL = result.OfferURL
 	response.Endpoint = result.Endpoints[0].Name
+	response.ConnectionsCount = len(result.Connections)
 
 	//no model name is returned but it can be parsed from the resulting offer URL to ensure parity
 	//TODO: verify if we can fetch information another way

internal/provider/resource_integration.go

@@ -411,8 +411,24 @@ func (r *integrationResource) Delete(ctx context.Context, req resource.DeleteReq
 		return
 	}
 
-	//If one of the endpoints is an offer then we need to remove the remote offer rather than destroying the integration
+	var removeRemoteOffer bool = false
+	//If one of the endpoints is an offer then we need to remove the remote offer if there is one consumer
 	if offer != nil {
+		offer_response, err  := r.client.Offers.ReadOffer(&juju.ReadOfferInput{
+			OfferURL: *offer,
+		})
+		if err != nil {
+			resp.Diagnostics.AddError("Client Error", err.Error())
+			return
+		}
+
+		// If there is only one connection in the offer, remove the remote offer
+		if offer_response.ConnectionsCount == 1 {
+			removeRemoteOffer = true
+		}
+	}
+
+	if removeRemoteOffer {
 		errs := r.client.Offers.RemoveRemoteOffer(&juju.RemoveRemoteOfferInput{
 			ModelName: modelName,
 			OfferURL:  *offer,

internal/provider/resource_integration_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/hashicorp/terraform-plugin-testing/config"
 	"github.com/hashicorp/terraform-plugin-testing/helper/acctest"
 	"github.com/hashicorp/terraform-plugin-testing/helper/resource"
 	"github.com/hashicorp/terraform-plugin-testing/terraform"
@@ -250,3 +251,150 @@ resource "juju_integration" "a" {
 }
 `, srcModelName, dstModelName, viaCIDRs)
 }
+
+func TestAcc_ResourceIntegrationWithMultipleConsumers_Stable(t *testing.T) {
+        if testingCloud != LXDCloudTesting {
+                t.Skip(t.Name() + " only runs with LXD")
+        }
+        srcModelName := acctest.RandomWithPrefix("tf-test-integration")
+        dstModelName := acctest.RandomWithPrefix("tf-test-integration-dst")
+
+        resource.Test(t, resource.TestCase{
+                PreCheck: func() { testAccPreCheck(t) },
+                ExternalProviders: map[string]resource.ExternalProvider{
+                        "juju": {
+                                VersionConstraint: TestProviderStableVersion,
+                                Source:            "juju/juju",
+                        },
+                },
+                CheckDestroy: testAccCheckIntegrationDestroy,
+                Steps: []resource.TestStep{
+                        {
+				Config: testAccResourceIntegrationMultipleConsumers(srcModelName, dstModelName),
+				ConfigVariables: config.Variables{
+					"enable-b1-consumer": config.BoolVariable(true),
+					"enable-b2-consumer": config.BoolVariable(true),
+			        },
+                                Check: resource.ComposeTestCheckFunc(
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "model", dstModelName),
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "id", fmt.Sprintf("%v:%v:%v", dstModelName, "a:db-admin", "b1:backend-db-admin")),
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "application.#", "2"),
+                                        resource.TestCheckTypeSetElemNestedAttrs("juju_integration.b1.0", "application.*", map[string]string{"name": "b1", "endpoint": "backend-db-admin"}),
+					resource.TestCheckResourceAttr("juju_integration.b2.0", "model", dstModelName),
+                                        resource.TestCheckResourceAttr("juju_integration.b2.0", "id", fmt.Sprintf("%v:%v:%v", dstModelName, "a:db-admin", "b2:backend-db-admin")),
+                                        resource.TestCheckResourceAttr("juju_integration.b2.0", "application.#", "2"),
+                                        resource.TestCheckTypeSetElemNestedAttrs("juju_integration.b2.0", "application.*", map[string]string{"name": "b2", "endpoint": "backend-db-admin"}),
+                                ),
+                        },
+			{
+                                Config: testAccResourceIntegrationMultipleConsumers(srcModelName, dstModelName),
+                                ConfigVariables: config.Variables{
+                                        "enable-b1-consumer": config.BoolVariable(true),
+                                        "enable-b2-consumer": config.BoolVariable(false),
+                                },
+                                Check: resource.ComposeTestCheckFunc(
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "model", dstModelName),
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "id", fmt.Sprintf("%v:%v:%v", dstModelName, "a:db-admin", "b1:backend-db-admin")),
+                                        resource.TestCheckResourceAttr("juju_integration.b1.0", "application.#", "2"),
+                                        resource.TestCheckTypeSetElemNestedAttrs("juju_integration.b1.0", "application.*", map[string]string{"name": "b1", "endpoint": "backend-db-admin"}),
+                                ),
+                        },
+			{
+                                Config: testAccResourceIntegrationMultipleConsumers(srcModelName, dstModelName),
+                                ConfigVariables: config.Variables{
+                                        "enable-b1-consumer": config.BoolVariable(false),
+                                        "enable-b2-consumer": config.BoolVariable(false),
+                                },
+                        },
+                },
+        })
+}
+
+// testAccResourceIntegrationWithMultipleConusmers generates a plan where a
+// two pgbouncer applications relates to postgresql:db-admin offer.
+func testAccResourceIntegrationMultipleConsumers(srcModelName string, dstModelName string) string {
+        return fmt.Sprintf(`
+resource "juju_model" "a" {
+        name = %q
+}
+
+resource "juju_application" "a" {
+        model = juju_model.a.name
+        name  = "a"
+
+        charm {
+                name    = "postgresql"
+                series  = "jammy"
+		channel = "14/edge"
+        }
+}
+
+resource "juju_offer" "a" {
+        model            = juju_model.a.name
+        application_name = juju_application.a.name
+        endpoint         = "db-admin"
+}
+
+resource "juju_model" "b" {
+        name = %q
+}
+
+resource "juju_application" "b1" {
+        model = juju_model.b.name
+        name  = "b1"
+
+        charm {
+                name   = "pgbouncer"
+                series = "focal"
+        }
+}
+
+resource "juju_integration" "b1" {
+	count = var.enable-b1-consumer ? 1 : 0
+        model = juju_model.b.name
+
+        application {
+                name     = juju_application.b1.name
+                endpoint = "backend-db-admin"
+        }
+
+        application {
+                offer_url = juju_offer.a.url
+        }
+}
+
+resource "juju_application" "b2" {
+        model = juju_model.b.name
+        name  = "b2"
+
+        charm {
+                name   = "pgbouncer"
+                series = "focal"
+        }
+}
+
+resource "juju_integration" "b2" {
+	count = var.enable-b2-consumer ? 1 : 0
+        model = juju_model.b.name
+
+        application {
+                name     = juju_application.b2.name
+                endpoint = "backend-db-admin"
+        }
+
+        application {
+                offer_url = juju_offer.a.url
+        }
+}
+
+variable "enable-b1-consumer" {
+	description = "Enable integration for b1 with offer"
+	default     = false
+}
+
+variable "enable-b2-consumer" {
+        description = "Enable integration for b2 with offer"
+        default     = false
+}
+`, srcModelName, dstModelName)
+}