New Resource: aws_s3outposts_endpoint

Reference: #15412
Reference: #15417

Output from acceptance testing:

```
--- PASS: TestAccAWSS3OutpostsEndpoint_basic (193.07s)
--- PASS: TestAccAWSS3OutpostsEndpoint_disappears (193.29s)
```

aws/internal/service/s3outposts/finder/finder.go

@@ -0,0 +1,29 @@
+package finder
+
+import (
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/s3outposts"
+)
+
+// Endpoint returns matching Endpoint by ARN.
+func Endpoint(conn *s3outposts.S3Outposts, endpointArn string) (*s3outposts.Endpoint, error) {
+	input := &s3outposts.ListEndpointsInput{}
+	var result *s3outposts.Endpoint
+
+	err := conn.ListEndpointsPages(input, func(page *s3outposts.ListEndpointsOutput, lastPage bool) bool {
+		if page == nil {
+			return !lastPage
+		}
+
+		for _, endpoint := range page.Endpoints {
+			if aws.StringValue(endpoint.EndpointArn) == endpointArn {
+				result = endpoint
+				return false
+			}
+		}
+
+		return !lastPage
+	})
+
+	return result, err
+}

aws/internal/service/s3outposts/waiter/status.go

@@ -0,0 +1,30 @@
+package waiter
+
+import (
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/s3outposts"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/s3outposts/finder"
+)
+
+const (
+	EndpointStatusNotFound = "NotFound"
+	EndpointStatusUnknown  = "Unknown"
+)
+
+// EndpointStatus fetches the Endpoint and its Status
+func EndpointStatus(conn *s3outposts.S3Outposts, endpointArn string) resource.StateRefreshFunc {
+	return func() (interface{}, string, error) {
+		endpoint, err := finder.Endpoint(conn, endpointArn)
+
+		if err != nil {
+			return nil, EndpointStatusUnknown, err
+		}
+
+		if endpoint == nil {
+			return nil, EndpointStatusNotFound, nil
+		}
+
+		return endpoint, aws.StringValue(endpoint.Status), nil
+	}
+}

aws/internal/service/s3outposts/waiter/waiter.go

@@ -0,0 +1,37 @@
+package waiter
+
+import (
+	"time"
+
+	"github.com/aws/aws-sdk-go/service/s3outposts"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
+)
+
+const (
+	// API model constant is incorrectly AVAILABLE
+	EndpointStatusAvailable = "Available"
+
+	// API model constant is incorrectly PENDING
+	EndpointStatusPending = "Pending"
+
+	// Maximum amount of time to wait for Endpoint to return Available on creation
+	EndpointStatusCreatedTimeout = 5 * time.Minute
+)
+
+// EndpointStatusCreated waits for Endpoint to return Available
+func EndpointStatusCreated(conn *s3outposts.S3Outposts, endpointArn string) (*s3outposts.Endpoint, error) {
+	stateConf := &resource.StateChangeConf{
+		Pending: []string{EndpointStatusPending, EndpointStatusNotFound},
+		Target:  []string{EndpointStatusAvailable},
+		Refresh: EndpointStatus(conn, endpointArn),
+		Timeout: EndpointStatusCreatedTimeout,
+	}
+
+	outputRaw, err := stateConf.WaitForState()
+
+	if v, ok := outputRaw.(*s3outposts.Endpoint); ok {
+		return v, err
+	}
+
+	return nil, err
+}

aws/provider.go

@@ -854,6 +854,7 @@ func Provider() *schema.Provider {
 			"aws_s3_bucket_notification":                              resourceAwsS3BucketNotification(),
 			"aws_s3_bucket_metric":                                    resourceAwsS3BucketMetric(),
 			"aws_s3_bucket_inventory":                                 resourceAwsS3BucketInventory(),
+			"aws_s3outposts_endpoint":                                 resourceAwsS3OutpostsEndpoint(),
 			"aws_security_group":                                      resourceAwsSecurityGroup(),
 			"aws_network_interface_sg_attachment":                     resourceAwsNetworkInterfaceSGAttachment(),
 			"aws_default_security_group":                              resourceAwsDefaultSecurityGroup(),

aws/resource_aws_s3outposts_endpoint.go

@@ -0,0 +1,212 @@
+package aws
+
+import (
+	"fmt"
+	"log"
+	"strings"
+	"time"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/arn"
+	"github.com/aws/aws-sdk-go/service/s3outposts"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/s3outposts/finder"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/s3outposts/waiter"
+)
+
+func resourceAwsS3OutpostsEndpoint() *schema.Resource {
+	return &schema.Resource{
+		Create: resourceAwsS3OutpostsEndpointCreate,
+		Read:   resourceAwsS3OutpostsEndpointRead,
+		Delete: resourceAwsS3OutpostsEndpointDelete,
+
+		Importer: &schema.ResourceImporter{
+			State: resourceAwsS3OutpostsEndpointImportState,
+		},
+
+		Schema: map[string]*schema.Schema{
+			"arn": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+			"cidr_block": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+			"creation_time": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+			"network_interfaces": {
+				Type:     schema.TypeSet,
+				Computed: true,
+				Elem: &schema.Resource{
+					Schema: map[string]*schema.Schema{
+						"network_interface_id": {
+							Type:     schema.TypeString,
+							Computed: true,
+						},
+					},
+				},
+			},
+			"outpost_id": {
+				Type:         schema.TypeString,
+				Required:     true,
+				ForceNew:     true,
+				ValidateFunc: validation.StringIsNotEmpty,
+			},
+			"security_group_id": {
+				Type:         schema.TypeString,
+				Required:     true,
+				ForceNew:     true,
+				ValidateFunc: validation.StringIsNotEmpty,
+			},
+			"subnet_id": {
+				Type:         schema.TypeString,
+				Required:     true,
+				ForceNew:     true,
+				ValidateFunc: validation.StringIsNotEmpty,
+			},
+		},
+	}
+}
+
+func resourceAwsS3OutpostsEndpointCreate(d *schema.ResourceData, meta interface{}) error {
+	conn := meta.(*AWSClient).s3outpostsconn
+
+	input := &s3outposts.CreateEndpointInput{
+		OutpostId:       aws.String(d.Get("outpost_id").(string)),
+		SecurityGroupId: aws.String(d.Get("security_group_id").(string)),
+		SubnetId:        aws.String(d.Get("subnet_id").(string)),
+	}
+
+	output, err := conn.CreateEndpoint(input)
+
+	if err != nil {
+		return fmt.Errorf("error creating S3 Outposts Endpoint: %w", err)
+	}
+
+	if output == nil {
+		return fmt.Errorf("error creating S3 Outposts Endpoint: empty response")
+	}
+
+	d.SetId(aws.StringValue(output.EndpointArn))
+
+	if _, err := waiter.EndpointStatusCreated(conn, d.Id()); err != nil {
+		return fmt.Errorf("error waiting for S3 Outposts Endpoint (%s) to become available: %w", d.Id(), err)
+	}
+
+	return resourceAwsS3OutpostsEndpointRead(d, meta)
+}
+
+func resourceAwsS3OutpostsEndpointRead(d *schema.ResourceData, meta interface{}) error {
+	conn := meta.(*AWSClient).s3outpostsconn
+
+	endpoint, err := finder.Endpoint(conn, d.Id())
+
+	if err != nil {
+		return fmt.Errorf("error reading S3 Outposts Endpoint (%s): %w", d.Id(), err)
+	}
+
+	if endpoint == nil {
+		if d.IsNewResource() {
+			return fmt.Errorf("error reading S3 Outposts Endpoint (%s): not found after creation", d.Id())
+		}
+
+		log.Printf("[WARN] S3 Outposts Endpoint (%s) not found, removing from state", d.Id())
+		d.SetId("")
+		return nil
+	}
+
+	d.Set("arn", endpoint.EndpointArn)
+	d.Set("cidr_block", endpoint.CidrBlock)
+
+	if endpoint.CreationTime != nil {
+		d.Set("creation_time", aws.TimeValue(endpoint.CreationTime).Format(time.RFC3339))
+	}
+
+	if err := d.Set("network_interfaces", flattenS3outpostsNetworkInterfaces(endpoint.NetworkInterfaces)); err != nil {
+		return fmt.Errorf("error setting network_interfaces: %w", err)
+	}
+
+	d.Set("outpost_id", endpoint.OutpostsId)
+
+	return nil
+}
+
+func resourceAwsS3OutpostsEndpointDelete(d *schema.ResourceData, meta interface{}) error {
+	conn := meta.(*AWSClient).s3outpostsconn
+
+	parsedArn, err := arn.Parse(d.Id())
+
+	if err != nil {
+		return fmt.Errorf("error parsing S3 Outposts Endpoint ARN (%s): %w", d.Id(), err)
+	}
+
+	// ARN resource format: outpost/<outpost-id>/endpoint/<endpoint-id>
+	arnResourceParts := strings.Split(parsedArn.Resource, "/")
+
+	if parsedArn.AccountID == "" || len(arnResourceParts) != 4 {
+		return fmt.Errorf("error parsing S3 Outposts Endpoint ARN (%s): unknown format", d.Id())
+	}
+
+	input := &s3outposts.DeleteEndpointInput{
+		EndpointId: aws.String(arnResourceParts[3]),
+		OutpostId:  aws.String(arnResourceParts[1]),
+	}
+
+	_, err = conn.DeleteEndpoint(input)
+
+	if err != nil {
+		return fmt.Errorf("error deleting S3 Outposts Endpoint (%s): %w", d.Id(), err)
+	}
+
+	return nil
+}
+
+func resourceAwsS3OutpostsEndpointImportState(d *schema.ResourceData, meta interface{}) ([]*schema.ResourceData, error) {
+	idParts := strings.Split(d.Id(), ",")
+
+	if len(idParts) != 3 || idParts[0] == "" || idParts[1] == "" || idParts[2] == "" {
+		return nil, fmt.Errorf("unexpected format of ID (%s), expected ENDPOINT-ARN,SECURITY-GROUP-ID,SUBNET-ID", d.Id())
+	}
+
+	endpointArn := idParts[0]
+	securityGroupId := idParts[1]
+	subnetId := idParts[2]
+
+	d.SetId(endpointArn)
+	d.Set("security_group_id", securityGroupId)
+	d.Set("subnet_id", subnetId)
+
+	return []*schema.ResourceData{d}, nil
+}
+
+func flattenS3outpostsNetworkInterfaces(apiObjects []*s3outposts.NetworkInterface) []interface{} {
+	var tfList []interface{}
+
+	for _, apiObject := range apiObjects {
+		if apiObject == nil {
+			continue
+		}
+
+		tfList = append(tfList, flattenS3outpostsNetworkInterface(apiObject))
+	}
+
+	return tfList
+}
+
+func flattenS3outpostsNetworkInterface(apiObject *s3outposts.NetworkInterface) map[string]interface{} {
+	if apiObject == nil {
+		return nil
+	}
+
+	tfMap := map[string]interface{}{}
+
+	if v := apiObject.NetworkInterfaceId; v != nil {
+		tfMap["network_interface_id"] = aws.StringValue(v)
+	}
+
+	return tfMap
+}