d/lb_listener: get listener from load balancer and listener port

aws/data_source_aws_lb_listener.go

@@ -1,24 +1,34 @@
 package aws
 
-import "github.com/hashicorp/terraform/helper/schema"
+import (
+	"errors"
+	"fmt"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/elbv2"
+	"github.com/hashicorp/terraform/helper/schema"
+)
 
 func dataSourceAwsLbListener() *schema.Resource {
 	return &schema.Resource{
 		Read: dataSourceAwsLbListenerRead,
 
 		Schema: map[string]*schema.Schema{
 			"arn": {
-				Type:     schema.TypeString,
-				Required: true,
+				Type:          schema.TypeString,
+				Optional:      true,
+				ConflictsWith: []string{"load_balancer_arn", "port"},
 			},
 
 			"load_balancer_arn": {
-				Type:     schema.TypeString,
-				Computed: true,
+				Type:          schema.TypeString,
+				Optional:      true,
+				ConflictsWith: []string{"arn"},
 			},
 			"port": {
-				Type:     schema.TypeInt,
-				Computed: true,
+				Type:          schema.TypeInt,
+				Optional:      true,
+				ConflictsWith: []string{"arn"},
 			},
 
 			"protocol": {
@@ -57,6 +67,34 @@ func dataSourceAwsLbListener() *schema.Resource {
 }
 
 func dataSourceAwsLbListenerRead(d *schema.ResourceData, meta interface{}) error {
-	d.SetId(d.Get("arn").(string))
-	return resourceAwsLbListenerRead(d, meta)
+	if _, ok := d.GetOk("arn"); ok {
+		d.SetId(d.Get("arn").(string))
+		//log.Printf("[DEBUG] read listener %s", d.Get("arn").(string))
+		return resourceAwsLbListenerRead(d, meta)
+	}
+
+	conn := meta.(*AWSClient).elbv2conn
+	lbArn, lbOk := d.GetOk("load_balancer_arn")
+	port, portOk := d.GetOk("port")
+	if !lbOk || !portOk {
+		return errors.New("both load_balancer_arn and port must be set")
+	}
+	resp, err := conn.DescribeListeners(&elbv2.DescribeListenersInput{
+		LoadBalancerArn: aws.String(lbArn.(string)),
+	})
+	if err != nil {
+		return err
+	}
+	if len(resp.Listeners) == 0 {
+		return fmt.Errorf("[DEBUG] no listener exists for load balancer: %s", lbArn)
+	}
+	for _, listener := range resp.Listeners {
+		if *listener.Port == int64(port.(int)) {
+			//log.Printf("[DEBUG] get listener arn for %s:%s: %s", lbArn, port, *listener.Port)
+			d.SetId(*listener.ListenerArn)
+			return resourceAwsLbListenerRead(d, meta)
+		}
+	}
+
+	return errors.New("failed to get listener arn with given arguments")
 }