aws/arn: Package for parsing and producing ARNs

aws/arn/arn.go

@@ -0,0 +1,86 @@
+// Package arn provides a parser for interacting with Amazon Resource Names.
+package arn
+
+import (
+	"errors"
+	"strings"
+)
+
+const (
+	arnDelimiter = ":"
+	arnSections  = 6
+	arnPrefix    = "arn:"
+
+	// zero-indexed
+	sectionPartition = 1
+	sectionService   = 2
+	sectionRegion    = 3
+	sectionAccountID = 4
+	sectionResource  = 5
+
+	// errors
+	invalidPrefix   = "arn: invalid prefix"
+	invalidSections = "arn: not enough sections"
+)
+
+// ARN captures the individual fields of an Amazon Resource Name.
+// See http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html for more information.
+type ARN struct {
+	// The partition that the resource is in. For standard AWS regions, the partition is "aws". If you have resources in
+	// other partitions, the partition is "aws-partitionname". For example, the partition for resources in the China
+	// (Beijing) region is "aws-cn".
+	Partition string
+
+	// The service namespace that identifies the AWS product (for example, Amazon S3, IAM, or Amazon RDS). For a list of
+	// namespaces, see
+	// http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html#genref-aws-service-namespaces.
+	Service string
+
+	// The region the resource resides in. Note that the ARNs for some resources do not require a region, so this
+	// component might be omitted.
+	Region string
+
+	// The ID of the AWS account that owns the resource, without the hyphens. For example, 123456789012. Note that the
+	// ARNs for some resources don't require an account number, so this component might be omitted.
+	AccountID string
+
+	// The content of this part of the ARN varies by service. It often includes an indicator of the type of resource —
+	// for example, an IAM user or Amazon RDS database - followed by a slash (/) or a colon (:), followed by the
+	// resource name itself. Some services allows paths for resource names, as described in
+	// http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html#arns-paths.
+	Resource string
+}
+
+// Parse parses an ARN into its constituent parts.
+//
+// Some example ARNs:
+// arn:aws:elasticbeanstalk:us-east-1:123456789012:environment/My App/MyEnvironment
+// arn:aws:iam::123456789012:user/David
+// arn:aws:rds:eu-west-1:123456789012:db:mysql-db
+// arn:aws:s3:::my_corporate_bucket/exampleobject.png
+func Parse(arn string) (ARN, error) {
+	if !strings.HasPrefix(arn, arnPrefix) {
+		return ARN{}, errors.New(invalidPrefix)
+	}
+	sections := strings.SplitN(arn, arnDelimiter, arnSections)
+	if len(sections) != arnSections {
+		return ARN{}, errors.New(invalidSections)
+	}
+	return ARN{
+		Partition: sections[sectionPartition],
+		Service:   sections[sectionService],
+		Region:    sections[sectionRegion],
+		AccountID: sections[sectionAccountID],
+		Resource:  sections[sectionResource],
+	}, nil
+}
+
+// String returns the canonical representation of the ARN
+func (arn ARN) String() string {
+	return arnPrefix +
+		arn.Partition + arnDelimiter +
+		arn.Service + arnDelimiter +
+		arn.Region + arnDelimiter +
+		arn.AccountID + arnDelimiter +
+		arn.Resource
+}

aws/arn/arn_test.go

@@ -0,0 +1,90 @@
+// +build go1.7
+
+package arn
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestParseARN(t *testing.T) {
+	cases := []struct {
+		input string
+		arn   ARN
+		err   error
+	}{
+		{
+			input: "invalid",
+			err:   errors.New(invalidPrefix),
+		},
+		{
+			input: "arn:nope",
+			err:   errors.New(invalidSections),
+		},
+		{
+			input: "arn:aws:ecr:us-west-2:123456789012:repository/foo/bar",
+			arn: ARN{
+				Partition: "aws",
+				Service:   "ecr",
+				Region:    "us-west-2",
+				AccountID: "123456789012",
+				Resource:  "repository/foo/bar",
+			},
+		},
+		{
+			input: "arn:aws:elasticbeanstalk:us-east-1:123456789012:environment/My App/MyEnvironment",
+			arn: ARN{
+				Partition: "aws",
+				Service:   "elasticbeanstalk",
+				Region:    "us-east-1",
+				AccountID: "123456789012",
+				Resource:  "environment/My App/MyEnvironment",
+			},
+		},
+		{
+			input: "arn:aws:iam::123456789012:user/David",
+			arn: ARN{
+				Partition: "aws",
+				Service:   "iam",
+				Region:    "",
+				AccountID: "123456789012",
+				Resource:  "user/David",
+			},
+		},
+		{
+			input: "arn:aws:rds:eu-west-1:123456789012:db:mysql-db",
+			arn: ARN{
+				Partition: "aws",
+				Service:   "rds",
+				Region:    "eu-west-1",
+				AccountID: "123456789012",
+				Resource:  "db:mysql-db",
+			},
+		},
+		{
+			input: "arn:aws:s3:::my_corporate_bucket/exampleobject.png",
+			arn: ARN{
+				Partition: "aws",
+				Service:   "s3",
+				Region:    "",
+				AccountID: "",
+				Resource:  "my_corporate_bucket/exampleobject.png",
+			},
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.input, func(t *testing.T) {
+			spec, err := Parse(tc.input)
+			if tc.arn != spec {
+				t.Errorf("Expected %q to parse as %v, but got %v", tc.input, tc.arn, spec)
+			}
+			if err == nil && tc.err != nil {
+				t.Errorf("Expected err to be %v, but got nil", tc.err)
+			} else if err != nil && tc.err == nil {
+				t.Errorf("Expected err to be nil, but got %v", err)
+			} else if err != nil && tc.err != nil && err.Error() != tc.err.Error() {
+				t.Errorf("Expected err to be %v, but got %v", tc.err, err)
+			}
+		})
+	}
+}