Fix --region flag on stats usage to filter response by region

The Fastly API returns data for all regions regardless of the region
query parameter.

So, do client-side filtering for now.

Author: jedisct1

pkg/commands/stats/usage.go

@@ -78,6 +78,8 @@ func (c *UsageCommand) execPlain(out io.Writer, input *fastly.GetUsageInput) err
 		return fmt.Errorf("non-success response: %s", fastly.ToValue(resp.Message))
 	}
 
+	filterUsageByRegion(resp.Data, c.region)
+
 	switch c.formatFlag {
 	case "json":
 		return writeUsageJSON(out, resp.Data)
@@ -97,6 +99,8 @@ func (c *UsageCommand) execByService(out io.Writer, input *fastly.GetUsageInput)
 		return fmt.Errorf("non-success response: %s", fastly.ToValue(resp.Message))
 	}
 
+	filterUsageByServiceByRegion(resp.Data, c.region)
+
 	switch c.formatFlag {
 	case "json":
 		return writeUsageByServiceJSON(out, resp.Data)
@@ -182,6 +186,28 @@ func usageToMap(data fastly.RegionsUsage) map[string]any {
 	return result
 }
 
+func filterUsageByRegion(data *fastly.RegionsUsage, region string) {
+	if region == "" || data == nil {
+		return
+	}
+	for k := range *data {
+		if k != region {
+			delete(*data, k)
+		}
+	}
+}
+
+func filterUsageByServiceByRegion(data *fastly.ServicesByRegionsUsage, region string) {
+	if region == "" || data == nil {
+		return
+	}
+	for k := range *data {
+		if k != region {
+			delete(*data, k)
+		}
+	}
+}
+
 func usageEntry(u *fastly.Usage) map[string]any {
 	if u == nil {
 		return map[string]any{

pkg/commands/stats/usage_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"strings"
 	"testing"
 
 	"github.com/fastly/go-fastly/v13/fastly"
@@ -22,6 +23,7 @@ func TestUsage(t *testing.T) {
 		api        mock.API
 		wantError  string
 		wantOutput string
+		wantAbsent string
 	}{
 		{
 			name:       "success plain",
@@ -59,6 +61,20 @@ func TestUsage(t *testing.T) {
 			api:        mock.API{GetUsageFn: getUsageWithNilEntry},
 			wantOutput: "Region: europe",
 		},
+		{
+			name:       "region filter plain",
+			args:       args("stats usage --region=europe"),
+			api:        mock.API{GetUsageFn: getUsageMultiRegion},
+			wantOutput: "Region: europe",
+			wantAbsent: "usa",
+		},
+		{
+			name:       "region filter by-service",
+			args:       args("stats usage --by-service --region=europe"),
+			api:        mock.API{GetUsageByServiceFn: getUsageByServiceMultiRegion},
+			wantOutput: "Region: europe",
+			wantAbsent: "usa",
+		},
 		{
 			name:      "non-success status",
 			args:      args("stats usage"),
@@ -83,6 +99,9 @@ func TestUsage(t *testing.T) {
 			err := app.Run(tc.args, nil)
 			testutil.AssertErrorContains(t, err, tc.wantError)
 			testutil.AssertStringContains(t, stdout.String(), tc.wantOutput)
+			if tc.wantAbsent != "" && strings.Contains(stdout.String(), tc.wantAbsent) {
+				t.Errorf("output should not contain %q, got: %s", tc.wantAbsent, stdout.String())
+			}
 		})
 	}
 }
@@ -138,6 +157,46 @@ func getUsageWithNilEntry(_ context.Context, _ *fastly.GetUsageInput) (*fastly.U
 	}, nil
 }
 
+func getUsageMultiRegion(_ context.Context, _ *fastly.GetUsageInput) (*fastly.UsageResponse, error) {
+	return &fastly.UsageResponse{
+		Status: fastly.ToPointer("success"),
+		Data: &fastly.RegionsUsage{
+			"usa": &fastly.Usage{
+				Bandwidth:       fastly.ToPointer(uint64(1000)),
+				Requests:        fastly.ToPointer(uint64(500)),
+				ComputeRequests: fastly.ToPointer(uint64(100)),
+			},
+			"europe": &fastly.Usage{
+				Bandwidth:       fastly.ToPointer(uint64(2000)),
+				Requests:        fastly.ToPointer(uint64(300)),
+				ComputeRequests: fastly.ToPointer(uint64(50)),
+			},
+		},
+	}, nil
+}
+
+func getUsageByServiceMultiRegion(_ context.Context, _ *fastly.GetUsageInput) (*fastly.UsageByServiceResponse, error) {
+	return &fastly.UsageByServiceResponse{
+		Status: fastly.ToPointer("success"),
+		Data: &fastly.ServicesByRegionsUsage{
+			"usa": &fastly.ServicesUsage{
+				"svc123": &fastly.Usage{
+					Bandwidth:       fastly.ToPointer(uint64(1000)),
+					Requests:        fastly.ToPointer(uint64(500)),
+					ComputeRequests: fastly.ToPointer(uint64(100)),
+				},
+			},
+			"europe": &fastly.ServicesUsage{
+				"svc456": &fastly.Usage{
+					Bandwidth:       fastly.ToPointer(uint64(2000)),
+					Requests:        fastly.ToPointer(uint64(300)),
+					ComputeRequests: fastly.ToPointer(uint64(50)),
+				},
+			},
+		},
+	}, nil
+}
+
 func getUsageNonSuccess(_ context.Context, _ *fastly.GetUsageInput) (*fastly.UsageResponse, error) {
 	return &fastly.UsageResponse{
 		Status:  fastly.ToPointer("error"),