fix(status): correct external disk capacity totals

cmd/status/metrics_disk_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"context"
+	"errors"
 	"testing"
 
 	"github.com/shirou/gopsutil/v4/disk"
@@ -58,3 +60,91 @@ func TestShouldSkipDiskPartition(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractPlistUint(t *testing.T) {
+	t.Run("prefers first matching key", func(t *testing.T) {
+		raw := `<plist><dict>
+<key>TotalSize</key><integer>1099511627776</integer>
+<key>DiskSize</key><integer>2199023255552</integer>
+</dict></plist>`
+
+		got, err := extractPlistUint(raw, "TotalSize", "DiskSize")
+		if err != nil {
+			t.Fatalf("extractPlistUint() error = %v", err)
+		}
+		if got != 1099511627776 {
+			t.Fatalf("extractPlistUint() = %d, want %d", got, uint64(1099511627776))
+		}
+	})
+
+	t.Run("falls back to later keys", func(t *testing.T) {
+		raw := `<plist><dict><key>DiskSize</key><integer>1099511627776</integer></dict></plist>`
+
+		got, err := extractPlistUint(raw, "TotalSize", "DiskSize", "Size")
+		if err != nil {
+			t.Fatalf("extractPlistUint() error = %v", err)
+		}
+		if got != 1099511627776 {
+			t.Fatalf("extractPlistUint() = %d, want %d", got, uint64(1099511627776))
+		}
+	})
+
+	t.Run("returns error for malformed integer", func(t *testing.T) {
+		raw := `<plist><dict><key>TotalSize</key><integer>oops</integer></dict></plist>`
+
+		if _, err := extractPlistUint(raw, "TotalSize"); err == nil {
+			t.Fatalf("extractPlistUint() expected parse error")
+		}
+	})
+}
+
+func TestCorrectDiskTotalBytes(t *testing.T) {
+	origRunCmd := runCmd
+	origCommandExists := commandExists
+	t.Cleanup(func() {
+		runCmd = origRunCmd
+		commandExists = origCommandExists
+	})
+
+	commandExists = func(name string) bool {
+		return name == "diskutil"
+	}
+
+	t.Run("uses diskutil total when meaningfully different", func(t *testing.T) {
+		runCmd = func(ctx context.Context, name string, args ...string) (string, error) {
+			if name != "diskutil" {
+				return "", errors.New("unexpected command")
+			}
+			return `<plist><dict><key>TotalSize</key><integer>1099511627776</integer></dict></plist>`, nil
+		}
+
+		got := correctDiskTotalBytes("/Volumes/Backup", 2199023255552)
+		if got != 1099511627776 {
+			t.Fatalf("correctDiskTotalBytes() = %d, want %d", got, uint64(1099511627776))
+		}
+	})
+
+	t.Run("keeps raw total for small differences", func(t *testing.T) {
+		runCmd = func(ctx context.Context, name string, args ...string) (string, error) {
+			return `<plist><dict><key>TotalSize</key><integer>1000500000000</integer></dict></plist>`, nil
+		}
+
+		const rawTotal = 1000000000000
+		got := correctDiskTotalBytes("/Volumes/FastSSD", rawTotal)
+		if got != rawTotal {
+			t.Fatalf("correctDiskTotalBytes() = %d, want %d", got, uint64(rawTotal))
+		}
+	})
+
+	t.Run("keeps raw total when diskutil fails", func(t *testing.T) {
+		runCmd = func(ctx context.Context, name string, args ...string) (string, error) {
+			return "", errors.New("diskutil failed")
+		}
+
+		const rawTotal = 1099511627776
+		got := correctDiskTotalBytes("/Volumes/FastSSD", rawTotal)
+		if got != rawTotal {
+			t.Fatalf("correctDiskTotalBytes() = %d, want %d", got, uint64(rawTotal))
+		}
+	})
+}