add docker hot update management

internal/service/system_update_test.go

@@ -0,0 +1,77 @@
+package service
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestRenderSystemUpdateCommand(t *testing.T) {
+	status := SystemUpdateStatus{
+		Image:           "ghcr.io/shukebta/mediastation-go:latest",
+		WatchtowerImage: "containrrr/watchtower:latest",
+		ContainerID:     "abc123def456",
+		ContainerName:   "mediastation-go",
+	}
+
+	got := renderSystemUpdateCommand(
+		"docker run {{watchtower_image}} --run-once {{container}} --image {{image}} --id {{container_id}}",
+		status,
+	)
+	for _, marker := range []string{"{{watchtower_image}}", "{{container}}", "{{image}}", "{{container_id}}"} {
+		if strings.Contains(got, marker) {
+			t.Fatalf("command still contains marker %s: %q", marker, got)
+		}
+	}
+	for _, want := range []string{
+		"containrrr/watchtower:latest",
+		"mediastation-go",
+		"ghcr.io/shukebta/mediastation-go:latest",
+		"abc123def456",
+	} {
+		if !strings.Contains(got, want) {
+			t.Fatalf("command %q does not contain %q", got, want)
+		}
+	}
+}
+
+func TestParseContainerInspectLine(t *testing.T) {
+	name, imageID := parseContainerInspectLine("/mediastation-go|sha256:abc")
+	if name != "mediastation-go" || imageID != "sha256:abc" {
+		t.Fatalf("parse inspect line = %q %q", name, imageID)
+	}
+
+	name, imageID = parseContainerInspectLine("/fallback")
+	if name != "fallback" || imageID != "" {
+		t.Fatalf("parse fallback line = %q %q", name, imageID)
+	}
+}
+
+func TestDockerDigestHelpers(t *testing.T) {
+	const local = "sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+	const remote = "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
+
+	raw := `{"Descriptor":{"digest":"` + remote + `"}}`
+	if got := firstDockerDigest(raw); got != remote {
+		t.Fatalf("firstDockerDigest = %q, want %q", got, remote)
+	}
+	if got := compareDockerDigests("", remote); got != nil {
+		t.Fatalf("missing local digest should be unknown, got %#v", *got)
+	}
+	if got := compareDockerDigests(local, remote); got == nil || !*got {
+		t.Fatalf("different digests should mean update available, got %#v", got)
+	}
+	if got := compareDockerDigests(local, local); got == nil || *got {
+		t.Fatalf("same digests should mean no update, got %#v", got)
+	}
+}
+
+func TestSystemUpdateOutputDetailsKeepsTail(t *testing.T) {
+	lines := make([]string, 0, 14)
+	for i := 0; i < 14; i++ {
+		lines = append(lines, "line")
+	}
+	got := systemUpdateOutputDetails(strings.Join(lines, "\n"))
+	if len(got) != 12 {
+		t.Fatalf("details length = %d, want 12", len(got))
+	}
+}