feat(discovery): parse Compose-managed labels

internal/discovery/labels.go

@@ -0,0 +1,71 @@
+package discovery
+
+import (
+	"fmt"
+	"strings"
+)
+
+// ComposeLabels captures the four Compose-managed labels we need
+// to drive a `docker compose pull`/`up -d` against the right stack.
+type ComposeLabels struct {
+	Project     string
+	Service     string
+	WorkingDir  string
+	ConfigFiles []string
+}
+
+const (
+	labelProject     = "com.docker.compose.project"
+	labelService     = "com.docker.compose.service"
+	labelWorkingDir  = "com.docker.compose.project.working_dir"
+	labelConfigFiles = "com.docker.compose.project.config_files"
+)
+
+// ParseComposeLabels extracts the Compose labels we need. Returns an
+// error naming the missing label if any required field is absent —
+// in practice this should only happen if the container was not
+// started by Compose.
+func ParseComposeLabels(labels map[string]string) (ComposeLabels, error) {
+	get := func(key string) (string, error) {
+		v, ok := labels[key]
+		if !ok || v == "" {
+			return "", fmt.Errorf("missing required label: %s", key)
+		}
+		return v, nil
+	}
+
+	project, err := get(labelProject)
+	if err != nil {
+		return ComposeLabels{}, err
+	}
+	service, err := get(labelService)
+	if err != nil {
+		return ComposeLabels{}, err
+	}
+	workingDir, err := get(labelWorkingDir)
+	if err != nil {
+		return ComposeLabels{}, err
+	}
+	configFilesRaw, err := get(labelConfigFiles)
+	if err != nil {
+		return ComposeLabels{}, err
+	}
+
+	files := strings.Split(configFilesRaw, ",")
+	for i, f := range files {
+		files[i] = strings.TrimSpace(f)
+	}
+
+	return ComposeLabels{
+		Project:     project,
+		Service:     service,
+		WorkingDir:  workingDir,
+		ConfigFiles: files,
+	}, nil
+}
+
+// HasOptIn reports whether the labels include the opt-in marker with
+// value "true" (exact, case-sensitive — anything else is excluded).
+func HasOptIn(labels map[string]string, key string) bool {
+	return labels[key] == "true"
+}

internal/discovery/labels_test.go

@@ -0,0 +1,88 @@
+package discovery_test
+
+import (
+	"testing"
+
+	"github.com/shcizo/package-updater/internal/discovery"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseComposeLabels_Success(t *testing.T) {
+	labels := map[string]string{
+		"com.docker.compose.project":                  "myapp-prod",
+		"com.docker.compose.service":                  "web",
+		"com.docker.compose.project.working_dir":      "/home/shcizo/self-hosted/myapp-prod",
+		"com.docker.compose.project.config_files":     "/home/shcizo/self-hosted/myapp-prod/docker-compose.yml",
+		"se.shcizo.auto-update":                       "true",
+	}
+	got, err := discovery.ParseComposeLabels(labels)
+	require.NoError(t, err)
+	require.Equal(t, "myapp-prod", got.Project)
+	require.Equal(t, "web", got.Service)
+	require.Equal(t, "/home/shcizo/self-hosted/myapp-prod", got.WorkingDir)
+	require.Equal(t, []string{"/home/shcizo/self-hosted/myapp-prod/docker-compose.yml"}, got.ConfigFiles)
+}
+
+func TestParseComposeLabels_MultipleConfigFiles(t *testing.T) {
+	labels := map[string]string{
+		"com.docker.compose.project":                  "myapp",
+		"com.docker.compose.service":                  "web",
+		"com.docker.compose.project.working_dir":      "/srv/myapp",
+		"com.docker.compose.project.config_files":     "/srv/myapp/docker-compose.yml,/srv/myapp/docker-compose.prod.yml",
+	}
+	got, err := discovery.ParseComposeLabels(labels)
+	require.NoError(t, err)
+	require.Equal(t, []string{
+		"/srv/myapp/docker-compose.yml",
+		"/srv/myapp/docker-compose.prod.yml",
+	}, got.ConfigFiles)
+}
+
+func TestParseComposeLabels_MissingFieldsError(t *testing.T) {
+	cases := []struct {
+		name    string
+		missing string
+		labels  map[string]string
+	}{
+		{"project", "com.docker.compose.project", map[string]string{
+			"com.docker.compose.service":              "web",
+			"com.docker.compose.project.working_dir":  "/x",
+			"com.docker.compose.project.config_files": "/x/y.yml",
+		}},
+		{"service", "com.docker.compose.service", map[string]string{
+			"com.docker.compose.project":              "p",
+			"com.docker.compose.project.working_dir":  "/x",
+			"com.docker.compose.project.config_files": "/x/y.yml",
+		}},
+		{"working_dir", "com.docker.compose.project.working_dir", map[string]string{
+			"com.docker.compose.project":              "p",
+			"com.docker.compose.service":              "web",
+			"com.docker.compose.project.config_files": "/x/y.yml",
+		}},
+		{"config_files", "com.docker.compose.project.config_files", map[string]string{
+			"com.docker.compose.project":             "p",
+			"com.docker.compose.service":             "web",
+			"com.docker.compose.project.working_dir": "/x",
+		}},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			_, err := discovery.ParseComposeLabels(c.labels)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), c.missing)
+		})
+	}
+}
+
+func TestHasOptIn(t *testing.T) {
+	require.True(t, discovery.HasOptIn(map[string]string{
+		"se.shcizo.auto-update": "true",
+	}, "se.shcizo.auto-update"))
+	require.False(t, discovery.HasOptIn(map[string]string{
+		"se.shcizo.auto-update": "false",
+	}, "se.shcizo.auto-update"))
+	require.False(t, discovery.HasOptIn(map[string]string{
+		"se.shcizo.auto-update": "TRUE",
+	}, "se.shcizo.auto-update"))
+	require.False(t, discovery.HasOptIn(map[string]string{}, "se.shcizo.auto-update"))
+}