fix: align build version source with tags and VERSION fallback

internal/version/version.go

@@ -0,0 +1,129 @@
+package version
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// BuildVersion can be injected at build time via -ldflags.
+// In release builds it should come from Git tag (e.g. v2.3.5).
+var BuildVersion = ""
+
+var (
+	currentOnce sync.Once
+	currentVal  string
+	sourceVal   string
+)
+
+func Current() (value string, source string) {
+	currentOnce.Do(func() {
+		if build := strings.TrimSpace(BuildVersion); build != "" {
+			currentVal = normalize(build)
+			sourceVal = "build-ldflags"
+			return
+		}
+		if fv := readVersionFile(); fv != "" {
+			currentVal = normalize(fv)
+			sourceVal = "file:VERSION"
+			return
+		}
+		currentVal = "dev"
+		sourceVal = "default"
+	})
+	return currentVal, sourceVal
+}
+
+func readVersionFile() string {
+	candidates := []string{"VERSION"}
+	if wd, err := os.Getwd(); err == nil {
+		candidates = append(candidates, filepath.Join(wd, "VERSION"))
+	}
+	if _, file, _, ok := runtime.Caller(0); ok {
+		repoRoot := filepath.Clean(filepath.Join(filepath.Dir(file), "../.."))
+		candidates = append(candidates, filepath.Join(repoRoot, "VERSION"))
+	}
+	seen := map[string]struct{}{}
+	for _, c := range candidates {
+		c = filepath.Clean(strings.TrimSpace(c))
+		if c == "" {
+			continue
+		}
+		if _, ok := seen[c]; ok {
+			continue
+		}
+		seen[c] = struct{}{}
+		b, err := os.ReadFile(c)
+		if err != nil {
+			continue
+		}
+		if v := strings.TrimSpace(string(b)); v != "" {
+			return v
+		}
+	}
+	return ""
+}
+
+func normalize(v string) string {
+	v = strings.TrimSpace(v)
+	if v == "" {
+		return ""
+	}
+	return strings.TrimPrefix(v, "v")
+}
+
+func Tag(v string) string {
+	v = normalize(v)
+	if v == "" || v == "dev" {
+		return v
+	}
+	return "v" + v
+}
+
+func Compare(a, b string) int {
+	pa := parse(normalize(a))
+	pb := parse(normalize(b))
+	for i := 0; i < 3; i++ {
+		if pa[i] < pb[i] {
+			return -1
+		}
+		if pa[i] > pb[i] {
+			return 1
+		}
+	}
+	return 0
+}
+
+func parse(v string) [3]int {
+	var out [3]int
+	parts := strings.SplitN(v, ".", 4)
+	for i := 0; i < 3 && i < len(parts); i++ {
+		n := readLeadingInt(parts[i])
+		out[i] = n
+	}
+	return out
+}
+
+func readLeadingInt(s string) int {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return 0
+	}
+	i := 0
+	for ; i < len(s); i++ {
+		if s[i] < '0' || s[i] > '9' {
+			break
+		}
+	}
+	if i == 0 {
+		return 0
+	}
+	n, err := strconv.Atoi(s[:i])
+	if err != nil {
+		return 0
+	}
+	return n
+}

internal/version/version_test.go

@@ -0,0 +1,24 @@
+package version
+
+import "testing"
+
+func TestNormalizeAndTag(t *testing.T) {
+	if got := normalize("v2.3.5"); got != "2.3.5" {
+		t.Fatalf("normalize failed: %q", got)
+	}
+	if got := Tag("2.3.5"); got != "v2.3.5" {
+		t.Fatalf("tag failed: %q", got)
+	}
+}
+
+func TestCompare(t *testing.T) {
+	if Compare("2.3.5", "2.3.5") != 0 {
+		t.Fatal("expected equal")
+	}
+	if Compare("2.3.5", "2.3.6") >= 0 {
+		t.Fatal("expected less")
+	}
+	if Compare("v2.10.0", "2.3.9") <= 0 {
+		t.Fatal("expected greater")
+	}
+}