fix(themehost): keep the active theme first and sort the rest naturally

internal/themehost/manager.go

@@ -86,7 +86,7 @@ func (m *Manager) List(ctx context.Context) ([]Installed, error) {
 			Active: true,
 		})
 	}
-	return installed, nil
+	return ordered(installed), nil
 }
 
 // mark labels each theme with the operator's choice and the one answering, reporting the choice found.

internal/themehost/manager_list_order_test.go

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package themehost_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/gopherium/gophenberg/internal/themehost"
+)
+
+// WordPress keeps the active theme on top and sorts the rest with case ignored
+// and numbers in natural order. Sorting by raw bytes put a capitalised or
+// accented name out of place and read theme10 before theme2 (#509).
+func TestManagerListPutsTheActiveThemeFirstAndSortsTheRestNaturally(t *testing.T) {
+	t.Parallel()
+
+	settings := newSettings()
+	settings.values[themehost.ActiveKey] = "theme2"
+	manager := managerOver(t, settings, "", "Zoe", "theme10", "alba", "Álvaro", "theme2")
+
+	installed, err := manager.List(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := make([]string, len(installed))
+	for i, theme := range installed {
+		got[i] = theme.Name
+	}
+	want := []string{"theme2", "alba", "theme10", "Zoe", "Álvaro"}
+	if len(got) != len(want) {
+		t.Fatalf("listed %d themes, want %d: %v", len(got), len(want), got)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("theme order = %v, want %v", got, want)
+		}
+	}
+	if !installed[0].Active {
+		t.Fatalf("the first theme is %q, not the active one", installed[0].Name)
+	}
+}

internal/themehost/order.go

@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package themehost
+
+import (
+	"sort"
+	"unicode"
+)
+
+// ordered puts the active theme first and sorts the rest by name with case
+// ignored and digit runs compared by value. WordPress builds its themes screen
+// with wp_prepare_themes_for_js, which keeps the active theme on top and sorts
+// the rest with WP_Theme::sort_by_name; raw byte order moved a capitalised or
+// accented name out of place and read theme10 before theme2 (#509).
+func ordered(themes []Installed) []Installed {
+	sort.SliceStable(themes, func(i, j int) bool {
+		if themes[i].Active != themes[j].Active {
+			return themes[i].Active
+		}
+		return naturalLess(themes[i].Name, themes[j].Name)
+	})
+	return themes
+}
+
+// naturalLess compares two names the way PHP's strnatcasecmp does: letters
+// case-insensitively, and each run of digits by its numeric value so theme2
+// comes before theme10.
+func naturalLess(a, b string) bool { return naturalCompare(a, b) < 0 }
+
+func naturalCompare(a, b string) int {
+	ar, br := []rune(a), []rune(b)
+	i, j := 0, 0
+	for i < len(ar) && j < len(br) {
+		if isDigit(ar[i]) && isDigit(br[j]) {
+			ai, bj := i, j
+			for ai < len(ar) && isDigit(ar[ai]) {
+				ai++
+			}
+			for bj < len(br) && isDigit(br[bj]) {
+				bj++
+			}
+			if c := compareDigits(string(ar[i:ai]), string(br[j:bj])); c != 0 {
+				return c
+			}
+			i, j = ai, bj
+			continue
+		}
+		al, bl := unicode.ToLower(ar[i]), unicode.ToLower(br[j])
+		if al != bl {
+			if al < bl {
+				return -1
+			}
+			return 1
+		}
+		i++
+		j++
+	}
+	switch {
+	case i < len(ar):
+		return 1
+	case j < len(br):
+		return -1
+	}
+	return 0
+}
+
+func compareDigits(a, b string) int {
+	at, bt := trimLeadingZeros(a), trimLeadingZeros(b)
+	if len(at) != len(bt) {
+		if len(at) < len(bt) {
+			return -1
+		}
+		return 1
+	}
+	if at != bt {
+		if at < bt {
+			return -1
+		}
+		return 1
+	}
+	if len(a) != len(b) {
+		if len(a) < len(b) {
+			return -1
+		}
+		return 1
+	}
+	return 0
+}
+
+func trimLeadingZeros(s string) string {
+	for len(s) > 1 && s[0] == '0' {
+		s = s[1:]
+	}
+	return s
+}
+
+func isDigit(r rune) bool { return r >= '0' && r <= '9' }