View switching feature

pagesettings.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// handleSettings persists the listing view/sort/order to the folder's
+// .page-settings file. Values are validated against the allowed sets (unknown
+// values fall back to defaults). Triggered by POST /{path}?settings.
+func (h *handler) handleSettings(w http.ResponseWriter, r *http.Request, urlPath, fsPath string) {
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "bad request", http.StatusBadRequest)
+		return
+	}
+	view := validateView(r.FormValue("view"))
+	sortKey := validateSort(r.FormValue("sort"))
+	order := validateOrder(r.FormValue("order"))
+
+	if err := writePageSettings(fsPath, view, sortKey, order); err != nil {
+		http.Error(w, "write failed: "+err.Error(), http.StatusInternalServerError)
+		return
+	}
+	http.Redirect(w, r, urlPath, http.StatusSeeOther)
+}
+
+// writePageSettings performs a read-modify-write of <dir>/.page-settings,
+// updating the view/sort/order lines while preserving every other line
+// (other keys, comments, blank lines, ordering) verbatim. Missing keys are
+// appended. The write is atomic (temp file + rename).
+func writePageSettings(dir, view, sortKey, order string) error {
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return err
+	}
+	p := filepath.Join(dir, ".page-settings")
+	existing, err := os.ReadFile(p)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	updated := updateSettingsLines(existing, view, sortKey, order)
+	return writeFileAtomic(p, updated, 0644)
+}
+
+// updateSettingsLines rewrites the view/sort/order lines in existing while
+// leaving all other lines untouched. Every occurrence of a known key is
+// updated (so the reader's last-wins parse stays consistent); keys absent from
+// the file are appended in a stable order. The result always ends in a newline.
+func updateSettingsLines(existing []byte, view, sortKey, order string) []byte {
+	targets := map[string]string{"view": view, "sort": sortKey, "order": order}
+	appendOrder := []string{"view", "sort", "order"}
+	seen := map[string]bool{}
+
+	var lines []string
+	if len(existing) > 0 {
+		s := string(existing)
+		s = strings.TrimSuffix(s, "\n")
+		lines = strings.Split(s, "\n")
+	}
+
+	for i, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		eq := strings.IndexByte(line, '=')
+		if eq < 0 {
+			continue
+		}
+		key := strings.TrimSpace(line[:eq])
+		if val, ok := targets[key]; ok {
+			lines[i] = key + " = " + val
+			seen[key] = true
+		}
+	}
+
+	for _, k := range appendOrder {
+		if !seen[k] {
+			lines = append(lines, k+" = "+targets[k])
+		}
+	}
+
+	out := strings.Join(lines, "\n")
+	if out != "" {
+		out += "\n"
+	}
+	return []byte(out)
+}