Custom URLs: validated slugs with reserved words, uniqueness across pastes and cans

customslug.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var slugRE = regexp.MustCompile(`^[a-zA-Z0-9][a-zA-Z0-9-_]{0,63}$`)
+
+// reserved words that would collide with routes
+var reservedSlugs = map[string]bool{
+	"api": true, "raw": true, "can": true, "cans": true, "public": true,
+	"history": true, "static": true, "assets": true, "favicon.ico": true,
+	"new": true, "login": true, "logout": true, "admin": true, "settings": true,
+}
+
+var errInvalidSlug = errors.New("custom slug must be 1-64 chars: letters, digits, dash, underscore; must start with letter or digit")
+var errReservedSlug = errors.New("that slug is reserved")
+var errSlugTaken = errors.New("that slug is already taken")
+
+func ValidateCustomSlug(slug string) error {
+	if !slugRE.MatchString(slug) {
+		return errInvalidSlug
+	}
+	if reservedSlugs[strings.ToLower(slug)] {
+		return errReservedSlug
+	}
+	return nil
+}
+
+func (s *Store) SlugTaken(slug string) (bool, error) {
+	var n int
+	err := s.db.QueryRow(`SELECT COUNT(*) FROM pastes WHERE custom_slug = ? OR id = ?`, slug, slug).Scan(&n)
+	if err != nil {
+		return false, err
+	}
+	if n > 0 {
+		return true, nil
+	}
+	err = s.db.QueryRow(`SELECT COUNT(*) FROM paste_cans WHERE id = ?`, slug).Scan(&n)
+	if err != nil {
+		return false, err
+	}
+	return n > 0, nil
+}
+
+var _ = fmt.Sprintf // keep fmt if unused later