add package pathrouter

1 files changed, 34 insertions, 0 deletions

diff --git a/pathrouter/element.go b/pathrouter/element.go
new file mode 100644
index 0000000..9512924
--- /dev/null
+++ b/pathrouter/element.go
@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package pathrouter
+
+import "go.xyrillian.de/gg/options"
+
+// Element is a [Matcher] that accepts subpaths with at least one path element.
+// The first path element must be equal to the given value,
+// and the remaining subpath will have to be accepted by the next matcher.
+func Element(value string, matcher Matcher) Matcher {
+	return element(value, matcher.downcast())
+}
+
+func element(value string, matcher realMatcher) Matcher {
+	switch value {
+	case "":
+		panic(`Element() called with value = ""`)
+	case "/":
+		value = "" // trailing slash will lead to an empty element in `path`, e.g. strings.Split("foo/bar/") == []string{"foo","bar",""}
+	default:
+	}
+
+	return realMatcher{
+		minLength: matcher.minLength + 1,
+		maxLength: options.Map(matcher.maxLength, increment),
+		accept: func(path []string, vars map[string]string) HandlerFunc {
+			if len(path) == 0 || path[0] != value {
+				return nil
+			}
+			return matcher.accept(path[1:], vars)
+		},
+	}
+}