add package pathrouter

1 files changed, 60 insertions, 0 deletions

diff --git a/pathrouter/catchallvariable.go b/pathrouter/catchallvariable.go
new file mode 100644
index 0000000..1b98672
--- /dev/null
+++ b/pathrouter/catchallvariable.go
@@ -0,0 +1,60 @@
+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package pathrouter
+
+import (
+	"strings"
+
+	. "go.xyrillian.de/gg/option"
+)
+
+// CatchAllVariable is a [Matcher] that accepts subpaths with an arbitrary number of path elements.
+// The value of any amount of leading path elements will be collected into vars[name],
+// such that the remainder is accepted by the next matcher.
+// At least one element must be collected into vars[name].
+//
+// CatchAllVariable() may appear at any point within the routing tree,
+// but it may not contain another CatchAllVariable() anywhere within it.
+func CatchAllVariable(name string, matcher Matcher) Matcher {
+	return catchAllVariable(name, matcher.downcast())
+}
+
+func catchAllVariable(name string, matcher realMatcher) Matcher {
+	// NOTE: The specific behavior of CatchAllVariable() is why this package exists in the first place.
+	//       I wanted to replace gorilla/mux with something more performance in Keppel,
+	//       but all the fast routers do not accept catch-all variables in the middle of a path
+	//       like the OCI Distribution API requires (e.g. "/v2/*repo/manifests/:reference" with "repo" being a full path).
+
+	innerMinLength := matcher.minLength
+	innerMaxLength, ok := matcher.maxLength.Unpack()
+	if !ok {
+		panic("matcher within CatchAllVariable() may not accept unlimited path lengths")
+	}
+
+	accept := func(path []string, vars map[string]string) HandlerFunc {
+		for length := innerMinLength; length <= innerMaxLength; length++ {
+			if length > len(path) {
+				break
+			}
+			caughtPath, subpath := path[0:len(path)-length], path[len(path)-length:]
+			if len(caughtPath) == 0 {
+				continue
+			}
+
+			handlerFunc := matcher.accept(subpath, vars)
+			if handlerFunc == nil {
+				continue
+			}
+			vars[name] = pathUnescape(strings.Join(caughtPath, "/"))
+			return handlerFunc
+		}
+		return nil
+	}
+
+	return realMatcher{
+		minLength: innerMinLength + 1,
+		maxLength: None[int](),
+		accept:    accept,
+	}
+}