From 17d8de63af08ad6f9531ae0e0f0606dc92779360 Mon Sep 17 00:00:00 2001
From: Adam Fowler <adamfowler71@gmail.com>
Date: Sat, 28 Dec 2024 08:09:04 +0000
Subject: [PATCH] Router validation (#637)

---
 .../Router/Router+validation.swift            | 105 ++++++++++++++++++
 Sources/Hummingbird/Router/Router.swift       |  29 ++---
 Tests/HummingbirdTests/RouterTests.swift      |  44 +++++++-
 3 files changed, 154 insertions(+), 24 deletions(-)
 create mode 100644 Sources/Hummingbird/Router/Router+validation.swift

diff --git a/Sources/Hummingbird/Router/Router+validation.swift b/Sources/Hummingbird/Router/Router+validation.swift
new file mode 100644
index 00000000..9417454f
--- /dev/null
+++ b/Sources/Hummingbird/Router/Router+validation.swift
@@ -0,0 +1,105 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Hummingbird server framework project
+//
+// Copyright (c) 2024 the Hummingbird authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See hummingbird/CONTRIBUTORS.txt for the list of Hummingbird authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import HTTPTypes
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
+import Foundation
+#endif
+
+extension Router {
+    /// Route description
+    public struct RouteDescription: CustomStringConvertible {
+        /// Route path
+        public let path: RouterPath
+        /// Route method
+        public let method: HTTPRequest.Method
+
+        public var description: String { "\(method) \(path)" }
+    }
+
+    /// List of routes added to router
+    public var routes: [RouteDescription] {
+        let trieValues = self.trie.root.values()
+        return trieValues.flatMap { endpoint in
+            endpoint.value.methods.keys
+                .sorted { $0.rawValue < $1.rawValue }
+                .map { RouteDescription(path: endpoint.path, method: $0) }
+        }
+    }
+
+    /// Validate router
+    ///
+    /// Verify that routes are not clashing
+    public func validate() throws {
+        try self.trie.root.validate()
+    }
+}
+
+extension RouterPathTrieBuilder.Node {
+    func validate(_ root: String = "") throws {
+        let sortedChildren = children.sorted { $0.key.priority > $1.key.priority }
+        if sortedChildren.count > 1 {
+            for index in 1..<sortedChildren.count {
+                let exampleElement =
+                    switch sortedChildren[index].key.value {
+                    case .path(let path):
+                        String(path)
+                    case .capture:
+                        UUID().uuidString
+                    case .prefixCapture(let suffix, _):
+                        "\(UUID().uuidString)\(suffix)"
+                    case .suffixCapture(let prefix, _):
+                        "\(prefix)/\(UUID().uuidString)"
+                    case .wildcard:
+                        UUID().uuidString
+                    case .prefixWildcard(let suffix):
+                        "\(UUID().uuidString)\(suffix)"
+                    case .suffixWildcard(let prefix):
+                        "\(prefix)/\(UUID().uuidString)"
+                    case .recursiveWildcard:
+                        UUID().uuidString
+                    case .null:
+                        ""
+                    }
+                // test path element against all the previous trie entries in this node
+                for trieEntry in sortedChildren[0..<index] {
+                    if case trieEntry.key = exampleElement {
+                        throw RouterValidationError(
+                            path: "\(root)/\(sortedChildren[index].key)",
+                            override: "\(root)/\(trieEntry.key)"
+                        )
+                    }
+                }
+
+            }
+        }
+
+        for child in self.children {
+            try child.validate("\(root)/\(child.key)")
+        }
+    }
+}
+
+/// Router validation error
+public struct RouterValidationError: Error, CustomStringConvertible {
+    let path: RouterPath
+    let override: RouterPath
+
+    public var description: String {
+        "Route \(override) overrides \(path)"
+    }
+}
diff --git a/Sources/Hummingbird/Router/Router.swift b/Sources/Hummingbird/Router/Router.swift
index 73b1e333..045f27a9 100644
--- a/Sources/Hummingbird/Router/Router.swift
+++ b/Sources/Hummingbird/Router/Router.swift
@@ -56,6 +56,13 @@ public final class Router<Context: RequestContext>: RouterMethods, HTTPResponder
 
     /// build responder from router
     public func buildResponder() -> RouterResponder<Context> {
+        #if DEBUG
+        do {
+            try self.validate()
+        } catch {
+            assertionFailure("\(error)")
+        }
+        #endif
         if self.options.contains(.autoGenerateHeadEndpoints) {
             // swift-format-ignore: ReplaceForEachWithForLoop
             self.trie.forEach { node in
@@ -128,25 +135,3 @@ public struct RouterOptions: OptionSet, Sendable {
     /// For every GET request that does not have a HEAD request, auto generate the HEAD request
     public static var autoGenerateHeadEndpoints: Self { .init(rawValue: 1 << 1) }
 }
-
-extension Router {
-    /// Route description
-    public struct RouteDescription: CustomStringConvertible {
-        /// Route path
-        public let path: RouterPath
-        /// Route method
-        public let method: HTTPRequest.Method
-
-        public var description: String { "\(method) \(path)" }
-    }
-
-    /// List of routes added to router
-    public var routes: [RouteDescription] {
-        let trieValues = self.trie.root.values()
-        return trieValues.flatMap { endpoint in
-            endpoint.value.methods.keys
-                .sorted { $0.rawValue < $1.rawValue }
-                .map { RouteDescription(path: endpoint.path, method: $0) }
-        }
-    }
-}
diff --git a/Tests/HummingbirdTests/RouterTests.swift b/Tests/HummingbirdTests/RouterTests.swift
index 0dfc2eb2..55b6820a 100644
--- a/Tests/HummingbirdTests/RouterTests.swift
+++ b/Tests/HummingbirdTests/RouterTests.swift
@@ -735,7 +735,7 @@ final class RouterTests: XCTestCase {
         router.get("test/this") { _, _ in "" }
         router.put("test") { _, _ in "" }
         router.post("{test}/{what}") { _, _ in "" }
-        router.get("wildcard/*") { _, _ in "" }
+        router.get("wildcard/*/*") { _, _ in "" }
         router.get("recursive_wildcard/**") { _, _ in "" }
         router.patch("/test/longer/path/name") { _, _ in "" }
         let routes = router.routes
@@ -750,11 +750,51 @@ final class RouterTests: XCTestCase {
         XCTAssertEqual(routes[3].method, .patch)
         XCTAssertEqual(routes[4].path.description, "/{test}/{what}")
         XCTAssertEqual(routes[4].method, .post)
-        XCTAssertEqual(routes[5].path.description, "/wildcard/*")
+        XCTAssertEqual(routes[5].path.description, "/wildcard/*/*")
         XCTAssertEqual(routes[5].method, .get)
         XCTAssertEqual(routes[6].path.description, "/recursive_wildcard/**")
         XCTAssertEqual(routes[6].method, .get)
     }
+
+    func testValidateOrdering() throws {
+        let router = Router()
+        router.post("{test}/{what}") { _, _ in "" }
+        router.get("test/this") { _, _ in "" }
+        try router.validate()
+    }
+
+    func testValidateParametersVsWildcards() throws {
+        let router = Router()
+        router.get("test/*") { _, _ in "" }
+        router.get("test/{what}") { _, _ in "" }
+        XCTAssertThrowsError(try router.validate()) { error in
+            guard let error = error as? RouterValidationError else {
+                XCTFail()
+                return
+            }
+            XCTAssertEqual(error.description, "Route /test/{what} overrides /test/*")
+        }
+    }
+
+    func testValidateParametersVsRecursiveWildcard() throws {
+        let router = Router()
+        router.get("test/**") { _, _ in "" }
+        router.get("test/{what}") { _, _ in "" }
+        XCTAssertThrowsError(try router.validate()) { error in
+            guard let error = error as? RouterValidationError else {
+                XCTFail()
+                return
+            }
+            XCTAssertEqual(error.description, "Route /test/{what} overrides /test/**")
+        }
+    }
+
+    func testValidateDifferentParameterNames() throws {
+        let router = Router()
+        router.get("test/{this}") { _, _ in "" }
+        router.get("test/{what}") { _, _ in "" }
+        XCTAssertThrowsError(try router.validate())
+    }
 }
 
 struct TestRouterContext2: RequestContext {