Add PathParams method.

router.go

@@ -23,18 +23,30 @@ type Router struct {
 	routes          []route
 }
 
+// endpoint is comes at the end of each valid path in the tree. It contains the information you
+// need to call the endpoint, including path parameter names.
+type endpoint struct {
+	callback   http.HandlerFunc
+	path       string
+	pathParams []string
+}
+
+// route is not part of the tree, but is saved on the router to represent all the available
+// routes in the tree.
 type route struct {
 	callback http.HandlerFunc
 	method   string
 	path     string
 }
 
+// segment is a tree node. It can have children, or endpoints, or both attached to it. It also
+// has a special child called "parameter" which represents a path parameter. If a route string
+// doesn't match any of the children, and there is a parameter child present, it will match that
+// parameter child.
 type segment struct {
 	children  map[string]*segment
-	methods       map[string]http.HandlerFunc
+	endpoints map[string]*endpoint
-	path          string
 	parameter *segment
-	parameterName string
 }
 
 // NotFoundHandler is the default function for handling routes that are not found. If you wish to
@@ -49,12 +61,12 @@ var NotFoundHandler http.Handler = http.HandlerFunc(
 // method already have a callback registered to them, an error is returned.
 func (r *Router) AddRoute(method string, path string, callback http.HandlerFunc) (err error) {
 	keys := setupKeys(strings.Split(path, "/"))
+	pathParams := []string{}
 
 	if r.root == nil {
 		r.root = &segment{}
 		r.root.children = map[string]*segment{}
-		r.root.methods = map[string]http.HandlerFunc{}
+		r.root.endpoints = map[string]*endpoint{}
-		r.root.path = "/"
 	}
 
 	curr := r.root
@@ -64,7 +76,12 @@ func (r *Router) AddRoute(method string, path string, callback http.HandlerFunc)
 			continue
 		}
 
-		if child, ok := curr.children[key]; !ok {
+		if isParameter(key) {
+			pathParams = append(pathParams, key[2:])
+
+		}
+
+		if child, _ := getChild(key, curr); child == nil {
 			seg := addSegment(curr, key)
 			curr = seg
 		} else {
@@ -72,18 +89,43 @@ func (r *Router) AddRoute(method string, path string, callback http.HandlerFunc)
 		}
 	}
 
-	if _, ok := curr.methods[method]; ok {
+	if _, ok := curr.endpoints[method]; ok {
 		err = errors.New("path already exists")
 
 		return
 	}
 
-	curr.methods[method] = callback
+	curr.endpoints[method] = &endpoint{callback, path, pathParams}
 	r.routes = append(r.routes, route{callback, method, path})
 
 	return
 }
 
+// PathParams takes a path and returns the values for any path parameters
+// in the path.
+func (r *Router) PathParams(method string, reqPath string) (params map[string]string, err error) {
+	end, err := r.getEndpoint(method, reqPath)
+	path := end.path
+
+	reqParts := strings.Split(reqPath, "/")
+	reqKeys := setupKeys(reqParts)
+
+	pathParts := strings.Split(path, "/")
+	pathKeys := setupKeys(pathParts)
+
+	params = map[string]string{}
+
+	for i, pathKey := range pathKeys {
+		if isParameter(pathKey) {
+			name := pathKey[2:]
+			value := reqKeys[i][1:]
+			params[name] = value
+		}
+	}
+
+	return
+}
+
 // Get is a convinience method which calls Router.AddRoute with the "GET" method.
 func (r *Router) Get(path string, callback http.HandlerFunc) {
 	r.AddRoute(http.MethodGet, path, callback)
@@ -99,33 +141,16 @@ func (r *Router) Get(path string, callback http.HandlerFunc) {
 func (r *Router) Handler(req *http.Request) (h http.Handler, pattern string) {
 	method := req.Method
 	path := req.URL.Path
-	root := r.root
-	curr := root
-
-	segments := strings.Split(path, "/")
-	keys := setupKeys(segments)
 
 	if r.NotFoundHandler == nil {
 		h = NotFoundHandler
 	}
 
-	for _, v := range keys {
+	endpoint, err := r.getEndpoint(method, path)
-		if v == "/" {
-			continue
-		}
 
-		seg := getChild(v, curr)
+	if err == nil {
-
+		h = endpoint.callback
-		if seg == nil {
+		pattern = endpoint.path
-			return
-		}
-
-		curr = seg
-	}
-
-	if cb, ok := curr.methods[method]; ok {
-		h = cb
-		pattern = curr.path
 	}
 
 	return
@@ -137,25 +162,26 @@ func (r *Router) Handler(req *http.Request) (h http.Handler, pattern string) {
 //
 // In the case of this router, all it needs to do is lookup the Handler that has been saved at a given
 // path and then call its ServeHTTP.
-func (r Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	handler, _ := r.Handler(req)
 	handler.ServeHTTP(w, req)
 
 	return
 }
 
+// addSegment create a new segment either as a child or as a parameter depending on whether the key
+// qualifies as a parameter. A pointer to the created segment is then returned.
 func addSegment(curr *segment, key string) (seg *segment) {
-	if curr.parameterName == key {
+	if curr.parameter != nil {
 		seg = curr.parameter
 
 	} else if child, ok := curr.children[key]; !ok { // child does not match...
 		var isParam bool
 
-		seg, isParam = newSegment(curr.path, key)
+		seg, isParam = newSegment(key)
 
 		if isParam {
 			curr.parameter = seg
-			curr.parameterName = key[2:]
 
 		} else {
 			curr.children[key] = seg
@@ -170,33 +196,60 @@ func addSegment(curr *segment, key string) (seg *segment) {
 	return
 }
 
-func getChild(key string, curr *segment) (child *segment) {
+// getChild takes a path part and finds the appropriate segment child for it. If it is an exact match to a
+// child on the segment, then that child segment is returned. If it is not a match, then the parameter child
+// is returned. If there is no parameter child, nil is returned. isParam is true if the parameter child is
+// being returned.
+func getChild(key string, curr *segment) (child *segment, isParam bool) {
 	if seg, ok := curr.children[key]; ok { // is there an exact match?
-
 		child = seg
+
 	} else if curr.parameter != nil { // could this be a parameter?
 		child = curr.parameter
-
+		isParam = true
 	}
 
 	return
 }
 
-func newSegment(parentPath string, key string) (seg *segment, isParam bool) {
+// getEndpoint takes a path and traverses the tree until it finds the endpoint associated with that path.
-	var path string
+// If no endpoint if found, an error is returned.
+func (r *Router) getEndpoint(method string, path string) (end *endpoint, err error) {
+	curr := r.root
+	segments := strings.Split(path, "/")
+	keys := setupKeys(segments)
 
-	if parentPath == "/" {
+	for _, v := range keys {
-		path = key
+		if v == "/" {
-
+			continue
-	} else {
-		path = parentPath + key
 		}
 
+		seg, _ := getChild(v, curr)
+
+		if seg == nil {
+			return
+		}
+
+		curr = seg
+	}
+
+	if _, ok := curr.endpoints[method]; !ok {
+		err = errors.New("route not found")
+	}
+
+	end = curr.endpoints[method]
+
+	return
+}
+
+// TODO: refactor out newSegment as it's not longer needed.
+
+// newSegment constructs a new, empty segment and reports back if the key is a parameter.
+func newSegment(key string) (seg *segment, isParam bool) {
 	seg = &segment{}
 
 	seg.children = map[string]*segment{}
-	seg.methods = map[string]http.HandlerFunc{}
+	seg.endpoints = map[string]*endpoint{}
-	seg.path = path
 
 	if isParameter(key) {
 		isParam = true
@@ -205,6 +258,8 @@ func newSegment(parentPath string, key string) (seg *segment, isParam bool) {
 	return
 }
 
+// setupKeys takes an array of strings representing the parts of a path, and returns a new slice
+// made up of the parts with "/" prepended to each.
 func setupKeys(slice []string) (keys []string) {
 	keys = append(keys, "/")
 	for _, v := range slice {
@@ -217,8 +272,8 @@ func setupKeys(slice []string) (keys []string) {
 }
 
 // isParameter returns true if the key is more than one character long and starts with a ':'
-func isParameter(key string) (isVar bool) {
+func isParameter(key string) (isParam bool) {
-	if len([]rune(key)) <= 2 {
+	if len([]rune(key)) <= 1 {
 		return // avoid empty variables, i.e. /somepath/:/someotherpath
 	}
 
@@ -226,7 +281,7 @@ func isParameter(key string) (isVar bool) {
 		return
 	}
 
-	isVar = true
+	isParam = true
 
 	return
 }

router_test.go

@@ -11,7 +11,7 @@ import (
 var testLevel = 1
 
 func TestAddRouter(t *testing.T) {
-	describeTests("Test AddRouter function")
+	describeTests("Test AddRouter method")
 
 	router := Router{}
 
@@ -22,7 +22,7 @@ func TestAddRouter(t *testing.T) {
 }
 
 func TestServeHTTP(t *testing.T) {
-	describeTests("Test ServeHTTP function")
+	describeTests("Test ServeHTTP method")
 
 	router := Router{}
 
@@ -31,6 +31,14 @@ func TestServeHTTP(t *testing.T) {
 	testMatchesPathParam(router, t)
 }
 
+func TestPathParams(t *testing.T) {
+	describeTests("Test PathParams method")
+
+	router := Router{}
+
+	testParamValues(router, t)
+}
+
 func addAndCheckRoute(r *Router, method string, path string, callback http.HandlerFunc) (err error) {
 	routeCount := len(r.routes)
 
@@ -71,7 +79,7 @@ func addAndCheckRoute(r *Router, method string, path string, callback http.Handl
 
 // checkLookup prints out the various saved routes. It's not needed for any test, but is a helpful debugging tool.
 func checkLookup(curr *segment) {
-	fmt.Printf("%p { path: \"%s\", methods: %v, children: %v, parameter: %v, parameterName: \"%s\"}\n", curr, curr.path, curr.methods, curr.children, curr.parameter, curr.parameterName)
+	fmt.Printf("%p { methods: %v, children: %v, parameter: %v\"}\n", curr, curr.endpoints, curr.children, curr.parameter)
 
 	for _, v := range curr.children {
 		checkLookup(v)
@@ -226,6 +234,52 @@ func testMatchesRoot(router Router, t *testing.T) {
 	}
 }
 
+func testParamValues(router Router, t *testing.T) {
+	defer testOutcome("returns param names and values", t)
+
+	method := http.MethodOptions
+	path := "/users/:userID/edit/:status"
+	userID := "46"
+	status := "inactive"
+	expectedBody := "done"
+	expectedStatus := 200
+	reqPath := fmt.Sprintf("/users/%s/edit/%s", userID, status)
+
+	router.AddRoute(method, path, func(w http.ResponseWriter, r *http.Request) {
+		requestPath := r.URL.Path
+		requestMethod := r.Method
+
+		params, err := router.PathParams(requestMethod, requestPath)
+
+		if err != nil {
+			t.Error("An error occurred while getting path parameters")
+		}
+
+		if len(params) != 2 {
+			t.Errorf("Received the wrong number of parameters. Expected 2, recieved %d", len(params))
+		}
+
+		if params["userID"] != userID {
+			t.Errorf("userID should be %s, but it is %s", userID, params["userID"])
+		}
+
+		if params["status"] != status {
+			t.Errorf("status should be %s, but it is %s", status, params["status"])
+		}
+
+		w.WriteHeader(expectedStatus)
+		w.Write([]byte(expectedBody))
+	})
+
+	err := matchAndCheckRoute(&router, method, reqPath, expectedBody, expectedStatus)
+
+	if err != nil {
+		t.Error("Did not find the expected callback handler", err)
+
+		return
+	}
+}
+
 func testOutcome(message string, t *testing.T) {
 	var status string