Add context.FindClosest(n) to find closest paths - useful for 404 pages to suggest valid pages

Former-commit-id: 90ff7c9da5369df5bd99fbbecf9955a8c555fea5

context/application.go

@@ -60,4 +60,8 @@ type Application interface {
 	// RouteExists reports whether a particular route exists
 	// It will search from the current subdomain of context's host, if not inside the root domain.
 	RouteExists(ctx Context, method, path string) bool
+	// FindClosestPaths returns a list of "n" paths close to "path" under the given "subdomain".
+	//
+	// Order may change.
+	FindClosestPaths(subdomain, searchPath string, n int) []string
 }

context/context.go

@@ -310,6 +310,12 @@ type Context interface {
 	// Subdomain returns the subdomain of this request, if any.
 	// Note that this is a fast method which does not cover all cases.
 	Subdomain() (subdomain string)
+	// FindClosest returns a list of "n" paths close to
+	// this request based on subdomain and request path.
+	//
+	// Order may change.
+	// Example: https://github.com/kataras/iris/tree/master/_examples/routing/not-found-suggests
+	FindClosest(n int) []string
 	// IsWWW returns true if the current subdomain (if any) is www.
 	IsWWW() bool
 	// FullRqeuestURI returns the full URI,
@@ -1600,6 +1606,15 @@ func (ctx *context) Subdomain() (subdomain string) {
 	return
 }
 
+// FindClosest returns a list of "n" paths close to
+// this request based on subdomain and request path.
+//
+// Order may change.
+// Example: https://github.com/kataras/iris/tree/master/_examples/routing/not-found-suggests
+func (ctx *context) FindClosest(n int) []string {
+	return ctx.Application().FindClosestPaths(ctx.Subdomain(), ctx.Path(), n)
+}
+
 // IsWWW returns true if the current subdomain (if any) is www.
 func (ctx *context) IsWWW() bool {
 	host := ctx.Host()

context/route.go

@@ -31,6 +31,10 @@ type RouteReadOnly interface {
 	// IsOnline returns true if the route is marked as "online" (state).
 	IsOnline() bool
 
+	// IsStatic reports whether this route is a static route.
+	// Does not contain dynamic path parameters,
+	// is online and registered on GET HTTP Method.
+	IsStatic() bool
 	// StaticPath returns the static part of the original, registered route path.
 	// if /user/{id} it will return /user
 	// if /user/{id}/friend/{friendid:uint64} it will return /user too