router.go

package scf

import (
	"net/http"
	"strings"
)

type Router struct {
	trees map[string]*node

	maxParams uint16

	// If enabled, adds the matched route path onto the http.Request context
	// before invoking the handler.
	// The matched route path is only added to handlers of routes that were
	// registered when this option was enabled.
	SaveMatchedRoutePath bool

	// Enables automatic redirection if the current route can't be matched but a
	// handler for the path with (without) the trailing slash exists.
	// For example if /foo/ is requested but a route only exists for /foo, the
	// client is redirected to /foo with http status code 301 for GET requests
	// and 308 for all other request methods.
	RedirectTrailingSlash bool

	// If enabled, the router tries to fix the current request path, if no
	// handle is registered for it.
	// First superfluous path elements like ../ or // are removed.
	// Afterwards the router does a case-insensitive lookup of the cleaned path.
	// If a handle can be found for this route, the router makes a redirection
	// to the corrected path with status code 301 for GET requests and 308 for
	// all other request methods.
	// For example /FOO and /..//Foo could be redirected to /foo.
	// RedirectTrailingSlash is independent of this option.
	RedirectFixedPath bool

	// If enabled, the router checks if another method is allowed for the
	// current route, if the current request can not be routed.
	// If this is the case, the request is answered with 'Method Not Allowed'
	// and HTTP status code 405.
	// If no other Method is allowed, the request is delegated to the NotFound
	// handler.
	HandleMethodNotAllowed bool

	// If enabled, the router automatically replies to OPTIONS requests.
	// Custom OPTIONS handlers take priority over automatic replies.
	HandleOPTIONS bool

	// An optional http.Handler that is called on automatic OPTIONS requests.
	// The handler is only called if HandleOPTIONS is true and no OPTIONS
	// handler for the specific path was set.
	// The "Allowed" header is set before calling the handler.
	GlobalOPTIONS http.Handler

	// Cached value of global (*) allowed methods
	globalAllowed string

	// Configurable http.Handler which is called when no matching route is
	// found. If it is not set, http.NotFound is used.
	NotFound http.Handler

	// Configurable http.Handler which is called when a request
	// cannot be routed and HandleMethodNotAllowed is true.
	// If it is not set, http.Error with http.StatusMethodNotAllowed is used.
	// The "Allow" header with allowed request methods is set before the handler
	// is called.
	MethodNotAllowed http.Handler

	// Function to handle panics recovered from http handlers.
	// It should be used to generate a error page and return the http error code
	// 500 (Internal Server Error).
	// The handler can be used to keep your server from crashing because of
	// unrecovered panics.
	PanicHandler func(http.ResponseWriter, *http.Request, interface{})
}

func NewRouter() *Router {
	return &Router{}
}

func (r *Router) Route(method, path string, handler Handler) {
	//if router[method] == nil {
	//	router[method] = make(map[string]Handler)
	//}
	//router[method][path] = handler
	varsCount := uint16(0)

	if method == "" {
		panic("method must not be empty")
	}

	if path[0] != '/' {
		path = "/" + path
	}

	if len(path) < 1 || path[0] != '/' {
		panic("path must begin with '/' in path '" + path + "'")
	}
	if handler == nil {
		panic("handle must not be nil")
	}

	if r.SaveMatchedRoutePath {
		varsCount++
		handler = r.saveMatchedRoutePath(path, handler)
	}

	if r.trees == nil {
		r.trees = make(map[string]*node)
	}

	root := r.trees[method]
	if root == nil {
		root = new(node)
		r.trees[method] = root

		r.globalAllowed = r.allowed("*", "")
	}

	root.addRoute(path, handler)
}

func (r *Router) GET(path string, handler Handler) {
	r.Route(http.MethodGet, path, handler)
}

func (r *Router) POST(path string, handler Handler) {
	r.Route(http.MethodPost, path, handler)
}

func (r *Router) OPTIONS(path string, handler Handler) {
	r.Route(http.MethodOptions, path, handler)
}

func (r *Router) PUT(path string, handler Handler) {
	r.Route(http.MethodPut, path, handler)
}

func (r *Router) DELETE(path string, handler Handler) {
	r.Route(http.MethodDelete, path, handler)
}

func (r *Router) HEAD(path string, handler Handler) {
	r.Route(http.MethodHead, path, handler)
}

func (r *Router) ANY(path string, handler Handler) {
	r.GET(path, handler)
	r.POST(path, handler)
	r.PUT(path, handler)
	r.DELETE(path, handler)
	r.HEAD(path, handler)
}

func (r *Router) saveMatchedRoutePath(path string, handle Handler) Handler {
	return func(ctx *Context) Reply {
		return handle(ctx)
	}
}

func (r *Router) allowed(path, reqMethod string) (allow string) {
	allowed := make([]string, 0, 9)

	if path == "*" { // server-wide
		// empty method is used for internal calls to refresh the cache
		if reqMethod == "" {
			for method := range r.trees {
				if method == http.MethodOptions {
					continue
				}
				// Add request method to list of allowed methods
				allowed = append(allowed, method)
			}
		} else {
			return r.globalAllowed
		}
	} else { // specific path
		for method := range r.trees {
			// Skip the requested method - we already tried this one
			if method == reqMethod || method == http.MethodOptions {
				continue
			}

			handle, _, _ := r.trees[method].getValue(path, nil)
			if handle != nil {
				// Add request method to list of allowed methods
				allowed = append(allowed, method)
			}
		}
	}

	if len(allowed) > 0 {
		// Add request method to list of allowed methods
		allowed = append(allowed, http.MethodOptions)

		// Sort allowed methods.
		// sort.Strings(allowed) unfortunately causes unnecessary allocations
		// due to allowed being moved to the heap and interface conversion
		for i, l := 1, len(allowed); i < l; i++ {
			for j := i; j > 0 && allowed[j] < allowed[j-1]; j-- {
				allowed[j], allowed[j-1] = allowed[j-1], allowed[j]
			}
		}

		// return as comma separated list
		return strings.Join(allowed, ", ")
	}

	return allow
}