capstan/router_bind.go

package capstan

import (
	"net/http"
	pth "path"
	"reflect"
	"strings"

	"git.destrealm.org/go/vfs"
	"github.com/gorilla/websocket"
)

var validMethods = map[string]struct{}{
	"GET":     struct{}{},
	"HEAD":    struct{}{},
	"POST":    struct{}{},
	"PUT":     struct{}{},
	"PATCH":   struct{}{},
	"DELETE":  struct{}{},
	"CONNECT": struct{}{},
	"OPTIONS": struct{}{},
	"TRACE":   struct{}{},
}

// Bind the specified endpoint.
//
// This method is the core of the router and handles all method routes directly
// and farms out other route types to separate functions (also located in this
// file). Bind() will also setup routes and map them.
//
// The use of route.Copy() may appear confusing at first blush, but its purpose
// is to create a copy of (most of) the route and its data, which is then used
// to bind a method/endpoint tuple with go-chi. route.Copy() only performs a
// shallow copy; slicens and map pointers are replicate across all dependents.
func (r *Router) Bind(endpoint Controller) error {
	var hasIndex bool
	var middleware []func(http.Handler) http.Handler
	var rt *Route
	routes := make([]*Route, 0)
	r.dependencies.Apply(endpoint)
	route, props := r.toRoute(endpoint)

	r.cnames[route.Name] = struct{}{}
	r.pathmap[endpoint.path()] = route

	// IndexHandler should come first as it gets special treatment. Note: To
	// prevent the likelihood that the GET route might share the same route as
	// this method, we prioritize this one.
	if e, ok := endpoint.(IndexHandler); ok {
		iprops := r.ParseRoute(endpoint.index())
		iprops.mergeBase(props)

		hasIndex = true
		rt = route.Copy()
		rt.Method = "GET"
		rt.Suffix = "index"
		rt.Endpoint = e.Index
		rt.Path = iprops.route
		rt.OptionalSlash = iprops.optionalSlash
		rt.MandatoryNoSlash = iprops.mandatoryNoSlash
		rt.MandatorySlash = iprops.mandatorySlash
		rt.SlashIsDefault = iprops.slashIsDefault
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(GetHandler); ok {
		// Add the GET handler *only* if the defined route has no Index() method
		// OR if the handler route and controller baseRoute differ. In other
		// words, if the Index() route has a separate path assignment defined by
		// BaseController.Index, we'll still accept both handlers since they can
		// be mounted at separate locations.
		if !hasIndex || props.route != props.baseRoute {
			rt = route.Copy()
			rt.Method = "GET"
			rt.Endpoint = e.Get
			if endpoint.options().Get != "" {
				iprops := r.ParseRoute(endpoint.options().Get)
				rt.Path = pth.Join(rt.Path, iprops.route)
				rt.OptionalSlash = iprops.optionalSlash
				rt.MandatoryNoSlash = iprops.mandatoryNoSlash
				rt.MandatorySlash = iprops.mandatorySlash
				rt.SlashIsDefault = iprops.slashIsDefault
			}
			routes = append(routes, rt)
		}
	}

	if e, ok := endpoint.(WebSocketHandler); ok {
		rt = route.Copy()
		rt.Method = "GET"
		rt.Endpoint = e.WebSocket

		rt.Upgrader = endpoint.upgrader()
		if rt.Upgrader == nil {
			rt.Upgrader = &websocket.Upgrader{}
		}

		if endpoint.webSocketPath() != "" {
			if strings.HasSuffix(rt.Path, "/") {
				rt.Path = rt.Path[:len(rt.Path)-1]
			}
			rt.Path = rt.Path + endpoint.webSocketPath()
		}

		if _, ok := endpoint.(GetHandler); ok {
			if endpoint.webSocketPath() == "" {
				panic("controller must set BaseController.WebSocketPath if both Get() and WebSocket() endpoints are present")
			}
		}

		routes = append(routes, rt)
	}

	if e, ok := endpoint.(ConnectHandler); ok {
		rt = route.Copy()
		rt.Method = "CONNECT"
		rt.Endpoint = e.Connect
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(DeleteHandler); ok {
		rt = route.Copy()
		rt.Method = "DELETE"
		rt.Endpoint = e.Delete
		if endpoint.options().Delete != "" {
			iprops := r.ParseRoute(endpoint.options().Delete)
			rt.Path = pth.Join(rt.Path, iprops.route)
			rt.OptionalSlash = iprops.optionalSlash
			rt.MandatoryNoSlash = iprops.mandatoryNoSlash
			rt.MandatorySlash = iprops.mandatorySlash
			rt.SlashIsDefault = iprops.slashIsDefault
		}
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(HeadHandler); ok {
		rt = route.Copy()
		rt.Method = "HEAD"
		rt.Endpoint = e.Head
		if endpoint.options().Head != "" {
			iprops := r.ParseRoute(endpoint.options().Head)
			rt.Path = pth.Join(rt.Path, iprops.route)
			rt.OptionalSlash = iprops.optionalSlash
			rt.MandatoryNoSlash = iprops.mandatoryNoSlash
			rt.MandatorySlash = iprops.mandatorySlash
			rt.SlashIsDefault = iprops.slashIsDefault
		}
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(OptionsHandler); ok {
		rt = route.Copy()
		rt.Method = "OPTIONS"
		rt.Endpoint = e.Options
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(PostHandler); ok {
		rt = route.Copy()
		rt.Method = "POST"
		rt.Endpoint = e.Post
		if endpoint.options().Post != "" {
			iprops := r.ParseRoute(endpoint.options().Post)
			rt.Path = pth.Join(rt.Path, iprops.route)
			rt.OptionalSlash = iprops.optionalSlash
			rt.MandatoryNoSlash = iprops.mandatoryNoSlash
			rt.MandatorySlash = iprops.mandatorySlash
			rt.SlashIsDefault = iprops.slashIsDefault
		}
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(PutHandler); ok {
		rt = route.Copy()
		rt.Method = "PUT"
		rt.Endpoint = e.Put
		if endpoint.options().Put != "" {
			iprops := r.ParseRoute(endpoint.options().Put)
			rt.Path = pth.Join(rt.Path, iprops.route)
			rt.OptionalSlash = iprops.optionalSlash
			rt.MandatoryNoSlash = iprops.mandatoryNoSlash
			rt.MandatorySlash = iprops.mandatorySlash
			rt.SlashIsDefault = iprops.slashIsDefault
		}
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(PatchHandler); ok {
		rt = route.Copy()
		rt.Method = "PATCH"
		rt.Endpoint = e.Patch
		if endpoint.options().Patch != "" {
			iprops := r.ParseRoute(endpoint.options().Patch)
			rt.Path = pth.Join(rt.Path, iprops.route)
			rt.OptionalSlash = iprops.optionalSlash
			rt.MandatoryNoSlash = iprops.mandatoryNoSlash
			rt.MandatorySlash = iprops.mandatorySlash
			rt.SlashIsDefault = iprops.slashIsDefault
		}
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(TraceHandler); ok {
		rt = route.Copy()
		rt.Method = "TRACE"
		rt.Endpoint = e.Trace
		routes = append(routes, rt)
	}

	if e, ok := endpoint.(MiddlewareHandler); ok {
		middleware = e.Middleware()
	}

	if rts := r.bindSpecial(endpoint, route); rts != nil {
		routes = append(routes, rts...)
	}

	// Endpoint instance implements Binder and may handle some routes on its
	// own.
	if e, ok := endpoint.(Binder); ok {
		e.Bind(r)
	}

	for _, rt := range routes {

		if r.name != "" {
			rt.Prefix = r.name
		}

		rt.contextMaker = r.contextMaker

		if r.group != nil {
			rt.Headers = r.group.Header()
			if r.group.options != nil {
				rt.ContentType = r.group.options.ContentType
			}
		}

		// Assign renderer if none defined for this route.
		if rt.Renderer == nil {
			rt.Renderer = r.renderer
		}

		if rt.Renderer != nil {
			rt.Renderer.SetFunc("url", URLForGen(r, false))
			rt.Renderer.SetFunc("external", URLForGen(r, true))
			rt.Renderer.GlobalContext("_route", rt)
		}

		// Assign before/after response handlers.
		if e, ok := endpoint.(BaseController); ok {
			rt.BeforeResponse = append(rt.BeforeResponse, e.beforeResponseHandlers()...)
		}
		if e, ok := endpoint.(BaseController); ok {
			rt.AfterResponse = append(rt.AfterResponse, e.afterResponseHandlers()...)
		}

		if middleware != nil {
			rt.Middleware = append(rt.Middleware, middleware...)
		}

		bindRoute(r, rt)

		// Append route to map for possible rebinding.
		r.routes = append(r.routes, rt)

		// Map the route after being bound to the muxer. Guarantees route values
		// reflect their final state. (Note: bindRoute() also corrects slash
		// termination based on trailing syntax.)
		r.urls.Map(rt)
	}

	return nil
}

// ManualBind is used with Bind() routes to manually bind a given `endpoint` to
// the specified `path` with the HTTP request `method` and URLFor `suffix`
// provided. The controller must also be specified to correctly assemble the
// route.
func (r *Router) ManualBind(method, path, suffix string, controller Controller, endpoint Endpoint) {
	// Derive middleware globally or from controller (if implementing the
	// middleware interface)?
	var middleware []func(http.Handler) http.Handler

	props := r.ParseRoute(path)
	route := &Route{
		router:           r,
		Prefix:           controller.prefix(),
		Path:             props.route,
		CapPath:          pth.Join(controller.path(), path),
		BasePath:         r.basePath, // TODO: Support CapBasePath.
		MandatoryNoSlash: props.mandatoryNoSlash,
		MandatorySlash:   props.mandatorySlash,
		OptionalSlash:    props.optionalSlash,
		SlashIsDefault:   props.slashIsDefault,
		ParamTypes:       props.params,
		Method:           method,
		// FIXME: needs to be []MiddlewareFunc
		//Middleware:     controller.middleware(),
		Controller:     controller,
		Renderer:       controller.renderer(),
		Suffix:         suffix,
		Endpoint:       endpoint,
		AfterResponse:  make([]func(Context, error) error, len(r.afterResponse)),
		BeforeResponse: make([]func(Context, *Route) error, len(r.beforeResponse)),
	}

	r.cnames[route.Name] = struct{}{}
	r.pathmap[controller.path()] = route

	if r.name != "" {
		route.Prefix = r.name
	}

	// Append route to map for possible rebinding.
	r.routes = append(r.routes, route)

	if r.group != nil {
		route.Headers = r.group.Header()
		if r.group.options != nil {
			route.ContentType = r.group.options.ContentType
		}
	}

	// Assign renderer if none defined for this route.
	if route.Renderer == nil {
		route.Renderer = r.renderer
	}

	if route.Renderer != nil {
		route.Renderer.SetFunc("url", URLForGen(r, false))
		route.Renderer.SetFunc("external", URLForGen(r, true))
		route.Renderer.GlobalContext("_route", route)
	}

	// Assign before/after response handlers.
	if e, ok := controller.(BaseController); ok {
		route.BeforeResponse = append(route.BeforeResponse, e.beforeResponseHandlers()...)
	}
	if e, ok := controller.(BaseController); ok {
		route.AfterResponse = append(route.AfterResponse, e.afterResponseHandlers()...)
	}

	if middleware != nil {
		route.Middleware = append(route.Middleware, middleware...)
	}

	bindRoute(r, route)

	// Map the route after being bound to the muxer. Guarantees route values
	// reflect their final state. (Note: bindRoute() also corrects slash
	// termination based on trailing syntax.)
	r.urls.Map(route)
}

// Static binds the path described by `urlroot` to the filesystem `path` as a
// source for hosting static assets.
//
// Being as this makes use of the Golang default http.FileServer implementation,
// it's worth considering a reverse proxy for better performance.
func (r *Router) Static(urlroot, path string) {
	r.Mux().Get(urlroot, func(w http.ResponseWriter, r *http.Request) {
		http.StripPrefix(path, http.FileServer(http.Dir(path))).ServeHTTP(w, r)
	})
}

// Static binds the path described by `urlroot` to the filesystem `path` as
// contained in the virtual filesystem implementation `fs` as a source for
// hosting static assets. This should work with any VFS implementation
// compatible with vfs.FileSystem but is primarily intended to work with
// Embedder.
//
// Being as this makes use of the Golang default http.FileServer implementation,
// it's worth considering a reverse proxy for better performance.
func (r *Router) StaticVFS(urlroot, path string, fs vfs.FileSystem) {
	if !strings.HasSuffix(urlroot, "*") {
		if !strings.HasSuffix(urlroot, "/") {
			urlroot += "/"
		}
		urlroot += "*"
	}

	if !strings.HasSuffix(path, "/") {
		path += "/"
	}

	r.Mux().Get(urlroot, func(w http.ResponseWriter, r *http.Request) {
		http.StripPrefix(path, http.FileServer(vfs.HTTPDir(fs))).ServeHTTP(w, r)
	})
}

// Bind special endpoints. These are, for example, endpoints that map their own
// handlers or provide special methods.
func (r *Router) bindSpecial(endpoint Controller, baseRoute *Route) []*Route {
	routes := make([]*Route, 0)
	basePath := baseRoute.Path
	has := make(map[string]struct{})

	if strings.HasSuffix(basePath, "/") {
		basePath = basePath[:len(basePath)-1]
	}

	// Check if endpoint handles mapping.
	if e, ok := endpoint.(MapperHandler); ok {
		for path, mapper := range e.Mapper() {
			rt := baseRoute.Copy()
			if !strings.HasPrefix(path, "/") {
				path = "/" + path
			}
			rt.Path = path
			rt.Endpoint = mapper.Endpoint
			rt.Method = strings.ToUpper(mapper.Method)
			has[rt.Method+":"+path] = struct{}{}
			routes = append(routes, rt)
		}
	}

	// ...endpoint doesn't, so we'll continue examining it ourselves.
	typ := reflect.TypeOf(endpoint)

	// First, handle values configured from the BaseController provided to
	// BindRoute() by the caller (manually configuring routes).
	//
	// FIXME: Reflection will be broken as below, previously, and should be
	// fixed accordingly.
	for path, flag := range endpoint.endpoints() {
		var field reflect.Method
		var ok bool

		if field, ok = typ.MethodByName(flag.Endpoint); !ok {
			continue
		}

		if _, ok := r.reserved[field.Name]; ok {
			continue
		}

		if !field.Type.AssignableTo(reflect.TypeOf(Endpoint(nil))) {
			continue
		}

		if !strings.HasPrefix(path, "/") {
			path = "/" + path
		}

		// Already mapped.
		if _, ok = has[flag.Method+":"+path]; ok {
			continue
		}

		rt := baseRoute.Copy()
		rt.Path = path
		rt.Method = strings.ToUpper(flag.Method)

		ev := reflect.ValueOf(rt.Endpoint)
		ev.Set(reflect.ValueOf(field))

		has[rt.Method+":"+path] = struct{}{}

		routes = append(routes, rt)
	}

	// Finally, scan through the custom base paths. These are attached exported
	// methods for the pattern <Method>Name or Name. These routes will be
	// bound to hyphen-case versions of the same; e.g. GetListUsers would be
	// translated to an endpoint of the path "/list-users" accessible via an
	// HTTP GET. Slash optionality can be determined by the suffix "O", for
	// optional trailing slash; "S", for mandatory trailing slash; or "N" for
	// mandatory no-trailing-slash.
	//
	// Underscores are also converted to hyphens in the final interpolated path.
	ev := reflect.ValueOf(endpoint)
	et := ev.Type()
	for i := 0; i < ev.NumMethod(); i++ {
		var method string
		var ok bool
		var path string
		var hasSlash bool

		// Copy() doesn't reset defaults and instead inherits these values from
		// the base path. Since we're creating a separate route independent from
		// the base, we'll reset these values to their original state.
		rt := baseRoute.Copy()
		rt.OptionalSlash = false
		rt.MandatoryNoSlash = false
		rt.MandatorySlash = false
		rt.SlashIsDefault = false

		field := et.Method(i)

		// Already handled by other methods.
		if _, ok := reserved[field.Name]; ok {
			continue
		}

		// Manually reserved fields.
		if _, ok := r.reserved[field.Name]; ok {
			continue
		}

		var fn func(Context) error
		fv := ev.Method(i)
		fnv := reflect.ValueOf(&fn)
		if fnv.Elem().CanSet() && fv.Type() == fnv.Elem().Type() {
			fnv.Elem().Set(fv)
		} else {
			// Don't bother attempting to infer anything further about this
			// endpoint; it cannot be converted to our type.
			continue
		}

		for _, c := range field.Name {
			if method == "" {
				method += string(c)
				continue
			}
			if int32(c) > 122 || int32(c) < 97 {
				break
			}
			method += string(c)
		}

		// If no method is provided, we default to GET.
		if _, ok := validMethods[strings.ToUpper(method)]; !ok {
			path = field.Name
			method = "GET"
		} else {
			path = field.Name[len(method):]
		}

		switch path[len(path)-1:] {
		case "S":
			path = path[:len(path)-1]
			hasSlash = true
			rt.MandatorySlash = true
		case "O":
			path = path[:len(path)-1]
			hasSlash = true
			rt.OptionalSlash = true
			rt.SlashIsDefault = true
		case "N":
			path = path[:len(path)-1]
			rt.MandatoryNoSlash = true
		default:
			rt.OptionalSlash = true
		}

		rt.Path = ""
		for _, c := range path {
			switch {
			case int32(c) >= 97 && int32(c) <= 122:
				rt.Path += strings.ToLower(string(c))
			case c == '_':
				break
			case int32(c) > 47 && int32(c) < 58:
				rt.Path += "-"
				rt.Path += string(c)
			case strings.ToUpper(string(c)) == string(c):
				if rt.Path == "" {
					rt.Path = strings.ToLower(string(c))
					break
				}
				rt.Path += "-"
				rt.Path += strings.ToLower(string(c))
			default:
				rt.Path += strings.ToLower(string(c))
			}
		}

		// Already mapped.
		if _, ok = has[rt.Method+":"+path]; ok {
			continue
		}

		rt.special = strings.ToLower(method + "-" + rt.Path)
		rt.Path = basePath + "/" + rt.Path
		rt.Method = strings.ToUpper(method)
		rt.Endpoint = Endpoint(fn)

		if hasSlash {
			rt.Path += "/"
		}

		routes = append(routes, rt)
	}

	return routes
}