router/server.go

package router

import (
	"net/http"

	"somehole.com/common/log"
)

type stage uint8

const (
	pre stage = iota
	main
	post
	numStages
)

type ServeFunc func(req RequestBuilder, res Response) (errRes ErrorResponse)

type server struct {
	prototype Prototype
	logger    log.Logger
	serve     [numStages][]ServeFunc
}

func NewServer[RB RequestBuilder, R Response](requestBuilder RB, response R, logger log.Logger, serve func(RB) (R, ErrorResponse)) (srv *server) {
	srv = &server{
		prototype: Prototype{
			PrototypeRequestBuilder: requestBuilder.Prototype(),
			PrototypeResponse:       response.Prototype(),
		},
		logger: logger,
		serve:  [numStages][]ServeFunc{},
	}
	srv.serve[main] = append(srv.serve[main], func(req RequestBuilder, res Response) (errRes ErrorResponse) {
		res, errRes = serve(req.(RB))
		return
	})
	return srv
}

func (srv *server) addServeFunc(when stage, serve ServeFunc) *server {
	if srv.serve[when] == nil {
		srv.serve[when] = make([]ServeFunc, 0)
	}
	srv.serve[when] = append(srv.serve[when], serve)
	return srv
}

func (srv *server) PreServeFunc(serve ServeFunc) *server {
	return srv.addServeFunc(pre, serve)
}

func (srv *server) AddServeFunc(serve ServeFunc) *server {
	return srv.addServeFunc(main, serve)
}

func (srv *server) PostServeFunc(serve ServeFunc) *server {
	return srv.addServeFunc(post, serve)
}

func (srv *server) handleError(errRes ErrorResponse, w http.ResponseWriter) (ok bool) {
	if !errRes.Ok() {
		w.WriteHeader(errRes.HttpStatus())
		w.Write(errRes.BodyBytes())
		srv.logger.Logf(log.LevelError, errRes.String())
		return false
	}
	return true
}

func (srv *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	p := srv.prototype
	req := p.PrototypeRequestBuilder.RequestBuilder()
	if ok := srv.handleError(req.Allowed(r.Method), w); !ok {
		return
	}
	if ok := srv.handleError(req.Header(Header(r.Header)), w); !ok {
		return
	}
	if ok := srv.handleError(req.ReadBody(r.Body), w); !ok {
		return
	}
	r.ParseForm()
	if ok := srv.handleError(req.Values(Values(r.Form)), w); !ok {
		return
	}
	res := p.PrototypeResponse.Response()
	for _, stage := range srv.serve {
		for _, s := range stage {
			if ok := srv.handleError(s(req, res), w); !ok {
				return
			}
			header := res.Header()
			if header != nil {
				for key, value := range res.Header() {
					for _, v := range value {
						w.Header().Add(key, v)
					}
				}
			}
		}
	}
	w.Write(res.BodyBytes())
}