router/server.go

package router

import (
	"io"
	"net/http"
	"net/url"

	"somehole.com/common/log"
)

type response struct {
	Status int
	Header Header
	Body   Body
}

type Response[RSB ResponseBuilder] struct {
	response
}

func NewResponse[RSB ResponseBuilder](rsb RSB) *Response[RSB] {
	return &Response[RSB]{*rsb.Response()}
}

type Error interface {
	Error(e Error) (err Error)
	Status() (code int)
	String() (out string)
	Response() (res *response)
}

type request struct {
	Url    url.URL
	Header Header
	Values Values
	Body   Body
}

type Request[RQB RequestBuilder] struct {
	request
}

func NewRequest[RQB RequestBuilder](rqb RQB) *Request[RQB] {
	return &Request[RQB]{*rqb.Request()}
}

func (*Request[RQB]) RequestBuilder() RequestBuilder {
	var rqb RQB
	return rqb.New()
}

type RequestBuilder interface {
	mustEmbedDefaultRequestBuilder()
	New() (rqb RequestBuilder)
	Allowed(method string) (err Error)
	Url(url url.URL) (err Error)
	Header(map[string][]string) (err Error)
	Values(map[string][]string) (err Error)
	Body(body io.ReadCloser) (err Error)
	Request() *request
}

func (*Response[RSB]) ResponseBuilder() ResponseBuilder {
	var rsb RSB
	return rsb.New()
}

type ResponseBuilder interface {
	mustEmbedDefaultResponseBuilder()
	New() (rsb ResponseBuilder)
	Header(header Header) (err Error)
	Write(body []byte) (err Error)
	Response() *response
}

type writer struct {
	http.ResponseWriter
	log.Logger
}

func (w *writer) handleError(err Error) (ok bool) {
	if err != nil {
		res := err.Response()
		for key, value := range res.Header {
			for _, v := range value {
				w.Header().Add(key, v)
			}
		}
		w.WriteHeader(res.Status)
		w.Write(res.Body)
		w.Logf(log.LevelError, err.String())
		return false
	}
	return true
}

type serveStage uint8

const (
	servePre serveStage = iota
	serveMain
	servePost
	numServeStages
)

type ServeFunc[RQB RequestBuilder, RSB ResponseBuilder] func(req *Request[RQB]) (res *Response[RSB], err Error)

type server[RQB RequestBuilder, RSB ResponseBuilder] struct {
	logger log.Logger
	serve  [numServeStages][]ServeFunc[RQB, RSB]
}

func NewServer[RQB RequestBuilder, RSB ResponseBuilder](serve ServeFunc[RQB, RSB]) (srv *server[RQB, RSB]) {
	srv = &server[RQB, RSB]{
		serve: [numServeStages][]ServeFunc[RQB, RSB]{},
	}
	srv.serve[serveMain] = append(srv.serve[serveMain], serve)
	return srv
}

func (srv *server[RQB, RSB]) SetLogger(logger log.Logger) *server[RQB, RSB] {
	srv.logger = logger
	return srv
}

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

func (srv *server[RQB, RSB]) PreServeFunc(serve ServeFunc[RQB, RSB]) *server[RQB, RSB] {
	return srv.addServeFunc(servePre, serve)
}

func (srv *server[RQB, RSB]) AddServeFunc(serve ServeFunc[RQB, RSB]) *server[RQB, RSB] {
	return srv.addServeFunc(serveMain, serve)
}

func (srv *server[RQB, RSB]) PostServeFunc(serve ServeFunc[RQB, RSB]) *server[RQB, RSB] {
	return srv.addServeFunc(servePost, serve)
}

func (srv *server[RQB, RSB]) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	var rqb RQB
	rqb = rqb.New().(RQB)
	wr := writer{ResponseWriter: w, Logger: srv.logger}
	if ok := wr.handleError(rqb.Allowed(r.Method)); !ok {
		return
	}
	if ok := wr.handleError(rqb.Url(*r.URL)); !ok {
		return
	}
	if ok := wr.handleError(rqb.Header(r.Header)); !ok {
		return
	}
	if ok := wr.handleError(rqb.Body(r.Body)); !ok {
		return
	}
	r.ParseForm()
	if ok := wr.handleError(rqb.Values(r.Form)); !ok {
		return
	}
	for _, stage := range srv.serve {
		for _, s := range stage {
			res, err := s(NewRequest(rqb))
			if ok := wr.handleError(err); !ok {
				return
			}
			if res.Header != nil {
				for key, value := range res.Header {
					for _, v := range value {
						wr.Header().Add(key, v)
					}
				}
			}
			if len(res.Body) > 0 {
				wr.Write(res.Body)
			}
		}
	}
}