router/server.go

package router

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

	"somehole.com/common/log"
)

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

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

type Request[RQB RequestBuilder] struct {
	GenericRequest
	requestBuilder RQB
}

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

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

type RequestBuilder interface {
	mustEmbedDefaultRequestBuilder()
	New() (rqb RequestBuilder)
	SetAllowed(method string) (err Error)
	SetUrl(url url.URL) (err Error)
	SetHeader(map[string][]string) (err Error)
	SetValues(map[string][]string) (err Error)
	SetBody(body io.ReadCloser) (err Error)
	Request() *GenericRequest
}

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

type GenericResponse struct {
	Status int
	Header Header
	Body   Body
}

type Response[RSB ResponseBuilder] struct {
	GenericResponse
	responseBuilder RSB
}

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

func (res *Response[RSB]) ResponseBuilder() RSB {
	return res.responseBuilder
}

type ResponseBuilder interface {
	mustEmbedDefaultResponseBuilder()
	New() (rsb ResponseBuilder)
	SetHeader(map[string][]string) (err Error)
	SetBody(body []byte) (err Error)
	Response() *GenericResponse
}

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

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

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

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

func (srv *server[RQB, RSB]) PostServe(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 = NewRequestBuilder[RQB]()
		rsb = NewResponseBuilder[RSB]()
	)
	wr := writer{ResponseWriter: w, Logger: srv.logger}
	if ok := wr.handleError(rqb.SetAllowed(r.Method)); !ok {
		return
	}
	if ok := wr.handleError(rqb.SetUrl(*r.URL)); !ok {
		return
	}
	if ok := wr.handleError(rqb.SetHeader(r.Header)); !ok {
		return
	}
	if ok := wr.handleError(rqb.SetBody(r.Body)); !ok {
		return
	}
	r.ParseForm()
	if ok := wr.handleError(rqb.SetValues(r.Form)); !ok {
		return
	}
	req := NewRequest(rqb)
	for _, stage := range srv.serve {
		for _, serve := range stage {
			err := serve(req, rsb)
			if ok := wr.handleError(err); !ok {
				return
			}
		}
	}
	res := NewResponse(rsb)
	if res.Header != nil {
		for key, value := range res.Header {
			for _, v := range value {
				wr.Header().Add(key, v)
			}
		}
	}
	wr.WriteHeader(res.Status)
	if len(res.Body) > 0 {
		wr.Write(res.Body)
	}
}