package main

import (
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/signal"
	"reflect"
	"strings"
	"syscall"
	"time"
)

type http_method uint8; const (
	GET http_method = iota
	POST
	PATCH
	PUT
	DELETE
)
func (method http_method) to_string() string {
	switch method {
	case GET:
		return http.MethodGet
	case POST:
		return http.MethodPost
	case PATCH:
		return http.MethodPatch
	case PUT:
		return http.MethodPut
	case DELETE:
		return http.MethodDelete
	}

	return ""
}


type http_status_code int; const (
	OK http_status_code = http.StatusOK
	INTERNAL_SERVER_ERROR http_status_code = http.StatusInternalServerError
	BAD_REQUEST http_status_code = http.StatusBadRequest
)

type empty_request_body struct {}
/* T Representing any request body struct
   S Representing any response body struct */
func http_new_route[T any, S any](method http_method, route string, handle_func func(body T, raw_request *http.Request) (S, http_status_code)) {
	http.HandleFunc(method.to_string() + " /" + route, func(response http.ResponseWriter, request *http.Request) {
		request_body_bytes, err := io.ReadAll(request.Body)
		if err != nil {
			response.WriteHeader(int(INTERNAL_SERVER_ERROR))
			log.Panicln(err)
			return
		}
		var decode_result T
		if len(request_body_bytes) != 0 {
			decoder := json.NewDecoder(strings.NewReader(string(request_body_bytes)))
			decoder.DisallowUnknownFields()
			err = decoder.Decode(&decode_result)
			if err != nil {
				response.WriteHeader(int(BAD_REQUEST))
				response.Write([]byte(err.Error()))
				log.Println(err)
				return
			}
		}

		body, status_code := handle_func(decode_result, request)
		encode_result, err := json.Marshal(body)
		if err != nil {
			response.WriteHeader(int(INTERNAL_SERVER_ERROR))
			log.Panicln(err)
			return
		}
		fmt.Println(reflect.VisibleFields(reflect.TypeOf(body)))

		response.WriteHeader(int(status_code))
		response.Write(encode_result)
	})

}

func main() {
	type foo_request_body struct {
		Arg1 int
		Arg2 int
	}
	type foo_response_body struct {
		Field1 string
		Field2 int
	}
	foo_route_handler := func(body foo_request_body, raw_request *http.Request) (foo_response_body, http_status_code) {
		return foo_response_body {
			Field1: "hi there on foo!",
			Field2: body.Arg1 + body.Arg2,
		}, OK
	}
	http_new_route(GET, "foo", foo_route_handler)

	type bar_response_body struct {
		Response int
		Message string
	}
	bar_route_handler := func(body empty_request_body, raw_request *http.Request) (bar_response_body, http_status_code) {
		return bar_response_body {
			Response: 400,
			Message: "hi there on bar!",
		}, INTERNAL_SERVER_ERROR
	}
	http_new_route(GET, "bar", bar_route_handler)

	http_server := &http.Server{
		Addr: ":8080",
		Handler: nil,
		ReadTimeout: 10 * time.Second,
		WriteTimeout: 10 * time.Second,
		MaxHeaderBytes: 1 << 20,
	}
	go func() {
		log.Fatal(http_server.ListenAndServe())
	}()
	fmt.Println("Server started! Listening in on ", http_server.Addr)

	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, os.Interrupt, syscall.SIGTERM)
	<-sigs
	fmt.Println("Server stopped!")
	os.Exit(1)
}