package main

import (
	"fmt"
	"io"
	"net"
	"log"
	"net/http"
	"net/url"
	"time"
)

type ReverseProxy struct {
	URL    *url.URL
	jwtKey string
}

func (rp *ReverseProxy) reverseProxyHandlerFunc() http.Handler {
	return http.HandlerFunc(rp.reverseProxyHandler)
}

func (rp *ReverseProxy) reverseProxyHandler(rw http.ResponseWriter, req *http.Request) {
	fmt.Printf("[sidoxy] Reverse proxy received request at: %s\n", time.Now())

	// set req Host, URL and Request URI to forward a request to the origin server
	req.Host = rp.URL.Host
	req.URL.Host = rp.URL.Host
	req.URL.Scheme = rp.URL.Scheme
	req.RequestURI = ""

	// set X-FORWARDED-FOR
	xForwardedFor := req.Header.Get("X-Forwarded-For")
	var remoteAddr string
	if xForwardedFor != "" {
		remoteAddr = xForwardedFor
	} else {
		remoteAddr, _, _ = net.SplitHostPort(req.RemoteAddr)
	}
	req.Header.Set("X-Forwarded-For", remoteAddr)
	fmt.Printf("[sidoxy] Reverse proxy setting X-Forwarded-For to %s\n", remoteAddr)

	// TODO: To be implemented
	// decode JWT if key present
	if rp.jwtKey != "" {
		jwtDecode(rp.jwtKey, req.Header.Get("JWT_TOKEN"), req)
	}

	// save the response from the origin server
	originServerResponse, err := http.DefaultClient.Do(req)
	if err != nil {
		rw.WriteHeader(http.StatusInternalServerError)
		_, _ = fmt.Fprint(rw, err)
		return
	}

	fmt.Printf("[sidoxy] Reverse proxy setting the following return headers\n")
	// return Header response
	for key, values := range originServerResponse.Header {
		for _, value := range values {
			fmt.Printf("[sidoxy] \t%v: %v\n", key, value)
			rw.Header().Set(key, value)
		}
	}

	// support stream
	done := make(chan bool)
	defer close(done)
	go func() {
		for {
			select {
			case <-time.Tick(10 * time.Millisecond):
				rw.(http.Flusher).Flush()
			case <-done:
				return
			}
		}
	}()

	// return response to the client
	rw.WriteHeader(http.StatusOK)
	io.Copy(rw, originServerResponse.Body)
}

func parse_url(host_url string) *url.URL {
	h_url, err := url.Parse(host_url)
	if err != nil {
		log.Fatal("[sidoxy] Invalid server URL: " + host_url)
	}
	return h_url
}

func listen_and_serve(address string, handler http.Handler) error {
	return http.ListenAndServe(address, handler)
}