//           ___   ____               ___       ___
// \ \  / / | _   |  __| \ \  / / || | __  || || _ |
//  \ \/ /  |___  | |__   \ \/ /  || |___  || ||___|
//   \  /   | _   | _  |   \  /   ||  __ | || ||\\
//    \/    |___  |___ |    \/    || ____| || || \\
//
// Copyright (c) 2021 Piotr Biernat. https://pbiernat.dev. MIT License
// Repo: https://git.pbiernat.dev/golang/vegvisir

package server

import (
	"context"
	"fmt"
	"git.pbiernat.dev/golang/vegvisir/pkg/cache"
	"git.pbiernat.dev/golang/vegvisir/pkg/config"
	"github.com/valyala/fasthttp"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"
)

const (
	// ServerVersion static
	ServerVersion = "0.1-dev"
	// ServerName static
	ServerName = "Vegvisir/" + ServerVersion
)

// Server struct
type Server struct {
	config *config.Config
	router *Router
	respCM cache.Manager
	daemon *fasthttp.Server
}

// NewServer function
func NewServer(cPath string) *Server {
	cfg := config.New(cPath)

	if err := cfg.Load(); err != nil {
		log.Fatalln("Unable to find config file: ", cPath, err)
	}

	datastore := cache.GetDatastore(cfg.Cache)

	return &Server{
		config: cfg,
		router: NewRouter(cfg, cache.NewMemoryDatastore(), cfg.Cache.RouteTTL),
		// ^^ INFO: Routes always use memoryCache cause low size and fast read time (optimalization)
		respCM: cache.NewCachedManager(*datastore, "response_", cfg.Cache.ResponseTTL, cache.HttpRequestHandler),
		// ^^ FIXME: add handler detection option by config etc...
	}
}

// Run function
func (s *Server) Run() {
	//s.memo = cache.New(s.processUrl)

	log.Println("Starting server...")
	go func() {
		serverAddress := s.config.Server.Address + ":" + fmt.Sprint(s.config.Server.Port)
		s.daemon = &fasthttp.Server{
			Handler:            s.mainHandler,
			ReadTimeout:        15 * time.Second,
			WriteTimeout:       20 * time.Second,
			MaxConnsPerIP:      500,
			MaxRequestsPerConn: 500,
			IdleTimeout:        15 * time.Second, // aka KeepAlive
			//CloseOnShutdown: true,
		}

		if err := s.daemon.ListenAndServe(serverAddress); err != nil {
			log.Fatalf("Server panic! Error message: %s", err)
		}
	}()

	// Wait for an interrupt and attempt a graceful shutdown
	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt, syscall.SIGTERM)
	<-interrupt
	log.Println("SIGKILL or SIGINT caught, shutting down...")
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	s.Shutdown(ctx)
	log.Println("Server shutdown successfully.")
}

// Shutdown function
func (s *Server) Shutdown(ctx context.Context) { // TODO: wait for all connections to finish
	//defer s.respCM.Close()
	//defer s.daemon.Shutdown()

	log.Println("Shutting down...")
}

func (s *Server) mainHandler(ctx *fasthttp.RequestCtx) {
	// http := client.NewHttpClient(ctx)

	// move all below logic to concrete handler or sth....
	reqURL, sReqURL, sReqMethod := ctx.RequestURI(), string(ctx.RequestURI()), string(ctx.Method())
	//log.Println("Incoming request:", sReqMethod, sReqURL)

	found, route := s.router.FindByRequestURL(reqURL)
	if !found {
		// FIXME: return 404 or 5xx error in response? Maybe define it in concrete Backend config?
		ctx.SetStatusCode(fasthttp.StatusNotFound)
		//ctx.SetConnectionClose()

		log.Println("404:", sReqMethod, sReqURL)
		return
	}

	response, err := s.respCM.Fetch(sReqURL, sReqMethod, route)
	//err, response := s.processUrl(sReqURL, sReqMethod, route)
	if err != nil {
		// FIXME: Response read error(sending 500 error response)
		ctx.SetStatusCode(fasthttp.StatusInternalServerError)
		//ctx.SetConnectionClose() // not sure if change abything with connection: keep-alive/close issue ^^

		log.Println("Response read error(sending 500 error response)", err)
		return
	}

	ctx.Response.Header.SetBytesV(fasthttp.HeaderContentType, response.Headers.ContentType())
	ctx.SetStatusCode(response.Code)
	ctx.SetBodyString(response.Body)
	//ctx.SetConnectionClose()
}

//func (s *Server) processUrl(url, method string, route *cache.RouteCache) (error, *cache.ResponseCache) {
//	// handle response caching
//	cacheKey := method + "_" + url
//	if ok, data := s.respCM.load(cacheKey, &cache.ResponseCache{}); ok {
//		log.Println("Read resp from cache: ", route.TargetURL, url)
//
//		return nil, data.(*cache.ResponseCache) // FIXME #67 - simplify
//	} else {
//		//log.Println("Send req to backend url: ", route.TargetURL, url)
//		////start := time.Now()
//		//bckReq := fasthttp.AcquireRequest()
//		//bckResp := fasthttp.AcquireResponse()
//		//defer fasthttp.ReleaseRequest(bckReq)
//		//defer fasthttp.ReleaseResponse(bckResp)
//		//
//		//// copy headers from backend response and prepare request for backend - separate
//		//bckReq.SetRequestURI(route.TargetURL)
//		//bckReq.Header.SetMethod(method)
//		//
//		//err := fasthttp.Do(bckReq, bckResp)
//		//if err != nil {
//		//	return err, nil
//		//}
//		//
//		//body, code := bckResp.Body(), bckResp.StatusCode()
//		////log.Printf("%s, %s, %d bytes\n", url, time.Since(start), len(body))
//		//// save response to cache
//		//respCache := cache.NewResponseCache(url, method, body, code, &bckResp.Header)
//		//s.respCM.save(cacheKey, respCache)
//		//
//		//return nil, respCache
//	}
//}