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

package server

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/signal"
	"time"
	"vegvisir/pkg/cache"
	"vegvisir/pkg/config"

	"github.com/valyala/fasthttp"
)

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

type Server struct {
	config *config.Config
	router *Router
	respCM cache.ResponseCacheManager // Redis response cache
}

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

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

	datastore := cache.GetCacheDatastore(config.Cache)

	return &Server{
		config: config,
		router: NewRouter(config, *datastore, config.Cache.RouteTtl),
		respCM: cache.NewResponseCacheManager(*datastore, config.Cache.ResponseTtl),
	}
}

func (s *Server) Run() {
	go func() {
		serverAddress := s.config.Server.Address + ":" + fmt.Sprint(s.config.Server.Port)
		if err := fasthttp.ListenAndServe(serverAddress, s.mainHandler); err != nil {
			log.Fatalf("Server panic! Error message: %s", err)
		}
	}()

	log.Println("Server started")

	// Wait for an interrupt
	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt, os.Kill)
	<-interrupt

	log.Println("SIGKILL or SIGINT caught, shutting down...")

	// Attempt a graceful shutdown
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

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

func (s *Server) Shutdown(ctx context.Context) { // TODO: wait for all connections to finish
	log.Println("Shuting down finished")
}

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 404/5xx error in repsonse, maybe define it in Backend config?
		ctx.SetStatusCode(fasthttp.StatusNotFound)
		return
	}

	// handle response caching
	if ok, data := s.respCM.Load(sReqUrl); ok {
		log.Println("Read resp from cache: ", route.TargetUrl)

		// copy headers and body from cache
		ctx.Response.Header.DisableNormalizing()
		for key, value := range data.Headers {
			ctx.Response.Header.Set(key, value)
		}
		ctx.SetBody([]byte(data.Body))
	} else {
		log.Println("Send req to backend url: ", route.TargetUrl)

		// prepare to send request to backend - separate
		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(sReqMethod)

		err := fasthttp.Do(bckReq, bckResp)
		if err != nil {
			ctx.SetStatusCode(fasthttp.StatusInternalServerError)
			return
		}

		headers := make(cache.Headers)
		// rewrite headers from backend to gateway response
		bckResp.Header.Set(fasthttp.HeaderServer, ServerName)
		bckResp.Header.Del(fasthttp.HeaderXPoweredBy)
		ctx.Response.Header.DisableNormalizing()
		bckResp.Header.VisitAll(func(key, value []byte) {
			headers[string(key)] = string(value)
			ctx.Response.Header.SetBytesKV(key, value)
		})
		// ctx.SetStatusCode(bckResp.StatusCode())
		ctx.SetBody(bckResp.Body())

		// save response to cache
		respCache := cache.ResponseCache{
			URL:     sReqUrl,
			Body:    string(bckResp.Body()),
			Headers: headers,
		} // FIXME: prepare resp cache struct in respCM.Save method or other service...
		s.respCM.Save(sReqUrl, respCache)
	}
}