package web

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"sync"
	"sync/atomic"

	"git.loafle.net/commons/logging-go"
	"git.loafle.net/commons/server-go"
	"git.loafle.net/commons/server-go/socket"
	"github.com/valyala/fasthttp"
)

type Server struct {
	ServerHandler ServerHandler

	ctx      server.ServerCtx
	stopChan chan struct{}
	stopWg   sync.WaitGroup

	srw socket.ServerReadWriter

	hs       *fasthttp.Server
	upgrader *Upgrader
}

func (s *Server) ListenAndServe() error {
	var (
		err      error
		listener net.Listener
	)
	if nil == s.ServerHandler {
		return fmt.Errorf("Server: server handler must be specified")
	}
	s.ServerHandler.Validate()

	if s.stopChan != nil {
		return fmt.Errorf(s.serverMessage("already running. Stop it before starting it again"))
	}

	s.ctx = s.ServerHandler.ServerCtx()
	if nil == s.ctx {
		return fmt.Errorf(s.serverMessage("ServerCtx is nil"))
	}

	s.hs = &fasthttp.Server{
		Handler:         s.httpHandler,
		Name:            s.ServerHandler.GetName(),
		Concurrency:     s.ServerHandler.GetConcurrency(),
		ReadBufferSize:  s.ServerHandler.GetReadBufferSize(),
		WriteBufferSize: s.ServerHandler.GetWriteBufferSize(),
		ReadTimeout:     s.ServerHandler.GetReadTimeout(),
		WriteTimeout:    s.ServerHandler.GetWriteTimeout(),
	}

	s.upgrader = &Upgrader{
		HandshakeTimeout:  s.ServerHandler.GetHandshakeTimeout(),
		ReadBufferSize:    s.ServerHandler.GetReadBufferSize(),
		WriteBufferSize:   s.ServerHandler.GetWriteBufferSize(),
		CheckOrigin:       s.ServerHandler.(ServerHandler).CheckOrigin,
		Error:             s.onError,
		EnableCompression: s.ServerHandler.IsEnableCompression(),
	}

	if err = s.ServerHandler.Init(s.ctx); nil != err {
		return err
	}

	if listener, err = s.ServerHandler.Listener(s.ctx); nil != err {
		return err
	}

	s.stopChan = make(chan struct{})

	s.srw.ReadwriteHandler = s.ServerHandler
	s.srw.ServerStopChan = s.stopChan
	s.srw.ServerStopWg = &s.stopWg

	s.stopWg.Add(1)
	return s.handleServer(listener)
}

func (s *Server) Shutdown(ctx context.Context) error {
	if s.stopChan == nil {
		return fmt.Errorf("server must be started before stopping it")
	}
	close(s.stopChan)
	s.stopWg.Wait()

	s.ServerHandler.Destroy(s.ctx)

	s.stopChan = nil

	return nil
}

func (s *Server) serverMessage(msg string) string {
	return fmt.Sprintf("Server[%s]: %s", s.ServerHandler.GetName(), msg)
}

func (s *Server) handleServer(listener net.Listener) error {
	var (
		err      error
		stopping atomic.Value
	)

	defer func() {
		if nil != listener {
			listener.Close()
		}
		s.ServerHandler.OnStop(s.ctx)

		logging.Logger().Infof(s.serverMessage("Stopped"))

		s.stopWg.Done()
	}()

	if err = s.ServerHandler.OnStart(s.ctx); nil != err {
		return err
	}

	hsCloseChan := make(chan error)
	go func() {
		if err := s.hs.Serve(listener); nil != err {
			if nil == stopping.Load() {
				hsCloseChan <- err
				return
			}
		}
		hsCloseChan <- nil
	}()

	logging.Logger().Infof(s.serverMessage("Started"))

	select {
	case err, _ := <-hsCloseChan:
		if nil != err {
			return err
		}
	case <-s.stopChan:
		stopping.Store(true)
		listener.Close()
		<-hsCloseChan
		listener = nil
	}

	return nil
}

func (s *Server) httpHandler(ctx *fasthttp.RequestCtx) {
	var (
		servlet Servlet
		err     error
	)

	if 0 < s.ServerHandler.GetConcurrency() {
		sz := s.srw.ConnectionSize()
		if sz >= s.ServerHandler.GetConcurrency() {
			logging.Logger().Warnf(s.serverMessage(fmt.Sprintf("max connections size %d, refuse", sz)))
			s.onError(ctx, fasthttp.StatusServiceUnavailable, err)
			return
		}
	}

	if servlet = s.ServerHandler.Servlet(s.ctx, ctx); nil == servlet {
		s.onError(ctx, fasthttp.StatusInternalServerError, err)
		return
	}

	var responseHeader *fasthttp.ResponseHeader
	servletCtx := servlet.ServletCtx(s.ctx)

	if responseHeader, err = servlet.Handshake(servletCtx, ctx); nil != err {
		s.onError(ctx, http.StatusNotAcceptable, fmt.Errorf("Handshake err: %v", err))
		return
	}

	s.upgrader.Upgrade(ctx, responseHeader, func(conn *socket.SocketConn, err error) {
		if err != nil {
			s.onError(ctx, fasthttp.StatusInternalServerError, err)
			return
		}

		s.stopWg.Add(1)
		s.srw.HandleConnection(servlet, servletCtx, conn)
	})
}

func (s *Server) onError(ctx *fasthttp.RequestCtx, status int, reason error) {
	s.ServerHandler.(ServerHandler).OnError(s.ctx, ctx, status, reason)
}