package server

import (
	"tunnel/pkg/config"
	"tunnel/pkg/netstring"
	"strings"
	"errors"
	"bytes"
	"sync"
	"time"
	"fmt"
	"log"
	"net"
	"io"
)

type Server struct {
	listen net.Listener
	since time.Time

	wg sync.WaitGroup
	mu sync.Mutex

	once sync.Once
	done chan struct{}

	tunnels automap
	env env

	nextCid int
}

type client struct {
	id int

	s *Server

	conn net.Conn

	nextRid int
}

type request struct {
	id int

	c *client

	cmd *cmd

	argc int
	args []string

	out *bytes.Buffer
}

type requestError string

var errNotImplemented = errors.New("not implemented")

func (c *client) String() string {
	return fmt.Sprintf("client(%d)", c.id)
}

func (r *request) String() string {
	return fmt.Sprintf("request(%d)", r.id)
}

func (r *request) Print(v ...interface{}) {
	fmt.Fprint(r.out, v...)
}

func (r *request) Printf(format string, v ...interface{}) {
	fmt.Fprintf(r.out, format, v...)
}

func (r *request) Println(v ...interface{}) {
	fmt.Fprintln(r.out, v...)
}

func (r *request) Fatal(v ...interface{}) {
	panic(requestError(fmt.Sprint(v...)))
}

func (r *request) Fatalf(format string, v ...interface{}) {
	panic(requestError(fmt.Sprintf(format, v...)))
}

func (r *request) expect(c ...int) {
	desc := func (n int) string {
		var sep string

		if n == 1 {
			sep = " is "
		} else {
			sep = " are "
		}

		return fmt.Sprint(n, sep, "expected")
	}

	check := func (cond bool, args ...interface{}) {
		if cond {
			r.Fatal(args...)
		}
	}

	switch len(c) {
	case 0:
		check(r.argc > 0, "args are not expected")
	case 1:
		check(r.argc < c[0], "not enough args: ", desc(c[0]))
		check(r.argc > c[0], "too many args: ", desc(c[0]))
	case 2:
		check(r.argc < c[0], "not enough args: at least ", desc(c[0]))
		check(r.argc > c[1], "too many args: no more than ", desc(c[1]))
	}
}

func (s *Server) isDone() bool {
	select {
	case <- s.done:
		return true
	default:
		return false
	}
}

func New() (*Server, error) {
	listen, err := net.Listen(config.SockType, config.SockPath)
	if err != nil {
		return nil, err
	}

	s := &Server{
		listen: listen,
		since: time.Now(),
		done: make(chan struct{}),
		tunnels: make(automap),
	}

	return s, nil
}

func (s *Server) Run() {
	for {
		conn, err := s.listen.Accept()
		if err != nil {
			if s.isDone() {
				break
			}

			log.Print(err)
			continue
		}

		c := s.newClient(conn)

		log.Println(c, "accept")

		s.wg.Add(1)

		go c.handle()
	}

	s.wg.Wait()
}

func (s *Server) Stop() {
	s.once.Do(func () {
		close(s.done)
		s.listen.Close()
	})
}

func (s *Server) newClient(conn net.Conn) *client {
	c := &client{
		s:	s,
		conn:	conn,
		id:	s.nextCid,
	}

	s.nextCid++

	return c
}

func (c *client) newRequest() *request {
	r := &request{
		c:	c,
		id:	c.nextRid,
		out:	new(bytes.Buffer),
	}

	c.nextRid++

	return r
}

func (c *client) handle() {
	defer c.close()

	buf := make([]byte, config.BufSize)

	for {
		nr, er := c.conn.Read(buf)
		if er != nil {
			if er != io.EOF {
				log.Println(c, "handle:", er)
			}
			break
		}

		query := string(buf[:nr])

		r := c.newRequest()

		r.run(query)

		if r.out.Len() == 0 {
			r.out.Write([]byte("\n"))
		}

		_, ew := c.conn.Write(r.out.Bytes())
		if ew != nil {
			log.Println(c, "handle:", ew)
			break
		}
	}
}

func (r *request) decode(query string) []string {
	dec := netstring.NewDecoder(bytes.NewReader([]byte(query)))
	var t []string

	for {
		if s, err := dec.Decode(); err == nil {
			t = append(t, s)
		} else {
			if err == io.EOF {
				break
			}

			r.Fatal("failed to parse request")
		}
	}

	return t
}

func (r *request) eval(args []string) []string {
	repl := func (v string) string {
		if v, ok := r.c.s.env.get(v[1:]); ok {
			return v
		}

		r.Fatal("unbound variable ", v)

		return v
	}

	eval := func (s string) string {
		var t string

		for ;; s = t {
			t = varTokenRe.ReplaceAllStringFunc(s, repl)

			if s == t {
				return s
			}
		}
	}

	for n, s := range args {
		if strings.HasPrefix(s, "^") {
			args[n] = s[1:]
		} else {
			args[n] = eval(s)
		}
	}

	return args
}

func (r *request) parse(query string) {
	args := r.eval(r.decode(query))

	c, args := getCmd(args)
	if c == nil {
		r.Fatal("command not found")
	}

	r.args = args
	r.argc = len(args)
	r.cmd = c
}

func (r *request) run(query string) {
	defer func () {
		switch err := recover().(type) {
		case requestError:
			r.Print(err)
		default:
			panic(err)
		case nil:
		}
	}()

	r.parse(query)

	log.Println(r.c, r, ">", r.cmd.name, strings.Join(r.args, " "))

	r.c.s.mu.Lock()
	defer r.c.s.mu.Unlock()

	r.cmd.f(r)
}

func (c *client) close() {
	log.Println(c, "close")

	c.conn.Close()
	c.s.wg.Done()
}