package nslcd_proto

import (
	"encoding/binary"
	"fmt"
	"io"
	"net"
	"reflect"
	"syscall"
)

type NslcdObject interface {
	NslcdWrite(fd io.Writer)
}
type NslcdObjectPtr interface {
	NslcdRead(fd io.Reader)
}

func write(fd io.Writer, data interface{}) {
	switch data := data.(type) {
	// basic data types
	case []byte:
		_, err := fd.Write(data)
		if err != nil {
			panic(err)
		}
	case int32:
		err := binary.Write(fd, binary.BigEndian, data)
		if err != nil {
			panic(err)
		}
	case NslcdObject:
		data.NslcdWrite(fd)
	// composite datatypes
	case string:
		write(fd, int32(len(data)))
		write(fd, []byte(data))
	case []string:
		write(fd, int32(len(data)))
		for _, item := range data {
			write(fd, item)
		}
	case net.IP:
		var af int32 = -1
		switch len(data) {
		case net.IPv4len:
			af = syscall.AF_INET
		case net.IPv6len:
			af = syscall.AF_INET6
		}
		var bytes []byte
		if af < 0 {
			bytes = make([]byte, 0)
		} else {
			bytes = data
		}
		write(fd, af)
		write(fd, int32(len(bytes)))
		write(fd, bytes)
	case []net.IP:
		write(fd, int32(len(data)))
		for _, item := range data {
			write(fd, item)
		}
	default:
		v := reflect.ValueOf(data)
		switch v.Kind() {
		case reflect.Struct:
			for i, n := 0, v.NumField(); i < n; i++ {
				write(fd, v.Field(i).Interface())
			}
		default:
			panic("Invalid structure for NSLCD protocol data")
		}
	}
	panic("not reached")
}

func read(fd io.Reader, data interface{}) {
	switch data := data.(type) {
	// basic data types
	case *[]byte:
		_, err := fd.Read(*data)
		if err != nil {
			panic(err)
		}
	case *int32:
		err := binary.Read(fd, binary.BigEndian, data)
		if err != nil {
			panic(err)
		}
	case NslcdObjectPtr:
		data.NslcdRead(fd)
	// composite datatypes
	case *string:
		var len int32
		read(fd, &len)
		buf := make([]byte, len)
		read(fd, &buf)
		*data = string(buf)
	case *[]string:
		var num int32
		read(fd, &num)
		*data = make([]string, num)
		for i := 0; i < int(num); i++ {
			read(fd, &((*data)[i]))
		}
	case *net.IP:
		var af int32
		read(fd, &af)
		var _len int32
		switch af {
		case syscall.AF_INET:
			_len = net.IPv4len
		case syscall.AF_INET6:
			_len = net.IPv6len
		default:
			panic(NslcdError(fmt.Sprintf("incorrect address family specified: %d", af)))
		}
		var len int32
		read(fd, &len)
		if len != _len {
			panic(NslcdError(fmt.Sprintf("address length incorrect: %d", len)))
		}
		buf := make([]byte, len)
		read(fd, &buf)
		*data = buf
	case *[]net.IP:
		var num int32
		read(fd, &num)
		*data = make([]net.IP, num)
		for i := 0; i < int(num); i++ {
			read(fd, &((*data)[i]))
		}
	default:
		v := reflect.ValueOf(data)
		switch v.Kind() {
		case reflect.Struct:
			for i, n := 0, v.NumField(); i < n; i++ {
				read(fd, v.Field(i).Interface())
			}
		default:
			panic("Invalid structure for NSLCD protocol data")
		}
	}
	panic("not reached")
}