package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"html/template"
	"log"
	"net"
	"sync"

	"github.com/codegangsta/martini"
	"github.com/codegangsta/martini-contrib/render"
)

type Header int32
type Packet [50]uint16

var mutex sync.Mutex
var templateMap = make(map[string]interface{})
var controlTable, stateTable string

func main() {
	go ListenUDP()

	m := martini.Classic()

	m.Use(render.Renderer())

	m.Get("/", func(r render.Render) {
		mutex.Lock()
		defer mutex.Unlock()

		r.HTML(200, "main", templateMap)
	})

	m.Run()
}

func ListenUDP() {
	addr, err := net.ResolveUDPAddr("udp", ":40001")
	if err != nil {
		log.Fatal(err)
	}

	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	for {
		b := make([]byte, 1024)
		_, _, err := conn.ReadFromUDP(b)
		if err != nil {
			log.Fatal(err)
		}

		buf := bytes.NewReader(b)

		var header Header
		err = binary.Read(buf, binary.LittleEndian, &header)
		if err != nil {
			log.Fatal(err)
		}

		var packet Packet
		err = binary.Read(buf, binary.LittleEndian, &packet)
		if err != nil {
			log.Fatal(err)
		}

		switch header {
		case 0:
			mapControl(packet)
		case 1:
			mapState(packet)
		}
	}
}

func mapControl(packet Packet) {
	mutex.Lock()
	defer mutex.Unlock()

	controlTable = ""
	for i, v := range packet {
		controlTable += fmt.Sprintf("<tr><td>%v</td><td>0x%04X</td><td>0x%04X</td><td>%d</td></tr>\n", 30001+i, i, v, v)
	}

	templateMap["Table_Control"] = template.HTML(controlTable)
}

func mapState(packet Packet) {
	mutex.Lock()
	defer mutex.Unlock()

	stateTable = ""
	for i, v := range packet {
		stateTable += fmt.Sprintf("<tr><td>%v</td><td>0x%04X</td><td>0x%04X</td><td>%d</td></tr>\n", 40001+i, i, v, v)
	}

	templateMap["Table_State"] = template.HTML(stateTable)
}