package main

import (
	"encoding/json"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/exec"
	"strconv"
	"strings"
)

type Configuration struct {
	Listen string
	Vcp string
}

var configuration = Configuration{
	Listen: "127.0.0.1:49281",
	Vcp: "10"}

type Brightness struct {
	Lock         bool
	Value        int
	ToggledValue int
}

var currentBrightness Brightness

func update() {
	if currentBrightness.Lock == false {
		currentBrightness.Lock = true
		cmd := exec.Command("ddcutil", "getvcp", "--brief", configuration.Vcp)
		log.Println(cmd.String())
		out, err := cmd.CombinedOutput()
		if err != nil {
			log.Println(err)
			return
		}
		outString := strings.Split(strings.Trim(string(out), "\n"), " ")
		currentBrightness.Value, err = strconv.Atoi(outString[len(outString)-2])
		if err != nil {
			log.Println(err)
			return
		}
		log.Println("Current brightness is", currentBrightness.Value)
		currentBrightness.Lock = false
	} else {
		log.Println("Active lock, no operation performed")
		return
	}
}

func get(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
                log.Println("Current brightness cached value is",
			currentBrightness.Value)
	}
}

func ddcutilSetBrightness(brightness Brightness) {
	if currentBrightness.Lock == false {
		currentBrightness.Lock = true
		cmd := exec.Command("ddcutil", "setvcp", configuration.Vcp,
			strconv.Itoa(brightness.Value))
		log.Println(cmd.String())
		_, err := cmd.CombinedOutput()
		if err != nil {
			log.Println(err)
			return
		}
		currentBrightness.Value = brightness.Value
		currentBrightness.Lock = false
	} else {
		log.Println("Active lock, no operation performed")
		return
	}
}

func set(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		body, err := io.ReadAll(r.Body)
		if err != nil {
			log.Println(err)
			return
		}
		var brightness Brightness
		json.Unmarshal([]byte(body), &brightness)
		ddcutilSetBrightness(brightness)
	}
}

func decrease(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		body, err := io.ReadAll(r.Body)
		if err != nil {
			log.Println(err)
			return
		}
		var brightness Brightness
		json.Unmarshal([]byte(body), &brightness)
		newValue := Brightness{Value: currentBrightness.Value - brightness.Value}
		if newValue.Value < 0 {
			log.Println("Brightness is minimum")
		} else {
			ddcutilSetBrightness(newValue)
			log.Println("Current brightness is", currentBrightness.Value)
		}
	} else {
		log.Println("Active lock, no operation performed")
		return
	}
}

func increase(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		body, err := io.ReadAll(r.Body)
		if err != nil {
			log.Println(err)
			return
		}
		var brightness Brightness
		json.Unmarshal([]byte(body), &brightness)
		newValue := Brightness{Value: currentBrightness.Value + brightness.Value}
		if newValue.Value > 100 {
			log.Println("Brightness is maximum")
		} else {
			ddcutilSetBrightness(newValue)
			log.Println("Current brightness is", currentBrightness.Value)
		}
	} else {
		log.Println("Active lock, no operation performed")
		return
	}
}

func toggle(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		if currentBrightness.Value == 0 {
			ddcutilSetBrightness(Brightness{Value: currentBrightness.ToggledValue})
			log.Println("Current brightness is", currentBrightness.Value)
		} else {
			currentBrightness.ToggledValue = currentBrightness.Value
			ddcutilSetBrightness(Brightness{Value: 0})
			log.Println("Current brightness is", currentBrightness.Value)
		}
	}
}

func main() {
	jsonFile, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln(err)
	}
	byteValue, err := ioutil.ReadAll(jsonFile)
	if err != nil {
		log.Fatalln(err)
	}
	var configuration Configuration
	json.Unmarshal(byteValue, &configuration)
	jsonFile.Close()

	currentBrightness.Lock = false
	update()
	http.HandleFunc("/update", func(w http.ResponseWriter, r *http.Request) {
		update()
	})
	http.HandleFunc("/get", get)
	http.HandleFunc("/set", set)
	http.HandleFunc("/decrease", decrease)
	http.HandleFunc("/increase", increase)
	http.HandleFunc("/toggle", toggle)
	log.Fatal(http.ListenAndServe(configuration.Listen, nil))
}