package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path"
	"strconv"
	"strings"
	"time"
)

type sunsetConfig struct {
	Files []sunsetImage `json:"files"`
}

type sunsetImage struct {
	File string `json:"file"`
	Time string `json:"time"`
}

func loadSunsetConfig(filepath string) sunsetConfig {
	data, err := ioutil.ReadFile(filepath)

	var result sunsetConfig

	err = json.Unmarshal(data, &result)
	if err != nil {
		log.Fatal("Failed to load file: ", err.Error())
	}

	return result
}

func currentIndex(config sunsetConfig) int {
	currentTime := getCurrentTime()

	var min int = 2401
	var minIndex int = -1

	for i := 0; i < len(config.Files); i++ {
		element := getTimeSimple(config.Files[i].Time)

		diff := currentTime - element

		if diff < 0 {
			diff = 2400 - (diff * -1)
		}

		if diff < min {
			min = diff
			minIndex = i
		}
	}

	return minIndex
}

func nextIndex(config sunsetConfig) int {
	currentTime := getCurrentTime()

	var min int = 2401
	var minIndex int = -1

	for i := 0; i < len(config.Files); i++ {
		element := getTimeSimple(config.Files[i].Time)

		diff := element - currentTime

		if diff < 0 {
			diff = 2400 - (diff * -1)
		}

		if diff < min {
			min = diff
			minIndex = i
		}
	}

	return minIndex
}

func getCurrentTime() int {
	now := time.Now()

	hr := now.Hour()
	min := now.Minute()

	return hr*100 + min
}

func getTimeSimple(timeString string) int {
	hr, min := getTime(timeString)

	return hr*100 + min
}

func getNextTime(config sunsetConfig) string {
	index := nextIndex(config)
	return config.Files[index].Time
}

func getTime(timeString string) (int, int) {
	splits := strings.Split(timeString, ":")
	hr, _ := strconv.ParseInt(splits[0], 10, 32)
	min, _ := strconv.ParseInt(splits[1], 10, 32)
	// res, err := time.Parse("15:04", fmt.Sprintf("%02d:%02d", hr, min))
	// if err != nil {
	// 	log.Fatal(err)
	// }
	return int(hr), int(min)
}

func getNextWait(config sunsetConfig) (int, int) {
	index := nextIndex(config)
	now := time.Now()
	nextHr, nextMin := getTime(config.Files[index].Time)

	var diffHr int
	var diffMin int

	// FIXME still not working
	if now.Hour() >= nextHr && now.Minute() >= nextMin {
		diffHr = 24 - (now.Hour() - nextHr)
		diffMin = 60 - (now.Minute() - nextMin)
	} else {
		diffHr = nextHr - now.Hour()
		diffMin = nextMin - now.Minute()
	}

	return diffHr, diffMin
}

func block(config sunsetConfig, command string) {
	for {
		nextHr, nextMin := getNextWait(config)
		timer := time.NewTimer((time.Duration(nextHr) * time.Hour) + (time.Duration(nextMin) * time.Minute))
		<-timer.C
		log.Printf("Running command: %s\n", command)
		go runCommand(command)
	}
}

func runCommand(command string) {
	cmd := exec.Command("/usr/bin/env", "sh", "-c", command)
	err := cmd.Run()
	if err != nil {
		log.Printf("Command %s returned a non 0 code", command)
	}
}

func main() {
	printNextTime := flag.Bool("next", false, "Print the time to the next change")
	printNextWait := flag.Bool("wait", false, "Print the time to wait for the next change")
	blockFlag := flag.Bool("block", false, "Block and call the provided command when the background changes")
	blockCommand := flag.String("command", "", "Specify a command to run when the background changed")
	configFile := flag.String("file", "./sunset.json", "Specify the file to load")
	flag.Parse()

	conf := loadSunsetConfig(*configFile)

	if *printNextTime {
		fmt.Printf("%s", getNextTime(conf))
	} else if *printNextWait {
		hr, min := getNextWait(conf)
		fmt.Printf("%dh%dm", hr, min)

	} else if *blockFlag {
		if *blockCommand == "" {
			fmt.Println("Must provide a command.")
			os.Exit(1)
		}
		block(conf, *blockCommand)
	} else {
		index := currentIndex(conf)
		absoluteImagePath := path.Join(path.Dir(*configFile), conf.Files[index].File)
		fmt.Printf("%s", absoluteImagePath)
	}

}