package main

// imports
import (
	"encoding/json"
	"flag"
	"fmt"
	"image"
	_ "image/jpeg"
	"image/png"
	"io"
	"log"
	"math/rand"
	"net/http"
	"os"
	"time"

	"github.com/kbinani/screenshot"
	"github.com/reujab/wallpaper"
)

var (
	sourceImgName   string
	outputImgName   string
	useNasa         bool
	useRandom       bool
	setWallpaper    bool
	useSketch       bool
	nasaAPI         string
	totalCycleCount = 5000
)

func init() {
	flag.BoolVar(&useNasa, "nasa", false, "Use NASA Astronomy Pic Of the Day as a source image")
	flag.BoolVar(&setWallpaper, "set", false, "Set user wallpaper to the output.")
	flag.BoolVar(&useRandom, "unsplash", false, "Use random unsplash image for seed (Will grab dimensions from background or source if set)")
	flag.BoolVar(&useSketch, "sketch", false, "Use Sketch to generate a new image.")
	flag.StringVar(&sourceImgName, "source", "", "Source image, will override current background")
	flag.StringVar(&outputImgName, "output", "out.png", "Output image filename")
	flag.StringVar(&nasaAPI, "nasa-key", "DEMO_KEY", "Supply your own API Key for NASA APOD")
}

func main() {
	flag.Parse()

	bounds := screenshot.GetDisplayBounds(0)

	var img image.Image
	var err error
	if useRandom {
		img, err = loadRandomUnsplashImage(bounds.Dx(), bounds.Dy())
		if err != nil {
			log.Panicln(err)
		}
	} else if useNasa {
		resp, err := http.Get(fmt.Sprintf("https://api.nasa.gov/planetary/apod?api_key=%+v", nasaAPI))
		if err != nil {
			log.Fatalf("\nUnable to get NASA API Response\n")
			return
		}
		var apod APODResponse
		decoder := json.NewDecoder(resp.Body)
		err = decoder.Decode(&apod)
		if err != nil {
			log.Fatalf("\nUnable to decode APOD Response: \n%+v\n", resp)
			return
		}
		file, err := os.CreateTemp(".", apod.Hdurl)
		if err != nil {
			log.Panicln(err)
		}
		defer os.Remove(file.Name())
		downloadFile(file.Name(), apod.Hdurl)
		img, err = loadImage(file.Name())
		if err != nil {
			log.Panicln(err)
		}
	} else if len(sourceImgName) > 0 {
		img, err = loadImage(sourceImgName)
		if err != nil {
			log.Panicln(err)
		}
	} else {
		background, err := wallpaper.Get()
		if err != nil {
			log.Panicln(err)
		}
		img, err = loadImage(background)
		if err != nil {
			log.Println(background)
			log.Panicln(err)
		}
	}

	s := NewSketch(img, UserParams{
		StrokeRatio:              0.75,
		DestWidth:                bounds.Dx(),
		DestHeight:               bounds.Dy(),
		InitialAlpha:             0.1,
		StrokeReduction:          0.002,
		AlphaIncrease:            0.06,
		StrokeInversionThreshold: 0.05,
		StrokeJitter:             int(0.1 * float64(bounds.Dx())),
		MinEdgeCount:             3,
		MaxEdgeCount:             8,
	})

	rand.Seed(time.Now().Unix())

	if useSketch {
		for i := 0; i < totalCycleCount; i++ {
			s.Update()
		}

		saveOutput(s.Output(), outputImgName)
	} else {

		saveOutput(img, outputImgName)
	}

	if setWallpaper {
		err = wallpaper.SetFromFile(outputImgName)
		if err != nil {
			log.Panicln(err)
		}
	}
}

func loadRandomUnsplashImage(width, height int) (image.Image, error) {
	url := fmt.Sprintf("https://source.unsplash.com/random/%dx%d", width, height)
	res, err := http.Get(url)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()

	img, _, err := image.Decode(res.Body)
	return img, err
}

func loadImage(src string) (image.Image, error) {
	file, _ := os.Open(sourceImgName)
	defer file.Close()
	img, _, err := image.Decode(file)
	return img, err
}

func saveOutput(img image.Image, filePath string) error {
	f, err := os.Create(filePath)
	if err != nil {
		return err
	}
	defer f.Close()

	// Encode to `PNG` with `DefaultCompression` level
	// then save to file
	err = png.Encode(f, img)
	if err != nil {
		return err
	}

	return nil
}

// https://stackoverflow.com/questions/33845770/how-do-i-download-a-file-with-a-http-request-in-go-language/33845771
func downloadFile(filepath string, url string) (err error) {

	// Create the file
	out, err := os.Create(filepath)
	if err != nil {
		return err
	}
	defer out.Close()

	// Get the data
	resp, err := http.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	// Writer the body to file
	_, err = io.Copy(out, resp.Body)
	if err != nil {
		return err
	}

	return nil
}