package watermark

import (
	"errors"
	"github.com/nfnt/resize"
	"image"
	"image/draw"
	"image/jpeg"
	"image/png"
	"os"
	"sync"
)

func AddWatermark(origImage string, watermarkImage string) (image.Image, error) {
	wg := sync.WaitGroup{}

	var img image.Image
	var watermark image.Image

	wg.Add(1)
	go func() {
		defer wg.Done()
		var err error
		file, err := os.Open(origImage)
		if err != nil {
			return
		}
		defer file.Close()

		img, err = jpeg.Decode(file)
		if err != nil {
			return
		}
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()
		var err error
		watermarkFile, err := os.Open(watermarkImage)
		if err != nil {
			return
		}
		defer watermarkFile.Close()

		watermark, err = png.Decode(watermarkFile)
		if err != nil {
			return
		}
	}()
	wg.Wait()

	if img == nil || watermark == nil {
		return nil, errors.New("failed to decode image")
	}

	offset := image.Pt(10, 10)
	b := img.Bounds()
	m := image.NewRGBA(b)
	draw.Draw(m, b, img, image.Point{}, draw.Src)
	draw.Draw(m, watermark.Bounds().Add(offset), watermark, image.Point{}, draw.Over)
	return m, nil
}

func Resize(img image.Image, width int) image.Image {
	return resize.Resize(uint(width), 0, img, resize.Lanczos3)
}