package main

import (
	"fmt"
	"os"
	"path"
	"math"
	"bytes"
	"strings"
	"io/ioutil"

	"image"
	"image/color"
	"image/jpeg"
	_ "image/png"

	"github.com/gonum/plot/vg"
	"github.com/gonum/plot/vg/vgimg"
)

func addLabel(img image.Image, x, y int, label string) image.Image {
	bounds := img.Bounds()
	var w, h vg.Length
	w = vg.Length(bounds.Max.X) * vg.Inch / 96
	h = vg.Length(bounds.Max.Y) * vg.Inch / 96
	// imgx = vg.Length(x) * vg.Inch / 96
	// imgy = vg.Length(y) * vg.Inch / 96
	c := vgimg.New(w, h)
	rect := vg.Rectangle{}
	rect.Max.X = w
	rect.Max.Y = h
	c.DrawImage(rect, img)
	font, _ := vg.MakeFont("Courier", vg.Inch*0.7)
	c.SetColor(color.RGBA{0, 0, 0, 122})
	c.Rotate(math.Pi / 4)
	// FIXME:效率低
	for i := vg.Inch; i < vg.Inch*10000; i += vg.Inch * 100 {
		offset := i / 96
		if offset > 3*w && offset > 3*h {
			break
		}
		c.FillString(font, vg.Point{X: -2*w + offset, Y: -2*h + offset}, label)
	}
	c.Rotate(-math.Pi / 4)
	jc := vgimg.JpegCanvas{c}
	buff := new(bytes.Buffer)
	jc.WriteTo(buff)
	img, _ = jpeg.Decode(buff)
	return img
}

// MarkingPicture for marking picture with text
func MarkingPicture(filepath, text string) (image.Image, error) {
	f, err := os.Open(filepath)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	img, _, err := image.Decode(f)
	bounds := img.Bounds()
	img = addLabel(img, bounds.Max.X/2, bounds.Max.Y/2, text)
	if err != nil {
		return nil, err
	}
	return img, nil
}

func main() {
	if len(os.Args) < 3 {
		panic(fmt.Errorf("Please using like this:$ %s [file or directory] [text]", os.Args[0]))
	}

	target := os.Args[1]
	text := os.Args[2]

	if stat, err := os.Stat(target); err == nil && stat.IsDir() {
		files, _ := ioutil.ReadDir(target)
		for _, fn := range files {
			img, err := MarkingPicture(path.Join(target, fn.Name()), text)
			if err != nil {
				continue
			}
			ext := path.Ext(fn.Name())
			base := strings.Split(fn.Name(), ".")[0] + "_marked"
			f, err := os.Create(base + ext)
			if err != nil {
				panic(err)
			}
			jpeg.Encode(f, img, &jpeg.Options{Quality: 100})
		}
	}

}