package vision

import (
	"image"
	"image/color"
	"image/draw"
)

// Position 水印位置
type Position int

const (
	TopLeft Position = iota
	TopCenter
	TopRight
	LeftCenter
	Center
	RightCenter
	BottomLeft
	BottomCenter
	BottomRight
)

// Watermark 给画布添加图片水印
// mark: 水印画布
// pos: 位置
// opacity: 透明度 (0.0 - 1.0)
// padding: 边距
// angle: 旋转角度 (弧度)
func (c *Canvas) Watermark(mark *Canvas, pos Position, opacity float64, padding int, angle ...float64) {
	if mark == nil || opacity < 0.01 {
		return
	}

	w, h := c.Width(), c.Height()
	mw, mh := mark.Width(), mark.Height()

	var x, y int
	switch pos {
	case TopLeft:
		x, y = padding, padding
	case TopCenter:
		x, y = (w-mw)/2, padding
	case TopRight:
		x, y = w-mw-padding, padding
	case LeftCenter:
		x, y = padding, (h-mh)/2
	case Center:
		x, y = (w-mw)/2, (h-mh)/2
	case RightCenter:
		x, y = w-mw-padding, (h-mh)/2
	case BottomLeft:
		x, y = padding, h-mh-padding
	case BottomCenter:
		x, y = (w-mw)/2, h-mh-padding
	case BottomRight:
		x, y = w-mw-padding, h-mh-padding
	}

	c.dc.Push()
	if len(angle) > 0 && angle[0] != 0 {
		c.dc.RotateAbout(angle[0], float64(x+mw/2), float64(y+mh/2))
	}

	// 处理透明度
	if opacity >= 0.99 {
		c.dc.DrawImage(mark.dc.Image(), x, y)
	} else {
		mask := image.NewUniform(color.Alpha{uint8(255 * opacity)})
		draw.DrawMask(c.dc.Image().(draw.Image), mark.dc.Image().Bounds().Add(image.Pt(x, y)), mark.dc.Image(), image.Point{}, mask, image.Point{}, draw.Over)
	}
	c.dc.Pop()
}

// TileWatermark 平铺图片水印
// spacing: 间距
// angle: 旋转角度 (弧度)
func (c *Canvas) TileWatermark(mark *Canvas, opacity float64, spacing int, angle float64) {
	if mark == nil || opacity < 0.01 {
		return
	}

	mw, mh := mark.Width(), mark.Height()
	w, h := c.Width(), c.Height()

	stepX := mw + spacing
	stepY := mh + spacing

	for y := -mh; y < h+mh; y += stepY {
		for x := -mw; x < w+mw; x += stepX {
			c.dc.Push()
			c.dc.RotateAbout(angle, float64(x+mw/2), float64(y+mh/2))
			if opacity >= 0.99 {
				c.dc.DrawImage(mark.dc.Image(), x, y)
			} else {
				mask := image.NewUniform(color.Alpha{uint8(255 * opacity)})
				draw.DrawMask(c.dc.Image().(draw.Image), mark.dc.Image().Bounds().Add(image.Pt(x, y)), mark.dc.Image(), image.Point{}, mask, image.Point{}, draw.Over)
			}
			c.dc.Pop()
		}
	}
}

// TextWatermark 给画布添加文字水印
func (c *Canvas) TextWatermark(text string, pos Position, style *DrawStyle, opacity float64, padding int, angle ...float64) {
	// 创建一个临时画布来渲染文字，然后调用 Watermark
	c.dc.Push()
	tw, th := c.dc.MeasureString(text)
	temp := New(int(tw)+4, int(th)+4)
	if style != nil && style.FillColor != "" {
		temp.dc.SetColor(ParseColor(style.FillColor))
	} else {
		temp.dc.SetColor(color.Black)
	}
	temp.dc.DrawString(text, 2, th+2)
	
	ang := 0.0
	if len(angle) > 0 {
		ang = angle[0]
	}
	c.Watermark(temp, pos, opacity, padding, ang)
	c.dc.Pop()
}

// TileTextWatermark 平铺文字水印
func (c *Canvas) TileTextWatermark(text string, style *DrawStyle, opacity float64, spacing int, angle float64) {
	c.dc.Push()
	tw, th := c.dc.MeasureString(text)
	temp := New(int(tw)+4, int(th)+4)
	if style != nil && style.FillColor != "" {
		temp.dc.SetColor(ParseColor(style.FillColor))
	} else {
		temp.dc.SetColor(color.Black)
	}
	temp.dc.DrawString(text, 2, th+2)
	
	c.TileWatermark(temp, opacity, spacing, angle)
	c.dc.Pop()
}