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
func (c *Canvas) Watermark(mark *Canvas, pos Position, opacity float64, padding int) {
	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
	}

	// 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)
	}
}

// TextWatermark 给画布添加文字水印
func (c *Canvas) TextWatermark(text string, pos Position, style *DrawStyle, opacity float64, padding int) {
	// 创建一个临时画布来渲染文字，然后调用 Watermark
	// 这样可以利用 Watermark 的位置计算逻辑
	c.dc.Push()
	if style != nil && style.FillColor != "" {
		c.SetColor(style.FillColor)
	}
	
	// 这里简化实现，实际可以先测量文字宽度
	tw, th := c.dc.MeasureString(text)
	temp := New(int(tw)+2, int(th)+2)
	temp.dc.SetColor(ParseColor(style.FillColor))
	temp.dc.DrawString(text, 0, th)
	
	c.Watermark(temp, pos, opacity, padding)
	c.dc.Pop()
}