package canvas

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

	"golang.org/x/image/font"
)

// Context 画布上下文
type Context struct {
	img    *image.RGBA     // 底层图像
	state  *contextState   // 当前状态
	states []*contextState // 状态栈
	path   *path           // 当前路径
}

type contextState struct {
	fillStyle     interface{} // color.Color 或 Gradient
	strokeStyle   interface{} // color.Color 或 Gradient
	lineWidth     float64
	globalAlpha   float64
	transform     [6]float64 // 变换矩阵 [a, b, c, d, e, f]
	fontFace      font.Face
	textAlign     string
	textBaseline  string
	shadowColor   color.Color
	shadowOffsetX float64
	shadowOffsetY float64
	shadowBlur    float64
}

// NewContext 创建新的画布上下文
func NewContext(width, height int) *Context {
	img := image.NewRGBA(image.Rect(0, 0, width, height))
	// 白色背景
	draw.Draw(img, img.Bounds(), image.NewUniform(color.White), image.Point{}, draw.Src)

	initialState := &contextState{
		fillStyle:     color.Black,
		strokeStyle:   color.Black,
		lineWidth:     1.0,
		globalAlpha:   1.0,
		transform:     [6]float64{1, 0, 0, 1, 0, 0}, // 单位矩阵
		textAlign:     "start",
		textBaseline:  "alphabetic",
		shadowColor:   color.RGBA{0, 0, 0, 128},
		shadowOffsetX: 0,
		shadowOffsetY: 0,
		shadowBlur:    0,
	}
	return &Context{
		img:    img,
		state:  initialState,
		states: []*contextState{},
		path:   &path{},
	}
}

// Image 返回底层图像
func (c *Context) Image() image.Image {
	return c.img
}