// Copyright ©2020 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package vg

import (
	"image"
	"image/color"

	"gonum.org/v1/plot/font"
)

// MultiCanvas creates a canvas that duplicates its drawing operations to all
// the provided canvases, similar to the Unix tee(1) command.
//
// Each drawing operation is sent to each listed canvas, one at a time.
func MultiCanvas(cs ...Canvas) Canvas {
	return teeCanvas{cs}
}

type teeCanvas struct {
	cs []Canvas
}

// SetLineWidth sets the width of stroked paths.
// If the width is not positive then stroked lines
// are not drawn.
func (tee teeCanvas) SetLineWidth(w Length) {
	for _, c := range tee.cs {
		c.SetLineWidth(w)
	}
}

// SetLineDash sets the dash pattern for lines.
// The pattern slice specifies the lengths of
// alternating dashes and gaps, and the offset
// specifies the distance into the dash pattern
// to start the dash.
func (tee teeCanvas) SetLineDash(pattern []Length, offset Length) {
	for _, c := range tee.cs {
		c.SetLineDash(pattern, offset)
	}
}

// SetColor sets the current drawing color.
// Note that fill color and stroke color are
// the same, so if you want different fill
// and stroke colors then you must set a color,
// draw fills, set a new color and then draw lines.
func (tee teeCanvas) SetColor(c color.Color) {
	for _, canvas := range tee.cs {
		canvas.SetColor(c)
	}
}

// Rotate applies a rotation transform to the context.
// The parameter is specified in radians.
func (tee teeCanvas) Rotate(rad float64) {
	for _, c := range tee.cs {
		c.Rotate(rad)
	}
}

// Translate applies a translational transform to the context.
func (tee teeCanvas) Translate(pt Point) {
	for _, c := range tee.cs {
		c.Translate(pt)
	}
}

// Scale applies a scaling transform to the context.
func (tee teeCanvas) Scale(x, y float64) {
	for _, c := range tee.cs {
		c.Scale(x, y)
	}
}

// Push saves the current line width, the
// current dash pattern, the current
// transforms, and the current color
// onto a stack so that the state can later
// be restored by calling Pop().
func (tee teeCanvas) Push() {
	for _, c := range tee.cs {
		c.Push()
	}
}

// Pop restores the context saved by the
// corresponding call to Push().
func (tee teeCanvas) Pop() {
	for _, c := range tee.cs {
		c.Pop()
	}
}

// Stroke strokes the given path.
func (tee teeCanvas) Stroke(p Path) {
	for _, c := range tee.cs {
		c.Stroke(p)
	}
}

// Fill fills the given path.
func (tee teeCanvas) Fill(p Path) {
	for _, c := range tee.cs {
		c.Fill(p)
	}
}

// FillString fills in text at the specified
// location using the given font.
// If the font size is zero, the text is not drawn.
func (tee teeCanvas) FillString(f font.Face, pt Point, text string) {
	for _, c := range tee.cs {
		c.FillString(f, pt, text)
	}
}

// DrawImage draws the image, scaled to fit
// the destination rectangle.
func (tee teeCanvas) DrawImage(rect Rectangle, img image.Image) {
	for _, c := range tee.cs {
		c.DrawImage(rect, img)
	}
}

var _ Canvas = (*teeCanvas)(nil)