package x

import "image"
import "image/draw"
import "golang.org/x/image/math/fixed"

import "git.tebibyte.media/sashakoshka/stone"

func (backend *Backend) Draw () {
	backend.drawLock.Lock()
	defer backend.drawLock.Unlock()

	boundsChanged :=
		backend.memory.windowWidth  != backend.metrics.windowWidth ||
		backend.memory.windowHeight != backend.metrics.windowHeight
	backend.memory.windowWidth  = backend.metrics.windowWidth
	backend.memory.windowHeight = backend.metrics.windowHeight

	if boundsChanged {
		backend.reallocateCanvas()
		backend.drawCells(true)
		backend.canvas.XDraw()
		backend.canvas.XPaint(backend.window.Id)
	} else {
		backend.updateWindowAreas(backend.drawCells(false)...)
	}
}

func (backend *Backend) updateWindowAreas (areas ...image.Rectangle) {
	backend.canvas.XPaintRects(backend.window.Id, areas...)
}

func (backend *Backend) drawRune (x, y int, character rune, runeColor stone.Color) {
	// TODO: cache these draws as non-transparent buffers with the
	// application background color as the background. that way, we won't
	// need to redraw the characters *or* composite them.
	
	fillRectangle (
		&image.Uniform {
			C: backend.config.Color(stone.ColorBackground),
		},
		backend.canvas,
		backend.boundsOfCell(x, y))

	if character < 32 { return }
	
	origin := backend.originOfCell(x, y + 1)
	destinationRectangle, mask, maskPoint, _, _ := backend.font.face.Glyph (
		fixed.Point26_6 {
			X: fixed.I(origin.X),
			Y: fixed.I(origin.Y - backend.metrics.descent),
		},
		character)

	if backend.drawCellBounds {	
		strokeRectangle (
			&image.Uniform {
				C: backend.config.Color(stone.ColorForeground),
			},
			backend.canvas,
			backend.boundsOfCell(x, y))
	}
		
	draw.DrawMask (
		backend.canvas,
		destinationRectangle,
		&image.Uniform {
			C: backend.config.Color(runeColor),
		},
		image.Point { },
		mask,
		maskPoint,
		draw.Over)
}

func (backend *Backend) drawCells (forceRedraw bool) (areas []image.Rectangle) {
	width, height := backend.application.Size()
	for y := 0; y < height; y ++ {
	for x := 0; x < width;  x ++ {
		if !forceRedraw && backend.application.Clean(x, y) { continue }
		backend.application.MarkClean(x, y)

		cell := backend.application.Cell(x, y)
		content := cell.Rune()

		if forceRedraw && content < 32 { continue }

		areas = append(areas, backend.boundsOfCell(x, y))
		backend.drawRune(x, y, content, cell.Color())
	}}

	if backend.drawBufferBounds && forceRedraw {
		strokeRectangle (
			&image.Uniform {
				C: backend.config.Color(stone.ColorForeground),
			},
			backend.canvas,
			image.Rectangle {
				Min: backend.originOfCell(0, 0),
				Max: backend.originOfCell(width, height),
			})
	}
	return
}

func fillRectangle (
	source      image.Image,
	destination draw.Image,
	bounds      image.Rectangle,
) {
	for y := bounds.Min.Y; y < bounds.Max.Y; y ++ {
	for x := bounds.Min.X; x < bounds.Max.X; x ++ {
		destination.Set(x, y, source.At(x, y))
	}}
}

func strokeRectangle (
	source      image.Image,
	destination draw.Image,
	bounds      image.Rectangle,
) {
	x := 0
	y := bounds.Min.Y
	for x = bounds.Min.X; x < bounds.Max.X; x ++ {
		destination.Set(x, y, source.At(x, y))
	}

	y = bounds.Max.Y - 1
	for x = bounds.Min.X; x < bounds.Max.X; x ++ {
		destination.Set(x, y, source.At(x, y))
	}

	x = bounds.Min.X
	for y = bounds.Min.Y; y < bounds.Max.Y; y ++ {
		destination.Set(x, y, source.At(x, y))
	}

	x = bounds.Max.X - 1
	for y = bounds.Min.Y; y < bounds.Max.Y; y ++ {
		destination.Set(x, y, source.At(x, y))
	}
}