package x

// import "fmt"
import "sync"
import "image"
import "golang.org/x/image/font"

// import "github.com/jezek/xgb"
import "github.com/jezek/xgbutil"
import "github.com/jezek/xgbutil/ewmh"
import "github.com/jezek/xgbutil/xwindow"
import "github.com/jezek/xgbutil/xgraphics"

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

type Backend struct {
	application *stone.Application
	config      *stone.Config
	connection  *xgbutil.XUtil
	window      *xwindow.Window
	canvas      *xgraphics.Image
	channel     chan(stone.Event)

	drawCellBounds   bool
	drawBufferBounds bool

	drawLock sync.Mutex

	font struct {
		face font.Face
	}

	colors [4]xgraphics.BGRA
	
	metrics struct {
		windowWidth  int
		windowHeight int
		cellWidth    int
		cellHeight   int
		padding      int
		paddingX     int
		paddingY     int
		descent      int
	}

	memory struct {
		windowWidth  int
		windowHeight int
	}
}

func (backend *Backend) SetTitle (title string) (err error) {
	err = ewmh.WmNameSet(backend.connection, backend.window.Id, title)
	return
}

func (backend *Backend) SetIcon (icons []image.Image) (err error) {
	wmIcons := []ewmh.WmIcon { }
	
	for _, icon := range icons {
		width  := icon.Bounds().Max.X
		height := icon.Bounds().Max.Y
		wmIcon := ewmh.WmIcon {
			Width:  uint(width),
			Height: uint(height),
			Data:   make ([]uint, width * height),
		}

		// manually convert image data beacuse of course we have to do
		// this
		index := 0
		for y := 0; y < height; y ++ {
		for x := 0; x < width;  x ++ {
			r, g, b, a := icon.At(x, y).RGBA()
			r >>= 8
			g >>= 8
			b >>= 8
			a >>= 8
			wmIcon.Data[index] =
				(uint(a) << 24) |
				(uint(r) << 16) |
				(uint(g) << 8)  |
				(uint(b) << 0)
			index ++
		}}
		
		wmIcons = append(wmIcons, wmIcon)
	}

	err = ewmh.WmIconSet(backend.connection, backend.window.Id, wmIcons)
	return
}

// calculateWindowSize calculates window bounds based on the internal buffer
// size.
func (backend *Backend) calculateWindowSize () (x, y int) {
	width, height := backend.application.Size()
	x =
		width * backend.metrics.cellWidth +
		backend.metrics.padding * 2
	y =
		height * backend.metrics.cellHeight +
		backend.metrics.padding * 2
	return
}

func (backend *Backend) calculateBufferSize () (width, height int) {
	width =
		(backend.metrics.windowWidth - backend.metrics.padding * 2) /
		backend.metrics.cellWidth
	height =
		(backend.metrics.windowHeight - backend.metrics.padding * 2) /
		backend.metrics.cellHeight
	return
}

func (backend *Backend) reallocateCanvas () {
	if backend.canvas != nil {
		backend.canvas.Destroy()
	}
	backend.canvas = xgraphics.New (
		backend.connection,
		image.Rect (
			0, 0,
			backend.metrics.windowWidth,
			backend.metrics.windowHeight))
	backend.canvas.For (func (x, y int) xgraphics.BGRA {
		return backend.colors[stone.ColorApplication]
	})
	
	backend.canvas.XSurfaceSet(backend.window.Id)
}

func (backend *Backend) cellAt (onScreen image.Point) (x, y int) {
	x = (onScreen.X - backend.metrics.paddingX) / backend.metrics.cellWidth
	y = (onScreen.Y - backend.metrics.paddingY) / backend.metrics.cellHeight
	return
}

func (backend *Backend) cellSubImage (x, y int) (cell *xgraphics.Image) {
	cell = backend.canvas.SubImage(backend.boundsOfCell(x, y)).(*xgraphics.Image)
	return
}

func (backend *Backend) originOfCell (x, y int) (origin image.Point) {
	origin = image.Point {
		X: x * backend.metrics.cellWidth  + backend.metrics.paddingX,
		Y: y * backend.metrics.cellHeight + backend.metrics.paddingY,
	}
	return
}

func (backend *Backend) boundsOfCell (x, y int) (bounds image.Rectangle) {
	bounds = image.Rectangle {
		Min: backend.originOfCell(x, y),
		Max: backend.originOfCell(x + 1, y + 1),
	}
	return
}