package x

import "image"
import "errors"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/xgbkb"
import "git.tebibyte.media/tomo/tomo/canvas"
import "git.tebibyte.media/tomo/backend/x/canvas"
import "git.tebibyte.media/tomo/backend/internal/system"

import "github.com/jezek/xgbutil"
import "github.com/jezek/xgb/xproto"
import "github.com/jezek/xgbutil/xevent"
import "github.com/jezek/xgbutil/keybind"
import "github.com/jezek/xgbutil/mousebind"

type Backend struct {
	x         *xgbutil.XUtil
	system    *system.System
	
	doChannel chan func()
	windows   map[xproto.Window] *window
	open      bool
}

type backendLink struct {
	backend *Backend
}

func (this *backendLink) NewTexture (source image.Image) canvas.TextureCloser {
	return this.backend.NewTexture(source)
}

func (this *backendLink) NewCanvas (bounds image.Rectangle) canvas.Canvas {
	return this.backend.NewCanvas(bounds)
}

func (this *backendLink) NewSurface (bounds image.Rectangle) (system.SurfaceLink, error) {
	// TODO
	return nil, errors.New("x: not implemented")
}

func New () (tomo.Backend, error) {
	backend := &Backend {
		doChannel: make(chan func (), 32),
		windows:   make(map[xproto.Window] *window),
		open:      true,
	}
	link := &backendLink {
		backend: backend,
	}
	
	backend.system = system.New(link)
	
	var err error
	backend.x, err = xgbutil.NewConn()
	if err != nil { return nil, err }

	keybind  .Initialize(backend.x)
	xgbkb    .Initialize(backend.x)
	mousebind.Initialize(backend.x)
	
	return backend, nil
}

func (this *Backend) Run () error {
	this.assert()
	pingBefore,
	pingAfter,
	pingQuit := xevent.MainPing(this.x)
	for {
		select {
		case <- pingBefore:
			<- pingAfter
		case callback := <- this.doChannel:
			callback()
		case <- pingQuit:
			return nil // FIXME: if we exited due to an error say so
		}
		this.afterEvent()
	}
}

func (this *Backend) Stop () {
	this.assert()
	if !this.open { return }
	this.open = false
	
	toClose := []*window { }
	for _, panel := range this.windows {
		toClose = append(toClose, panel)
	}
	for _, panel := range toClose {
		panel.Close()
	}
	xevent.Quit(this.x)
	this.x.Conn().Close()
}

func (this *Backend) Do (callback func ()) {
	this.assert()
	this.doChannel <- callback
}

func (this *Backend) NewBox () tomo.Box {
	return this.system.NewBox()
}

func (this *Backend) NewCanvasBox () tomo.CanvasBox {
	return this.system.NewCanvasBox()
}

func (this *Backend) NewContainerBox () tomo.ContainerBox {
	return this.system.NewContainerBox()
}

func (this *Backend) NewSurfaceBox () (tomo.SurfaceBox, error) {
	return this.system.NewSurfaceBox()
}

func (this *Backend) NewTextBox () tomo.TextBox {
	return this.system.NewTextBox()
}

func (this *Backend) NewTexture (source image.Image) canvas.TextureCloser {
	return xcanvas.NewTextureFrom(source)
}

func (this *Backend) NewCanvas (bounds image.Rectangle) canvas.Canvas {
	return xcanvas.NewCanvas(this.x, bounds)
}

func (this *Backend) assert () {
	if this == nil { panic("x: nil backend") }
}

func (this *Backend) afterEvent () {	
	for _, window := range this.windows {
		window.hierarchy.AfterEvent()
	}
}