package x

import "bytes"
import "image"
import "errors"
import "git.tebibyte.media/sashakoshka/tomo/input"
import "git.tebibyte.media/sashakoshka/tomo/elements"

import "github.com/jezek/xgbutil"
import "github.com/jezek/xgb/xproto"
import "github.com/jezek/xgbutil/xprop"
import "github.com/jezek/xgbutil/xevent"

type scrollSum struct {
	x, y int
}

const scrollDistance = 16

func (sum *scrollSum) add (button xproto.Button, window *window, state uint16) {
	shift := 
		(state & xproto.ModMaskShift)                    > 0 ||
		(state & window.backend.modifierMasks.shiftLock) > 0
	if shift {
		switch button {
		case 4:
			sum.x -= scrollDistance
		case 5:
			sum.x += scrollDistance
		case 6:
			sum.y -= scrollDistance
		case 7:
			sum.y += scrollDistance
		}
	} else {
		switch button {
		case 4:
			sum.y -= scrollDistance
		case 5:
			sum.y += scrollDistance
		case 6:
			sum.x -= scrollDistance
		case 7:
			sum.x += scrollDistance
		}
	}

}

func (window *window) handleExpose (
	connection *xgbutil.XUtil,
	event xevent.ExposeEvent,
) {
	_, region := window.compressExpose(*event.ExposeEvent)
	window.pushRegion(region)
}

func (window *window) handleConfigureNotify (
	connection *xgbutil.XUtil,
	event xevent.ConfigureNotifyEvent,
) {
	if window.child == nil { return }

	configureEvent := *event.ConfigureNotifyEvent
	
	newWidth  := int(configureEvent.Width)
	newHeight := int(configureEvent.Height)
	sizeChanged :=
		window.metrics.width  != newWidth ||
		window.metrics.height != newHeight
	window.metrics.width  = newWidth
	window.metrics.height = newHeight

	if sizeChanged {
		configureEvent = window.compressConfigureNotify(configureEvent)
		window.metrics.width  = int(configureEvent.Width)
		window.metrics.height = int(configureEvent.Height)
		window.reallocateCanvas()
		window.resizeChildToFit()

		if !window.exposeEventFollows(configureEvent) {
			window.redrawChildEntirely()
		}
	}
}

func (window *window) exposeEventFollows (event xproto.ConfigureNotifyEvent) (found bool) {	
	nextEvents := xevent.Peek(window.backend.connection)
	if len(nextEvents) > 0 {
		untypedEvent := nextEvents[0]
		if untypedEvent.Err == nil {
			typedEvent, ok :=
				untypedEvent.Event.(xproto.ConfigureNotifyEvent)
			
			if ok && typedEvent.Window == event.Window {
				return true
			}
		}
	}
	return false
}

func (window *window) modifiersFromState (
	state uint16,
) (
	modifiers input.Modifiers,
) {
	return input.Modifiers {
		Shift:
			(state & xproto.ModMaskShift)                    > 0 ||
			(state & window.backend.modifierMasks.shiftLock) > 0,
		Control: (state & xproto.ModMaskControl)              > 0,
		Alt:     (state & window.backend.modifierMasks.alt)   > 0,
		Meta:    (state & window.backend.modifierMasks.meta)  > 0,
		Super:   (state & window.backend.modifierMasks.super) > 0,
		Hyper:   (state & window.backend.modifierMasks.hyper) > 0,
	}
}

func (window *window) handleKeyPress (
	connection *xgbutil.XUtil,
	event xevent.KeyPressEvent,
) {
	if window.child == nil { return }
	if window.hasModal     { return }
	
	keyEvent := *event.KeyPressEvent
	key, numberPad := window.backend.keycodeToKey(keyEvent.Detail, keyEvent.State)
	modifiers := window.modifiersFromState(keyEvent.State)
	modifiers.NumberPad = numberPad

	if key == input.KeyTab && modifiers.Alt {
		if child, ok := window.child.(elements.Focusable); ok {
			direction := input.KeynavDirectionForward
			if modifiers.Shift {
				direction = input.KeynavDirectionBackward
			}

			if !child.HandleFocus(direction) {
				child.HandleUnfocus()
			}
		}
	} else if child, ok := window.child.(elements.KeyboardTarget); ok {
		child.HandleKeyDown(key, modifiers)
	}
}

func (window *window) handleKeyRelease (
	connection *xgbutil.XUtil,
	event xevent.KeyReleaseEvent,
) {
	if window.child == nil { return }
	
	keyEvent := *event.KeyReleaseEvent

	// do not process this event if it was generated from a key repeat
	nextEvents := xevent.Peek(window.backend.connection)
	if len(nextEvents) > 0 {
		untypedEvent := nextEvents[0]
		if untypedEvent.Err == nil {
			typedEvent, ok :=
				untypedEvent.Event.(xproto.KeyPressEvent)
			
			if ok && typedEvent.Detail == keyEvent.Detail &&
				typedEvent.Event == keyEvent.Event &&
				typedEvent.State == keyEvent.State {

				return
			}
		}
	}
	
	key, numberPad := window.backend.keycodeToKey(keyEvent.Detail, keyEvent.State)
	modifiers := window.modifiersFromState(keyEvent.State)
	modifiers.NumberPad = numberPad
	
	if child, ok := window.child.(elements.KeyboardTarget); ok {
		child.HandleKeyUp(key, modifiers)
	}
}

func (window *window) handleButtonPress (
	connection *xgbutil.XUtil,
	event xevent.ButtonPressEvent,
) {
	if window.child == nil { return }
	if window.hasModal     { return }
	
	buttonEvent := *event.ButtonPressEvent
	if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 {
		if child, ok := window.child.(elements.ScrollTarget); ok {
			sum := scrollSum { }
			sum.add(buttonEvent.Detail, window, buttonEvent.State)
			window.compressScrollSum(buttonEvent, &sum)
			child.HandleScroll (
				int(buttonEvent.EventX),
				int(buttonEvent.EventY),
				float64(sum.x), float64(sum.y))
		}
	} else {
		if child, ok := window.child.(elements.MouseTarget); ok {
			child.HandleMouseDown (
				int(buttonEvent.EventX),
				int(buttonEvent.EventY),
				input.Button(buttonEvent.Detail))
		}
	}
	
}

func (window *window) handleButtonRelease (
	connection *xgbutil.XUtil,
	event xevent.ButtonReleaseEvent,
) {
	if window.child == nil { return }
	
	if child, ok := window.child.(elements.MouseTarget); ok {
		buttonEvent := *event.ButtonReleaseEvent
		if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 { return }
		child.HandleMouseUp (
			int(buttonEvent.EventX),
			int(buttonEvent.EventY),
			input.Button(buttonEvent.Detail))
	}
}

func (window *window) handleMotionNotify (
	connection *xgbutil.XUtil,
	event xevent.MotionNotifyEvent,
) {
	if window.child == nil { return }
	
	if child, ok := window.child.(elements.MotionTarget); ok {
		motionEvent := window.compressMotionNotify(*event.MotionNotifyEvent)
		child.HandleMotion (
			int(motionEvent.EventX),
			int(motionEvent.EventY))
	}
}

func (window *window) handleSelectionNotify (
	connection *xgbutil.XUtil,
	event xevent.SelectionNotifyEvent,
) {
	// Follow:
	// https://tronche.com/gui/x/icccm/sec-2.html#s-2.4
	if window.selectionRequest == nil { return }
	die := func (err error) { window.selectionRequest(nil, err) }

	// When using GetProperty to retrieve the value of a selection, the
	// property argument should be set to the corresponding value in the
	// SelectionNotify event. Because the requestor has no way of knowing
	// beforehand what type the selection owner will use, the type argument
	// should be set to AnyPropertyType. Several GetProperty requests may be
	// needed to retrieve all the data in the selection; each should set the
	// long-offset argument to the amount of data received so far, and the
	// size argument to some reasonable buffer size (see section 2.5). If
	// the returned value of bytes-after is zero, the whole property has
	// been transferred. 
	reply, err := xproto.GetProperty (
		connection.Conn(), false, window.xWindow.Id, event.Property,
		xproto.GetPropertyTypeAny, 0, (1 << 32) - 1).Reply()
	if err != nil { die(err); return }
	if reply.Format == 0 {
		die(errors.New("x: missing selection property"))
		return
	}

	// Once all the data in the selection has been retrieved (which may
	// require getting the values of several properties &emdash; see section
	// 2.7), the requestor should delete the property in the SelectionNotify
	// request by using a GetProperty request with the delete argument set
	// to True. As previously discussed, the owner has no way of knowing
	// when the data has been transferred to the requestor unless the
	// property is removed.
	propertyAtom, err := xprop.Atm(window.backend.connection, "TOMO_SELECTION")
	if err != nil { die(err); return }
	err = xproto.DeletePropertyChecked (
		window.backend.connection.Conn(),
		window.xWindow.Id,
		propertyAtom).Check()
	if err != nil { die(err); return }

	// TODO: possibly do some conversion here?
	window.selectionRequest(bytes.NewReader(reply.Value), nil)
	window.selectionRequest = nil
}

func (window *window) compressExpose (
	firstEvent xproto.ExposeEvent,
) (
	lastEvent xproto.ExposeEvent,
	region image.Rectangle,
) {
	region = image.Rect (
		int(firstEvent.X), int(firstEvent.Y),
		int(firstEvent.X + firstEvent.Width),
		int(firstEvent.Y + firstEvent.Height))
	
	window.backend.connection.Sync()
	xevent.Read(window.backend.connection, false)
	lastEvent = firstEvent
	
	for index, untypedEvent := range xevent.Peek(window.backend.connection) {
		if untypedEvent.Err != nil { continue }
		
		typedEvent, ok := untypedEvent.Event.(xproto.ExposeEvent)
		if !ok { continue }

		if firstEvent.Window == typedEvent.Window {
			region = region.Union (image.Rect (
				int(typedEvent.X), int(typedEvent.Y),
				int(typedEvent.X + typedEvent.Width),
				int(typedEvent.Y + typedEvent.Height)))
		
			lastEvent = typedEvent
			defer func (index int) {
				xevent.DequeueAt(window.backend.connection, index)
			} (index)
		}
	}

	return
}

func (window *window) compressConfigureNotify (
	firstEvent xproto.ConfigureNotifyEvent,
) (
	lastEvent xproto.ConfigureNotifyEvent,
) {
	window.backend.connection.Sync()
	xevent.Read(window.backend.connection, false)
	lastEvent = firstEvent
	
	for index, untypedEvent := range xevent.Peek(window.backend.connection) {
		if untypedEvent.Err != nil { continue }
		
		typedEvent, ok := untypedEvent.Event.(xproto.ConfigureNotifyEvent)
		if !ok { continue }
		
		if firstEvent.Event == typedEvent.Event &&
			firstEvent.Window == typedEvent.Window {

			lastEvent = typedEvent
			defer func (index int) {
				xevent.DequeueAt(window.backend.connection, index)
			} (index)
		}
	}

	return
}

func (window *window) compressScrollSum (
	firstEvent xproto.ButtonPressEvent,
	sum *scrollSum,
) {
	window.backend.connection.Sync()
	xevent.Read(window.backend.connection, false)
	
	for index, untypedEvent := range xevent.Peek(window.backend.connection) {
		if untypedEvent.Err != nil { continue }
		
		typedEvent, ok := untypedEvent.Event.(xproto.ButtonPressEvent)
		if !ok { continue }

		if firstEvent.Event == typedEvent.Event &&
			typedEvent.Detail >= 4 &&
			typedEvent.Detail <= 7 {

			sum.add(typedEvent.Detail, window, typedEvent.State)
			defer func (index int) {
				xevent.DequeueAt(window.backend.connection, index)
			} (index)
		}
	}

	return
}

func (window *window) compressMotionNotify (
	firstEvent xproto.MotionNotifyEvent,
) (
	lastEvent xproto.MotionNotifyEvent,
) {
	window.backend.connection.Sync()
	xevent.Read(window.backend.connection, false)
	lastEvent = firstEvent
	
	for index, untypedEvent := range xevent.Peek(window.backend.connection) {
		if untypedEvent.Err != nil { continue }
		
		typedEvent, ok := untypedEvent.Event.(xproto.MotionNotifyEvent)
		if !ok { continue }

		if firstEvent.Event == typedEvent.Event {
			lastEvent = typedEvent
			defer func (index int) {
				xevent.DequeueAt(window.backend.connection, index)
			} (index)
		}
	}

	return
}