package net.shadowfacts.cacao

import net.shadowfacts.cacao.geometry.Point
import net.shadowfacts.cacao.util.MouseButton
import net.shadowfacts.cacao.view.View
import net.shadowfacts.cacao.viewcontroller.ViewController
import net.shadowfacts.kiwidsl.dsl
import no.birkett.kiwi.Constraint
import no.birkett.kiwi.Solver
import no.birkett.kiwi.Variable

/**
 * A Window is the object at the top of a Cacao view hierarchy. It occupies the entirety of the Minecraft screen size
 * and provides the base coordinate system for its view hierarchy.
 *
 * The Window owns the Kiwi [Solver] object used for layout by all of its views.
 *
 * @author shadowfacts
 *
 * @param viewController The root view controller for this window.
 */
class Window(
		/**
		 * The root view controller for this window.
		 */
		val viewController: ViewController
) {

	/**
	 * The screen that this window belongs to.
	 * Not initialized until this window is added to a screen, using it before that point will throw a runtime exception.
	 */
	lateinit var screen: CacaoScreen

	/**
	 * The constraint solver used by this window and all its views and subviews.
	 */
	var solver = Solver()

	/**
	 * Layout anchor for the left edge of this view in the window's coordinate system.
	 */
	val leftAnchor = Variable("left")
	/**
	 * Layout anchor for the right edge of this view in the window's coordinate system.
	 */
	val rightAnchor = Variable("right")
	/**
	 * Layout anchor for the top edge of this view in the window's coordinate system.
	 */
	val topAnchor = Variable("top")
	/**
	 * Layout anchor for the bottom edge of this view in the window's coordinate system.
	 */
	val bottomAnchor = Variable("bottom")
	/**
	 * Layout anchor for the width of this view in the window's coordinate system.
	 */
	val widthAnchor = Variable("width")
	/**
	 * Layout anchor for the height of this view in the window's coordinate system.
	 */
	val heightAnchor = Variable("height")
	/**
	 * Layout anchor for the center X position of this view in the window's coordinate system.
	 */
	val centerXAnchor = Variable("centerX")
	/**
	 * Layout anchor for the center Y position of this view in the window's coordinate system.
	 */
	val centerYAnchor = Variable("centerY")

	// internal constraints that specify the window size based on the MC screen size
	// stored so that they can be removed when the screen is resized
	private var widthConstraint: Constraint? = null
	private var heightConstraint: Constraint? = null

	private var currentDragReceiver: View? = null

	init {
		createInternalConstraints()
	}

	fun wasAdded() {
		viewController.window = this
		viewController.loadView()

		viewController.view.window = this
		viewController.view.solver = solver
		viewController.view.wasAdded()
		viewController.createConstraints {
			viewController.view.leftAnchor equalTo leftAnchor
			viewController.view.rightAnchor equalTo rightAnchor
			viewController.view.topAnchor equalTo topAnchor
			viewController.view.bottomAnchor equalTo bottomAnchor
		}

		viewController.viewDidLoad()

		layout()
	}

	/**
	 * Creates the internal constraints used by the window.
	 * If overridden, the super-class method must be called.
	 */
	protected fun createInternalConstraints() {
		solver.dsl {
			leftAnchor equalTo 0
			topAnchor equalTo 0

			rightAnchor equalTo (leftAnchor + widthAnchor)
			bottomAnchor equalTo (topAnchor + heightAnchor)
			centerXAnchor equalTo (leftAnchor + widthAnchor / 2)
			centerYAnchor equalTo (topAnchor + heightAnchor / 2)
		}
	}

	/**
	 * Called by the window's [screen] when the Minecraft screen is resized.
	 * Used to update the window's width and height constraints and re-layout views.
	 */
	internal fun resize(width: Int, height: Int) {
		if (widthConstraint != null) solver.removeConstraint(widthConstraint)
		if (heightConstraint != null) solver.removeConstraint(heightConstraint)
		solver.dsl {
			widthConstraint = (widthAnchor equalTo width)
			heightConstraint = (heightAnchor equalTo height)
		}
		layout()
	}

	/**
	 * Convenience method that removes this window from its [screen].
	 */
	fun removeFromScreen() {
		viewController.viewWillDisappear()
		screen.removeWindow(this)
		viewController.viewDidDisappear()
	}

	/**
	 * Instructs the solver to solve all of the provided constraints.
	 * Should be called after the view hierarchy is setup.
	 */
	fun layout() {
		viewController.viewWillLayoutSubviews()
		solver.updateVariables()
		viewController.viewDidLayoutSubviews()
	}

	/**
	 * Draws this window and all of its views.
	 * This method is called by [CacaoScreen] and generally shouldn't be called directly.
	 *
	 * @param mouse The point in the coordinate system of the window.
	 * @param delta The time elapsed since the last frame.
	 */
	fun draw(mouse: Point, delta: Float) {
		val mouseInView = Point(mouse.x - viewController.view.frame.left, mouse.y - viewController.view.frame.top)
		viewController.view.draw(mouseInView, delta)
	}

	/**
	 * Called when a mouse button is clicked and this is the active window.
	 * This method is called by [CacaoScreen] and generally shouldn't be called directly.
	 *
	 * @param point The point in the window of the click.
	 * @param mouseButton The mouse button that was used to click.
	 * @return Whether the mouse click was handled by a view.
	 */
	fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
		if (point in viewController.view.frame) {
			val mouseInView = Point(point.x - viewController.view.frame.left, point.y - viewController.view.frame.top)
			return viewController.view.mouseClicked(mouseInView, mouseButton)
		} else {
			// remove the window from the screen when the mouse clicks outside the window and this is not the primary window
			if (screen.windows.size > 1) {
				removeFromScreen()
			}
		}
		return false
	}

	fun mouseDragged(startPoint: Point, delta: Point, mouseButton: MouseButton): Boolean {
		val currentlyDraggedView = this.currentDragReceiver
		if (currentlyDraggedView != null) {
			return currentlyDraggedView.mouseDragged(startPoint, delta, mouseButton)
		} else if (startPoint in viewController.view.frame) {
			val startInView = Point(startPoint.x - viewController.view.frame.left, startPoint.y - viewController.view.frame.top)
			var prevView: View? = null
			var view = viewController.view.subviewsAtPoint(startInView).maxBy(View::zIndex)
			while (view != null && !view.respondsToDragging) {
				prevView = view
				val pointInView = viewController.view.convert(startInView, to = view)
				view = view.subviewsAtPoint(pointInView).maxBy(View::zIndex)
			}
			this.currentDragReceiver = view ?: prevView
			return this.currentDragReceiver?.mouseDragged(startPoint, delta, mouseButton) ?: false
		}
		return false
	}

	fun mouseReleased(point: Point, mouseButton: MouseButton): Boolean {
		val currentlyDraggedView = this.currentDragReceiver
		if (currentlyDraggedView != null) {
			this.currentDragReceiver = null
			return true
		}
		return false
	}

}