ASMR/src/main/kotlin/net/shadowfacts/cacao/view/button/DropdownButton.kt

package net.shadowfacts.cacao.view.button

import net.minecraft.util.Identifier
import net.shadowfacts.cacao.Window
import net.shadowfacts.cacao.geometry.Axis
import net.shadowfacts.cacao.geometry.Point
import net.shadowfacts.cacao.geometry.Rect
import net.shadowfacts.cacao.util.MouseButton
import net.shadowfacts.cacao.util.NinePatchTexture
import net.shadowfacts.cacao.util.Texture
import net.shadowfacts.cacao.util.properties.ResettableLazyProperty
import net.shadowfacts.cacao.view.NinePatchView
import net.shadowfacts.cacao.view.StackView
import net.shadowfacts.cacao.view.TextureView
import net.shadowfacts.cacao.view.View
import net.shadowfacts.kiwidsl.dsl

/**
 * A button that provides a dropdown for the user to select from a list of values.
 * The button itself shows a [ContentView] representing the currently selected [Value] and an image indicator that serves
 * as a hint for the ability to click the button and display the dropdown.
 *
 * The dropdown list itself is displayed by presenting a new [Window] at the front of the window stack.
 * Each possible value is represented in the list by a button containing a [ContentView] for that value, with the button
 * for the current value being disabled.
 *
 * @author shadowfacts
 * @param Value The type of value that the dropdown selects.
 * @param ContentView The specific type of the [View] that represents selected item in the button and each item in the dropdown list.
 * @param initialValue The initial value of the dropdown button.
 * @param allValues List of all allowed values for the dropdown.
 * @param createView A function that creates a [ContentView] representing the given [Value].
 * 						Positioning of content views is handled by the dropdown.
 * @param updateView A function for updating the view used as the button's 'label' that's visible even when the dropdown isn't.
 */
class DropdownButton<Value, ContentView: View>(
		val initialValue: Value,
		val allValues: Iterable<Value>,
		val createView: (Value) -> ContentView,
		val updateView: (newValue: Value, view: ContentView) -> Unit,
		padding: Double = 4.0
): AbstractButton<DropdownButton<Value, ContentView>>(
		StackView(Axis.HORIZONTAL),
		padding
) {

	companion object {
		val DROPDOWN_INDICATOR = Texture(Identifier("asmr", "textures/gui/dropdown.png"), 0, 0)
	}

	private val stackView: StackView
		get() = content as StackView

	private val contentView: ContentView
		get() = stackView.arrangedSubviews.first() as ContentView

	private lateinit var dropdownIndicator: TextureView

	/**
	 * The currently selected [Value] of the dropdown.
	 */
	var value: Value = initialValue
		set(value) {
			field = value
			updateView(value, contentView)
			window.layout()
		}

	override fun wasAdded() {
		super.wasAdded()

		stackView.addArrangedSubview(createView(initialValue))
		dropdownIndicator = stackView.addArrangedSubview(TextureView(DROPDOWN_INDICATOR))

		solver.dsl {
			dropdownIndicator.widthAnchor equalTo 9
			dropdownIndicator.heightAnchor equalTo 9
		}
	}

	override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
		return if (mouseButton == MouseButton.LEFT || mouseButton == MouseButton.RIGHT) {
			showDropdown()
			true
		} else {
			super.mouseClicked(point, mouseButton)
		}
	}

	private fun showDropdown() {
		val dropdownWindow = window.screen.addWindow(Window())
		val dropdownBackground = dropdownWindow.addView(NinePatchView(DEFAULT_BG).apply {
			zIndex = -1.0
		})
		val stack = dropdownWindow.addView(StackView(Axis.VERTICAL, StackView.Distribution.LEADING))
		lateinit var selectedButton: View
		val buttons = mutableListOf<Button>()
		val last = allValues.count() - 1
		for ((index, value) in allValues.withIndex()) {
			val contentView = createView(value)
			val button = stack.addArrangedSubview(Button(contentView, padding).apply {
				background = null
				hoveredBackground = DropdownItemBackgroundView(index == 0, index == last, HOVERED_BG)
				disabledBackground = DropdownItemBackgroundView(index == 0, index == last, DISABLED_BG)
				disabled = value == this@DropdownButton.value
				handler = {
					dropdownWindow.removeFromScreen()
					valueSelected(value)
				}
			})
			if (value == this@DropdownButton.value) {
				selectedButton = button
			}
			buttons.add(button)
			dropdownWindow.solver.dsl {
				stack.widthAnchor greaterThanOrEqualTo button.widthAnchor
			}
		}
		dropdownWindow.solver.dsl {
			// constrain to the DropdownButton anchor's value constant, because we're crossing windows and
			// therefore solvers, which isn't allowed
			stack.leftAnchor equalTo this@DropdownButton.rightAnchor.value
			selectedButton.centerYAnchor equalTo this@DropdownButton.centerYAnchor.value

			dropdownBackground.leftAnchor equalTo stack.leftAnchor
			dropdownBackground.rightAnchor equalTo stack.rightAnchor
			dropdownBackground.topAnchor equalTo stack.topAnchor
			dropdownBackground.bottomAnchor equalTo stack.bottomAnchor
		}
		dropdownWindow.layout()
		dropdownWindow.solver.dsl {
			buttons.forEach {
				it.widthAnchor equalTo stack.frame.width
			}
		}
		dropdownWindow.layout()
	}

	private fun valueSelected(value: Value) {
		this.value = value
		handler?.invoke(this)
	}

}

private class DropdownItemBackgroundView(
		private val first: Boolean,
		private val last: Boolean,
		ninePatch: NinePatchTexture
): NinePatchView(ninePatch) {

	// Corners
	private val topLeftDelegate = ResettableLazyProperty {
		super.topLeft
		Rect(0.0, 0.0, ninePatch.cornerWidth.toDouble(), if (first) ninePatch.cornerHeight.toDouble() else 0.0)
	}
	override val topLeft by topLeftDelegate

	private val topRightDelegate = ResettableLazyProperty {
		Rect(bounds.width - ninePatch.cornerWidth, 0.0, topLeft.width, topLeft.height)
	}
	override val topRight by topRightDelegate

	private val bottomLeftDelegate = ResettableLazyProperty {
		Rect(topLeft.left, bounds.height - ninePatch.cornerHeight, topLeft.width, if (last) ninePatch.cornerHeight.toDouble() else 0.0)
	}
	override val bottomLeft by bottomLeftDelegate

	private val bottomRightDelegate = ResettableLazyProperty {
		Rect(topRight.left, bottomLeft.top, topLeft.width, bottomLeft.height)
	}
	override val bottomRight by bottomRightDelegate

	// Edges
	private val topMiddleDelegate = ResettableLazyProperty {
		Rect(ninePatch.cornerWidth.toDouble(), topLeft.top, bounds.width - 2 * ninePatch.cornerWidth, topLeft.height)
	}
	override val topMiddle by topMiddleDelegate

	private val bottomMiddleDelegate = ResettableLazyProperty {
		Rect(topMiddle.left, bottomLeft.top, topMiddle.width, bottomLeft.height)
	}
	override val bottomMiddle by bottomMiddleDelegate

	private val leftMiddleDelegate = ResettableLazyProperty {
		Rect(topLeft.left, topLeft.bottom, topLeft.width, bounds.height - (if (first && last) 2 else if (first || last) 1 else 0) * ninePatch.cornerHeight)
	}
	override val leftMiddle by leftMiddleDelegate

	private val rightMiddleDelegate = ResettableLazyProperty {
		Rect(topRight.left, topRight.bottom, topRight.width, leftMiddle.height)
	}
	override val rightMiddle by rightMiddleDelegate

	// Center
	private val centerDelegate = ResettableLazyProperty {
		Rect(topLeft.right, topMiddle.bottom, topMiddle.width, leftMiddle.height)
	}
	override val center by centerDelegate

	private val delegates = listOf(topLeftDelegate, topRightDelegate, bottomLeftDelegate, bottomRightDelegate, topMiddleDelegate, bottomMiddleDelegate, leftMiddleDelegate, rightMiddleDelegate, centerDelegate)

	override fun didLayout() {
		super.didLayout()

		delegates.forEach(ResettableLazyProperty<Rect>::reset)
	}

}