mihon/app/src/main/java/eu/kanade/tachiyomi/widget/ElevationAppBarLayout.kt

package eu.kanade.tachiyomi.widget

import android.animation.ValueAnimator
import android.content.Context
import android.util.AttributeSet
import android.widget.TextView
import androidx.annotation.FloatRange
import androidx.lifecycle.coroutineScope
import androidx.lifecycle.findViewTreeLifecycleOwner
import com.google.android.material.animation.AnimationUtils
import com.google.android.material.appbar.AppBarLayout
import com.google.android.material.appbar.MaterialToolbar
import eu.kanade.tachiyomi.R
import eu.kanade.tachiyomi.util.view.findChild
import kotlinx.coroutines.flow.launchIn
import kotlinx.coroutines.flow.onEach
import reactivecircus.flowbinding.android.view.HierarchyChangeEvent
import reactivecircus.flowbinding.android.view.hierarchyChangeEvents

class ElevationAppBarLayout @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null
) : AppBarLayout(context, attrs) {

    private var lifted = true
    private var transparent = false

    private val toolbar by lazy { findViewById<MaterialToolbar>(R.id.toolbar) }

    @FloatRange(from = 0.0, to = 1.0)
    var titleTextAlpha = 1F
        set(value) {
            field = value
            titleTextView?.alpha = field
        }

    private var titleTextView: TextView? = null
        set(value) {
            field = value
            field?.alpha = titleTextAlpha
        }

    private var elevationAnimator: ValueAnimator? = null
    private var backgroundAlphaAnimator: ValueAnimator? = null

    var isTransparentWhenNotLifted = false
        set(value) {
            if (field != value) {
                field = value
                updateBackgroundAlpha()
            }
        }

    /**
     * Disabled. Lift on scroll is handled manually with [TachiyomiCoordinatorLayout]
     */
    override fun isLiftOnScroll(): Boolean = false

    override fun isLifted(): Boolean = lifted

    override fun setLifted(lifted: Boolean): Boolean {
        return if (this.lifted != lifted) {
            this.lifted = lifted
            val from = elevation
            val to = if (lifted) {
                resources.getDimension(R.dimen.design_appbar_elevation)
            } else {
                0F
            }

            elevationAnimator?.cancel()
            elevationAnimator = ValueAnimator.ofFloat(from, to).apply {
                duration = resources.getInteger(R.integer.app_bar_elevation_anim_duration).toLong()
                interpolator = AnimationUtils.LINEAR_INTERPOLATOR
                addUpdateListener {
                    elevation = it.animatedValue as Float
                }
                start()
            }

            updateBackgroundAlpha()
            true
        } else {
            false
        }
    }

    override fun onAttachedToWindow() {
        super.onAttachedToWindow()
        titleTextView = toolbar.findChild<TextView>()
        findViewTreeLifecycleOwner()?.lifecycle?.coroutineScope?.let { scope ->
            toolbar.hierarchyChangeEvents()
                .onEach {
                    when (it) {
                        is HierarchyChangeEvent.ChildAdded -> {
                            if (it.child is TextView) {
                                titleTextView = it.child as TextView
                            }
                        }
                        is HierarchyChangeEvent.ChildRemoved -> {
                            if (it.child == titleTextView) {
                                titleTextView = null
                            }
                        }
                    }
                }
                .launchIn(scope)
        }
    }

    private fun updateBackgroundAlpha() {
        val newTransparent = if (lifted) false else isTransparentWhenNotLifted
        if (transparent != newTransparent) {
            transparent = newTransparent
            val fromAlpha = if (transparent) 255 else 0
            val toAlpha = if (transparent) 0 else 255

            backgroundAlphaAnimator?.cancel()
            backgroundAlphaAnimator = ValueAnimator.ofInt(fromAlpha, toAlpha).apply {
                duration = resources.getInteger(R.integer.app_bar_elevation_anim_duration).toLong()
                interpolator = AnimationUtils.LINEAR_INTERPOLATOR
                addUpdateListener {
                    val alpha = it.animatedValue as Int
                    background.alpha = alpha
                    toolbar?.background?.alpha = alpha
                    statusBarForeground?.alpha = alpha
                }
                start()
            }
        }
    }
}