LibreTube/app/src/main/java/com/github/libretube/util/PlayerGestureController.kt

package com.github.libretube.util

import android.annotation.SuppressLint
import android.content.res.Resources
import android.os.Handler
import android.os.Looper
import android.os.SystemClock
import android.view.GestureDetector
import android.view.MotionEvent
import android.view.ScaleGestureDetector
import android.view.View
import androidx.activity.viewModels
import com.github.libretube.ui.base.BaseActivity
import com.github.libretube.ui.interfaces.PlayerGestureOptions
import com.github.libretube.ui.models.PlayerViewModel
import kotlin.math.abs

class PlayerGestureController(activity: BaseActivity, private val listener: PlayerGestureOptions) :
    View.OnTouchListener {

    // width and height should be obtained each time using getter to adopt layout
    // size changes.
    private val width get() = Resources.getSystem().displayMetrics.widthPixels
    private val height get() = Resources.getSystem().displayMetrics.heightPixels
    private val elapsedTime get() = SystemClock.elapsedRealtime()

    private val playerViewModel: PlayerViewModel by activity.viewModels()
    private val handler: Handler = Handler(Looper.getMainLooper())

    private val gestureDetector: GestureDetector
    private val scaleGestureDetector: ScaleGestureDetector

    private var isFullscreen = false
    private var isMoving = false
    var isEnabled = true

    // Indicates last touch event was for click or other gesture, used to avoid single click
    // by runnable when scroll or pinch gesture already completed.
    var wasClick = true

    init {
        gestureDetector = GestureDetector(activity, GestureListener(), handler)
        scaleGestureDetector = ScaleGestureDetector(activity, ScaleGestureListener(), handler)

        playerViewModel.isFullscreen.observe(activity) {
            isFullscreen = it
            listener.onFullscreenChange(it)
        }
    }

    @SuppressLint("ClickableViewAccessibility")
    override fun onTouch(v: View, event: MotionEvent): Boolean {
        if (event.action == MotionEvent.ACTION_UP && isMoving) {
            isMoving = false
            listener.onSwipeEnd()
        }

        // Event can be already consumed by some view which may lead to NPE.
        try {
            scaleGestureDetector.onTouchEvent(event)
            gestureDetector.onTouchEvent(event)
        } catch (_: Exception) { }

        // If video is playing in full-screen mode, then allow `onScroll` to consume
        // event and return true.
        return isFullscreen
    }

    private inner class ScaleGestureListener : ScaleGestureDetector.OnScaleGestureListener {
        var scaleFactor: Float = 1f

        override fun onScale(detector: ScaleGestureDetector): Boolean {
            wasClick = false
            scaleFactor *= detector.scaleFactor
            return true
        }

        override fun onScaleBegin(detector: ScaleGestureDetector): Boolean {
            return true
        }

        override fun onScaleEnd(detector: ScaleGestureDetector) {
            when {
                scaleFactor < 0.8 -> listener.onMinimize()
                scaleFactor > 1.2 -> listener.onZoom()
            }
            scaleFactor = 1f
        }
    }

    private inner class GestureListener : GestureDetector.SimpleOnGestureListener() {
        private var lastClick = 0L
        private var lastDoubleClick = 0L
        private var xPos = 0.0F

        override fun onDown(e: MotionEvent): Boolean {
            // Initially assume this event is for click
            wasClick = true

            if (isMoving || scaleGestureDetector.isInProgress) return false

            if (isEnabled && isSecondClick()) {
                handler.removeCallbacks(runnable)
                lastDoubleClick = elapsedTime
                val eventPositionPercentageX = xPos / width

                when {
                    eventPositionPercentageX < 0.4 -> listener.onDoubleTapLeftScreen()
                    eventPositionPercentageX > 0.6 -> listener.onDoubleTapRightScreen()
                    else -> listener.onDoubleTapCenterScreen()
                }
            } else {
                if (recentDoubleClick()) return true
                handler.removeCallbacks(runnable)
                handler.postDelayed(runnable, MAX_TIME_DIFF)
                lastClick = elapsedTime
                xPos = e.x
            }
            return true
        }

        override fun onScroll(
            e1: MotionEvent,
            e2: MotionEvent,
            distanceX: Float,
            distanceY: Float
        ): Boolean {
            if (!isEnabled || scaleGestureDetector.isInProgress) return false

            val insideThreshHold = abs(e2.y - e1.y) <= MOVEMENT_THRESHOLD
            val insideBorder = (e1.x < BORDER_THRESHOLD || e1.y < BORDER_THRESHOLD || e1.x > width - BORDER_THRESHOLD || e1.y > height - BORDER_THRESHOLD)

            // If the movement is inside threshold or scroll is horizontal then return false
            if (
                !isMoving && (
                    insideThreshHold || insideBorder ||
                        abs(distanceX) > abs(
                            distanceY
                        )
                    )
            ) {
                return false
            }

            isMoving = true
            wasClick = false

            when {
                width * 0.5 > e1.x -> listener.onSwipeLeftScreen(distanceY)
                width * 0.5 < e1.x -> listener.onSwipeRightScreen(distanceY)
            }
            return true
        }

        private val runnable = Runnable {
            // If the last event was for scroll or pinch then avoid single tap call
            if (!wasClick || isSecondClick()) return@Runnable
            listener.onSingleTap()
        }

        private fun isSecondClick(): Boolean {
            return elapsedTime - lastClick < MAX_TIME_DIFF
        }

        private fun recentDoubleClick(): Boolean {
            return elapsedTime - lastDoubleClick < MAX_TIME_DIFF / 2
        }
    }

    companion object {
        private const val MAX_TIME_DIFF = 400L
        private const val MOVEMENT_THRESHOLD = 30
        private const val BORDER_THRESHOLD = 90
    }
}