RecyclerViewTouchHelper

import android.graphics.Canvas
import android.graphics.Color
import android.graphics.drawable.ColorDrawable
import android.graphics.drawable.Drawable
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.RecyclerView
import com.splashthat.host.R
import com.splashthat.host.api.Identifiable
import com.splashthat.host.extensions.getColorDrawable

@Suppress("MemberVisibilityCanBePrivate")
class RecyclerViewTouchHelper<T : Identifiable>(
    val provideItem: (Int) -> T?,
    val onSwipeLeft: ((Int) -> Unit)? = null,
    val onSwipeRight: ((Int) -> Unit)? = null,
    val onSwipeUp: ((Int) -> Unit)? = null,
    val onSwipeDown: ((Int) -> Unit)? = null
) : ItemTouchHelper.SimpleCallback(0,ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT) {
    
    private var icon: Drawable? = null
    private var iconLeft = 0
    private var iconRight = 0
    private var background = ColorDrawable(Color.TRANSPARENT)
    
    /**
     * Always returns false b/c we're not handling movement events
     */
    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ) : Boolean = false
    
    /**
     * Triggers after a full "swipe" gesture completes
     */
    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        
        val position = viewHolder.adapterPosition
        
        when (direction) {
            ItemTouchHelper.LEFT -> onSwipeLeft?.invoke(position)
            ItemTouchHelper.RIGHT -> onSwipeRight?.invoke(position)
            ItemTouchHelper.UP -> onSwipeUp?.invoke(position)
            ItemTouchHelper.DOWN -> onSwipeDown?.invoke(position)
        }
        
    }
    
    /**
     * Handles drawing the child view behind the real view
     */
    override fun onChildDraw(
        c: Canvas,
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        deltaX: Float,
        deltaY: Float,
        actionState: Int,
        isCurrentlyActive: Boolean
    ) {
        
        super.onChildDraw(c, recyclerView, viewHolder, deltaX, deltaY, actionState, isCurrentlyActive)
        
        // If a non-swiping gesture is happening, ignore
        if (actionState != ItemTouchHelper.ACTION_STATE_SWIPE) return
        
        val itemView = viewHolder.itemView
        
        val direction = when {
            deltaX > 0 -> ItemTouchHelper.RIGHT
            deltaX < 0 -> ItemTouchHelper.LEFT
            else -> null
        }
        
        // Icon to show underneath the view being dragged
        icon = when (direction) {
            ItemTouchHelper.RIGHT -> recyclerView.context.getDrawable(R.drawable.zzz_album)
            ItemTouchHelper.LEFT -> recyclerView.context.getDrawable(R.drawable.zzz_trash)
            else -> null
        }
        
        var iconMargin = 0
        var iconTop = 0
        var iconBottom = 0
        
        icon?.also {
            iconMargin = (itemView.height - it.intrinsicHeight) / 2
            iconTop = itemView.top + (itemView.height - it.intrinsicHeight) / 2
            iconBottom = iconTop + it.intrinsicHeight
        }
        
        when (direction) {
            
            ItemTouchHelper.RIGHT -> {
                
                icon = recyclerView.context.getDrawable(R.drawable.zzz_check)
                iconLeft = itemView.left + iconMargin
                iconRight = (icon?.intrinsicWidth ?: 0) + iconMargin
                
                background = recyclerView.context.getColorDrawable(R.color.money)
                background.setBounds(
                    itemView.left,
                    itemView.top,
                    itemView.left + deltaX.toInt(),
                    itemView.bottom
                )
                
            }
            
            ItemTouchHelper.LEFT -> {
                
                icon = recyclerView.context.getDrawable(R.drawable.zzz_trash)
                iconLeft = itemView.right - iconMargin - (icon?.intrinsicWidth ?: 0)
                iconRight = itemView.right - iconMargin
                
                background = recyclerView.context.getColorDrawable(R.color.hollywood)
                background.setBounds(
                    itemView.right + deltaX.toInt(),
                    itemView.top,
                    itemView.right,
                    itemView.bottom
                )
                
            }
            
            else -> {
                
                icon = null
                background = ColorDrawable(Color.TRANSPARENT)
                background.setBounds(0, 0, 0, 0)
                
            }
            
        }
        
        // Draw the background color first
        background.draw(c)
        
        // Draw the icon over the background
        icon?.setBounds(iconLeft, iconTop, iconRight, iconBottom)
        icon?.draw(c)
        
    }
    
}