fenix/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SwipeToDeleteCallback.kt

/* This Source Code Form is subject to the terms of the Mozilla Public
   License, v. 2.0. If a copy of the MPL was not distributed with this
   file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.fenix.home.sessioncontrol

import android.content.Context
import android.content.res.Resources
import android.graphics.Canvas
import android.graphics.Paint
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.RecyclerView
import io.reactivex.Observer
import org.mozilla.fenix.R
import org.mozilla.fenix.home.sessioncontrol.viewholders.TabViewHolder
import android.graphics.drawable.Drawable

class SwipeToDeleteCallback(
    val actionEmitter: Observer<SessionControlAction>
) : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT) {
    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ): Boolean {
        // We don't support drag and drop so this method will never be called
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        if (viewHolder is TabViewHolder) {
            actionEmitter.onNext(TabAction.Close(viewHolder.tab?.sessionId!!))
        }
    }

    override fun onChildDraw(
        c: Canvas,
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        dX: Float,
        dY: Float,
        actionState: Int,
        isCurrentlyActive: Boolean
    ) {
        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
        val icon = ContextCompat.getDrawable(recyclerView.context, R.drawable.ic_delete)
        val background = ContextCompat.getDrawable(
            recyclerView.context,
            R.drawable.session_background
        )

        background?.let {
            icon?.let {
                val itemView = viewHolder.itemView
                val iconLeft: Int
                val iconRight: Int
                val margin = convertDpToPixel(MARGIN.toFloat())
                val iconWidth = icon.intrinsicWidth
                val iconHeight = icon.intrinsicHeight
                val cellHeight = itemView.bottom - itemView.top
                val iconTop = itemView.top + (cellHeight - iconHeight) / 2
                val iconBottom = iconTop + iconHeight

                when {
                    dX > 0 -> { // Swiping to the right
                        iconLeft = itemView.left + margin
                        iconRight = itemView.left + margin + iconWidth
                        background.setBounds(
                            itemView.left, itemView.top,
                            (itemView.left + dX).toInt() + BACKGROUND_CORNER_OFFSET,
                            itemView.bottom
                        )
                        icon.setBounds(iconLeft, iconTop, iconRight, iconBottom)
                        draw(background, icon, c, recyclerView.context, iconLeft, iconBottom)
                    }
                    dX < 0 -> { // Swiping to the left
                        iconLeft = itemView.right - margin - iconWidth
                        iconRight = itemView.right - margin
                        background.setBounds(
                            (itemView.right + dX).toInt() - BACKGROUND_CORNER_OFFSET,
                            itemView.top, itemView.right, itemView.bottom
                        )
                        icon.setBounds(iconLeft, iconTop, iconRight, iconBottom)
                        draw(background, icon, c, recyclerView.context, iconLeft, iconBottom)
                    }
                    else -> { // View not swiped
                        background.setBounds(0, 0, 0, 0)
                        icon.setBounds(0, 0, 0, 0)
                    }
                }
            }
        }
    }

    override fun getSwipeDirs(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder
    ): Int {
        return if (viewHolder is TabViewHolder) {
            super.getSwipeDirs(recyclerView, viewHolder)
        } else 0
    }

    companion object {
        const val BACKGROUND_CORNER_OFFSET = 40
        const val MARGIN = 32
        const val TEXT_MARGIN = 12
        const val TEXT_SIZE = 36f
        const val TEXT_MARGIN_X = 14
        const val DENSITY_CONVERSION = 160f

        @Suppress("LongParameterList")
        private fun draw(
            background: Drawable,
            icon: Drawable,
            c: Canvas,
            context: Context,
            iconLeft: Int,
            iconBottom: Int
        ) {
            background.draw(c)
            icon.draw(c)
            val textPaint = Paint()
            textPaint.color = ContextCompat.getColor(
                context,
                R.color.delete_color
            )
            textPaint.textSize = TEXT_SIZE
            val textX = iconLeft - TEXT_MARGIN_X
            val textY = iconBottom + convertDpToPixel(TEXT_MARGIN.toFloat())
            c.drawText(
                context.getString(R.string.current_session_delete),
                textX.toFloat(),
                textY.toFloat(),
                textPaint
            )
        }

        private fun convertDpToPixel(dp: Float): Int {
            val metrics = Resources.getSystem().displayMetrics
            val px = dp * (metrics.densityDpi / DENSITY_CONVERSION)
            return Math.round(px)
        }
    }
}