/*
 * Copyright 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.ui.core.demos.gestures

import androidx.compose.Composable
import androidx.compose.emptyContent
import androidx.compose.state
import androidx.ui.core.Alignment
import androidx.ui.core.DensityAmbient
import androidx.ui.core.Modifier
import androidx.ui.core.gesture.ScrollCallback
import androidx.ui.core.gesture.scrollGestureFilter
import androidx.ui.core.gesture.scrollorientationlocking.Orientation
import androidx.compose.foundation.Box
import androidx.compose.foundation.Text
import androidx.ui.geometry.Offset
import androidx.ui.graphics.Color
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.offset
import androidx.compose.foundation.layout.preferredSize
import androidx.compose.foundation.layout.wrapContentSize
import androidx.ui.unit.Dp
import androidx.ui.unit.dp

/**
 * Simple demo that shows off ScrollGestureFilter.
 */
@Composable
fun ScrollGestureFilterDemo() {
    Column {
        Text("Demonstrates scroll orientation locking")
        Text(
            "The inner box is composed inside of the outer.  If you start dragging the inner box" +
                    "vertically, it will drag vertically , the same pointer will only ever allow " +
                    "the box to be dragged vertically.  If drag the inner box horizontally, the " +
                    "container will start being dragged horizontally and that pointer will only " +
                    "ever drag horizontally."
        )
        ScrollableBox(240.dp, Orientation.Horizontal, Green, Yellow) {
            ScrollableBox(144.dp, Orientation.Vertical, Red, Blue)
        }
    }
}

@Composable
fun ScrollableBox(
    size: Dp,
    orientation: Orientation,
    activeColor: Color,
    idleColor: Color,
    children: @Composable () -> Unit = emptyContent()
) {

    val color = state { idleColor }
    val offsetPx = state { 0f }

    val offsetDp = with(DensityAmbient.current) {
        offsetPx.value.toDp()
    }

    val scrollCallback: ScrollCallback = object : ScrollCallback {
        override fun onStart(downPosition: Offset) {
            color.value = activeColor
        }

        override fun onScroll(scrollDistance: Float): Float {
            offsetPx.value += scrollDistance
            return scrollDistance
        }

        override fun onStop(velocity: Float) {
            color.value = idleColor
        }

        override fun onCancel() {
            color.value = idleColor
        }
    }

    val (offsetX, offsetY) = when (orientation) {
        Orientation.Horizontal -> offsetDp to Dp.Hairline
        Orientation.Vertical -> Dp.Hairline to offsetDp
    }

    Box(
            Modifier.offset(offsetX, offsetY)
                .fillMaxSize()
                .wrapContentSize(Alignment.Center)
                .scrollGestureFilter(scrollCallback, orientation)
                .preferredSize(size),
            backgroundColor = color.value
        ) {
            children()
        }
}