import android.animation.ValueAnimator
import android.annotation.SuppressLint
import android.content.Context
import android.content.res.Configuration
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import android.view.ViewConfiguration
import android.view.ViewGroup
import androidx.core.animation.addListener
import androidx.core.view.children
import com.silencefly96.module_common.R
import java.util.*
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.pow
import kotlin.math.roundToInt
/**
 * @author silence
 * @date 2022-10-20
 */
class DesktopLayerLayout @JvmOverloads constructor(
    context: Context,
    attributeSet: AttributeSet? = null,
    defStyleAttr: Int = 0
) : ViewGroup(context, attributeSet, defStyleAttr) {
    companion object{
        // 方向
        const val ORIENTATION_VERTICAL = 0
        const val ORIENTATION_HORIZONTAL = 1
        // 狀態(tài)
        const val SCROLL_STATE_IDLE = 0
        const val SCROLL_STATE_DRAGGING = 1
        const val SCROLL_STATE_SETTLING = 2
        // 默認(rèn)padding值
        const val DEFAULT_PADDING_VALUE = 50
        // 豎向默認(rèn)主界面比例
        const val DEFAULT_MAIN_PERCENT_VERTICAL = 0.8f
        // 橫向默認(rèn)主界面比例
        const val DEFAULT_MAIN_PERCENT_HORIZONTAL = 0.6f
        // 其他頁面相對(duì)主界面頁面最小的縮小比例
        const val DEFAULT_OTHER_VIEW_SCAN_SIZE = 0.5f
    }
    /**
     * 當(dāng)前主頁面的index
     */
    @Suppress("MemberVisibilityCanBePrivate")
    var curIndex = 0
    // 由于將view提高層級(jí)會(huì)搞亂順序，需要記錄原始位置信息
    private var mInitViews = ArrayList<View>()
    // view之間的間距
    private var mGateLength = 0
    // 滑動(dòng)距離
    private var mDxLen = 0f
    // 系統(tǒng)最小移動(dòng)距離
    private val mTouchSlop = ViewConfiguration.get(context).scaledTouchSlop
    // 控件狀態(tài)
    private var mState = SCROLL_STATE_IDLE
    // 當(dāng)前設(shè)置的屬性動(dòng)畫
    private var mValueAnimator: ValueAnimator? = null
    // 實(shí)際布局的左右坐標(biāo)值
    private var mRealLeft = 0
    private var mRealRight = 0
    // 上一次按下的橫豎坐標(biāo)
    private var mLastX = 0f
    // 方向，從XML內(nèi)獲得
    private var mOrientation: Int
    // 是否對(duì)屏幕方向自適應(yīng)，從XML內(nèi)獲得
    private val isAutoFitOrientation: Boolean
    // padding，從XML內(nèi)獲得，如果左右移動(dòng)，則上下要有padding，但左右沒有padding
    private val mPaddingValue: Int
    // 豎向主內(nèi)容比例，從XML內(nèi)獲得，剩余兩邊平分
    private val mMainPercentVertical: Float
    // 橫向主內(nèi)容比例，從XML內(nèi)獲得，剩余兩邊平分
    private val mMainPercentHorizontal: Float
    // 其他頁面相對(duì)主界面頁面最小的縮小比例
    private val mOtherViewScanMinSize: Float
    init {
        // 獲取XML參數(shù)
        val typedArray =
            context.obtainStyledAttributes(attributeSet, R.styleable.DesktopLayerLayout)
        mOrientation = typedArray.getInteger(R.styleable.DesktopLayerLayout_mOrientation,
            ORIENTATION_VERTICAL)
        isAutoFitOrientation =
            typedArray.getBoolean(R.styleable.DesktopLayerLayout_isAutoFitOrientation, true)
        mPaddingValue = typedArray.getInteger(R.styleable.DesktopLayerLayout_mPaddingValue,
            DEFAULT_PADDING_VALUE)
        mMainPercentVertical =
            typedArray.getFraction(R.styleable.DesktopLayerLayout_mMainPercentVertical,
            1, 1, DEFAULT_MAIN_PERCENT_VERTICAL)
        mMainPercentHorizontal =
            typedArray.getFraction(R.styleable.DesktopLayerLayout_mMainPercentHorizontal,
            1, 1, DEFAULT_MAIN_PERCENT_HORIZONTAL)
        mOtherViewScanMinSize =
            typedArray.getFraction(R.styleable.DesktopLayerLayout_mOtherViewScanMinSize,
            1, 1, DEFAULT_OTHER_VIEW_SCAN_SIZE)
        typedArray.recycle()
    }
    override fun onFinishInflate() {
        super.onFinishInflate()
        // 獲得所有xml內(nèi)的view，保留原始順序
        mInitViews.addAll(children)
    }
    // 屏幕方向變化并不會(huì)觸發(fā)，初始時(shí)會(huì)觸發(fā)，自適應(yīng)
    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        // Log.e("TAG", "onSizeChanged: w=$w, h=$h")
        // 根據(jù)屏幕變化修改方向，自適應(yīng)
        if (isAutoFitOrientation) {
            mOrientation = if (w > h) ORIENTATION_HORIZONTAL else ORIENTATION_VERTICAL
            requestLayout()
        }
    }
    // 需要在manifest中注冊(cè)捕捉事件類型，android:configChanges="orientation|keyboardHidden|screenSize"
    public override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)
        if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
            mOrientation = ORIENTATION_VERTICAL
            requestLayout()
        }else if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            mOrientation = ORIENTATION_HORIZONTAL
            requestLayout()
        }
    }
    // 排列規(guī)則：初始化第一個(gè)放中間，其他向右排列，中間最大，中心在左右邊上的最小，不可見的也是最小
    // view的大小應(yīng)該只和它在可見頁面的位置有關(guān)，不應(yīng)該和curIndex有關(guān)，是充分不必要關(guān)系
    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        // super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        // 獲取默認(rèn)尺寸，考慮背景大小
        val width = max(getDefaultSize(0, widthMeasureSpec), suggestedMinimumWidth)
        val height = max(getDefaultSize(0, heightMeasureSpec), suggestedMinimumHeight)
        // 設(shè)置間距
        mGateLength = width / 4
        // 中間 view 大小
        val maxWidth: Int
        val maxHeight: Int
        // 不同方向尺寸不同
        if (mOrientation == ORIENTATION_HORIZONTAL) {
            maxWidth = (width * mMainPercentHorizontal).toInt()
            maxHeight = height - 2 * mPaddingValue
        }else {
            maxWidth = (width * mMainPercentVertical).toInt()
            maxHeight = height - 2 * mPaddingValue
        }
        // 兩側(cè) view 大小，第三排
        val minWidth = (maxWidth * mOtherViewScanMinSize).toInt()
        val minHeight = (maxHeight * mOtherViewScanMinSize).toInt()
        var childWidth: Int
        var childHeight: Int
        for (i in 0 until childCount) {
            val child = mInitViews[i]
            val scanSize = getViewScanSize(i, scrollX)
            childWidth = minWidth + ((maxWidth - minWidth) * scanSize).toInt()
            childHeight = minHeight + ((maxHeight - minHeight) * scanSize).toInt()
            // Log.e("TAG", "onMeasure($i): childWidth=$childWidth, childHeight=$childHeight")
            child.measure(MeasureSpec.makeMeasureSpec(childWidth, MeasureSpec.EXACTLY),
                MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.EXACTLY))
        }
        setMeasuredDimension(width, height)
    }
    // 選中view為最大，可見部分會(huì)縮放，不可見部分和第三排一樣大
    private fun getViewScanSize(index: Int, scrolledLen: Int): Float {
        var scanSize = 0f
        // 開始時(shí)當(dāng)前view未測(cè)量，不計(jì)算
        if (measuredWidth == 0) return scanSize
        // 初始化的時(shí)候，第一個(gè)放中間，所以index移到可見范圍為[2+index, index-2]，可見!=可移動(dòng)
        val scrollLeftLimit = (index - 2) * mGateLength
        val scrollRightLimit = (index + 2) * mGateLength
        // 先判斷child是否可見
        if (scrolledLen in scrollLeftLimit..scrollRightLimit) {
            // 根據(jù)二次函數(shù)計(jì)算比例
            scanSize = scanByParabola(scrollLeftLimit, scrollRightLimit, scrolledLen).toFloat()
        }
        return scanSize
    }
    // 根據(jù)拋物線計(jì)算比例，y屬于[0, 1]
    // 映射關(guān)系：(form, 0) ((from + to) / 2, 0) (to, 0) -> (0, 0) (1, 1) (2, 0)
    @Suppress("SameParameterValue")
    private fun scanByParabola(from: Int, to: Int, cur: Int): Double {
        // 公式：val y = 1 - (x - 1).toDouble().pow(2.0)
        // Log.e("TAG", "scanByParabola:from=$from, to=$to, cur=$cur ")
        val x = ((cur - from) / (to - from).toFloat() * 2).toDouble()
        return 1 - (x - 1).pow(2.0)
    }
    // layout 按順序間距排列即可，大小有onMeasure控制,開始位置在中心，也和curIndex無關(guān)
    override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
        val startX = (r + l) / 2
        // 排列布局
        for (i in 0 until childCount) {
            val child = mInitViews[i]
            // 中間減去間距，再減去一半的寬度，得到左邊坐標(biāo)
            val left = startX + mGateLength * i - child.measuredWidth / 2
            val top = (b + t) / 2 - child.measuredHeight / 2
            val right = left + child.measuredWidth
            val bottom = top + child.measuredHeight
            // Log.e("TAG", "onLayout($i): left=$left, right=$right")
            child.layout(left, top, right, bottom)
        }
        // 修改大小，布局完成后移動(dòng)
        scrollBy(mDxLen.toInt(), 0)
        mDxLen = 0f
        // 完成布局及移動(dòng)后，繪制之前，將可見view提高層級(jí)
        val targetIndex = getCurrentIndex()
        for (i in 2 downTo 0) {
            val preIndex = targetIndex - i
            val aftIndex = targetIndex + i
            // 逐次提高層級(jí)，注意在mInitViews拿就可以，不可見不管
            if (preIndex in 0..childCount) {
                bringChildToFront(mInitViews[preIndex])
            }
            if (aftIndex != preIndex && aftIndex in 0 until childCount) {
                bringChildToFront(mInitViews[aftIndex])
            }
        }
    }
    // 根據(jù)滾動(dòng)距離獲得當(dāng)前index
    private fun getCurrentIndex()= (scrollX / mGateLength.toFloat()).roundToInt()
    override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {
        ev?.let {
            when(it.action) {
                MotionEvent.ACTION_DOWN -> {
                    mLastX = ev.x
                    if(mState == SCROLL_STATE_IDLE) {
                        mState = SCROLL_STATE_DRAGGING
                    }else if (mState == SCROLL_STATE_SETTLING) {
                        mState = SCROLL_STATE_DRAGGING
                        // 去除結(jié)束監(jiān)聽，結(jié)束動(dòng)畫
                        mValueAnimator?.removeAllListeners()
                        mValueAnimator?.cancel()
                    }
                }
                MotionEvent.ACTION_MOVE -> {
                    // 若ACTION_DOWN是本view攔截，則下面代碼不會(huì)觸發(fā)，要在onTouchEvent判斷
                    val dX = mLastX - ev.x
                    return checkScrollInView(scrollX + dX)
                }
                MotionEvent.ACTION_UP -> {}
            }
        }
        return super.onInterceptHoverEvent(ev)
    }
    // 根據(jù)可以滾動(dòng)的范圍，計(jì)算是否可以滾動(dòng)
    private fun checkScrollInView(length : Float): Boolean {
        // 一層情況
        if (childCount <= 1) return false
        // 左右兩邊最大移動(dòng)值，即把最后一個(gè)移到中間
        val leftScrollLimit = 0
        val rightScrollLimit = (childCount - 1) * mGateLength
        return (length >= leftScrollLimit && length <= rightScrollLimit)
    }
    @SuppressLint("ClickableViewAccessibility")
    override fun onTouchEvent(ev: MotionEvent?): Boolean {
        ev?.let {
            when(it.action) {
                // 防止點(diǎn)擊空白位置或者子view未處理touch事件
                MotionEvent.ACTION_DOWN -> return true
                MotionEvent.ACTION_MOVE -> {
                    // 如果是本view攔截的ACTION_DOWN，要在此判斷
                    val dX = mLastX - ev.x
                    if(checkScrollInView(scrollX + dX)) {
                        move(ev)
                    }
                }
                MotionEvent.ACTION_UP -> moveUp()
            }
        }
        return super.onTouchEvent(ev)
    }
    private fun move(ev: MotionEvent) {
        val dX = mLastX - ev.x
        // 修改mScrollLength，重新measure及l(fā)ayout，再onLayout的最后實(shí)現(xiàn)移動(dòng)
        mDxLen += dX
        if(abs(mDxLen) >= mTouchSlop) {
            requestLayout()
        }
        // 更新值
        mLastX = ev.x
    }
    private fun moveUp() {
        // 賦值
        val targetScrollLen = getCurrentIndex() * mGateLength
        // 不能使用scroller，無法在移動(dòng)的時(shí)候進(jìn)行測(cè)量
        // mScroller.startScroll(scrollX, scrollY, (targetScrollLen - scrollX), 0)
        // 這里使用ValueAnimator處理剩余的距離，模擬滑動(dòng)到需要的位置
        val animator = ValueAnimator.ofFloat(scrollX.toFloat(), targetScrollLen.toFloat())
        animator.addUpdateListener { animation ->
            // Log.e("TAG", "stopMove: " + animation.animatedValue as Float)
            mDxLen = animation.animatedValue as Float - scrollX
            requestLayout()
        }
        // 在動(dòng)畫結(jié)束時(shí)修改curIndex
        animator.addListener (onEnd = {
            curIndex = getCurrentIndex()
            mState = SCROLL_STATE_IDLE
        })
        // 設(shè)置狀態(tài)
        mState = SCROLL_STATE_SETTLING
        animator.duration = 300L
        animator.start()
    }
}

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name ="DesktopLayerLayout">
        <attr name="mOrientation">
            <enum name ="vertical" value="0" />
            <enum name ="horizontal" value="1" />
        </attr>
        <attr name="isAutoFitOrientation" format="boolean"/>
        <attr name="mPaddingValue" format="integer"/>
        <attr name="mMainPercentVertical" format="fraction"/>
        <attr name="mMainPercentHorizontal" format="fraction"/>
        <attr name="mOtherViewScanMinSize" format="fraction"/>
    </declare-styleable>
</resources>

    @Override
    public void bringChildToFront(View child) {
        final int index = indexOfChild(child);
        if (index >= 0) {
            removeFromArray(index);
            addInArray(child, mChildrenCount);
            child.mParent = this;
            requestLayout();
            invalidate();
        }
    }