import android.annotation.SuppressLint
import android.content.Context
import android.graphics.Color
import android.os.Build
import android.util.AttributeSet
import android.util.Log
import android.view.Gravity
import android.view.MotionEvent
import android.view.View
import android.view.ViewGroup
import android.widget.LinearLayout
import android.widget.TextView
import androidx.core.view.forEach
import androidx.core.widget.NestedScrollView
import kotlin.math.abs
/**
 * 內(nèi)容滾動造成header折疊的控件
 */
class ScrollingCollapseTopLayout @JvmOverloads constructor(
    context: Context,
    attributeSet: AttributeSet? = null,
    defStyleAttr: Int = 0
): ViewGroup(context, attributeSet, defStyleAttr) {
    //外部滑動距離
    private var mScrollHeight = 0f
    //上次縱坐標(biāo)
    private var mLastY = 0f
    //當(dāng)前控件寬高
    private var mHeight = 0
    private var mWidth = 0
    //兩個部分
    private val header: Header = Header(context).apply {
        //設(shè)置header垂直方向，寬度鋪滿，高度自適應(yīng)
        orientation = LinearLayout.VERTICAL
        layoutParams = LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)
    }
    //NestedScrollView只允許一個子view(和ScrollView一樣)，這里放一個垂直的LinearLayout
    private val scrollArea: NestedScrollView = NestedScrollView(context).apply {
        layoutParams = LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)
        addView(LinearLayout(context).apply {
            setBackgroundColor(Color.LTGRAY)
            orientation = LinearLayout.VERTICAL
            layoutParams = LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)
        })
    }
    //XML里面的view
    private val xmlViews: ArrayList<View> = ArrayList()
    //獲取XML內(nèi)view結(jié)束，沒執(zhí)行onMeasure
    override fun onFinishInflate() {
        super.onFinishInflate()
        //在這里獲得所有子view，攔截添加到scrollArea去
        if (xmlViews.size == 0) {
            forEach { view ->
                xmlViews.add(view)
            }
        }
        //更換view的節(jié)點
        removeAllViewsInLayout()
        addView(header)
        addView(scrollArea)
        //把當(dāng)前控件全部view放到NestedScrollView內(nèi)的LinearLayout內(nèi)去
        (scrollArea.getChildAt(0) as ViewGroup).also { linear->
            for(view in xmlViews) {
                linear.addView(view)
            }
        }
    }
    //在onSizeChanged才能獲得正確的寬高，會在onMeasure后得到，這里只是學(xué)一下
    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        mHeight = h
        mWidth = w
    }
    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        //測量header
        header.onScroll(mScrollHeight.toInt())
        header.measure(widthMeasureSpec,
            MeasureSpec.makeMeasureSpec(MeasureSpec.getSize(heightMeasureSpec),MeasureSpec.AT_MOST))
        //先measure一下獲得實際高度，再減去滑動的距離，也可以把header.measuredHeight寫成全局變量
        if (header.measuredHeight != 0) {
            val scrolledHeight = header.measuredHeight + mScrollHeight
            val headerHeightMeasureSpec = MeasureSpec.makeMeasureSpec(scrolledHeight.toInt(),
                MeasureSpec.getMode(MeasureSpec.EXACTLY))
            //再次測量的目的是后面滾動部分要占滿剩余高度
            header.measure(widthMeasureSpec, headerHeightMeasureSpec)
        }
        //測量滑動區(qū)域
        val leftHeight = MeasureSpec.getSize(heightMeasureSpec) - header.measuredHeight
        scrollArea.measure(widthMeasureSpec,
            MeasureSpec.makeMeasureSpec(leftHeight, MeasureSpec.EXACTLY))
        Log.e("TAG", "onMeasure: leftHeight=$leftHeight")
        Log.e("TAG", "onMeasure: scrollArea.height=${scrollArea.height}")
        Log.e("TAG", "onMeasure: scrollArea.measuredHeight=${scrollArea.measuredHeight}")
        //直接占滿寬高
        setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
            MeasureSpec.getSize(heightMeasureSpec))
    }
    override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
        //簡單布局下，上下兩部分
        header.layout(l, t, r, t + header.measuredHeight)
        scrollArea.layout(l, t + header.measuredHeight, r,b)
    }
    //事件沖突使用外部攔截
    override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {
        var isIntercepted = false
        ev?.let {
            when(ev.action) {
                //不攔截down事件
                MotionEvent.ACTION_DOWN -> mLastY = ev.y
                MotionEvent.ACTION_MOVE -> {
                    val dY = ev.y - mLastY
                    //如果折疊了，優(yōu)先滾動折疊欄
                    val canScrollTop = scrollArea.canScrollVertically(-1)
                    val canScrollBottom = scrollArea.canScrollVertically(1)
                    //可以滾動
                    isIntercepted = if (canScrollTop || canScrollBottom) {
                        //手指向上移動時，沒折疊前要攔截
                        val scrollUp = dY < 0 &&
                                mScrollHeight + dY > -header.collapsingArea.height.toFloat()
                        //手指向下移動時，沒展開前且到頂了要攔截
                        val scrollDown = dY > 0 &&
                                mScrollHeight + dY < 0f &&
                                !canScrollTop
                        scrollUp || scrollDown
                    }else {
                        //不能滾動
                        true
                    }
                }
                //不攔截up事件
                //MotionEvent.ACTION_UP ->
            }
        }
        return isIntercepted
    }
    @SuppressLint("ClickableViewAccessibility")
    override fun onTouchEvent(ev: MotionEvent?): Boolean {
        ev?.let {
            when(ev.action) {
                //MotionEvent.ACTION_DOWN ->
                MotionEvent.ACTION_MOVE -> {
                    //累加滑動值，請求重新布局
                    val dY = ev.y - mLastY
                    if (mScrollHeight + dY <= 0 &&
                        mScrollHeight + dY >= -header.collapsingArea.height) {
                            mScrollHeight += dY
                            requestLayout()
                    }
                    mLastY = ev.y
                }
                //MotionEvent.ACTION_UP ->
            }
        }
        return super.onTouchEvent(ev)
    }
    //這里就做一個簡單的折疊header，
    @Suppress("MemberVisibilityCanBePrivate")
    inner class Header @JvmOverloads constructor(
        context: Context,
        attributeSet: AttributeSet? = null,
        defStyleAttr: Int = 0,
    ): LinearLayout(context, attributeSet, defStyleAttr){
        //兩個區(qū)域
        val defaultArea: TextView
        val collapsingArea: TextView
        init {
            //添加兩個header區(qū)域
            defaultArea = makeTextView(context, "Default area", 80)
            collapsingArea = makeTextView(context, "Collapsing area", 300)
            addView(defaultArea)
            addView(collapsingArea)
        }
        //低配Behavior.onNestedPreScroll，這里就處理下ScrollingHideTopLayout傳過來的距離
        @SuppressLint("SetTextI18n")
        fun onScroll(scrollHeight: Int) {
            val expandHeight = collapsingArea.height + scrollHeight
            //這里就改一下背景色的透明度吧
            if (abs(expandHeight) <= collapsingArea.height) {
                val alpha = expandHeight.toFloat() / collapsingArea.height * 255
                defaultArea.text = "Default area:${alpha.toInt()}"
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    collapsingArea.setBackgroundColor(Color.argb(alpha.toInt(),88,88,88))
                }
            }
        }
        //創(chuàng)建TextView
        private fun makeTextView(context: Context, textStr: String, height: Int): TextView {
            //簡單點height和textSize應(yīng)該用dp和sp的，前面文章有
            return TextView(context).apply {
                layoutParams =
                    ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, height)
                text = textStr
                gravity = Gravity.CENTER
                textSize = 13f
                setBackgroundColor(Color.GRAY)
            }
        }
    }
}