import android.content.Context;
import android.content.res.TypedArray;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

public class DashboardWithSquaredCells extends ViewGroup {

    private int mRows;
    private int mColumns;
    private int mDividerOffset;

    public DashboardWithSquaredCells(Context context) {
        super(context);
        init(context, null);
    }

    public DashboardWithSquaredCells(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    public DashboardWithSquaredCells(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs);
    }

    private void init(final @NonNull Context context, final @Nullable AttributeSet attrs) {
        final TypedArray styledAttributes = context.obtainStyledAttributes(attrs, R.styleable.DashboardWithSquaredCells);
        try {
            mRows = Math.max(styledAttributes.getInt(R.styleable.DashboardWithSquaredCells_rows, 1), 1);
            mColumns = Math.max(styledAttributes.getInt(R.styleable.DashboardWithSquaredCells_columns, 1), 1);
            mDividerOffset = Math.max(styledAttributes.getDimensionPixelSize(R.styleable.DashboardWithSquaredCells_divider_offset, 0), 0);
        } finally {
            styledAttributes.recycle();
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int childSize = Math.max(0, (getMeasuredWidth() - mDividerOffset * (mColumns + 1)) / mColumns);
        final int childSizeSpec = MeasureSpec.makeMeasureSpec(childSize, MeasureSpec.AT_MOST);

        int visibleChilds = 0;
        for (int childIndex = 0, count = getChildCount(); childIndex < count; ++ childIndex) {
            final View child = getChildAt(childIndex);
            if (View.GONE != child.getVisibility()) {
                child.measure(childSizeSpec, childSizeSpec);
                ++ visibleChilds;
            }
        }

        final int visibleRows = (visibleChilds / mColumns) + ((visibleChilds % mColumns) > 0 ? 1 : 0);
        final int manuallyMeasuredHeight = childSize * visibleRows + (visibleRows + 1) * mDividerOffset;

        setMeasuredDimension(getMeasuredWidth(), manuallyMeasuredHeight);
    }

    @SuppressWarnings("ResourceType")
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        final int availableWidth = r - l;
        final int availableHeight = b - t;

        final int cellWidth = Math.max(0, (availableWidth - mDividerOffset * (mColumns + 1)) / mColumns);
        final int cellHeight = Math.max(0, (availableHeight - mDividerOffset * (mRows + 1)) / mRows);

        int visibleChildIndex = 0;
        for (int childIndex = 0, count = getChildCount(); childIndex < count; childIndex++) {
            final View child = getChildAt(childIndex);
            if (View.GONE == child.getVisibility()) {
                continue;
            }

            final int rowIndex = visibleChildIndex / mColumns;
            final int columnIndex = visibleChildIndex % mColumns;

            final int currentLeft = mDividerOffset * (columnIndex + 1) + cellWidth * columnIndex;
            final int currentTop = mDividerOffset * (rowIndex + 1) + cellHeight * rowIndex;
            final int currentRight = (0 == mDividerOffset && columnIndex == mColumns - 1) ? r : (currentLeft + cellWidth);
            final int currentBottom = (0 == mDividerOffset && rowIndex == mRows - 1) ? b : (currentTop + cellHeight);

            child.layout(currentLeft, currentTop, currentRight, currentBottom);

            ++ visibleChildIndex;
        }
    }

}