import android.app.Activity;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;
import android.text.TextUtils;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import androidx.annotation.IntRange;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

/**
 * 水印
 */
public class Watermark {
    /**
     * 水印文本
     */
    private String mText;
    /**
     * 字体颜色(argb)，十六进制形式，例如：0xAEAEAEAE
     */
    private int mTextColor;
    /**
     * 字体大小，单位为sp
     */
    private float mTextSize;
    /**
     * 旋转角度
     */
    private float mRotation;
    private static Watermark sInstance;

    private Watermark() {
        mText = "";
        mTextColor = 0xAECECECE;
        mTextSize = 18;
        mRotation = -45;
    }

    public static Watermark getInstance() {
        if (sInstance == null) {
            synchronized (Watermark.class) {
                sInstance = new Watermark();
            }
        }
        return sInstance;
    }

    /**
     * 设置水印文本
     *
     * @param text 文本
     * @return Watermark实例
     */
    public Watermark setText(String text) {
        mText = text;
        return sInstance;
    }

    /**
     * 设置字体颜色
     *
     * @param color 颜色，十六进制形式，例如：0xAEAEAEAE
     * @return Watermark实例
     */
    public Watermark setTextColor(int color) {
        mTextColor = color;
        return sInstance;
    }

    /**
     * 设置字体大小
     *
     * @param size 大小，单位为sp
     * @return Watermark实例
     */
    public Watermark setTextSize(float size) {
        mTextSize = size;
        return sInstance;
    }

    /**
     * 设置旋转角度
     *
     * @param degrees 度数
     * @return Watermark实例
     */
    public Watermark setRotation(float degrees) {
        mRotation = degrees;
        return sInstance;
    }

    /**
     * 显示水印，铺满整个页面
     *
     * @param activity 活动
     */
    public void show(Activity activity) {
        show(activity, mText);
    }

    /**
     * 显示水印，铺满整个页面
     *
     * @param activity 活动
     * @param text     水印
     */
    public void show(Activity activity, String text) {
        if (activity == null || TextUtils.isEmpty(text)) {
            return;
        }
        WatermarkDrawable drawable = new WatermarkDrawable();
        drawable.mText = text;
        drawable.mTextColor = mTextColor;
        drawable.mTextSize = mTextSize;
        drawable.mRotation = mRotation;

        ViewGroup rootView = activity.findViewById(android.R.id.content);
        FrameLayout layout = new FrameLayout(activity);
        layout.setLayoutParams(new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT));
        layout.setBackground(drawable);
        rootView.addView(layout);
    }

    /**
     * 显示水印，只给指定的View设置水印背景
     * @param view
     * @param text
     */
    public void show(View view, String text) {
        if (view == null || TextUtils.isEmpty(text)) {
            return;
        }
        WatermarkDrawable drawable = build(text);
        view.setBackground(drawable);
    }

    private WatermarkDrawable build(String text){
        WatermarkDrawable drawable = new WatermarkDrawable();
        drawable.mText = text;
        drawable.mTextColor = mTextColor;
        drawable.mTextSize = mTextSize;
        drawable.mRotation = mRotation;
        return drawable;
    }

    public FrameLayout buildWaterMarkFrame(Activity activity, String text) {
        FrameLayout layout = new FrameLayout(activity);
        layout.setLayoutParams(new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT));
        layout.setBackground(build(text));
        return layout;
    }

    private class WatermarkDrawable extends Drawable {
        private Paint mPaint;
        /**
         * 水印文本
         */
        private String mText;
        /**
         * 字体颜色，十六进制形式，例如：0xAEAEAEAE
         */
        private int mTextColor;
        /**
         * 字体大小，单位为sp
         */
        private float mTextSize;
        /**
         * 旋转角度
         */
        private float mRotation;

        private WatermarkDrawable() {
            mPaint = new Paint();
        }

        @Override
        public void draw(@NonNull Canvas canvas) {
            int width = getBounds().right;
            int height = getBounds().bottom;
            int diagonal = (int) Math.sqrt(width * width + height * height); // 对角线的长度

            mPaint.setColor(mTextColor);
            mPaint.setTextSize(spToPx(mTextSize));
            mPaint.setAntiAlias(true);
            float textWidth = mPaint.measureText(mText);

            canvas.drawColor(0x00000000);
            canvas.rotate(mRotation);

            int index = 0;
            float fromX;
            for (int positionY = diagonal / 7; positionY <= diagonal; positionY += diagonal / 7) {
                fromX = -width + (index++ % 2) * textWidth; // 上下两行的X轴起始点不一样，错开显示
                for (float positionX = fromX; positionX < width; positionX += textWidth * 3) {
                    canvas.drawText(mText, positionX, positionY, mPaint);
                }
            }

            canvas.save();
            canvas.restore();
        }

        @Override
        public void setAlpha(@IntRange(from = 0, to = 255) int alpha) {
        }

        @Override
        public void setColorFilter(@Nullable ColorFilter colorFilter) {
        }

        @Override
        public int getOpacity() {
            return PixelFormat.TRANSLUCENT;
        }

    }

    /**
     * Value of sp to value of px.
     *
     * @param spValue The value of sp.
     * @return value of px
     */
    public static int spToPx(float spValue) {
        float fontScale = Resources.getSystem().getDisplayMetrics().scaledDensity;
        return (int) (spValue * fontScale + 0.5f);
    }
}