/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.dubbo.rpc.protocol.rest.util;

import org.apache.dubbo.common.utils.Assert;
import org.apache.dubbo.common.utils.StringUtils;

import java.math.BigDecimal;
import java.math.BigInteger;

public class NumberUtils {

    public static <T> T parseNumber(String text, Class<T> targetClass) {
        Assert.notNull(text, "Text must not be null");
        Assert.notNull(targetClass, "Target class must not be null");
        String trimmed = trimAllWhitespace(text);

        if (Byte.class == targetClass || byte.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Byte.decode(trimmed) : Byte.valueOf(trimmed));
        } else if (Short.class == targetClass || short.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Short.decode(trimmed) : Short.valueOf(trimmed));
        } else if (Integer.class == targetClass || int.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Integer.decode(trimmed) : Integer.valueOf(trimmed));
        } else if (Long.class == targetClass || long.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? Long.decode(trimmed) : Long.valueOf(trimmed));
        } else if (BigInteger.class == targetClass) {
            return (T) (isHexNumber(trimmed) ? decodeBigInteger(trimmed) : new BigInteger(trimmed));
        } else if (Float.class == targetClass || float.class == targetClass) {
            return (T) Float.valueOf(trimmed);
        } else if (Double.class == targetClass || double.class == targetClass) {
            return (T) Double.valueOf(trimmed);
        } else if (BigDecimal.class == targetClass || Number.class == targetClass) {
            return (T) new BigDecimal(trimmed);
        } else {
            throw new IllegalArgumentException(
                    "Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
        }
    }

    private static boolean isHexNumber(String value) {
        int index = (value.startsWith("-") ? 1 : 0);
        return (value.startsWith("0x", index) || value.startsWith("0X", index) || value.startsWith("#", index));
    }

    private static BigInteger decodeBigInteger(String value) {
        int radix = 10;
        int index = 0;
        boolean negative = false;

        // Handle minus sign, if present.
        if (value.startsWith("-")) {
            negative = true;
            index++;
        }

        // Handle radix specifier, if present.
        if (value.startsWith("0x", index) || value.startsWith("0X", index)) {
            index += 2;
            radix = 16;
        } else if (value.startsWith("#", index)) {
            index++;
            radix = 16;
        } else if (value.startsWith("0", index) && value.length() > 1 + index) {
            index++;
            radix = 8;
        }

        BigInteger result = new BigInteger(value.substring(index), radix);
        return (negative ? result.negate() : result);
    }

    public static String trimAllWhitespace(String str) {
        if (StringUtils.isEmpty(str)) {
            return str;
        }

        int len = str.length();
        StringBuilder sb = new StringBuilder(str.length());
        for (int i = 0; i < len; i++) {
            char c = str.charAt(i);
            if (!Character.isWhitespace(c)) {
                sb.append(c);
            }
        }
        return sb.toString();
    }

    public static Object numberToBytes(Number number) {

        if (number instanceof Byte) {
            // Use default encoding.
            return Byte.toString(number.byteValue()).getBytes();
        } else if (number instanceof Double) {
            return Double.toString(number.doubleValue()).getBytes();
        } else if (number instanceof Float) {
            return Float.toString(number.floatValue()).getBytes();
        } else if (number instanceof Integer) {
            return Float.toString(number.intValue()).getBytes();
        } else if (number instanceof Long) {
            return Long.toString(number.longValue()).getBytes();
        } else if (number instanceof Short) {
            return Short.toString(number.shortValue()).getBytes();
        } else if (number instanceof BigDecimal) {
            return BigDecimal.class.cast(number).toString().getBytes();
        }

        return number;
    }
}