package com.imyeyu.utils;

import com.imyeyu.java.bean.timi.TimiCode;
import com.imyeyu.java.bean.timi.TimiException;

import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

/**
 * 编码操作
 *
 * @author 夜雨
 * @version 2021-02-13 10:59
 */
public class Decoder {

	/**
	 * 解码 Unicode 字符串
	 *
	 * @param data Unicode 字符串
	 * @return 解码结果
	 */
	public static String unicode(String data) {
		StringWriter out = new StringWriter(data.length());

		StringBuilder unicode = new StringBuilder(4);
		boolean hadSlash = false;
		boolean inUnicode = false;
		for (int i = 0, l = data.length(); i < l; i++) {
			char c = data.charAt(i);
			if (inUnicode) {
				unicode.append(c);
				if (unicode.length() == 4) {
					try {
						out.write((char) Integer.parseInt(unicode.toString(), 16));
						unicode.setLength(0);
						inUnicode = false;
					} catch (NumberFormatException nfe) {
						throw new TimiException(TimiCode.ERROR, "Unable to parse unicode value: " + unicode);
					}
				}
				continue;
			}
			if (hadSlash) {
				hadSlash = false;
				switch (c) {
					case '\\' -> out.write('\\');
					case '\'' -> out.write('\'');
					case '\"' -> out.write('"');
					case 'r' -> out.write('\r');
					case 'f' -> out.write('\f');
					case 't' -> out.write('\t');
					case 'n' -> out.write('\n');
					case 'b' -> out.write('\b');
					case 'u' -> inUnicode = true;
					default -> out.write(c);
				}
				continue;
			} else if (c == '\\') {
				hadSlash = true;
				continue;
			}
			out.write(c);
		}
		if (hadSlash) {
			out.write('\\');
		}
		return out.toString();
	}

	/**
	 * 解码 Base64 字符串
	 *
	 * @param data Base64 字符串
	 * @return 解码结果
	 */
	public static byte[] base64(String data) {
		return Base64.getDecoder().decode(data);
	}

	/**
	 * 解码 Base64 字符串
	 *
	 * @param data Base64 字符串
	 * @return 解码结果
	 */
	public static String base64String(String data) {
		return new String(base64(data), StandardCharsets.UTF_8);
	}

	/**
	 * 解码 URL 链接
	 *
	 * @param url 已编码的 URL 链接
	 * @return 解码结果
	 */
	public static String url(String url) {
		if (url == null) {
			return "";
		}
		return URLDecoder.decode(url, StandardCharsets.UTF_8);
	}

	/**
	 * 16 进制字符串转字节数据
	 *
	 * @param hex 16 进制字符串
	 * @return 字节数据
	 * @throws UnsupportedEncodingException 不支持的编码
	 */
	public static byte[] hex(String hex) throws UnsupportedEncodingException {
		final char[] c = hex.toCharArray();
		final byte[] b = new byte[c.length >> 1];

		final int len = c.length;
		if ((len & 0x01) != 0) {
			throw new UnsupportedEncodingException("Odd number of characters.");
		}

		final int outLen = len >> 1;
		if (c.length < outLen) {
			throw new UnsupportedEncodingException("Output array is not large enough to accommodate decoded data.");
		}
		for (int i = 0, j = 0; j < len; i++) {
			int f = toDigit(c[j], j) << 4;
			j++;
			f = f | toDigit(c[j], j);
			j++;
			b[i] = (byte) (f & 0xFF);
		}
		return b;
	}

	private static int toDigit(final char ch, final int index) throws UnsupportedEncodingException {
		final int digit = Character.digit(ch, 16);
		if (digit == -1) {
			throw new UnsupportedEncodingException("Illegal hexadecimal character " + ch + " at index " + index);
		}
		return digit;
	}
}