Gadgetbridge/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/StringUtils.java

/*  Copyright (C) 2017-2024 Andreas Shimokawa, Arjan Schrijver, Carsten
    Pfeiffer, Daniel Dakhno, Daniele Gobbetti, João Paulo Barraca, José Rebelo,
    Nephiel, Roi Greenberg, Taavi Eomäe, Zhong Jianxin

    This file is part of Gadgetbridge.

    Gadgetbridge is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Gadgetbridge is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.util;

import java.io.ByteArrayOutputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.StandardCharsets;

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

import org.apache.commons.lang3.ArrayUtils;

public class StringUtils {



    @NonNull
    public static String truncate(String s, int maxLength){
        if (s == null) {
            return "";
        }

        int length = Math.min(s.length(), maxLength);
        if(length < 0) {
            return "";
        }

        return s.substring(0, length);
    }

    /**
     * Truncate a string to a certain maximum number of bytes, assuming UTF-8 encoding.
     * Does not include the null terminator. Due to multi-byte characters, it's possible
     * that the resulting array is smaller than len, but never larger.
     */
    public static byte[] truncateToBytes(final String s, final int len) {
        if (StringUtils.isNullOrEmpty(s)) {
            return new byte[]{};
        }

        int i = 0;
        while (++i < s.length()) {
            final String subString = s.substring(0, i + 1);
            if (subString.getBytes(StandardCharsets.UTF_8).length > len) {
                break;
            }
        }

        return s.substring(0, i).getBytes(StandardCharsets.UTF_8);
    }

    public static int utf8ByteLength(String string, int length) {
        if (string == null) {
            return 0;
        }
        ByteBuffer outBuf = ByteBuffer.allocate(length);
        CharBuffer inBuf = CharBuffer.wrap(string.toCharArray());
        StandardCharsets.UTF_8.newEncoder().encode(inBuf, outBuf, true);
        return outBuf.position();
    }

    public static String pad(String s, int length){
        return pad(s, length, ' ');
    }

    public static String pad(String s, int length, char padChar) {
        StringBuilder sBuilder = new StringBuilder(s);
        while (sBuilder.length() < length) {
            sBuilder.append(padChar);
        }
        s = sBuilder.toString();
        return s;
    }

    /**
     * Joins the given elements and adds a separator between each element in the resulting string.
     * There will be no separator at the start or end of the string. There will be no consecutive
     * separators (even in case an element is null or empty).
     * @param separator the separator string
     * @param elements the elements to concatenate to a new string
     * @return the joined strings, separated by the separator
     */
    @NonNull
    public static StringBuilder join(String separator, String... elements) {
        StringBuilder builder = new StringBuilder();
        if (elements == null) {
            return builder;
        }
        boolean hasAdded = false;
        for (String element : elements) {
            if (element != null && element.length() > 0) {
                if (hasAdded) {
                    builder.append(separator);
                }
                builder.append(element);
                hasAdded = true;
            }
        }
        return builder;
    }

    @NonNull
    public static String getFirstOf(String first, String second) {
        if (first != null && first.length() > 0) {
            return first;
        }
        if (second != null) {
            return second;
        }
        return "";
    }

    public static boolean isNullOrEmpty(String string){
        return string == null || string.isEmpty();
    }

    public static boolean isEmpty(String string) {
        return string != null && string.length() == 0;
    }

    public static String ensureNotNull(String message) {
        if (message != null) {
            return message;
        }
        return "";
    }

    public static String terminateNull(String input) {
        if (input == null || input.length() == 0) {
            return new String(new byte[]{(byte) 0});
        }
        char lastChar = input.charAt(input.length() - 1);
        if (lastChar == 0) return input;

        byte[] newArray = new byte[input.getBytes().length + 1];
        System.arraycopy(input.getBytes(), 0, newArray, 0, input.getBytes().length);

        newArray[newArray.length - 1] = 0;

        return new String(newArray);
    }

    @Nullable
    public static String untilNullTerminator(final byte[] bytes, final int startOffset) {
        for (int i = startOffset; i < bytes.length; i++) {
            if (bytes[i] == 0) {
                return new String(ArrayUtils.subarray(bytes, startOffset, i));
            }
        }

        return null;
    }

    @Nullable
    public static String untilNullTerminator(final ByteBuffer buf) {
        final ByteArrayOutputStream baos = new ByteArrayOutputStream();

        while (buf.position() < buf.limit()) {
            final byte b = buf.get();

            if (b == 0) {
                return baos.toString();
            }

            baos.write(b);
        }

        return null;
    }

    public static String bytesToHex(byte[] array) {
        return GB.hexdump(array, 0, -1);
    }

    /**
     * Creates a shortened version of an Android package name by using only the first
     * character of every non-last part of the package name.
     * Example: "nodomain.freeyourgadget.gadgetbridge" is shortened to "n.f.gadgetbridge"
     * @param packageName the original package name
     * @return the shortened package name
     */
    public static String shortenPackageName(String packageName) {
        String[] parts = packageName.split("\\.");
        StringBuilder result = new StringBuilder();
        for (int index=0; index < parts.length; index++) {
            if (index == parts.length - 1) {
                result.append(parts[index]);
                break;
            }
            result.append(parts[index].charAt(0)).append(".");
        }
        return result.toString();
    }
}