/*
 * 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.brooklyn.util.text;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.StringTokenizer;
import javax.annotation.Nullable;

import org.apache.brooklyn.util.collections.MutableList;
import org.apache.brooklyn.util.collections.MutableMap;
import org.apache.brooklyn.util.guava.Maybe;
import org.apache.brooklyn.util.time.Time;

import com.google.common.base.CharMatcher;
import com.google.common.base.Functions;
import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;

public class Strings {

    /** The empty {@link String}. */
    public static final String EMPTY = "";

    /**
     * Checks if the given string is null or is an empty string.
     * Useful for pre-String.isEmpty.  And useful for StringBuilder etc.
     *
     * @param s the String to check
     * @return true if empty or null, false otherwise.
     *
     * @see #isNonEmpty(CharSequence)
     * @see #isBlank(CharSequence)
     * @see #isNonBlank(CharSequence)
     */
    public static boolean isEmpty(CharSequence s) {
        // Note guava has com.google.common.base.Strings.isNullOrEmpty(String),
        // but that is just for String rather than CharSequence
        return s == null || s.length()==0;
    }

    /**
     * Checks if the given string is empty or only consists of whitespace.
     *
     * @param s the String to check
     * @return true if blank, empty or null, false otherwise.
     *
     * @see #isEmpty(CharSequence)
     * @see #isNonEmpty(CharSequence)
     * @see #isNonBlank(CharSequence)
     */
    public static boolean isBlank(CharSequence s) {
        return isEmpty(s) || CharMatcher.WHITESPACE.matchesAllOf(s);
    }

    /**
     * The inverse of {@link #isEmpty(CharSequence)}.
     *
     * @param s the String to check
     * @return true if non empty, false otherwise.
     *
     * @see #isEmpty(CharSequence)
     * @see #isBlank(CharSequence)
     * @see #isNonBlank(CharSequence)
     */
    public static boolean isNonEmpty(CharSequence s) {
        return !isEmpty(s);
    }

    /**
     * The inverse of {@link #isBlank(CharSequence)}.
     *
     * @param s the String to check
     * @return true if non blank, false otherwise.
     *
     * @see #isEmpty(CharSequence)
     * @see #isNonEmpty(CharSequence)
     * @see #isBlank(CharSequence)
     */
    public static boolean isNonBlank(CharSequence s) {
        return !isBlank(s);
    }

    /** @return a {@link Maybe} object which is absent if the argument {@link #isBlank(CharSequence)} */
    public static <T extends CharSequence> Maybe<T> maybeNonBlank(T s) {
        if (isNonBlank(s)) return Maybe.of(s);
        return Maybe.absent();
    }

    /** throws IllegalArgument if string not empty; cf. guava Preconditions.checkXxxx */
    public static void checkNonEmpty(CharSequence s) {
        if (s==null) throw new IllegalArgumentException("String must not be null");
        if (s.length()==0) throw new IllegalArgumentException("String must not be empty");
    }
    /** throws IllegalArgument if string not empty; cf. guava Preconditions.checkXxxx */
    public static void checkNonEmpty(CharSequence s, String message) {
        if (isEmpty(s)) throw new IllegalArgumentException(message);
    }

    /**
     * Removes suffix from the end of the string. Returns string if it does not end with suffix.
     */
    public static String removeFromEnd(String string, String suffix) {
        if (isEmpty(string)) {
            return string;
        } else if (!isEmpty(suffix) && string.endsWith(suffix)) {
            return string.substring(0, string.length() - suffix.length());
        } else {
            return string;
        }
    }

    /**
     * As removeFromEnd, but repeats until all such suffixes are gone
     */
    public static String removeAllFromEnd(String string, String... suffixes) {
        if (isEmpty(string)) return string;
        int index = string.length();
        boolean anotherLoopNeeded = true;
        while (anotherLoopNeeded) {
            if (isEmpty(string)) return string;
            anotherLoopNeeded = false;
            for (String suffix : suffixes)
                if (!isEmpty(suffix) && string.startsWith(suffix, index - suffix.length())) {
                    index -= suffix.length();
                    anotherLoopNeeded = true;
                    break;
                }
        }
        return string.substring(0, index);
    }

    /**
     * Removes prefix from the beginning of string. Returns string if it does not begin with prefix.
     */
    public static String removeFromStart(String string, String prefix) {
        if (isEmpty(string)) {
            return string;
        } else if (!isEmpty(prefix) && string.startsWith(prefix)) {
            return string.substring(prefix.length());
        } else {
            return string;
        }
    }

    /**
     * As {@link #removeFromStart(String, String)}, repeating until all such prefixes are gone.
     */
    public static String removeAllFromStart(String string, String... prefixes) {
        int index = 0;
        boolean anotherLoopNeeded = true;
        while (anotherLoopNeeded) {
            if (isEmpty(string)) return string;
            anotherLoopNeeded = false;
            for (String prefix : prefixes) {
                if (!isEmpty(prefix) && string.startsWith(prefix, index)) {
                    index += prefix.length();
                    anotherLoopNeeded = true;
                    break;
                }
            }
        }
        return string.substring(index);
    }
    
    /**
     * Removes everything after the marker, optionally also removing the marker.
     * If marker not found the string is unchanged.
     */
    public static String removeAfter(String string, String marker, boolean includeMarker) {
        int i = string.indexOf(marker);
        if (i==-1) return string;
        return string.substring(0, i + (includeMarker ? marker.length() : 0));
    }
    
    /**
     * Removes everything before the marker, optionally also removing the marker.
     * If marker not found the string is unchanged.
     */
    public static String removeBefore(String string, String marker, boolean includeMarker) {
        int i = string.indexOf(marker);
        if (i==-1) return string;
        return string.substring(i + (includeMarker ? 0 : marker.length()));
    }
    
    /** convenience for {@link com.google.common.base.Joiner} */
    public static String join(Iterable<? extends Object> list, String separator) {
        if (list==null) return null;
        boolean app = false;
        StringBuilder out = new StringBuilder();
        for (Object s: list) {
            if (app) out.append(separator);
            out.append(s);
            app = true;
        }
        return out.toString();
    }
    /** convenience for {@link com.google.common.base.Joiner} */
    public static String join(Object[] list, String separator) {
        boolean app = false;
        StringBuilder out = new StringBuilder();
        for (Object s: list) {
            if (app) out.append(separator);
            out.append(s);
            app = true;
        }
        return out.toString();
    }

    /** convenience for joining lines together */
    public static String lines(String ...lines) {
        if (lines==null) return null;
        return lines(Arrays.asList(lines));
    }
    
    /** convenience for joining lines together */
    public static String lines(Iterable<String> lines) {
        if (lines==null) return null;
        return Joiner.on("\n").join(lines);
    }

    public static String removeLines(String multiline, Predicate<CharSequence> patternToRemove) {
        if (multiline==null) return null;
        return lines(Iterables.filter(Arrays.asList(multiline.split("\n")), Predicates.not(patternToRemove)));
    }

    /** NON-REGEX - replaces all key->value entries from the replacement map in source (non-regex) */
    @SuppressWarnings("rawtypes")
    public static String replaceAll(String source, Map replacements) {
        for (Object rr: replacements.entrySet()) {
            Map.Entry r = (Map.Entry)rr;
            source = replaceAllNonRegex(source, ""+r.getKey(), ""+r.getValue());
        }
        return source;
    }

    /** NON-REGEX replaceAll - see the better, explicitly named {@link #replaceAllNonRegex(String, String, String)}. */
    public static String replaceAll(String source, String pattern, String replacement) {
        return replaceAllNonRegex(source, pattern, replacement);
    }

    /** 
     * Replaces all instances in source, of the given pattern, with the given replacement
     * (not interpreting any arguments as regular expressions).
     * <p>
     * This is actually the same as the very ambiguous {@link String#replace(CharSequence, CharSequence)},
     * which does replace all, but not using regex like the similarly ambiguous {@link String#replaceAll(String, String)} as.
     * Alternatively see {@link #replaceAllRegex(String, String, String)}.
     */
    public static String replaceAllNonRegex(String source, String pattern, String replacement) {
        if (source==null) return source;
        StringBuilder result = new StringBuilder(source.length());
        for (int i=0; i<source.length(); ) {
            if (source.substring(i).startsWith(pattern)) {
                result.append(replacement);
                i += pattern.length();
            } else {
                result.append(source.charAt(i));
                i++;
            }
        }
        return result.toString();
    }

    /** REGEX replacement -- explicit method name for readability, doing same as {@link String#replaceAll(String, String)}. */
    public static String replaceAllRegex(String source, String pattern, String replacement) {
        return source.replaceAll(pattern, replacement);
    }

    /** Valid non alphanumeric characters for filenames. */
    public static final String VALID_NON_ALPHANUM_FILE_CHARS = "-_.";

    /**
     * Returns a valid filename based on the input.
     *
     * A valid filename starts with the first alphanumeric character, then include
     * all alphanumeric characters plus those in {@link #VALID_NON_ALPHANUM_FILE_CHARS},
     * with any runs of invalid characters being replaced by {@literal _}.
     *
     * @throws NullPointerException if the input string is null.
     * @throws IllegalArgumentException if the input string is blank.
     */
    public static String makeValidFilename(String s) {
        Preconditions.checkNotNull(s, "Cannot make valid filename from null string");
        Preconditions.checkArgument(isNonBlank(s), "Cannot make valid filename from blank string");
        return CharMatcher.anyOf(VALID_NON_ALPHANUM_FILE_CHARS).or(CharMatcher.JAVA_LETTER_OR_DIGIT)
                .negate()
                .trimAndCollapseFrom(s, '_');
    }

    /**
     * A {@link CharMatcher} that matches valid Java identifier characters.
     *
     * @see Character#isJavaIdentifierPart(char)
     */
    public static final CharMatcher IS_JAVA_IDENTIFIER_PART = CharMatcher.forPredicate(new Predicate<Character>() {
        @Override
        public boolean apply(@Nullable Character input) {
            return input != null && Character.isJavaIdentifierPart(input);
        }
    });

    /**
     * Returns a valid Java identifier name based on the input.
     *
     * Removes certain characterss (like apostrophe), replaces one or more invalid
     * characterss with {@literal _}, and prepends {@literal _} if the first character
     * is only valid as an identifier part (not start).
     * <p>
     * The result is usually unique to s, though this isn't guaranteed, for example if
     * all characters are invalid. For a unique identifier use {@link #makeValidUniqueJavaName(String)}.
     *
     * @see #makeValidUniqueJavaName(String)
     */
    public static String makeValidJavaName(String s) {
        if (s==null) return "__null";
        if (s.length()==0) return "__empty";
        String name = IS_JAVA_IDENTIFIER_PART.negate().collapseFrom(CharMatcher.is('\'').removeFrom(s), '_');
        if (!Character.isJavaIdentifierStart(s.charAt(0))) return "_" + name;
        return name;
    }

    /**
     * Returns a unique valid java identifier name based on the input.
     *
     * Translated as per {@link #makeValidJavaName(String)} but with {@link String#hashCode()}
     * appended where necessary to guarantee uniqueness.
     *
     * @see #makeValidJavaName(String)
     */
    public static String makeValidUniqueJavaName(String s) {
        String name = makeValidJavaName(s);
        if (isEmpty(s) || IS_JAVA_IDENTIFIER_PART.matchesAllOf(s) || CharMatcher.is('\'').matchesNoneOf(s)) {
            return name;
        } else {
            return name + "_" + s.hashCode();
        }
    }

    /** @see {@link Identifiers#makeRandomId(int)} */
    public static String makeRandomId(int l) {
        return Identifiers.makeRandomId(l);
    }

    /** pads the string with 0's at the left up to len; no padding if i longer than len */
    public static String makeZeroPaddedString(int i, int len) {
        return makePaddedString(""+i, len, "0", "");
    }

    /** pads the string with "pad" at the left up to len; no padding if base longer than len */
    public static String makePaddedString(String base, int len, String left_pad, String right_pad) {
        String s = ""+(base==null ? "" : base);
        while (s.length()<len) s=left_pad+s+right_pad;
        return s;
    }

    public static void trimAll(String[] s) {
        for (int i=0; i<s.length; i++)
            s[i] = (s[i]==null ? "" : s[i].trim());
    }

    /** creates a string from a real number, with specified accuracy (more iff it comes for free, ie integer-part);
     * switches to E notation if needed to fit within maxlen; can be padded left up too (not useful)
     * @param x number to use
     * @param maxlen maximum length for the numeric string, if possible (-1 to suppress)
     * @param prec number of digits accuracy desired (more kept for integers)
     * @param leftPadLen will add spaces at left if necessary to make string this long (-1 to suppress) [probably not usef]
     * @return such a string
     */
    public static String makeRealString(double x, int maxlen, int prec, int leftPadLen) {
        return makeRealString(x, maxlen, prec, leftPadLen, 0.00000000001, true);
    }
    /** creates a string from a real number, with specified accuracy (more iff it comes for free, ie integer-part);
     * switches to E notation if needed to fit within maxlen; can be padded left up too (not useful)
     * @param x number to use
     * @param maxlen maximum length for the numeric string, if possible (-1 to suppress)
     * @param prec number of digits accuracy desired (more kept for integers)
     * @param leftPadLen will add spaces at left if necessary to make string this long (-1 to suppress) [probably not usef]
     * @param skipDecimalThreshhold if positive it will not add a decimal part if the fractional part is less than this threshhold
     *    (but for a value 3.00001 it would show zeroes, e.g. with 3 precision and positive threshhold <= 0.00001 it would show 3.00);
     *    if zero or negative then decimal digits are always shown
     * @param useEForSmallNumbers whether to use E notation for numbers near zero (e.g. 0.001)
     * @return such a string
     */
    public static String makeRealString(double x, int maxlen, int prec, int leftPadLen, double skipDecimalThreshhold, boolean useEForSmallNumbers) {
        if (x<0) return "-"+makeRealString(-x, maxlen, prec, leftPadLen);
        NumberFormat df = DecimalFormat.getInstance();
        //df.setMaximumFractionDigits(maxlen);
        df.setMinimumFractionDigits(0);
        //df.setMaximumIntegerDigits(prec);
        df.setMinimumIntegerDigits(1);
        df.setGroupingUsed(false);
        String s;
        if (x==0) {
            if (skipDecimalThreshhold>0 || prec<=1) s="0";
            else {
                s="0.0";
                while (s.length()<prec+1) s+="0";
            }
        } else {
//            long bits= Double.doubleToLongBits(x);
//            int s = ((bits >> 63) == 0) ? 1 : -1;
//            int e = (int)((bits >> 52) & 0x7ffL);
//            long m = (e == 0) ?
//            (bits & 0xfffffffffffffL) << 1 :
//            (bits & 0xfffffffffffffL) | 0x10000000000000L;
//            //s*m*2^(e-1075);
            int log = (int)Math.floor(Math.log10(x));
            int numFractionDigits = (log>=prec ? 0 : prec-log-1);
            if (numFractionDigits>0) { //need decimal digits
                if (skipDecimalThreshhold>0) {
                    int checkFractionDigits = 0;
                    double multiplier = 1;
                    while (checkFractionDigits < numFractionDigits) {
                        if (Math.abs(x - Math.rint(x*multiplier)/multiplier)<skipDecimalThreshhold)
                            break;
                        checkFractionDigits++;
                        multiplier*=10;
                    }
                    numFractionDigits = checkFractionDigits;
                }
                df.setMinimumFractionDigits(numFractionDigits);
                df.setMaximumFractionDigits(numFractionDigits);
            } else {
                //x = Math.rint(x);
                df.setMaximumFractionDigits(0);
            }
            s = df.format(x);
            if (maxlen>0 && s.length()>maxlen) {
                //too long:
                double signif = x/Math.pow(10,log);
                if (s.indexOf(getDefaultDecimalSeparator())>=0) {
                    //have a decimal point; either we are very small 0.000001
                    //or prec is larger than maxlen
                    if (Math.abs(x)<1 && useEForSmallNumbers) {
                        //very small-- use alternate notation
                        s = makeRealString(signif, -1, prec, -1) + "E"+log;
                    } else {
                        //leave it alone, user error or E not wanted
                    }
                } else {
                    //no decimal point, integer part is too large, use alt notation
                    s = makeRealString(signif, -1, prec, -1) + "E"+log;
                }
            }
        }
        if (leftPadLen>s.length())
            return makePaddedString(s, leftPadLen, " ", "");
        else
            return s;
    }

    /** creates a string from a real number, with specified accuracy (more iff it comes for free, ie integer-part);
     * switches to E notation if needed to fit within maxlen; can be padded left up too (not useful)
     * @param x number to use
     * @param maxlen maximum length for the numeric string, if possible (-1 to suppress)
     * @param prec number of digits accuracy desired (more kept for integers)
     * @param leftPadLen will add spaces at left if necessary to make string this long (-1 to suppress) [probably not usef]
     * @return such a string
     */
    public static String makeRealStringNearZero(double x, int maxlen, int prec, int leftPadLen) {
        if (Math.abs(x)<0.0000000001) x=0;
        NumberFormat df = DecimalFormat.getInstance();
        //df.setMaximumFractionDigits(maxlen);
        df.setMinimumFractionDigits(0);
        //df.setMaximumIntegerDigits(prec);
        df.setMinimumIntegerDigits(1);
        df.setGroupingUsed(false);
        String s;
        if (x==0) {
            if (prec<=1) s="0";
            else {
                s="0.0";
                while (s.length()<prec+1) s+="0";
            }
        } else {
//            long bits= Double.doubleToLongBits(x);
//            int s = ((bits >> 63) == 0) ? 1 : -1;
//            int e = (int)((bits >> 52) & 0x7ffL);
//            long m = (e == 0) ?
//            (bits & 0xfffffffffffffL) << 1 :
//            (bits & 0xfffffffffffffL) | 0x10000000000000L;
//            //s*m*2^(e-1075);
            int log = (int)Math.floor(Math.log10(x));
            int scale = (log>=prec ? 0 : prec-log-1);
            if (scale>0) { //need decimal digits
                double scale10 = Math.pow(10, scale);
                x = Math.rint(x*scale10)/scale10;
                df.setMinimumFractionDigits(scale);
                df.setMaximumFractionDigits(scale);
            } else {
                //x = Math.rint(x);
                df.setMaximumFractionDigits(0);
            }
            s = df.format(x);
            if (maxlen>0 && s.length()>maxlen) {
                //too long:
                double signif = x/Math.pow(10,log);
                if (s.indexOf('.')>=0) {
                    //have a decimal point; either we are very small 0.000001
                    //or prec is larger than maxlen
                    if (Math.abs(x)<1) {
                        //very small-- use alternate notation
                        s = makeRealString(signif, -1, prec, -1) + "E"+log;
                    } else {
                        //leave it alone, user error
                    }
                } else {
                    //no decimal point, integer part is too large, use alt notation
                    s = makeRealString(signif, -1, prec, -1) + "E"+log;
                }
            }
        }
        if (leftPadLen>s.length())
            return makePaddedString(s, leftPadLen, " ", "");
        else
            return s;
    }

    /** returns the first word (whitespace delimited text), or null if there is none (input null or all whitespace) */
    public static String getFirstWord(String s) {
        if (s==null) return null;
        int start = 0;
        while (start<s.length()) {
            if (!Character.isWhitespace(s.charAt(start)))
                break;
            start++;
        }
        int end = start;
        if (end >= s.length())
            return null;
        while (end<s.length()) {
            if (Character.isWhitespace(s.charAt(end)))
                break;
            end++;
        }
        return s.substring(start, end);
    }

    /** returns the last word (whitespace delimited text), or null if there is none (input null or all whitespace) */
    public static String getLastWord(String s) {
        if (s==null) return null;
        int end = s.length()-1;
        while (end >= 0) {
            if (!Character.isWhitespace(s.charAt(end)))
                break;
            end--;
        }
        int start = end;
        if (start < 0)
            return null;
        while (start >= 0) {
            if (Character.isWhitespace(s.charAt(start)))
                break;
            start--;
        }
        return s.substring(start+1, end+1);
    }

    /** returns the first word after the given phrase, or null if no such phrase;
     * if the character immediately after the phrase is not whitespace, the non-whitespace
     * sequence starting with that character will be returned */
    public static String getFirstWordAfter(String context, String phrase) {
        if (context==null || phrase==null) return null;
        int index = context.indexOf(phrase);
        if (index<0) return null;
        return getFirstWord(context.substring(index + phrase.length()));
    }

   /**
    * searches in context for the given phrase, and returns the <b>untrimmed</b> remainder of the first line
    * on which the phrase is found
    */
    public static String getRemainderOfLineAfter(String context, String phrase) {
        if (context == null || phrase == null) return null;
        int index = context.indexOf(phrase);
        if (index < 0) return null;
        int lineEndIndex = context.indexOf("\n", index);
        if (lineEndIndex <= 0) {
            return context.substring(index + phrase.length());
        } else {
            return context.substring(index + phrase.length(), lineEndIndex);
        }
    }

    /** @deprecated use {@link Time#makeTimeStringRounded(long)} */
    @Deprecated
    public static String makeTimeString(long utcMillis) {
        return Time.makeTimeStringRounded(utcMillis);
    }

    /** returns e.g. { "prefix01", ..., "prefix96" };
     * see more functional NumericRangeGlobExpander for "prefix{01-96}"
     */
    public static String[] makeArray(String prefix, int count) {
        String[] result = new String[count];
        int len = (""+count).length();
        for (int i=1; i<=count; i++)
            result[i-1] = prefix + makePaddedString("", len, "0", ""+i);
        return result;
    }

    public static String[] combineArrays(String[] ...arrays) {
        int totalLen = 0;
        for (String[] array : arrays) {
            if (array!=null) totalLen += array.length;
        }
        String[] result = new String[totalLen];
        int i=0;
        for (String[] array : arrays) {
            if (array!=null) for (String s : array) {
                result[i++] = s;
            }
        }
        return result;
    }

    public static String toInitialCapOnly(String value) {
        if (value==null || value.length()==0) return value;
        return value.substring(0, 1).toUpperCase(Locale.ENGLISH) + value.substring(1).toLowerCase(Locale.ENGLISH);
    }

    public static String reverse(String name) {
        return new StringBuffer(name).reverse().toString();
    }

    public static boolean isLowerCase(String s) {
        return s.toLowerCase().equals(s);
    }

    public static String makeRepeated(char c, int length) {
        StringBuilder result = new StringBuilder(length);
        for (int i = 0; i < length; i++) {
            result.append(c);
        }
        return result.toString();
    }

    public static String trim(String s) {
        if (s==null) return null;
        return s.trim();
    }

    public static String trimEnd(String s) {
        if (s==null) return null;
        return ("a"+s).trim().substring(1);
    }

    /** returns up to maxlen characters from the start of s */
    public static String maxlen(String s, int maxlen) {
        return maxlenWithEllipsis(s, maxlen, "");
    }

    /** as {@link #maxlenWithEllipsis(String, int, String) with "..." as the ellipsis */
    public static String maxlenWithEllipsis(String s, int maxlen) {
        return maxlenWithEllipsis(s, maxlen, "...");
    }
    /** as {@link #maxlenWithEllipsis(String, int) but replacing the last few chars with the given ellipsis */
    public static String maxlenWithEllipsis(String s, int maxlen, String ellipsis) {
        if (s==null) return null;
        if (ellipsis==null) ellipsis="";
        if (s.length()<=maxlen) return s;
        return s.substring(0, Math.max(maxlen-ellipsis.length(), 0))+ellipsis;
    }

    /** returns toString of the object if it is not null, otherwise null */
    public static String toString(Object o) {
        return toStringWithValueForNull(o, null);
    }

    /** returns toString of the object if it is not null, otherwise the given value */
    public static String toStringWithValueForNull(Object o, String valueIfNull) {
        if (o==null) return valueIfNull;
        return o.toString();
    }

    public static boolean containsLiteralIgnoreCase(CharSequence input, CharSequence fragment) {
        if (input==null) return false;
        if (isEmpty(fragment)) return true;
        int lastValidStartPos = input.length()-fragment.length();
        char f0u = Character.toUpperCase(fragment.charAt(0));
        char f0l = Character.toLowerCase(fragment.charAt(0));
        i: for (int i=0; i<=lastValidStartPos; i++) {
            char ii = input.charAt(i);
            if (ii==f0l || ii==f0u) {
                for (int j=1; j<fragment.length(); j++) {
                    if (Character.toLowerCase(input.charAt(i+j))!=Character.toLowerCase(fragment.charAt(j)))
                        continue i;
                }
                return true;
            }
        }
        return false;
    }

    public static boolean containsLiteral(CharSequence input, CharSequence fragment) {
        if (input==null) return false;
        if (isEmpty(fragment)) return true;
        int lastValidStartPos = input.length()-fragment.length();
        char f0 = fragment.charAt(0);
        i: for (int i=0; i<=lastValidStartPos; i++) {
            char ii = input.charAt(i);
            if (ii==f0) {
                for (int j=1; j<fragment.length(); j++) {
                    if (input.charAt(i+j)!=fragment.charAt(j))
                        continue i;
                }
                return true;
            }
        }
        return false;
    }

    public static boolean containsAny(CharSequence input, CharSequence ...candidates) {
        for (CharSequence candidate: candidates) {
            if (containsLiteral(input, candidate)) return true;
        }
        return false;
    }

    /** Returns a size string using metric suffixes from {@link ByteSizeStrings#metric()}, e.g. 23.5MB */
    public static String makeSizeString(long sizeInBytes) {
        return ByteSizeStrings.metric().makeSizeString(sizeInBytes);
    }

    /** Returns a size string using ISO suffixes from {@link ByteSizeStrings#iso()}, e.g. 23.5MiB */
    public static String makeISOSizeString(long sizeInBytes) {
        return ByteSizeStrings.iso().makeSizeString(sizeInBytes);
    }

    /** Returns a size string using Java suffixes from {@link ByteSizeStrings#java()}, e.g. 23m */
    public static String makeJavaSizeString(long sizeInBytes) {
        return ByteSizeStrings.java().makeSizeString(sizeInBytes);
    }

    /** returns a configurable shortener */
    public static StringShortener shortener() {
        return new StringShortener();
    }

    public static Supplier<String> toStringSupplier(Object src) {
        return Suppliers.compose(Functions.toStringFunction(), Suppliers.ofInstance(src));
    }

    /** wraps a call to {@link String#format(String, Object...)} in a toString, i.e. using %s syntax,
     * useful for places where we want deferred evaluation
     * (e.g. as message to {@link Preconditions} to skip concatenation when not needed) */
    public static FormattedString format(String pattern, Object... args) {
        return new FormattedString(pattern, args);
    }

    /** returns "s" if the argument is not 1, empty string otherwise; useful when constructing plurals */
    public static String s(int count) {
        return count==1 ? "" : "s";
    }
    /** as {@link #s(int)} based on size of argument */
    public static String s(@Nullable Map<?,?> x) {
        return s(x==null ? 0 : x.size());
    }
    /** as {@link #s(int)} based on size of argument */
    public static String s(Iterable<?> x) {
        if (x==null) return s(0);
        return s(x.iterator());
    }
    /** as {@link #s(int)} based on size of argument */
    public static String s(Iterator<?> x) {
        int count = 0;
        if (x==null || !x.hasNext()) {}
        else {
            x.next(); count++;
            if (x.hasNext()) count++;
        }
        return s(count);
    }

    /** returns "ies" if the argument is not 1, "y" otherwise; useful when constructing plurals */
    public static String ies(int count) {
        return count==1 ? "y" : "ies";
    }
    /** as {@link #ies(int)} based on size of argument */
    public static String ies(@Nullable Map<?,?> x) {
        return ies(x==null ? 0 : x.size());
    }
    /** as {@link #ies(int)} based on size of argument */
    public static String ies(Iterable<?> x) {
        if (x==null) return ies(0);
        return ies(x.iterator());
    }
    /** as {@link #ies(int)} based on size of argument */
    public static String ies(Iterator<?> x) {
        int count = 0;
        if (x==null || !x.hasNext()) {}
        else {
            x.next(); count++;
            if (x.hasNext()) count++;
        }
        return ies(count);
    }

    /** converts a map of any objects to a map of strings, using {@link Object#toString()},
     * with the second argument used where a value (or key) is null */
    public static Map<String, String> toStringMap(Map<?,?> map, String valueIfNull) {
        if (map==null) return null;
        Map<String,String> result = MutableMap.<String, String>of();
        for (Map.Entry<?,?> e: map.entrySet()) {
            result.put(toStringWithValueForNull(e.getKey(), valueIfNull), toStringWithValueForNull(e.getValue(), valueIfNull));
        }
        return result;
    }
    
    /** converts a list of any objects to a list of strings, using {@link Object#toString()},
     * with the second argument used where an entry is null */
    public static List<String> toStringList(List<?> list, String valueIfNull) {
        if (list==null) return null;
        List<String> result = MutableList.of();
        for (Object v: list) result.add(toStringWithValueForNull(v, valueIfNull));
        return result;
    }

    /**
     * Tries to convert v to a list of strings.
     * <p>
     * If v is <code>null</code> then the method returns an empty immutable list.
     * If v is {@link Iterable} or an <code>Object[]</code> then toString is called on its elements.
     * If v is a {@link String} then a singleton list containing v is returned.
     * Otherwise the method throws an {@link IllegalArgumentException}.
     */
    public static List<String> toStringList(Object v) {
        if (v == null) return ImmutableList.of();
        List<String> result = Lists.newArrayList();
        if (v instanceof Iterable) {
            for (Object o : (Iterable<?>) v) {
                result.add(o.toString());
            }
        } else if (v instanceof Object[]) {
            for (int i = 0; i < ((Object[]) v).length; i++) {
                result.add(((Object[]) v)[i].toString());
            }
        } else if (v instanceof String) {
            result.add((String) v);
        } else {
            throw new IllegalArgumentException("Invalid type for List<String>: " + v + " of type " + v.getClass());
        }
        return result;
    }

    /** returns base repeated count times */
    public static String repeat(String base, int count) {
        if (base==null) return null;
        StringBuilder result = new StringBuilder();
        for (int i=0; i<count; i++)
            result.append(base);
        return result.toString();
    }

    /** returns comparator which compares based on length, with shorter ones first (and null before that);
     * in event of a tie, it uses the toString order */
    public static Ordering<String> lengthComparator() {
        return Ordering.<Integer>natural().onResultOf(StringFunctions.length()).compound(Ordering.<String>natural()).nullsFirst();
    }

    public static boolean isMultiLine(String s) {
        if (s==null) return false;
        if (s.indexOf('\n')>=0 || s.indexOf('\r')>=0) return true;
        return false;
    }
    public static String getFirstLine(String s) {
        int idx = s.indexOf('\n');
        if (idx==-1) return s;
        return s.substring(0, idx);
    }

    /** looks for first section of text in following the prefix and, if present, before the suffix;
     * null if the prefix is not present in the string, and everything after the prefix if suffix is not present in the string;
     * if either prefix or suffix is null, it is treated as the start/end of the string */
    public static String getFragmentBetween(String input, String prefix, String suffix) {
        if (input==null) return null;
        int index;
        if (prefix!=null) {
            index = input.indexOf(prefix);
            if (index==-1) return null;
            input = input.substring(index + prefix.length());
        }
        if (suffix!=null) {
            index = input.indexOf(suffix);
            if (index>=0) input = input.substring(0, index);
        }
        return input;
    }

    public static int getWordCount(String phrase, boolean respectQuotes) {
        if (phrase==null) return 0;
        phrase = phrase.trim();
        if (respectQuotes)
            return new QuotedStringTokenizer(phrase).remainderAsList().size();
        else
            return Collections.list(new StringTokenizer(phrase)).size();
    }

    public static char getDecimalSeparator(Locale locale) {
        DecimalFormatSymbols dfs = new DecimalFormatSymbols(locale);
        return dfs.getDecimalSeparator();
    }

    public static char getDefaultDecimalSeparator() {
        return getDecimalSeparator(Locale.getDefault());
    }

    /** replaces each sequence of whitespace in the first string with the replacement in the second string */
    public static String collapseWhitespace(String x, String whitespaceReplacement) {
        if (x==null) return null;
        return replaceAllRegex(x, "\\s+", whitespaceReplacement);
    }

    public static String toLowerCase(String value) {
        if (value==null || value.length()==0) return value;
        return value.toLowerCase(Locale.ENGLISH);
    }

    /**
     * @return null if var is null or empty string, otherwise return var
     */
    public static String emptyToNull(String var) {
        if (isNonEmpty(var)) {
            return var;
        } else {
            return null;
        }
    }
    
    /** Returns canonicalized string from the given object, made "unique" by:
     * <li> putting sets into the toString order
     * <li> appending a hash code if it's longer than the max (and the max is bigger than 0) */
    public static String toUniqueString(Object x, int optionalMax) {
        if (x instanceof Iterable && !(x instanceof List)) {
            // unsorted collections should have a canonical order imposed
            MutableList<String> result = MutableList.of();
            for (Object xi: (Iterable<?>)x) {
                result.add(toUniqueString(xi, optionalMax));
            }
            Collections.sort(result);
            x = result.toString();
        }
        if (x==null) return "{null}";
        String xs = x.toString();
        if (xs.length()<=optionalMax || optionalMax<=0) return xs;
        return maxlenWithEllipsis(xs, optionalMax-8)+"/"+Integer.toHexString(xs.hashCode());
    }


    /**
     * Parses a string as comma separated values and returns a list of the entries with whitespace removed.
     * @param csv The "comma" separated values.
     * @param separatorRegex Regex of separatorRegex.
     */
    public static List<String> parseCsv(String csv, String separatorRegex) {
        List<String> result = MutableList.of();
        final String input = csv.trim();
        if ("".equals(input)) {
            return result;
        }
        for (String value: input.split(separatorRegex)) {
            result.add(value.trim());
        }
        return result;
    }

    public static List<String> parseCsv(String csv) {
        return parseCsv(csv, ",");
    }
    
    public static int countOccurrences(String phrase, char target) {
        if (phrase == null) return 0;
        int result = 0;
        for (int i = 0; i < phrase.length(); i++) {
            if (target == phrase.charAt(i)) {
                result++;
            }
        }
        return result;
    }

}
