/*
    * Copyright (C) 2009 The Guava Authors
    *
    * Licensed 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 com.google.common.base;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.Beta;
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import javax.annotation.CheckReturnValue;
  
  /**
   * Extracts non-overlapping substrings from an input string, typically by
   * recognizing appearances of a <i>separator</i> sequence. This separator can be
   * specified as a single {@linkplain #on(char) character}, fixed {@linkplain
   * #on(String) string}, {@linkplain #onPattern regular expression} or {@link
   * #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at
   * all, a splitter can extract adjacent substrings of a given {@linkplain
   * #fixedLength fixed length}.
   *
   * <p>For example, this expression: <pre>   {@code
   *
   *   Splitter.on(',').split("foo,bar,qux")}</pre>
   *
   * ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and
   * {@code "qux"}, in that order.
   *
   * <p>By default, {@code Splitter}'s behavior is simplistic and unassuming. The
   * following expression: <pre>   {@code
   *
   *   Splitter.on(',').split(" foo,,,  bar ,")}</pre>
   *
   * ... yields the substrings {@code [" foo", "", "", "  bar ", ""]}. If this
   * is not the desired behavior, use configuration methods to obtain a <i>new</i>
   * splitter instance with modified behavior: <pre>   {@code
   *
   *   private static final Splitter MY_SPLITTER = Splitter.on(',')
   *       .trimResults()
   *       .omitEmptyStrings();}</pre>
   *
   * <p>Now {@code MY_SPLITTER.split("foo,,,  bar ,")} returns just {@code ["foo",
   * "bar"]}. Note that the order in which these configuration methods are called
   * is never significant.
   *
   * <p><b>Warning:</b> Splitter instances are immutable. Invoking a configuration
   * method has no effect on the receiving instance; you must store and use the
   * new splitter instance it returns instead. <pre>   {@code
   *
   *   // Do NOT do this
   *   Splitter splitter = Splitter.on('/');
   *   splitter.trimResults(); // does nothing!
   *   return splitter.split("wrong / wrong / wrong");}</pre>
   *
   * <p>For separator-based splitters that do not use {@code omitEmptyStrings}, an
   * input string containing {@code n} occurrences of the separator naturally
   * yields an iterable of size {@code n + 1}. So if the separator does not occur
   * anywhere in the input, a single substring is returned containing the entire
   * input. Consequently, all splitters split the empty string to {@code [""]}
   * (note: even fixed-length splitters).
   *
   * <p>Splitter instances are thread-safe immutable, and are therefore safe to
   * store as {@code static final} constants.
   *
   * <p>The {@link Joiner} class provides the inverse operation to splitting, but
   * note that a round-trip between the two should be assumed to be lossy.
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/StringsExplained#Splitter">
   * {@code Splitter}</a>.
   *
   * @author Julien Silland
   * @author Jesse Wilson
   * @author Kevin Bourrillion
   * @author Louis Wasserman
  * @since 1.0
  */
 @GwtCompatible(emulated = true)
 public final class Splitter {
   private final CharMatcher trimmer;
   private final boolean omitEmptyStrings;
   private final Strategy strategy;
   private final int limit;
 
   private Splitter(Strategy strategy) {
     this(strategy, false, CharMatcher.NONE, Integer.MAX_VALUE);
   }
 
   private Splitter(Strategy strategy, boolean omitEmptyStrings,
       CharMatcher trimmer, int limit) {
     this.strategy = strategy;
     this.omitEmptyStrings = omitEmptyStrings;
     this.trimmer = trimmer;
     this.limit = limit;
   }
 
   /**
    * Returns a splitter that uses the given single-character separator. For
    * example, {@code Splitter.on(',').split("foo,,bar")} returns an iterable
    * containing {@code ["foo", "", "bar"]}.
    *
    * @param separator the character to recognize as a separator
    * @return a splitter, with default settings, that recognizes that separator
    */
   public static Splitter on(char separator) {
     return on(CharMatcher.is(separator));
   }
 
   /**
    * Returns a splitter that considers any single character matched by the
    * given {@code CharMatcher} to be a separator. For example, {@code
    * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an
    * iterable containing {@code ["foo", "", "bar", "quux"]}.
    *
    * @param separatorMatcher a {@link CharMatcher} that determines whether a
    *     character is a separator
    * @return a splitter, with default settings, that uses this matcher
    */
   public static Splitter on(final CharMatcher separatorMatcher) {
     checkNotNull(separatorMatcher);
 
     return new Splitter(new Strategy() {
       @Override public SplittingIterator iterator(
           Splitter splitter, final CharSequence toSplit) {
         return new SplittingIterator(splitter, toSplit) {
           @Override int separatorStart(int start) {
             return separatorMatcher.indexIn(toSplit, start);
           }
 
           @Override int separatorEnd(int separatorPosition) {
             return separatorPosition + 1;
           }
         };
       }
     });
   }
 
   /**
    * Returns a splitter that uses the given fixed string as a separator. For
    * example, {@code Splitter.on(", ").split("foo, bar,baz")} returns an
    * iterable containing {@code ["foo", "bar,baz"]}.
    *
    * @param separator the literal, nonempty string to recognize as a separator
    * @return a splitter, with default settings, that recognizes that separator
    */
   public static Splitter on(final String separator) {
     checkArgument(separator.length() != 0,
         "The separator may not be the empty string.");
 
     return new Splitter(new Strategy() {
       @Override public SplittingIterator iterator(
           Splitter splitter, CharSequence toSplit) {
         return new SplittingIterator(splitter, toSplit) {
           @Override public int separatorStart(int start) {
             int separatorLength = separator.length();
 
             positions:
             for (int p = start, last = toSplit.length() - separatorLength;
                 p <= last; p++) {
               for (int i = 0; i < separatorLength; i++) {
                 if (toSplit.charAt(i + p) != separator.charAt(i)) {
                   continue positions;
                 }
               }
               return p;
             }
             return -1;
           }
 
           @Override public int separatorEnd(int separatorPosition) {
             return separatorPosition + separator.length();
           }
         };
       }
     });
   }
 
   /**
    * Returns a splitter that considers any subsequence matching {@code
    * pattern} to be a separator. For example, {@code
    * Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string
    * into lines whether it uses DOS-style or UNIX-style line terminators.
    *
    * @param separatorPattern the pattern that determines whether a subsequence
    *     is a separator. This pattern may not match the empty string.
    * @return a splitter, with default settings, that uses this pattern
    * @throws IllegalArgumentException if {@code separatorPattern} matches the
    *     empty string
    */
   @GwtIncompatible("java.util.regex")
   public static Splitter on(final Pattern separatorPattern) {
     checkNotNull(separatorPattern);
     checkArgument(!separatorPattern.matcher("").matches(),
         "The pattern may not match the empty string: %s", separatorPattern);
 
     return new Splitter(new Strategy() {
       @Override public SplittingIterator iterator(
           final Splitter splitter, CharSequence toSplit) {
         final Matcher matcher = separatorPattern.matcher(toSplit);
         return new SplittingIterator(splitter, toSplit) {
           @Override public int separatorStart(int start) {
             return matcher.find(start) ? matcher.start() : -1;
           }
 
           @Override public int separatorEnd(int separatorPosition) {
             return matcher.end();
           }
         };
       }
     });
   }
 
   /**
    * Returns a splitter that considers any subsequence matching a given
    * pattern (regular expression) to be a separator. For example, {@code
    * Splitter.onPattern("\r?\n").split(entireFile)} splits a string into lines
    * whether it uses DOS-style or UNIX-style line terminators. This is
    * equivalent to {@code Splitter.on(Pattern.compile(pattern))}.
    *
    * @param separatorPattern the pattern that determines whether a subsequence
    *     is a separator. This pattern may not match the empty string.
    * @return a splitter, with default settings, that uses this pattern
    * @throws java.util.regex.PatternSyntaxException if {@code separatorPattern}
    *     is a malformed expression
    * @throws IllegalArgumentException if {@code separatorPattern} matches the
    *     empty string
    */
   @GwtIncompatible("java.util.regex")
   public static Splitter onPattern(String separatorPattern) {
     return on(Pattern.compile(separatorPattern));
   }
 
   /**
    * Returns a splitter that divides strings into pieces of the given length.
    * For example, {@code Splitter.fixedLength(2).split("abcde")} returns an
    * iterable containing {@code ["ab", "cd", "e"]}. The last piece can be
    * smaller than {@code length} but will never be empty.
    *
    * <p><b>Exception:</b> for consistency with separator-based splitters, {@code
    * split("")} does not yield an empty iterable, but an iterable containing
    * {@code ""}. This is the only case in which {@code
    * Iterables.size(split(input))} does not equal {@code
    * IntMath.divide(input.length(), length, CEILING)}. To avoid this behavior,
    * use {@code omitEmptyStrings}.
    *
    * @param length the desired length of pieces after splitting, a positive
    *     integer
    * @return a splitter, with default settings, that can split into fixed sized
    *     pieces
    * @throws IllegalArgumentException if {@code length} is zero or negative
    */
   public static Splitter fixedLength(final int length) {
     checkArgument(length > 0, "The length may not be less than 1");
 
     return new Splitter(new Strategy() {
       @Override public SplittingIterator iterator(
           final Splitter splitter, CharSequence toSplit) {
         return new SplittingIterator(splitter, toSplit) {
           @Override public int separatorStart(int start) {
             int nextChunkStart = start + length;
             return (nextChunkStart < toSplit.length() ? nextChunkStart : -1);
           }
 
           @Override public int separatorEnd(int separatorPosition) {
             return separatorPosition;
           }
         };
       }
     });
   }
 
   /**
    * Returns a splitter that behaves equivalently to {@code this} splitter, but
    * automatically omits empty strings from the results. For example, {@code
    * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an
    * iterable containing only {@code ["a", "b", "c"]}.
    *
    * <p>If either {@code trimResults} option is also specified when creating a
    * splitter, that splitter always trims results first before checking for
    * emptiness. So, for example, {@code
    * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns
    * an empty iterable.
    *
    * <p>Note that it is ordinarily not possible for {@link #split(CharSequence)}
    * to return an empty iterable, but when using this option, it can (if the
    * input sequence consists of nothing but separators).
    *
    * @return a splitter with the desired configuration
    */
   @CheckReturnValue
   public Splitter omitEmptyStrings() {
     return new Splitter(strategy, true, trimmer, limit);
   }
 
   /**
    * Returns a splitter that behaves equivalently to {@code this} splitter but
    * stops splitting after it reaches the limit.
    * The limit defines the maximum number of items returned by the iterator.
    *
    * <p>For example,
    * {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable
    * containing {@code ["a", "b", "c,d"]}.  When omitting empty strings, the
    * omitted strings do no count.  Hence,
    * {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")}
    * returns an iterable containing {@code ["a", "b", "c,d"}.
    * When trim is requested, all entries, including the last are trimmed.  Hence
    * {@code Splitter.on(',').limit(3).trimResults().split(" a , b , c , d ")}
    * results in @{code ["a", "b", "c , d"]}.
    *
    * @param limit the maximum number of items returns
    * @return a splitter with the desired configuration
    * @since 9.0
    */
   @CheckReturnValue
   public Splitter limit(int limit) {
     checkArgument(limit > 0, "must be greater than zero: %s", limit);
     return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
   }
 
   /**
    * Returns a splitter that behaves equivalently to {@code this} splitter, but
    * automatically removes leading and trailing {@linkplain
    * CharMatcher#WHITESPACE whitespace} from each returned substring; equivalent
    * to {@code trimResults(CharMatcher.WHITESPACE)}. For example, {@code
    * Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable
    * containing {@code ["a", "b", "c"]}.
    *
    * @return a splitter with the desired configuration
    */
   @CheckReturnValue
   public Splitter trimResults() {
     return trimResults(CharMatcher.WHITESPACE);
   }
 
   /**
    * Returns a splitter that behaves equivalently to {@code this} splitter, but
    * removes all leading or trailing characters matching the given {@code
    * CharMatcher} from each returned substring. For example, {@code
    * Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__")}
    * returns an iterable containing {@code ["a ", "b_ ", "c"]}.
    *
    * @param trimmer a {@link CharMatcher} that determines whether a character
    *     should be removed from the beginning/end of a subsequence
    * @return a splitter with the desired configuration
    */
   // TODO(kevinb): throw if a trimmer was already specified!
   @CheckReturnValue
   public Splitter trimResults(CharMatcher trimmer) {
     checkNotNull(trimmer);
     return new Splitter(strategy, omitEmptyStrings, trimmer, limit);
   }
 
   /**
    * Splits {@code sequence} into string components and makes them available
    * through an {@link Iterator}, which may be lazily evaluated. If you want
    * an eagerly computed {@link List}, use {@link #splitToList(CharSequence)}.
    *
    * @param sequence the sequence of characters to split
    * @return an iteration over the segments split from the parameter.
    */
   public Iterable<String> split(final CharSequence sequence) {
     checkNotNull(sequence);
 
     return new Iterable<String>() {
       @Override public Iterator<String> iterator() {
         return splittingIterator(sequence);
       }
       @Override public String toString() {
         return Joiner.on(", ")
             .appendTo(new StringBuilder().append('['), this)
             .append(']')
             .toString();
       }
     };
   }
 
   private Iterator<String> splittingIterator(CharSequence sequence) {
     return strategy.iterator(this, sequence);
   }
 
   /**
    * Splits {@code sequence} into string components and returns them as
    * an immutable list. If you want an {@link Iterable} which may be lazily
    * evaluated, use {@link #split(CharSequence)}.
    *
    * @param sequence the sequence of characters to split
    * @return an immutable list of the segments split from the parameter
    * @since 15.0
    */
   @Beta
   public List<String> splitToList(CharSequence sequence) {
     checkNotNull(sequence);
 
     Iterator<String> iterator = splittingIterator(sequence);
     List<String> result = new ArrayList<String>();
 
     while (iterator.hasNext()) {
       result.add(iterator.next());
     }
 
     return Collections.unmodifiableList(result);
   }
 
   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified separator.
    *
    * @since 10.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(String separator) {
     return withKeyValueSeparator(on(separator));
   }
 
   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified separator.
    *
    * @since 14.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(char separator) {
     return withKeyValueSeparator(on(separator));
   }
 
   /**
    * Returns a {@code MapSplitter} which splits entries based on this splitter,
    * and splits entries into keys and values using the specified key-value
    * splitter.
    *
    * @since 10.0
    */
   @CheckReturnValue
   @Beta
   public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) {
     return new MapSplitter(this, keyValueSplitter);
   }
 
   /**
    * An object that splits strings into maps as {@code Splitter} splits
    * iterables and lists. Like {@code Splitter}, it is thread-safe and
    * immutable.
    *
    * @since 10.0
    */
   @Beta
   public static final class MapSplitter {
     private static final String INVALID_ENTRY_MESSAGE =
         "Chunk [%s] is not a valid entry";
     private final Splitter outerSplitter;
     private final Splitter entrySplitter;
 
     private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) {
       this.outerSplitter = outerSplitter; // only "this" is passed
       this.entrySplitter = checkNotNull(entrySplitter);
     }
 
     /**
      * Splits {@code sequence} into substrings, splits each substring into
      * an entry, and returns an unmodifiable map with each of the entries. For
      * example, <code>
      * Splitter.on(';').trimResults().withKeyValueSeparator("=>")
      * .split("a=>b ; c=>b")
      * </code> will return a mapping from {@code "a"} to {@code "b"} and
      * {@code "c"} to {@code b}.
      *
      * <p>The returned map preserves the order of the entries from
      * {@code sequence}.
      *
      * @throws IllegalArgumentException if the specified sequence does not split
      *         into valid map entries, or if there are duplicate keys
      */
     public Map<String, String> split(CharSequence sequence) {
       Map<String, String> map = new LinkedHashMap<String, String>();
       for (String entry : outerSplitter.split(sequence)) {
         Iterator<String> entryFields = entrySplitter.splittingIterator(entry);
 
         checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
         String key = entryFields.next();
         checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key);
 
         checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
         String value = entryFields.next();
         map.put(key, value);
 
         checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry);
       }
       return Collections.unmodifiableMap(map);
     }
   }
 
   private interface Strategy {
     Iterator<String> iterator(Splitter splitter, CharSequence toSplit);
   }
 
   private abstract static class SplittingIterator extends AbstractIterator<String> {
     final CharSequence toSplit;
     final CharMatcher trimmer;
     final boolean omitEmptyStrings;
 
     /**
      * Returns the first index in {@code toSplit} at or after {@code start}
      * that contains the separator.
      */
     abstract int separatorStart(int start);
 
     /**
      * Returns the first index in {@code toSplit} after {@code
      * separatorPosition} that does not contain a separator. This method is only
      * invoked after a call to {@code separatorStart}.
      */
     abstract int separatorEnd(int separatorPosition);
 
     int offset = 0;
     int limit;
 
     protected SplittingIterator(Splitter splitter, CharSequence toSplit) {
       this.trimmer = splitter.trimmer;
       this.omitEmptyStrings = splitter.omitEmptyStrings;
       this.limit = splitter.limit;
       this.toSplit = toSplit;
     }
 
     @Override protected String computeNext() {
       /*
        * The returned string will be from the end of the last match to the
        * beginning of the next one. nextStart is the start position of the
        * returned substring, while offset is the place to start looking for a
        * separator.
        */
       int nextStart = offset;
       while (offset != -1) {
         int start = nextStart;
         int end;
 
         int separatorPosition = separatorStart(offset);
         if (separatorPosition == -1) {
           end = toSplit.length();
           offset = -1;
         } else {
           end = separatorPosition;
           offset = separatorEnd(separatorPosition);
         }
         if (offset == nextStart) {
           /*
            * This occurs when some pattern has an empty match, even if it
            * doesn't match the empty string -- for example, if it requires
            * lookahead or the like. The offset must be increased to look for
            * separators beyond this point, without changing the start position
            * of the next returned substring -- so nextStart stays the same.
            */
           offset++;
           if (offset >= toSplit.length()) {
             offset = -1;
           }
           continue;
         }
 
         while (start < end && trimmer.matches(toSplit.charAt(start))) {
           start++;
         }
         while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
           end--;
         }
 
         if (omitEmptyStrings && start == end) {
           // Don't include the (unused) separator in next split string.
           nextStart = offset;
           continue;
         }
 
         if (limit == 1) {
           // The limit has been reached, return the rest of the string as the
           // final item.  This is tested after empty string removal so that
           // empty strings do not count towards the limit.
           end = toSplit.length();
           offset = -1;
           // Since we may have changed the end, we need to trim it again.
           while (end > start && trimmer.matches(toSplit.charAt(end - 1))) {
             end--;
           }
         } else {
           limit--;
         }
 
         return toSplit.subSequence(start, end).toString();
       }
       return endOfData();
     }
   }
 }