/*
    * 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.commons.lang3;
  
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.StringJoiner;
  import java.util.function.Supplier;
  
  import org.apache.commons.lang3.exception.UncheckedException;
  import org.apache.commons.lang3.function.FailableBiConsumer;
  
  /**
   * Joins an array or {@link Iterable} into an existing {@link Appendable} like a {@link StringBuilder}; with the goal for call sites to avoid creating
   * intermediary Strings. This is like {@link String#join(CharSequence, CharSequence...)}, {@link String#join(CharSequence, Iterable)}, and {@link StringJoiner}.
   * <p>
   * Keep an instance in a (static) variable for efficient joining into an {@link Appendable} or {@link StringBuilder} without creating temporary Strings.
   * </p>
   * <p>
   * Use the builder and instance methods to reuse the same kind of joining prefix, suffix, delimiter, and string conversion.
   * </p>
   * <p>
   * For example:
   * </p>
   *
   * <pre>{@code
   * // A reuseable instance
   * private static final AppendableJoiner<Object> JOINER = AppendableJoiner.builder()
   *     .setPrefix("[")
   *     .setSuffix("]")
   *     .setDelimiter(", ")
   *     .get();
   * }
   * ...
   * // Builds straight into a StringBuilder:
   * StringBuilder sbuilder = new StringBuilder("1");
   * JOINER.join(sbuilder, "A", "B");
   * sbuilder.append("2");
   * JOINER.join(sbuilder, "C", "D");
   * sbuilder.append("3");
   * // Returns "1[A, B]2[C, D]3"
   * return sbuilder.toString();
   * }</pre>
   * <p>
   * To provide a custom Object element to {@link CharSequence} converter, call {@link Builder#setElementAppender(FailableBiConsumer)}, for example:
   * </p>
   *
   * <pre>{@code
   * private static final AppendableJoiner<Item> JOINER = AppendableJoiner.builder()
   *     .setElementAppender(e -> (a, e) -> a.append(e.getFoo())
   *                                        a.append(e.getBar())
   *                                        a.append('!'))
   *     ...
   *     .get();
   * }
   * }</pre>
   * <p>
   * This class is immutable and thread-safe.
   * </p>
   *
   * @param <T> the type of elements to join.
   * @see Appendable
   * @see StringBuilder
   * @see String#join(CharSequence, CharSequence...)
   * @see String#join(CharSequence, Iterable)
   * @see StringJoiner
   * @since 3.15.0
   */
  public final class AppendableJoiner<T> {
  
      /**
       * Builds instances of {@link AppendableJoiner}.
       *
       * @param <T> the type of elements to join.
       */
      public static final class Builder<T> implements Supplier<AppendableJoiner<T>> {
  
          /** The sequence of characters to be used at the beginning. */
          private CharSequence prefix;
  
          /** The sequence of characters to be used at the end. */
          private CharSequence suffix;
  
          /** The delimiter that separates each element. */
         private CharSequence delimiter;
 
         /** The consumer used to render each element of type {@code T} onto an {@link Appendable}. */
         private FailableBiConsumer<Appendable, T, IOException> appender;
 
         /**
          * Constructs a new instance.
          */
         Builder() {
             // empty
         }
 
         /**
          * Gets a new instance of {@link AppendableJoiner}.
          */
         @Override
         public AppendableJoiner<T> get() {
             return new AppendableJoiner<>(prefix, suffix, delimiter, appender);
         }
 
         /**
          * Sets the delimiter that separates each element.
          *
          * @param delimiter The delimiter that separates each element.
          * @return this instance.
          */
         public Builder<T> setDelimiter(final CharSequence delimiter) {
             this.delimiter = delimiter;
             return this;
         }
 
         /**
          * Sets the consumer used to render each element of type {@code T} onto an {@link Appendable}.
          *
          * @param appender The consumer used to render each element of type {@code T} onto an {@link Appendable}.
          * @return this instance.
          */
         public Builder<T> setElementAppender(final FailableBiConsumer<Appendable, T, IOException> appender) {
             this.appender = appender;
             return this;
         }
 
         /**
          * Sets the sequence of characters to be used at the beginning.
          *
          * @param prefix The sequence of characters to be used at the beginning.
          * @return this instance.
          */
         public Builder<T> setPrefix(final CharSequence prefix) {
             this.prefix = prefix;
             return this;
         }
 
         /**
          * Sets the sequence of characters to be used at the end.
          *
          * @param suffix The sequence of characters to be used at the end.
          * @return this instance.
          */
         public Builder<T> setSuffix(final CharSequence suffix) {
             this.suffix = suffix;
             return this;
         }
 
     }
 
     /**
      * Creates a new builder.
      *
      * @param <T> The type of elements.
      * @return a new builder.
      */
     public static <T> Builder<T> builder() {
         return new Builder<>();
     }
 
     /** Could be public in the future, in some form. */
     @SafeVarargs
     static <A extends Appendable, T> A joinA(final A appendable, final CharSequence prefix, final CharSequence suffix, final CharSequence delimiter,
             final FailableBiConsumer<Appendable, T, IOException> appender, final T... elements) throws IOException {
         return joinArray(appendable, prefix, suffix, delimiter, appender, elements);
     }
 
     private static <A extends Appendable, T> A joinArray(final A appendable, final CharSequence prefix, final CharSequence suffix, final CharSequence delimiter,
             final FailableBiConsumer<Appendable, T, IOException> appender, final T[] elements) throws IOException {
         appendable.append(prefix);
         if (elements != null) {
             if (elements.length > 0) {
                 appender.accept(appendable, elements[0]);
             }
             for (int i = 1; i < elements.length; i++) {
                 appendable.append(delimiter);
                 appender.accept(appendable, elements[i]);
             }
         }
         appendable.append(suffix);
         return appendable;
     }
 
     /** Could be public in the future, in some form. */
     static <T> StringBuilder joinI(final StringBuilder stringBuilder, final CharSequence prefix, final CharSequence suffix, final CharSequence delimiter,
             final FailableBiConsumer<Appendable, T, IOException> appender, final Iterable<T> elements) {
         try {
             return joinIterable(stringBuilder, prefix, suffix, delimiter, appender, elements);
         } catch (final IOException e) {
             // Cannot happen with a StringBuilder.
             throw new UncheckedException(e);
         }
     }
 
     private static <A extends Appendable, T> A joinIterable(final A appendable, final CharSequence prefix, final CharSequence suffix,
             final CharSequence delimiter, final FailableBiConsumer<Appendable, T, IOException> appender, final Iterable<T> elements) throws IOException {
         appendable.append(prefix);
         if (elements != null) {
             final Iterator<T> iterator = elements.iterator();
             if (iterator.hasNext()) {
                 appender.accept(appendable, iterator.next());
             }
             while (iterator.hasNext()) {
                 appendable.append(delimiter);
                 appender.accept(appendable, iterator.next());
             }
         }
         appendable.append(suffix);
         return appendable;
     }
 
     /** Could be public in the future, in some form. */
     @SafeVarargs
     static <T> StringBuilder joinSB(final StringBuilder stringBuilder, final CharSequence prefix, final CharSequence suffix, final CharSequence delimiter,
             final FailableBiConsumer<Appendable, T, IOException> appender, final T... elements) {
         try {
             return joinArray(stringBuilder, prefix, suffix, delimiter, appender, elements);
         } catch (final IOException e) {
             // Cannot happen with a StringBuilder.
             throw new UncheckedException(e);
         }
     }
 
     private static CharSequence nonNull(final CharSequence value) {
         return value != null ? value : StringUtils.EMPTY;
     }
 
     /** The sequence of characters to be used at the beginning. */
     private final CharSequence prefix;
 
     /** The sequence of characters to be used at the end. */
     private final CharSequence suffix;
 
     /** The delimiter that separates each element. */
     private final CharSequence delimiter;
 
     private final FailableBiConsumer<Appendable, T, IOException> appender;
 
     /**
      * Constructs a new instance.
      */
     private AppendableJoiner(final CharSequence prefix, final CharSequence suffix, final CharSequence delimiter,
             final FailableBiConsumer<Appendable, T, IOException> appender) {
         this.prefix = nonNull(prefix);
         this.suffix = nonNull(suffix);
         this.delimiter = nonNull(delimiter);
         this.appender = appender != null ? appender : (a, e) -> a.append(String.valueOf(e));
     }
 
     /**
      * Joins stringified objects from the given Iterable into a StringBuilder.
      *
      * @param stringBuilder The target.
      * @param elements      The source.
      * @return The given StringBuilder.
      */
     public StringBuilder join(final StringBuilder stringBuilder, final Iterable<T> elements) {
         return joinI(stringBuilder, prefix, suffix, delimiter, appender, elements);
     }
 
     /**
      * Joins stringified objects from the given array into a StringBuilder.
      *
      * @param stringBuilder The target.
      * @param elements      The source.
      * @return the given target StringBuilder.
      */
     public StringBuilder join(final StringBuilder stringBuilder, @SuppressWarnings("unchecked") final T... elements) {
         return joinSB(stringBuilder, prefix, suffix, delimiter, appender, elements);
     }
 
     /**
      * Joins stringified objects from the given Iterable into an Appendable.
      *
      * @param <A>        the Appendable type.
      * @param appendable The target.
      * @param elements   The source.
      * @return The given StringBuilder.
      * @throws IOException If an I/O error occurs
      */
     public <A extends Appendable> A joinA(final A appendable, final Iterable<T> elements) throws IOException {
         return joinIterable(appendable, prefix, suffix, delimiter, appender, elements);
     }
 
     /**
      * Joins stringified objects from the given array into an Appendable.
      *
      * @param <A>        the Appendable type.
      * @param appendable The target.
      * @param elements   The source.
      * @return The given StringBuilder.
      * @throws IOException If an I/O error occurs
      */
     public <A extends Appendable> A joinA(final A appendable, @SuppressWarnings("unchecked") final T... elements) throws IOException {
         return joinA(appendable, prefix, suffix, delimiter, appender, elements);
     }
 
 }