package com.legstar.jaxb.generator;

import java.io.IOException;
import java.util.Iterator;
import java.util.Map.Entry;
import java.util.Set;

import org.apache.commons.lang3.StringUtils;

import com.github.jknack.handlebars.Context;
import com.github.jknack.handlebars.Helper;
import com.github.jknack.handlebars.Options;

/**
 * You can iterate over a list using the built-in each helper. Inside the
 * block, you can use <code>this</code> to reference the element being
 * iterated over.
 *
 * @author edgar.espina
 * @since 0.3.0
 */
public class EachHelper implements Helper<Object> {

  /**
   * A singleton instance of this helper.
   */
  public static final Helper<Object> INSTANCE = new EachHelper();

  /**
   * The helper's name.
   */
  public static final String NAME = "each";

  @SuppressWarnings({"rawtypes", "unchecked" })
  public CharSequence apply(final Object context, final Options options)
      throws IOException {
    if (context == null) {
      return StringUtils.EMPTY;
    }
    if (context instanceof Iterable) {
      return iterableContext((Iterable) context, options);
    }
    return hashContext(context, options);
  }

  /**
   * Iterate over a hash like object.
   *
   * @param context The context object.
   * @param options The helper options.
   * @return The string output.
   * @throws IOException If something goes wrong.
   */
    private CharSequence hashContext(final Object context, final Options options)
            throws IOException {
        Set < Entry < String, Object >> propertySet = options
                .propertySet(context);
        StringBuilder buffer = new StringBuilder();
        Context parent = options.context;
        boolean first = true;
        for (Entry < String, Object > entry : propertySet) {
            Context current = Context.newBuilder(parent, entry.getValue())
                    .combine("@key", entry.getKey())
                    .combine("@first", first ? "first" : "").build();
            buffer.append(options.fn(current));
            current.destroy();
            first = false;
        }
        return buffer.toString();
    }

  /**
   * Iterate over an iterable object.
   *
   * @param context The context object.
   * @param options The helper options.
   * @return The string output.
   * @throws IOException If something goes wrong.
   */
  private CharSequence iterableContext(final Iterable<Object> context, final Options options)
      throws IOException {
    StringBuilder buffer = new StringBuilder();
    if (options.isFalsy(context)) {
      buffer.append(options.inverse());
    } else {
      Iterator<Object> iterator = context.iterator();
      int index = -1;
      Context parent = options.context;
      while (iterator.hasNext()) {
        index += 1;
        Object element = iterator.next();
        boolean first = index == 0;
        boolean even = index % 2 == 0;
        boolean last = !iterator.hasNext();
        Context current = Context.newBuilder(parent, element)
            .combine("@index", index)
            .combine("@first", first ? "first" : "")
            .combine("@last", last ? "last" : "")
            .combine("@odd", even ? "" : "odd")
            .combine("@even", even ? "even" : "")
            .build();
        buffer.append(options.fn(current));
        current.destroy();
      }
    }
    return buffer.toString();
  }

}