/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package org.mule.functional.logging;

import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;

/**
 * Allows to check log events occurrences in a test case.
 */
public class TestAppender extends AbstractAppender {

  private Set<Expectation> expectations = new HashSet<>();

  public void clear() {
    expectations.clear();
  }

  public void ensure(Expectation... expectationsToCheck) {
    Set s = new HashSet();
    s.addAll(Arrays.asList(expectationsToCheck));
    ensure(s);
  }

  public void ensure(Set<Expectation> expectationsToCheck) {
    if (!expectations.equals(expectationsToCheck)) {
      throw new RuntimeException(difference(expectationsToCheck, expectations));
    }
  }

  private String difference(Set<Expectation> expected, Set<Expectation> actual) {
    StringBuilder builder = new StringBuilder();
    addCollection(builder, CollectionUtils.subtract(actual, expected), "Not expected but received:");
    addCollection(builder, CollectionUtils.subtract(expected, actual), "Expected but not received:");
    return builder.toString();
  }

  private void addCollection(StringBuilder builder, Collection items, String description) {
    if (items != null && !items.isEmpty()) {
      builder.append('\n').append(description);
      for (Object item : items) {
        builder.append('\n').append(item);
      }
    }
  }

  public TestAppender(String name, Filter filter, Layout<? extends Serializable> layout) {
    super(name, filter, layout);
  }

  public TestAppender(String name, Filter filter, Layout<? extends Serializable> layout, boolean ignoreExceptions) {
    super(name, filter, layout, ignoreExceptions);
  }

  @Override
  public void append(LogEvent event) {
    expectations
        .add(new Expectation(event.getLevel().toString(), event.getLoggerName(), event.getMessage().getFormattedMessage()));
  }

  public static class Expectation {

    private String level;
    private String category;
    private String message;

    public Expectation(String level, String category, String message) {
      this.level = level;
      this.category = category;
      this.message = message;
    }

    @Override
    public String toString() {
      return String.format("Expectation {level='%s', category='%s', message='%s'}", level, category, message);
    }

    @Override
    public boolean equals(Object other) {
      return EqualsBuilder.reflectionEquals(this, other);
    }

    @Override
    public int hashCode() {
      return HashCodeBuilder.reflectionHashCode(this);
    }
  }
}