using System;
using System.Collections.Generic;

namespace Swan.Collections {
  /// <summary>
  /// Represents a generic collection of key/value pairs that does not store
  /// null values.
  /// </summary>
  /// <typeparam name="TKey">The type of keys in the dictionary. This must be a reference type.</typeparam>
  /// <typeparam name="TValue">The type of values in the dictionary. This must be a reference type.</typeparam>
  public interface IDataDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IReadOnlyDictionary<TKey, TValue> where TKey : class where TValue : class {
    /// <summary>
    /// Gets a value that indicates whether the <see cref="IDataDictionary{TKey,TValue}"/> is empty.
    /// </summary>
    /// <value>
    /// <see langword="true"/> if the <see cref="IDataDictionary{TKey,TValue}"/> is empty; otherwise, <see langword="false"/>.
    /// </value>
    Boolean IsEmpty {
      get;
    }

    /// <summary>
    /// Attempts to remove and return the value that has the specified key from the <see cref="IDataDictionary{TKey,TValue}"/>.
    /// </summary>
    /// <param name="key">The key of the element to remove and return.</param>
    /// <param name="value">When this method returns, the value removed from the <see cref="IDataDictionary{TKey,TValue}"/>,
    /// if the key is found; otherwise, <see langword="null"/>. This parameter is passed uninitialized.</param>
    /// <returns><see langword="true"/> if the value was removed successfully; otherwise, <see langword="false"/>.</returns>
    /// <exception cref="ArgumentNullException"><paramref name="key"/> is <see langword="null"/>.</exception>
    Boolean TryRemove(TKey key, out TValue value);
  }
}