using System;
using System.Collections;
using System.Collections.Generic;
using Swan.Configuration;

namespace Swan.Collections {
  /// <summary>
  /// <para>Implements a collection of components.</para>
  /// <para>Each component in the collection may be given a unique name for later retrieval.</para>
  /// </summary>
  /// <typeparam name="T">The type of components in the collection.</typeparam>
  /// <seealso cref="IComponentCollection{T}" />
  public class ComponentCollection<T> : ConfiguredObject, IComponentCollection<T> {
    private readonly List<T> _components = new List<T>();

    private readonly List<(String, T)> _componentsWithSafeNames = new List<(String, T)>();

    private readonly Dictionary<String, T> _namedComponents = new Dictionary<String, T>();

    /// <inheritdoc />
    public Int32 Count => this._components.Count;

    /// <inheritdoc />
    public IReadOnlyDictionary<String, T> Named => this._namedComponents;

    /// <inheritdoc />
    public IReadOnlyList<(String SafeName, T Component)> WithSafeNames => this._componentsWithSafeNames;

    /// <inheritdoc />
    public T this[Int32 index] => this._components[index];

    /// <inheritdoc />
    public T this[String key] => this._namedComponents[key];

    /// <inheritdoc />
    public IEnumerator<T> GetEnumerator() => this._components.GetEnumerator();

    /// <inheritdoc />
    IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable)this._components).GetEnumerator();

    /// <inheritdoc />
    /// <exception cref="InvalidOperationException">The collection is locked.</exception>
    public void Add(String name, T component) {
      this.EnsureConfigurationNotLocked();

      if(name != null) {
        if(name.Length == 0) {
          throw new ArgumentException("Component name is empty.", nameof(name));
        }

        if(this._namedComponents.ContainsKey(name)) {
          throw new ArgumentException("Duplicate component name.", nameof(name));
        }
      }

      if(component == null) {
        throw new ArgumentNullException(nameof(component));
      }

      if(this._components.Contains(component)) {
        throw new ArgumentException("Component has already been added.", nameof(component));
      }

      this._components.Add(component);
      this._componentsWithSafeNames.Add((name ?? $"<{component.GetType().Name}>", component));

      if(name != null) {
        this._namedComponents.Add(name, component);
      }
    }

    /// <summary>
    /// Locks the collection, preventing further additions.
    /// </summary>
    public void Lock() => this.LockConfiguration();
  }
}