using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace Swan.Mappers {
  /// <summary>
  /// Represents an object map.
  /// </summary>
  /// <typeparam name="TSource">The type of the source.</typeparam>
  /// <typeparam name="TDestination">The type of the destination.</typeparam>
  /// <seealso cref="IObjectMap" />
  public class ObjectMap<TSource, TDestination> : IObjectMap {
    internal ObjectMap(IEnumerable<PropertyInfo> intersect) {
      this.SourceType = typeof(TSource);
      this.DestinationType = typeof(TDestination);
      this.Map = intersect.ToDictionary(property => this.DestinationType.GetProperty(property.Name), property => new List<PropertyInfo> { this.SourceType.GetProperty(property.Name) });
    }

    /// <inheritdoc/>
    public Dictionary<PropertyInfo, List<PropertyInfo>> Map {
      get;
    }

    /// <inheritdoc/>
    public Type SourceType {
      get;
    }

    /// <inheritdoc/>
    public Type DestinationType {
      get;
    }

    /// <summary>
    /// Maps the property.
    /// </summary>
    /// <typeparam name="TDestinationProperty">The type of the destination property.</typeparam>
    /// <typeparam name="TSourceProperty">The type of the source property.</typeparam>
    /// <param name="destinationProperty">The destination property.</param>
    /// <param name="sourceProperty">The source property.</param>
    /// <returns>
    /// An object map representation of type of the destination property 
    /// and type of the source property.
    /// </returns>
    public ObjectMap<TSource, TDestination> MapProperty<TDestinationProperty, TSourceProperty>(Expression<Func<TDestination, TDestinationProperty>> destinationProperty, Expression<Func<TSource, TSourceProperty>> sourceProperty) {
      PropertyInfo propertyDestinationInfo = (destinationProperty.Body as MemberExpression)?.Member as PropertyInfo;

      if(propertyDestinationInfo == null) {
        throw new ArgumentException("Invalid destination expression", nameof(destinationProperty));
      }

      List<PropertyInfo> sourceMembers = GetSourceMembers(sourceProperty);

      if(sourceMembers.Any() == false) {
        throw new ArgumentException("Invalid source expression", nameof(sourceProperty));
      }

      // reverse order
      sourceMembers.Reverse();
      this.Map[propertyDestinationInfo] = sourceMembers;

      return this;
    }

    /// <summary>
    /// Removes the map property.
    /// </summary>
    /// <typeparam name="TDestinationProperty">The type of the destination property.</typeparam>
    /// <param name="destinationProperty">The destination property.</param>
    /// <returns>
    /// An object map representation of type of the destination property 
    /// and type of the source property. 
    /// </returns>
    /// <exception cref="System.Exception">Invalid destination expression.</exception>
    public ObjectMap<TSource, TDestination> RemoveMapProperty<TDestinationProperty>(Expression<Func<TDestination, TDestinationProperty>> destinationProperty) {
      PropertyInfo propertyDestinationInfo = (destinationProperty.Body as MemberExpression)?.Member as PropertyInfo;

      if(propertyDestinationInfo == null) {
        throw new ArgumentException("Invalid destination expression", nameof(destinationProperty));
      }

      if(this.Map.ContainsKey(propertyDestinationInfo)) {
        _ = this.Map.Remove(propertyDestinationInfo);
      }

      return this;
    }

    private static List<PropertyInfo> GetSourceMembers<TSourceProperty>(Expression<Func<TSource, TSourceProperty>> sourceProperty) {
      List<PropertyInfo> sourceMembers = new List<PropertyInfo>();
      MemberExpression initialExpression = sourceProperty.Body as MemberExpression;

      while(true) {
        PropertyInfo propertySourceInfo = initialExpression?.Member as PropertyInfo;

        if(propertySourceInfo == null) {
          break;
        }

        sourceMembers.Add(propertySourceInfo);
        initialExpression = initialExpression.Expression as MemberExpression;
      }

      return sourceMembers;
    }
  }
}