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

namespace zero.Core.Utils
{
  public class ObjectTraverser
  {
    private const string SEPARATOR = ".";

    private const string SQBKT_OPEN = "[";

    private const string SQBKT_CLOSE = "]";

    private const string NEWTONSOFT_NS = "Newtonsoft.Json";


    /// <summary>
    /// Find all instances of a given type in an object (features nested + enumerable content)
    /// </summary>
    public static List<Result<T>> Find<T>(object value) where T : class
    {
      HashSet<object> exploredObjects = new HashSet<object>();
      List<Result<T>> found = new List<Result<T>>();

      Find<T>(value, String.Empty, exploredObjects, found);

      return found;
    }


    /// <summary>
    /// Find all instances of a given type in an object (features nested + enumerable content)
    /// </summary>
    public static List<Result<T>> FindAttribute<T>(object value) where T : Attribute
    {
      HashSet<string> exploredObjects = new HashSet<string>();
      List<Result<T>> found = new List<Result<T>>();

      FindAttribute<T>(value, null, String.Empty, null, exploredObjects, found);

      return found;
    }


    /// <summary>
    /// Recursively ind all instances of a given type in an object
    /// </summary>
    private static void Find<T>(object value, string key, HashSet<object> exploredObjects, List<Result<T>> found) where T : class
    {
      if (value == null || value is string || exploredObjects.Contains(value) || value.GetType().FullName.StartsWith(NEWTONSOFT_NS))
      {
        return;
      }

      exploredObjects.Add(value);

      System.Collections.ICollection enumerable = value as System.Collections.ICollection;

      // this property is a list
      if (enumerable != null)
      {
        int idx = 0;
        foreach (object item in enumerable)
        {
          Find<T>(item, CombineKey(String.Empty, key, SQBKT_OPEN + idx + SQBKT_CLOSE), exploredObjects, found);
          idx += 1;
        }
        return;
      }

      // check if the current property is our searched type
      if (value is T)
      {
        found.Add(new Result<T>()
        {
          Path = key,
          Item = value as T
        });
        return;
      }

      // check if our property is a primitive type
      Type type = value.GetType();
      if (type.IsPrimitive)
      {
        return;
      }

      // iterate over nested properties
      PropertyInfo[] properties = type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty);
      foreach (PropertyInfo property in properties)
      {
        object propertyValue = property.GetValue(value, null);
        Find<T>(propertyValue, CombineKey(SEPARATOR, key, property.Name), exploredObjects, found);
      }
    }


    /// <summary>
    /// Recursively find all instances with the attribute of a given type in an object
    /// </summary>
    private static void FindAttribute<T>(object value, object parent, string key, PropertyInfo property, HashSet<string> exploredObjects, List<Result<T>> found) where T : Attribute
    {
      if (exploredObjects.Contains(key) || (value != null && value.GetType().FullName.StartsWith(NEWTONSOFT_NS)))
      {
        return;
      }

      exploredObjects.Add(key);

      System.Collections.ICollection enumerable = value as System.Collections.ICollection;

      // this property is a list
      if (enumerable != null && !(value is string))
      {
        int idx = 0;
        foreach (object item in enumerable)
        {
          FindAttribute<T>(item, value, CombineKey(String.Empty, key, SQBKT_OPEN + idx + SQBKT_CLOSE), null, exploredObjects, found);
          idx += 1;
        }
        return;
      }

      // check if the current property contains the attribute
      if (property != null)
      {
        T attribute = property.GetCustomAttribute<T>();

        if (attribute != null)
        {
          found.Add(new Result<T>()
          {
            Path = key,
            Item = attribute,
            Parent = parent,
            Property = property //parent.GetType().GetProperty(key)
          });
          return;
        }
      }

      // check if our property is a primitive type
      if (value == null || value.GetType().IsPrimitive || value is string || value is DateTime || value is DateTimeOffset || value is Uri)
      {
        return;
      }

      // iterate over nested properties
      PropertyInfo[] properties = value.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty);
      foreach (PropertyInfo nestedProperty in properties)
      {
        object propertyValue = nestedProperty.GetValue(value, null);
        FindAttribute<T>(propertyValue, value, CombineKey(SEPARATOR, key, nestedProperty.Name), nestedProperty, exploredObjects, found);
      }
    }


    private static string CombineKey(string sep, string key1, string key2)
    {
      if (String.IsNullOrEmpty(key1))
      {
        return key2;
      }
      return String.Join(sep, key1, key2);
    }


    public class Result<T>
    {
      public string Path { get; set; }

      public PropertyInfo Property { get; set; }

      public object Parent { get; set; }

      public T Item { get; set; }
    }
  }
}