using System;
using System.ComponentModel;
using System.Linq;

namespace Umbraco.Core
{

    /// <summary>
    /// Represents an entity identifier.
    /// </summary>
    /// <remarks>An Udi can be fully qualified or "closed" eg umb://document/{guid} or "open" eg umb://document.</remarks>
    [TypeConverter(typeof(UdiTypeConverter))]
    public abstract class Udi : IComparable<Udi>
    {
        public Uri UriValue { get; }

        /// <summary>
        /// Initializes a new instance of the Udi class.
        /// </summary>
        /// <param name="entityType">The entity type part of the identifier.</param>
        /// <param name="stringValue">The string value of the identifier.</param>
        protected Udi(string entityType, string stringValue)
        {
            EntityType = entityType;
            UriValue = new Uri(stringValue);
        }

        /// <summary>
        /// Initializes a new instance of the Udi class.
        /// </summary>
        /// <param name="uriValue">The uri value of the identifier.</param>
        protected Udi(Uri uriValue)
        {
            EntityType = uriValue.Host;
            UriValue = uriValue;
        }



        /// <summary>
        /// Gets the entity type part of the identifier.
        /// </summary>
        public string EntityType { get; private set; }

        public int CompareTo(Udi other)
        {
            return string.Compare(UriValue.ToString(), other.UriValue.ToString(), StringComparison.InvariantCultureIgnoreCase);
        }

        public override string ToString()
        {
            // UriValue is created in the ctor and is never null
            // use AbsoluteUri here and not ToString else it's not encoded!
            return UriValue.AbsoluteUri;
        }



        /// <summary>
        /// Creates a root Udi for an entity type.
        /// </summary>
        /// <param name="entityType">The entity type.</param>
        /// <returns>The root Udi for the entity type.</returns>
        public static Udi Create(string entityType)
        {
            return UdiParser.GetRootUdi(entityType);
        }

        /// <summary>
        /// Creates a string Udi.
        /// </summary>
        /// <param name="entityType">The entity type.</param>
        /// <param name="id">The identifier.</param>
        /// <returns>The string Udi for the entity type and identifier.</returns>
        public static Udi Create(string entityType, string id)
        {
            if (UdiParser.UdiTypes.TryGetValue(entityType, out var udiType) == false)
                throw new ArgumentException(string.Format("Unknown entity type \"{0}\".", entityType), "entityType");

            if (string.IsNullOrWhiteSpace(id))
                throw new ArgumentException("Value cannot be null or whitespace.", "id");
            if (udiType != UdiType.StringUdi)
                throw new InvalidOperationException(string.Format("Entity type \"{0}\" does not have string udis.", entityType));

            return new StringUdi(entityType, id);
        }

        /// <summary>
        /// Creates a Guid Udi.
        /// </summary>
        /// <param name="entityType">The entity type.</param>
        /// <param name="id">The identifier.</param>
        /// <returns>The Guid Udi for the entity type and identifier.</returns>
        public static Udi Create(string entityType, Guid id)
        {
            if (UdiParser.UdiTypes.TryGetValue(entityType, out var udiType) == false)
                throw new ArgumentException(string.Format("Unknown entity type \"{0}\".", entityType), "entityType");

            if (udiType != UdiType.GuidUdi)
                throw new InvalidOperationException(string.Format("Entity type \"{0}\" does not have guid udis.", entityType));
            if (id == default(Guid))
                throw new ArgumentException("Cannot be an empty guid.", "id");

            return new GuidUdi(entityType, id);
        }

        public static Udi Create(Uri uri)
        {
            // if it's a know type go fast and use ctors
            // else fallback to parsing the string (and guess the type)

            if (UdiParser.UdiTypes.TryGetValue(uri.Host, out var udiType) == false)
                throw new ArgumentException(string.Format("Unknown entity type \"{0}\".", uri.Host), "uri");

            if (udiType == UdiType.GuidUdi)
                return new GuidUdi(uri);
            if (udiType == UdiType.StringUdi)
                return new StringUdi(uri);

            throw new ArgumentException(string.Format("Uri \"{0}\" is not a valid udi.", uri));
        }

        public void EnsureType(params string[] validTypes)
        {
            if (validTypes.Contains(EntityType) == false)
                throw new Exception(string.Format("Unexpected entity type \"{0}\".", EntityType));
        }

        /// <summary>
        /// Gets a value indicating whether this Udi is a root Udi.
        /// </summary>
        /// <remarks>A root Udi points to the "root of all things" for a given entity type, e.g. the content tree root.</remarks>
        public abstract bool IsRoot { get; }

        /// <summary>
        /// Ensures that this Udi is not a root Udi.
        /// </summary>
        /// <returns>This Udi.</returns>
        /// <exception cref="Exception">When this Udi is a Root Udi.</exception>
        public Udi EnsureNotRoot()
        {
            if (IsRoot) throw new Exception("Root Udi.");
            return this;
        }

        public override bool Equals(object obj)
        {
            var other = obj as Udi;
            return other != null && GetType() == other.GetType() && UriValue == other.UriValue;
        }

        public override int GetHashCode()
        {
            return UriValue.GetHashCode();
        }

        public static bool operator ==(Udi udi1, Udi udi2)
        {
            if (ReferenceEquals(udi1, udi2)) return true;
            if ((object)udi1 == null || (object)udi2 == null) return false;
            return udi1.Equals(udi2);
        }

        public static bool operator !=(Udi udi1, Udi udi2)
        {
            return (udi1 == udi2) == false;
        }


    }
}