using Discord.WebSocket;
using Newtonsoft.Json.Linq;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace Kerobot.Common
{
    /// <summary>
    /// Represents a commonly-used configuration structure: an array of strings consisting of <see cref="EntityName"/> values.
    /// </summary>
    public class EntityList : IEnumerable<EntityName>
    {
        private readonly IReadOnlyCollection<EntityName> _innerList;

        /// <summary>Gets an enumerable collection of all role names defined in this list.</summary>
        public IEnumerable<EntityName> Roles
            => _innerList.Where(n => n.Type == EntityType.Role);

        /// <summary>Gets an enumerable collection of all channel names defined in this list.</summary>
        public IEnumerable<EntityName> Channels
            => _innerList.Where(n => n.Type == EntityType.Channel);

        /// <summary>Gets an enumerable collection of all user names defined in this list.</summary>
        public IEnumerable<EntityName> Users
            => _innerList.Where(n => n.Type == EntityType.User);

        /// <summary>
        /// Creates a new EntityList instance with no data.
        /// </summary>
        public EntityList() : this(null, false) { }

        /// <summary>
        /// Creates a new EntityList instance using the given JSON token as input.
        /// </summary>
        /// <param name="input">JSON array to be used for input. For ease of use, null values are also accepted.</param>
        /// <param name="enforceTypes">Specifies if all entities defined in configuration must have their type specified.</param>
        /// <exception cref="ArgumentException">The input is not a JSON array.</exception>
        /// <exception cref="ArgumentNullException">
        /// Unintiutively, this exception is thrown if a user-provided configuration value is blank.
        /// </exception>
        /// <exception cref="FormatException">
        /// When enforceTypes is set, this is thrown if an EntityName results in having its Type be Unspecified.
        /// </exception>
        public EntityList(JToken input, bool enforceTypes)
        {
            if (input == null)
            {
                _innerList = new List<EntityName>().AsReadOnly();
                return;
            }

            if (input.Type != JTokenType.Array)
                throw new ArgumentException("JToken input must be a JSON array.");
            var inputArray = (JArray)input;

            var list = new List<EntityName>();
            foreach (var item in inputArray.Values<string>())
            {
                var itemName = new EntityName(item);
                if (enforceTypes && itemName.Type == EntityType.Unspecified)
                    throw new FormatException($"The following value is not prefixed: {item}");
                list.Add(itemName);
            }
            _innerList = list.AsReadOnly();
        }
        
        /// <summary>
        /// Checks if the parameters of the given <see cref="SocketMessage"/> matches with
        /// any entity specified in this list.
        /// </summary>
        /// <param name="keepId">
        /// Specifies if EntityName instances within this list should have their internal ID value
        /// updated if found during the matching process.
        /// </param>
        /// <returns>
        /// True if the message author exists in this list, or if the message's channel exists in this list,
        /// or if the message author contains a role that exists in this list.
        /// </returns>
        public bool IsListMatch(SocketMessage msg, bool keepId)
        {
            var author = msg.Author as SocketGuildUser;
            var authorRoles = author.Roles;
            var channel = msg.Channel;
            
            foreach (var entry in this)
            {
                if (entry.Type == EntityType.Role)
                {
                    if (entry.Id.HasValue)
                    {
                        return authorRoles.Any(r => r.Id == entry.Id.Value);
                    }
                    else
                    {
                        foreach (var r in authorRoles)
                        {
                            if (!string.Equals(r.Name, entry.Name, StringComparison.OrdinalIgnoreCase)) break;
                            if (keepId) entry.SetId(r.Id);
                            return true;
                        }
                    }
                }
                else if (entry.Type == EntityType.Channel)
                {
                    if (entry.Id.HasValue)
                    {
                        return entry.Id.Value == channel.Id;
                    }
                    else
                    {
                        if (!string.Equals(channel.Name, entry.Name, StringComparison.OrdinalIgnoreCase)) break;
                        if (keepId) entry.SetId(channel.Id);
                        return true;
                    }
                }
                else // User
                {
                    if (entry.Id.HasValue)
                    {
                        return entry.Id.Value == author.Id;
                    }
                    else
                    {
                        if (!string.Equals(author.Username, entry.Name, StringComparison.OrdinalIgnoreCase)) break;
                        if (keepId) entry.SetId(author.Id);
                        return true;
                    }
                }
            }
            return false;
        }

        /// <summary>
        /// Determines if this list contains no entries.
        /// </summary>
        public bool IsEmpty() => _innerList.Count == 0;

        public override string ToString() => $"Entity list contains {_innerList.Count} item(s).";

        public IEnumerator<EntityName> GetEnumerator() => _innerList.GetEnumerator();

        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
    }
}