using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

namespace Discord.Rest
{
    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
    internal class RestVirtualMessageChannel : RestEntity<ulong>, IMessageChannel
    {
        public DateTimeOffset CreatedAt => SnowflakeUtils.FromSnowflake(Id);
        public string Mention => MentionUtils.MentionChannel(Id);

        internal RestVirtualMessageChannel(BaseDiscordClient discord, ulong id)
            : base(discord, id)
        {
        }
        internal static RestVirtualMessageChannel Create(BaseDiscordClient discord, ulong id)
        {
            return new RestVirtualMessageChannel(discord, id);
        }

        public Task<RestMessage> GetMessageAsync(ulong id, RequestOptions options = null)
            => ChannelHelper.GetMessageAsync(this, Discord, id, options);
        public IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(int limit = DiscordConfig.MaxMessagesPerBatch, RequestOptions options = null)
            => ChannelHelper.GetMessagesAsync(this, Discord, null, Direction.Before, limit, options);
        public IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(ulong fromMessageId, Direction dir, int limit = DiscordConfig.MaxMessagesPerBatch, RequestOptions options = null)
            => ChannelHelper.GetMessagesAsync(this, Discord, fromMessageId, dir, limit, options);
        public IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(IMessage fromMessage, Direction dir, int limit = DiscordConfig.MaxMessagesPerBatch, RequestOptions options = null)
            => ChannelHelper.GetMessagesAsync(this, Discord, fromMessage.Id, dir, limit, options);
        public Task<IReadOnlyCollection<RestMessage>> GetPinnedMessagesAsync(RequestOptions options = null)
            => ChannelHelper.GetPinnedMessagesAsync(this, Discord, options);

        public Task<RestUserMessage> SendMessageAsync(string text, bool isTTS, Embed embed = null, RequestOptions options = null)
            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, options);
#if FILESYSTEM
        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS, Embed embed = null, RequestOptions options = null)
            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, options);
#endif
        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed = null, RequestOptions options = null)
            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, options);

        public Task TriggerTypingAsync(RequestOptions options = null)
            => ChannelHelper.TriggerTypingAsync(this, Discord, options);
        public IDisposable EnterTypingState(RequestOptions options = null)
            => ChannelHelper.EnterTypingState(this, Discord, options);

        private string DebuggerDisplay => $"({Id}, Text)";

        //IMessageChannel
        async Task<IMessage> IMessageChannel.GetMessageAsync(ulong id, CacheMode mode, RequestOptions options)
        {
            if (mode == CacheMode.AllowDownload)
                return await GetMessageAsync(id, options);
            else
                return null;
        }
        IAsyncEnumerable<IReadOnlyCollection<IMessage>> IMessageChannel.GetMessagesAsync(int limit, CacheMode mode, RequestOptions options)
        {
            if (mode == CacheMode.AllowDownload)
                return GetMessagesAsync(limit, options);
            else
                return AsyncEnumerable.Empty<IReadOnlyCollection<IMessage>>();
        }
        IAsyncEnumerable<IReadOnlyCollection<IMessage>> IMessageChannel.GetMessagesAsync(ulong fromMessageId, Direction dir, int limit, CacheMode mode, RequestOptions options)
        {
            if (mode == CacheMode.AllowDownload)
                return GetMessagesAsync(fromMessageId, dir, limit, options);
            else
                return AsyncEnumerable.Empty<IReadOnlyCollection<IMessage>>();
        }
        IAsyncEnumerable<IReadOnlyCollection<IMessage>> IMessageChannel.GetMessagesAsync(IMessage fromMessage, Direction dir, int limit, CacheMode mode, RequestOptions options)
        {
            if (mode == CacheMode.AllowDownload)
                return GetMessagesAsync(fromMessage, dir, limit, options);
            else
                return AsyncEnumerable.Empty<IReadOnlyCollection<IMessage>>();
        }
        async Task<IReadOnlyCollection<IMessage>> IMessageChannel.GetPinnedMessagesAsync(RequestOptions options)
            => await GetPinnedMessagesAsync(options);

#if FILESYSTEM
        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options)
            => await SendFileAsync(filePath, text, isTTS, embed, options);
#endif
        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options)
            => await SendFileAsync(stream, filename, text, isTTS, embed, options);
        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options)
            => await SendMessageAsync(text, isTTS, embed, options);
        IDisposable IMessageChannel.EnterTypingState(RequestOptions options)
            => EnterTypingState(options);

        //IChannel
        string IChannel.Name { get { throw new NotSupportedException(); } }
        IAsyncEnumerable<IReadOnlyCollection<IUser>> IChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
        {
            throw new NotSupportedException();
        }
        Task<IUser> IChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)
        {
            throw new NotSupportedException();
        }
    }
}
