using System.Collections.Generic;
using System.Threading.Tasks;

using Myriad.Cache;
using Myriad.Rest;
using Myriad.Types;

namespace Myriad.Extensions
{
    public static class CacheExtensions
    {
        public static async Task<Guild> GetGuild(this IDiscordCache cache, ulong guildId)
        {
            if (!(await cache.TryGetGuild(guildId) is Guild guild))
                throw new KeyNotFoundException($"Guild {guildId} not found in cache");
            return guild;
        }

        public static async Task<Channel> GetChannel(this IDiscordCache cache, ulong channelId)
        {
            if (!(await cache.TryGetChannel(channelId) is Channel channel))
                throw new KeyNotFoundException($"Channel {channelId} not found in cache");
            return channel;
        }

        public static async Task<User> GetUser(this IDiscordCache cache, ulong userId)
        {
            if (!(await cache.TryGetUser(userId) is User user))
                throw new KeyNotFoundException($"User {userId} not found in cache");
            return user;
        }

        public static async Task<Role> GetRole(this IDiscordCache cache, ulong roleId)
        {
            if (!(await cache.TryGetRole(roleId) is Role role))
                throw new KeyNotFoundException($"Role {roleId} not found in cache");
            return role;
        }

        public static async ValueTask<User?> GetOrFetchUser(this IDiscordCache cache, DiscordApiClient rest, ulong userId)
        {
            if (await cache.TryGetUser(userId) is User cacheUser)
                return cacheUser;

            var restUser = await rest.GetUser(userId);
            if (restUser != null)
                await cache.SaveUser(restUser);
            return restUser;
        }

        public static async ValueTask<Channel?> GetOrFetchChannel(this IDiscordCache cache, DiscordApiClient rest, ulong channelId)
        {
            if (await cache.TryGetChannel(channelId) is { } cacheChannel)
                return cacheChannel;

            var restChannel = await rest.GetChannel(channelId);
            if (restChannel != null)
                await cache.SaveChannel(restChannel);
            return restChannel;
        }

        public static async Task<Channel> GetOrCreateDmChannel(this IDiscordCache cache, DiscordApiClient rest, ulong recipientId)
        {
            if (await cache.TryGetDmChannel(recipientId) is { } cacheChannel)
                return cacheChannel;

            var restChannel = await rest.CreateDm(recipientId);
            await cache.SaveChannel(restChannel);
            return restChannel;
        }

        public static async Task<Channel> GetRootChannel(this IDiscordCache cache, ulong channelOrThread)
        {
            var channel = await cache.GetChannel(channelOrThread);
            if (!channel.IsThread())
                return channel;

            var parent = await cache.GetChannel(channel.ParentId!.Value);
            return parent;
        }
    }
}