nadekobot/src/NadekoBot/_Extensions/IMessageChannelExtensions.cs

using Discord;
using Discord.Commands;
using Discord.WebSocket;
using System.Threading.Tasks;
using NadekoBot.Services;

namespace NadekoBot.Extensions;

public static class IMessageChannelExtensions
{
    public static Task<IUserMessage> EmbedAsync(this IMessageChannel ch, IEmbedBuilder embed, string msg = "")
        => ch.SendMessageAsync(msg, embed: embed.Build(),
            options: new RequestOptions() { RetryMode  = RetryMode.AlwaysRetry });

    // this is a huge problem, because now i don't have
    // access to embed builder service
    // as this is an extension of the message channel
    public static Task<IUserMessage> SendErrorAsync(this IMessageChannel ch, IEmbedBuilderService eb, string title, string error, string url = null, string footer = null)
    {
        var embed = eb.Create()
            .WithErrorColor()
            .WithDescription(error)
            .WithTitle(title);

        if (url != null && Uri.IsWellFormedUriString(url, UriKind.Absolute))
            embed.WithUrl(url);
                    
        if (!string.IsNullOrWhiteSpace(footer))
            embed.WithFooter(footer);
            
        return ch.SendMessageAsync("", embed: embed.Build());
    }

    public static Task<IUserMessage> SendErrorAsync(this IMessageChannel ch, IEmbedBuilderService eb, string error)
        => ch.SendMessageAsync("",
            embed: eb.Create()
                .WithErrorColor()
                .WithDescription(error)
                .Build());

    public static Task<IUserMessage> SendPendingAsync(this IMessageChannel ch, IEmbedBuilderService eb, string message)
        => ch.SendMessageAsync("", embed: eb.Create()
            .WithPendingColor()
            .WithDescription(message)
            .Build());
        
    public static Task<IUserMessage> SendConfirmAsync(this IMessageChannel ch, IEmbedBuilderService eb, string title, string text, string url = null, string footer = null)
    {
        var embed = eb.Create().WithOkColor().WithDescription(text)
            .WithTitle(title);
            
        if (url != null && Uri.IsWellFormedUriString(url, UriKind.Absolute))
            embed.WithUrl(url);
            
        if (!string.IsNullOrWhiteSpace(footer))
            embed.WithFooter(footer);
            
        return ch.SendMessageAsync("", embed: embed.Build());
    }

    public static Task<IUserMessage> SendConfirmAsync(this IMessageChannel ch, IEmbedBuilderService eb, string text)
        => ch.SendMessageAsync("", embed: eb.Create()
            .WithOkColor()
            .WithDescription(text)
            .Build());

    public static Task<IUserMessage> SendTableAsync<T>(this IMessageChannel ch, string seed, IEnumerable<T> items, Func<T, string> howToPrint, int columns = 3)
    {
        return ch.SendMessageAsync($@"{seed}```css
{string.Join("\n", items.Chunk(columns)
    .Select(ig => string.Concat(ig.Select(el => howToPrint(el)))))}
```");
    }

    public static Task<IUserMessage> SendTableAsync<T>(this IMessageChannel ch, IEnumerable<T> items, Func<T, string> howToPrint, int columns = 3) =>
        ch.SendTableAsync("", items, howToPrint, columns);
        
    private static readonly IEmote arrow_left = new Emoji("⬅");
    private static readonly IEmote arrow_right = new Emoji("➡");

    public static Task SendPaginatedConfirmAsync(this ICommandContext ctx,
        int currentPage, Func<int, IEmbedBuilder> pageFunc, int totalElements,
        int itemsPerPage, bool addPaginatedFooter = true)
        => ctx.SendPaginatedConfirmAsync(currentPage,
            (x) => Task.FromResult(pageFunc(x)), totalElements, itemsPerPage, addPaginatedFooter);
    /// <summary>
    /// danny kamisama
    /// </summary>
    public static async Task SendPaginatedConfirmAsync(this ICommandContext ctx, int currentPage, 
        Func<int, Task<IEmbedBuilder>> pageFunc, int totalElements, int itemsPerPage, bool addPaginatedFooter = true)
    {
        var embed = await pageFunc(currentPage).ConfigureAwait(false);

        var lastPage = (totalElements - 1) / itemsPerPage;
            
        var canPaginate = true;
        var sg = ctx.Guild as SocketGuild;
        if (sg is not null && !sg.CurrentUser.GetPermissions((IGuildChannel) ctx.Channel).AddReactions)
            canPaginate = false;
            
        if (!canPaginate)
            embed.WithFooter("⚠️ AddReaction permission required for pagination.");
        else if (addPaginatedFooter)
            embed.AddPaginatedFooter(currentPage, lastPage);

        var msg = await ctx.Channel.EmbedAsync(embed).ConfigureAwait(false) as IUserMessage;

        if (lastPage == 0 || !canPaginate)
            return;

        await msg.AddReactionAsync(arrow_left).ConfigureAwait(false);
        await msg.AddReactionAsync(arrow_right).ConfigureAwait(false);

        await Task.Delay(2000).ConfigureAwait(false);

        var lastPageChange = DateTime.MinValue;

        async Task changePage(SocketReaction r)
        {
            try
            {
                if (r.UserId != ctx.User.Id)
                    return;
                if (DateTime.UtcNow - lastPageChange < TimeSpan.FromSeconds(1))
                    return;
                if (r.Emote.Name == arrow_left.Name)
                {
                    if (currentPage == 0)
                        return;
                    lastPageChange = DateTime.UtcNow;
                    var toSend = await pageFunc(--currentPage).ConfigureAwait(false);
                    if (addPaginatedFooter)
                        toSend.AddPaginatedFooter(currentPage, lastPage);
                    await msg.ModifyAsync(x => x.Embed = toSend.Build()).ConfigureAwait(false);
                }
                else if (r.Emote.Name == arrow_right.Name)
                {
                    if (lastPage > currentPage)
                    {
                        lastPageChange = DateTime.UtcNow;
                        var toSend = await pageFunc(++currentPage).ConfigureAwait(false);
                        if (addPaginatedFooter)
                            toSend.AddPaginatedFooter(currentPage, lastPage);
                        await msg.ModifyAsync(x => x.Embed = toSend.Build()).ConfigureAwait(false);
                    }
                }
            }
            catch (Exception)
            {
                //ignored
            }
        }

        using (msg.OnReaction((DiscordSocketClient)ctx.Client, changePage, changePage))
        {
            await Task.Delay(30000).ConfigureAwait(false);
        }

        try
        {
            if(msg.Channel is ITextChannel && ((SocketGuild)ctx.Guild).CurrentUser.GuildPermissions.ManageMessages)
            {
                await msg.RemoveAllReactionsAsync().ConfigureAwait(false);
            }
            else
            {
                await Task.WhenAll(msg.Reactions.Where(x => x.Value.IsMe)
                    .Select(x => msg.RemoveReactionAsync(x.Key, ctx.Client.CurrentUser)));
            }
        }
        catch
        {
            // ignored
        }
    }

    public static Task OkAsync(this ICommandContext ctx)
        => ctx.Message.AddReactionAsync(new Emoji("✅"));
        
    public static Task ErrorAsync(this ICommandContext ctx)
        => ctx.Message.AddReactionAsync(new Emoji("❌"));
        
    public static Task WarningAsync(this ICommandContext ctx)
        => ctx.Message.AddReactionAsync(new Emoji("⚠️"));
}