forkmessager/backend/src/Modules/Chats/Infrastructure/Persistence/MessageRepository.cs

using Microsoft.Extensions.Configuration;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using Knot.Modules.Chats.Domain;
using Knot.Shared.Kernel;
using System.Text.RegularExpressions;
using MongoDB.Bson;

namespace Knot.Modules.Chats.Infrastructure.Persistence;

public sealed class MessageRepository : IMessageRepository
{
    private readonly IMongoCollection<Message> _messages;
    private readonly ChatsDbContext _dbContext;
    private readonly MediatR.IMediator _mediator;

    public MessageRepository(IMongoDatabase mongoDatabase, ChatsDbContext dbContext, MediatR.IMediator mediator)
    {
        _messages = mongoDatabase.GetCollection<Message>("messages");
        _dbContext = dbContext;
        _mediator = mediator;
    }

    public void Add(Message message)
    {
        _messages.InsertOne(message);

        // Publish domain events manualy for mongo entities
        var events = message.GetDomainEvents().ToList();
        message.ClearDomainEvents();
        
        // This runs synchronously or without waiting, better to run async but Add is void
        // In this implementation setting, fire and forget or wrap sync
        foreach (var domainEvent in events)
        {
            _mediator.Publish(domainEvent).GetAwaiter().GetResult();
        }
    }

    public async Task<Message?> GetByIdAsync(Guid id, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.Id, id);
        return await _messages.Find(filter).FirstOrDefaultAsync(cancellationToken);
    }

    public async Task<List<Message>> GetChatMessagesAsync(Guid chatId, int limit, int offset, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.ChatId, chatId);
        return await _messages.Find(filter)
            .SortByDescending(m => m.CreatedAt)
            .Skip(offset)
            .Limit(limit)
            .ToListAsync(cancellationToken);
    }

    public async Task<Message?> GetLatestChatMessageAsync(Guid chatId, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.ChatId, chatId);
        return await _messages.Find(filter)
            .SortByDescending(m => m.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);
    }

    public async Task<List<Message>> GetChatMessagesCursorAsync(Guid chatId, DateTime? cursor, int limit, CancellationToken cancellationToken)
    {
        var builder = Builders<Message>.Filter;
        var filter = builder.Eq(m => m.ChatId, chatId);
        
        if (cursor.HasValue)
        {
            filter &= builder.Lt(m => m.CreatedAt, cursor.Value);
        }

        return await _messages.Find(filter)
            .SortByDescending(m => m.CreatedAt)
            .Limit(limit)
            .ToListAsync(cancellationToken);
    }

    public async Task<List<Message>> SearchMessagesAsync(string query, Guid? chatId, Guid requestingUserId, CancellationToken cancellationToken)
    {
        // Not ideal for SQL/Mongo combination but keeping the signature
        var validChatIdsQuery = _dbContext.Chats
            .Where(c => c.Members.Any(m => m.UserId == requestingUserId))
            .Select(c => c.Id)
            .ToList();

        var builder = Builders<Message>.Filter;
        var filter = builder.In(m => m.ChatId, validChatIdsQuery);

        if (chatId.HasValue)
        {
            filter &= builder.Eq(m => m.ChatId, chatId.Value);
        }

        var textFilter = Builders<Message>.Filter.Regex("Content", new BsonRegularExpression(Regex.Escape(query), "i"));
        filter &= textFilter;

        return await _messages.Find(filter)
            .SortByDescending(m => m.CreatedAt)
            .Limit(ChatConstants.SearchMessagesLimit)
            .ToListAsync(cancellationToken);
    }

    public async Task AddReadReceiptsAsync(Guid userId, List<Guid> messageIds, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.In(m => m.Id, messageIds);

        var messages = await _messages.Find(filter).ToListAsync(cancellationToken);
        
        var writes = new List<WriteModel<Message>>();
        foreach (var msg in messages)
        {
            if (!msg.ReadBy.Any(r => r.UserId == userId))
            {
                var receipt = new ReadReceipt(msg.Id, userId);
                
                var pushUpdate = Builders<Message>.Update.Push("ReadBy", receipt);
                
                var updateModel = new UpdateOneModel<Message>(Builders<Message>.Filter.Eq(m => m.Id, msg.Id), pushUpdate);
                writes.Add(updateModel);
            }
        }

        if (writes.Any())
        {
            await _messages.BulkWriteAsync(writes, cancellationToken: cancellationToken);
        }
    }

    public async Task<bool> AddReactionAsync(Guid messageId, Guid userId, string emoji, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.Id, messageId);
        var msg = await _messages.Find(filter).FirstOrDefaultAsync(cancellationToken);
        if (msg == null) return false;

        if (msg.Reactions.Any(r => r.UserId == userId && r.Emoji == emoji))
        {
            return true;
        }

        var reaction = new Reaction(messageId, userId, emoji);
        var update = Builders<Message>.Update.Push("Reactions", reaction);
        await _messages.UpdateOneAsync(filter, update, cancellationToken: cancellationToken);
        return true;
    }

    public async Task<bool> RemoveReactionAsync(Guid messageId, Guid userId, string emoji, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.Id, messageId);
        var msg = await _messages.Find(filter).FirstOrDefaultAsync(cancellationToken);
        if (msg == null) return false;

        var reaction = msg.Reactions.FirstOrDefault(r => r.UserId == userId && r.Emoji == emoji);
        if (reaction == null) return false;

        var update = Builders<Message>.Update.PullFilter("Reactions", 
            Builders<BsonDocument>.Filter.And(
                Builders<BsonDocument>.Filter.Eq("UserId", userId),
                Builders<BsonDocument>.Filter.Eq("Emoji", emoji)
            ));
        
        await _messages.UpdateOneAsync(filter, update, cancellationToken: cancellationToken);
        return true;
    }

    public async Task<Message?> GetLastStoryMessageAsync(Guid chatId, Guid storyId, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.And(
            Builders<Message>.Filter.Eq(m => m.ChatId, chatId),
            Builders<Message>.Filter.Eq("_t", "StoryMessage"),
            Builders<Message>.Filter.Eq("StoryId", storyId)
        );

        return await _messages.Find(filter)
            .SortByDescending(m => m.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);
    }

    public async Task<int> GetUnreadCountAsync(Guid chatId, Guid userId, CancellationToken cancellationToken)
    {
        var notReadFilter = Builders<Message>.Filter.Not(
            Builders<Message>.Filter.ElemMatch("ReadBy", 
                Builders<BsonDocument>.Filter.Eq("UserId", userId))
        );

        var finalFilter = Builders<Message>.Filter.And(
            Builders<Message>.Filter.Eq(m => m.ChatId, chatId),
            Builders<Message>.Filter.Ne(m => m.SenderId, userId),
            notReadFilter
        );

        return (int)await _messages.CountDocumentsAsync(finalFilter, cancellationToken: cancellationToken);
    }

    public async Task UpdateAsync(Message message, CancellationToken cancellationToken)
    {
        var filter = Builders<Message>.Filter.Eq(m => m.Id, message.Id);
        await _messages.ReplaceOneAsync(filter, message, new ReplaceOptions { IsUpsert = true }, cancellationToken);

        // Publish domain events
        var events = message.GetDomainEvents().ToList();
        message.ClearDomainEvents();
        foreach (var domainEvent in events)
        {
            await _mediator.Publish(domainEvent, cancellationToken);
        }
    }
}