using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Knot.Modules.Relations.Domain;
using Knot.Shared.Kernel;
using Microsoft.EntityFrameworkCore;
using Knot.Modules.Relations.Application.Abstractions;

namespace Knot.Modules.Relations.Application.Contacts;

public record ContactDto(
    Guid Id,
    string Username,
    string DisplayName,
    string Avatar,
    bool IsOnline,
    DateTime? LastSeen,
    Guid RelationId,
    bool IsBlocked = false,
    bool IsExternal = false,
    string? Domain = null);

public record GetContactsQuery(Guid UserId) : IQuery<List<ContactDto>>;

internal sealed class GetContactsQueryHandler : IQueryHandler<GetContactsQuery, List<ContactDto>>
{
    private readonly IContactsDbContext _context;

    public GetContactsQueryHandler(IContactsDbContext context)
    {
        _context = context;
    }

    public async Task<Result<List<ContactDto>>> Handle(GetContactsQuery request, CancellationToken cancellationToken)
    {
        var relations = await _context.Contacts
            .Where(c => (c.UserId == request.UserId || c.ContactId == request.UserId) && c.Status == ContactStatus.Accepted)
            .ToListAsync(cancellationToken);

        var contactIds = relations.Select(c => c.UserId == request.UserId ? c.ContactId : c.UserId).ToList();
        
        var replicas = await _context.UserReplicas
            .Where(r => contactIds.Contains(r.Id))
            .ToListAsync(cancellationToken);

        var result = new List<ContactDto>();

        foreach (var replica in replicas)
        {
            var rel = relations.First(c => c.UserId == replica.Id || c.ContactId == replica.Id);
            
            result.Add(new ContactDto(
                replica.Id,
                replica.Username,
                replica.DisplayName,
                replica.Avatar,
                false, // Presence handled by another service or real-time
                null,
                rel.Id,
                rel.Status == ContactStatus.Blocked,
                replica.IsExternal,
                replica.Domain
            ));
        }

        return Result.Success(result);
    }
}