using System.Collections.Concurrent;

namespace Backend.Data.InMemory;

/// <summary>
/// Default implementation so the skeleton runs with no database. State is per-process
/// and lost on restart.
/// </summary>
public sealed class InMemoryUserRepository : IUserRepository
{
    private readonly ConcurrentDictionary<Guid, User> _users = new();

    public Task<IReadOnlyList<User>> GetAllAsync(CancellationToken cancellationToken = default)
    {
        IReadOnlyList<User> users = _users.Values
            .OrderBy(user => user.CreatedAt)
            .ToList();

        return Task.FromResult(users);
    }

    public Task<User?> GetByIdAsync(Guid id, CancellationToken cancellationToken = default)
    {
        _users.TryGetValue(id, out var user);

        return Task.FromResult(user);
    }

    public Task<User?> GetByEmailAsync(string email, CancellationToken cancellationToken = default)
    {
        var user = _users.Values
            .FirstOrDefault(candidate => string.Equals(candidate.Email, email, StringComparison.OrdinalIgnoreCase));

        return Task.FromResult(user);
    }

    public Task<User> AddAsync(User user, CancellationToken cancellationToken = default)
    {
        _users[user.Id] = user;

        return Task.FromResult(user);
    }

    public Task<User?> UpdateAsync(User user, CancellationToken cancellationToken = default)
    {
        if (!_users.ContainsKey(user.Id))
        {
            return Task.FromResult<User?>(null);
        }

        _users[user.Id] = user;

        return Task.FromResult<User?>(user);
    }

    public Task<bool> DeleteAsync(Guid id, CancellationToken cancellationToken = default)
        => Task.FromResult(_users.TryRemove(id, out _));
}