using MediatR;
using Microsoft.EntityFrameworkCore;
using SequenceAuth.Example.Domain;
using SequenceAuth.Example.Infrastructure;
using SequenceAuth.Lib;

namespace SequenceAuth.Example.Features.Auth;

public record LoginCommand(string Username) : IRequest<LoginResult>;
public record LoginResult(User User, string InitialSequence);

public class LoginCommandHandler(AppDbContext dbContext, ISequenceStore sequenceStore, Microsoft.AspNetCore.Http.IHttpContextAccessor httpContextAccessor, Microsoft.Extensions.Options.IOptions<SequenceAuth.Lib.SequenceAuthOptions> options) : IRequestHandler<LoginCommand, LoginResult>
{
    public async Task<LoginResult> Handle(LoginCommand request, CancellationToken cancellationToken)
    {
        var userOpt = await dbContext.Users.FirstOrDefaultAsync(u => u.Username == request.Username, cancellationToken);
        
        var user = userOpt switch
        {
            null => await CreateUser(request.Username, cancellationToken),
            _ => userOpt
        };

        var initialSequenceId = Guid.NewGuid().ToString("N");
        var sequenceData = new SequenceData(UserId: user.Id.ToString(), RequestsRemaining: 1000, State: SequenceState.Initialized, NextSequenceId: initialSequenceId);
        
        await sequenceStore.SaveSequenceAsync(initialSequenceId, sequenceData);

        httpContextAccessor.HttpContext?.Response.Headers.Append(options.Value.NextHeaderName, initialSequenceId);
        httpContextAccessor.HttpContext?.Response.Headers.Append(options.Value.RequestsRemainingHeaderName, "1000");

        return new LoginResult(user, initialSequenceId);
    }

    private async Task<User> CreateUser(string username, CancellationToken cancellationToken)
    {
        var user = new User(Guid.NewGuid(), username);
        dbContext.Users.Add(user);
        await dbContext.SaveChangesAsync(cancellationToken);
        return user;
    }
}