using Data.SeaHavenIndustries;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;

namespace SeaHaven.DataServices.Implementation
{
    public class ForgetPasswordDataService : IForgetPasswordDataService
    {
        private readonly ApplicationDbContext _context;

        public ForgetPasswordDataService(ApplicationDbContext context)
        {
            _context = context;
        }

        public async Task ReplaceCodeAsync(string email, string userId, string codeHash, string codeSalt, DateTime expiresAtUtc, DateTime nowUtc, CancellationToken cancellationToken)
        {
            var normalizedEmail = Normalize(email);

            await using var transaction = await _context.Database.BeginTransactionAsync(cancellationToken);

            // Every request also clears expired codes of any email, which keeps the
            // table bounded and gives each request the same database work.
            await _context.ForgetPasswordCodes
                .Where(u => u.Email.ToLower().Trim() == normalizedEmail || u.ExpiresAtUtc <= nowUtc)
                .ExecuteDeleteAsync(cancellationToken);

            _context.ForgetPasswordCodes.Add(new ForgetPasswordCode
            {
                Email = email,
                UserId = userId,
                Code = string.Empty,
                CodeHash = codeHash,
                CodeSalt = codeSalt,
                ExpiresAtUtc = expiresAtUtc,
                FailedAttempts = 0
            });
            await _context.SaveChangesAsync(cancellationToken);
            await transaction.CommitAsync(cancellationToken);
        }

        public async Task PurgeExpiredAsync(DateTime nowUtc, CancellationToken cancellationToken)
        {
            await _context.ForgetPasswordCodes
                .Where(u => u.ExpiresAtUtc <= nowUtc)
                .ExecuteDeleteAsync(cancellationToken);
        }

        public async Task<ForgetPasswordCode?> GetByEmailAsync(string email, CancellationToken cancellationToken)
        {
            var normalizedEmail = Normalize(email);

            return await _context.ForgetPasswordCodes
                .AsNoTracking()
                .Where(u => u.Email.ToLower().Trim() == normalizedEmail)
                .OrderByDescending(u => u.Id)
                .FirstOrDefaultAsync(cancellationToken);
        }

        public async Task<bool> TryConsumeAttemptAsync(int id, int maxAttempts, DateTime nowUtc, CancellationToken cancellationToken)
        {
            // A single conditional UPDATE, so concurrent checks can never consume
            // more than maxAttempts between them.
            var updated = await _context.ForgetPasswordCodes
                .Where(u => u.Id == id && u.FailedAttempts < maxAttempts && u.ExpiresAtUtc > nowUtc)
                .ExecuteUpdateAsync(
                    setters => setters.SetProperty(u => u.FailedAttempts, u => u.FailedAttempts + 1),
                    cancellationToken);
            return updated == 1;
        }

        public async Task RefundAttemptAsync(int id, CancellationToken cancellationToken)
        {
            await _context.ForgetPasswordCodes
                .Where(u => u.Id == id && u.FailedAttempts > 0)
                .ExecuteUpdateAsync(
                    setters => setters.SetProperty(u => u.FailedAttempts, u => u.FailedAttempts - 1),
                    cancellationToken);
        }

        public async Task RemoveByEmailAsync(string email, CancellationToken cancellationToken)
        {
            var normalizedEmail = Normalize(email);
            await _context.ForgetPasswordCodes
                .Where(code => code.Email.ToLower().Trim() == normalizedEmail)
                .ExecuteDeleteAsync(cancellationToken);
        }

        public async Task RemoveIssuedThroughAsync(string email, int throughId, CancellationToken cancellationToken)
        {
            var normalizedEmail = Normalize(email);
            await _context.ForgetPasswordCodes
                .Where(code => code.Email.ToLower().Trim() == normalizedEmail && code.Id <= throughId)
                .ExecuteDeleteAsync(cancellationToken);
        }

        private static string Normalize(string email) => email.ToLower().Trim();
    }
}