using Microsoft.EntityFrameworkCore;
using Tiku.Application.Auth;
using Tiku.Domain.Tenancy;
using Tiku.Infrastructure.Persistence;

namespace Tiku.Infrastructure.Auth;

public sealed class SmsVerificationService(TikuDbContext dbContext) : ISmsVerificationService
{
    private const int MaxPhoneRequestsPerHour = 5;
    private static readonly TimeSpan CodeLifetime = TimeSpan.FromMinutes(10);

    public async Task<SmsSendResult> CreateCodeAsync(
        SendSmsCodeRequest request,
        CancellationToken cancellationToken = default)
    {
        var phone = SmsCodeHashing.NormalizePhone(request.Phone);
        var bucketStart = TruncateToHour(DateTimeOffset.UtcNow);
        var scopeHash = SmsCodeHashing.Hash(request.TenantId, phone, request.Purpose, "phone-bucket");
        var rateLimit = await dbContext.SmsSendRateLimits.FindAsync(
            [request.TenantId, SmsRateLimitDimension.Phone, scopeHash, bucketStart],
            cancellationToken);

        if (rateLimit is null)
        {
            rateLimit = new SmsSendRateLimit
            {
                TenantId = request.TenantId,
                Dimension = SmsRateLimitDimension.Phone,
                ScopeHash = scopeHash,
                BucketStart = bucketStart
            };
            dbContext.SmsSendRateLimits.Add(rateLimit);
        }

        if (rateLimit.RequestCount >= MaxPhoneRequestsPerHour)
        {
            throw new SmsRateLimitedException();
        }

        rateLimit.RequestCount++;
        rateLimit.UpdatedAt = DateTimeOffset.UtcNow;

        var code = Random.Shared.Next(100000, 999999).ToString(System.Globalization.CultureInfo.InvariantCulture);
        var verification = new SmsVerificationCode
        {
            TenantId = request.TenantId,
            Phone = phone,
            Purpose = request.Purpose,
            CodeHash = SmsCodeHashing.Hash(request.TenantId, phone, request.Purpose, code),
            Provider = "mock",
            Status = SmsVerificationStatus.Sent,
            ExpiresAt = DateTimeOffset.UtcNow.Add(CodeLifetime),
            IpAddress = request.IpAddress,
            UserAgent = request.UserAgent
        };

        dbContext.SmsVerificationCodes.Add(verification);
        await dbContext.SaveChangesAsync(cancellationToken);

        return new SmsSendResult(verification.Id, verification.ExpiresAt);
    }

    public async Task VerifyCodeAsync(
        Guid tenantId,
        string phone,
        SmsPurpose purpose,
        string code,
        CancellationToken cancellationToken = default)
    {
        var normalizedPhone = SmsCodeHashing.NormalizePhone(phone);
        var now = DateTimeOffset.UtcNow;
        var codeHash = SmsCodeHashing.Hash(tenantId, normalizedPhone, purpose, code);
        var verification = await dbContext.SmsVerificationCodes
            .Where(entity =>
                entity.TenantId == tenantId &&
                entity.Phone == normalizedPhone &&
                entity.Purpose == purpose &&
                entity.ConsumedAt == null)
            .OrderByDescending(entity => entity.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);

        if (verification is null ||
            verification.ExpiresAt <= now ||
            verification.Status is SmsVerificationStatus.Expired or SmsVerificationStatus.Blocked)
        {
            throw new InvalidCredentialsException("invalid_sms_code");
        }

        verification.Attempts++;
        if (!string.Equals(verification.CodeHash, codeHash, StringComparison.Ordinal))
        {
            await dbContext.SaveChangesAsync(cancellationToken);
            throw new InvalidCredentialsException("invalid_sms_code");
        }

        verification.Status = SmsVerificationStatus.Verified;
        verification.ConsumedAt = now;
        await dbContext.SaveChangesAsync(cancellationToken);
    }

    private static DateTimeOffset TruncateToHour(DateTimeOffset value)
    {
        return new DateTimeOffset(
            value.Year,
            value.Month,
            value.Day,
            value.Hour,
            0,
            0,
            value.Offset);
    }
}