namespace HrynCo.NotificationService.DAL.EF.Repositories;

using HrynCo.NotificationService.DAL.Abstract.Push;
using HrynCo.NotificationService.DAL.EF.Entities;
using Microsoft.EntityFrameworkCore;

public sealed class PushDeliveryRepository(NotificationDbContext db) : IPushDeliveryRepository
{
    public async Task<PushDeliveryOutcome> DeliverOnceAsync(Guid messageId, string serviceName,
        Func<CancellationToken, Task<PushDeliveryOutcome>> deliver, CancellationToken cancellationToken)
    {
        // Thirty days exceeds the maximum payload lifetime; old replays cannot send expired data.
        var cutoff = DateTimeOffset.UtcNow.AddDays(-30);
        await db.Set<PushDeliveryEntity>().Where(x => x.CompletedAt < cutoff).ExecuteDeleteAsync(cancellationToken);
        await using var transaction = await db.Database.BeginTransactionAsync(cancellationToken);
        var identity = $"{serviceName}:{messageId:D}";
        await db.Database.ExecuteSqlInterpolatedAsync(
            $"SELECT pg_advisory_xact_lock(hashtextextended({identity}, 1074))", cancellationToken);
        var previous = await db.Set<PushDeliveryEntity>().AsNoTracking()
            .SingleOrDefaultAsync(x => x.MessageId == messageId && x.ServiceName == serviceName, cancellationToken);
        if (previous is not null)
            return new PushDeliveryOutcome(previous.Error, previous.InvalidRegistration);

        // One bounded provider call while holding this message's lock prevents concurrent sends.
        // A crash after FCM accepts still requires client-side message-id deduplication.
        var outcome = await deliver(cancellationToken);
        db.Add(new PushDeliveryEntity
        {
            MessageId = messageId, ServiceName = serviceName, Error = outcome.Error,
            InvalidRegistration = outcome.InvalidRegistration, CompletedAt = DateTimeOffset.UtcNow
        });
        await db.SaveChangesAsync(cancellationToken);
        await transaction.CommitAsync(cancellationToken);
        return outcome;
    }
}