using InboxIntel.Application.Abstractions;
using InboxIntel.Infrastructure.Configuration;
using InboxIntel.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace InboxIntel.Infrastructure.Notifications;

/// <summary>
/// Hourly tick that sends the inbox digest to opted-in users once their
/// configured frequency has elapsed. Mirrors <see cref="Sync.GmailSyncWorker"/>.
/// </summary>
public class DigestWorker : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly DigestOptions _options;
    private readonly ILogger<DigestWorker> _logger;

    public DigestWorker(IServiceScopeFactory scopeFactory, IOptions<DigestOptions> options, ILogger<DigestWorker> logger)
    {
        _scopeFactory = scopeFactory;
        _options = options.Value;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("DigestWorker started; send hour = {Hour}:00 UTC, frequency = {Days}d", _options.SendHourUtc, _options.FrequencyDays);

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                if (DateTimeOffset.UtcNow.Hour == _options.SendHourUtc)
                    await SendDueDigestsAsync(stoppingToken);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "DigestWorker tick failed");
            }

            await Task.Delay(TimeSpan.FromHours(1), stoppingToken);
        }
    }

    private async Task SendDueDigestsAsync(CancellationToken ct)
    {
        using var scope = _scopeFactory.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
        var digest = scope.ServiceProvider.GetRequiredService<IDigestService>();
        var emailSender = scope.ServiceProvider.GetRequiredService<IEmailSender>();
        if (!emailSender.IsEnabled) return;

        var cutoff = DateTimeOffset.UtcNow.AddDays(-_options.FrequencyDays);
        var dueUserIds = await db.Users
            .Where(u => u.DigestEnabled && (u.LastDigestSentUtc == null || u.LastDigestSentUtc <= cutoff))
            .Select(u => u.Id)
            .ToListAsync(ct);

        foreach (var userId in dueUserIds)
        {
            try { await digest.SendDigestAsync(userId, ct); }
            catch (Exception ex) { _logger.LogError(ex, "Digest send failed for user {UserId}", userId); }
        }
    }
}