using Microsoft.EntityFrameworkCore;
using Tiku.Application.Jobs;
using Tiku.Application.Security;
using Tiku.Domain.Common;
using Tiku.Domain.Operations;
using Tiku.Infrastructure.Persistence;

namespace Tiku.Infrastructure.Jobs;

internal sealed class BackgroundJobService(
    TikuDbContext dbContext,
    ITenantExecutionScope tenantExecutionScope) : IBackgroundJobService
{
    private static readonly TimeSpan LeaseDuration = TimeSpan.FromMinutes(5);

    public async Task<BackgroundJobItem> EnqueueAsync(
        CreateBackgroundJobCommand command,
        CancellationToken cancellationToken = default)
    {
        var job = new BackgroundJob
        {
            TenantId = command.TenantId,
            JobType = NormalizeJobType(command.JobType),
            Payload = command.Payload,
            RunAfter = command.RunAfter,
            MaxRetries = Math.Clamp(command.MaxRetries, 0, 20)
        };
        dbContext.BackgroundJobs.Add(job);
        await dbContext.SaveChangesAsync(cancellationToken);
        return ToItem(job);
    }

    public async Task<int> ProcessPendingAsync(
        string workerId,
        int batchSize,
        CancellationToken cancellationToken = default)
    {
        var now = DateTimeOffset.UtcNow;
        var jobs = await dbContext.BackgroundJobs
            .Where(job =>
                job.Status == BackgroundJobStatus.Pending &&
                (job.RunAfter == null || job.RunAfter <= now))
            .OrderBy(job => job.CreatedAt)
            .Take(Math.Clamp(batchSize, 1, 100))
            .ToArrayAsync(cancellationToken);

        var processed = 0;
        foreach (var job in jobs)
        {
            cancellationToken.ThrowIfCancellationRequested();
            job.Status = BackgroundJobStatus.Processing;
            job.LockedBy = workerId;
            job.LockExpiresAt = now.Add(LeaseDuration);
            job.StartedAt = now;
            await dbContext.SaveChangesAsync(cancellationToken);

            try
            {
                await tenantExecutionScope.ExecuteAsync(
                    job.TenantId,
                    $"Background job {job.JobType}",
                    (_, token) => ProcessCoreAsync(job, token),
                    cancellationToken);
                job.Status = BackgroundJobStatus.Succeeded;
                job.CompletedAt = DateTimeOffset.UtcNow;
                job.LastError = null;
                job.Result = JsonDefaults.Object();
            }
            catch (Exception exception) when (exception is not OperationCanceledException)
            {
                job.RetryCount++;
                job.LastError = exception.Message;
                job.Status = job.RetryCount > job.MaxRetries
                    ? BackgroundJobStatus.Failed
                    : BackgroundJobStatus.Pending;
                job.RunAfter = DateTimeOffset.UtcNow.AddSeconds(Math.Min(300, 10 * job.RetryCount));
            }
            finally
            {
                job.LockedBy = null;
                job.LockExpiresAt = null;
                processed++;
                await dbContext.SaveChangesAsync(cancellationToken);
            }
        }

        return processed;
    }

    public async Task<IReadOnlyCollection<BackgroundJobItem>> ListAsync(
        Guid tenantId,
        string? jobType = null,
        int limit = 50,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.BackgroundJobs.AsNoTracking()
            .Where(job => job.TenantId == tenantId);
        if (!string.IsNullOrWhiteSpace(jobType))
        {
            var normalized = NormalizeJobType(jobType);
            query = query.Where(job => job.JobType == normalized);
        }

        var jobs = await query
            .OrderByDescending(job => job.CreatedAt)
            .Take(Math.Clamp(limit, 1, 200))
            .ToArrayAsync(cancellationToken);
        return jobs.Select(ToItem).ToArray();
    }

    private static Task ProcessCoreAsync(BackgroundJob job, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();
        return job.JobType switch
        {
            "content_export" => Task.CompletedTask,
            "content_import" => Task.CompletedTask,
            "asset_security_scan" => Task.CompletedTask,
            "statistics_aggregation" => Task.CompletedTask,
            "commerce_reconciliation" => Task.CompletedTask,
            "tenant_domain_recheck" => Task.CompletedTask,
            _ => throw new InvalidOperationException($"Unsupported background job type '{job.JobType}'.")
        };
    }

    private static string NormalizeJobType(string jobType)
    {
        return jobType.Trim().ToLowerInvariant();
    }

    private static BackgroundJobItem ToItem(BackgroundJob job)
    {
        return new BackgroundJobItem(
            job.Id,
            job.TenantId,
            job.JobType,
            job.Status,
            job.RetryCount,
            job.MaxRetries,
            job.RunAfter,
            job.StartedAt,
            job.CompletedAt,
            job.LastError,
            job.OutputAssetId,
            job.Result);
    }
}