using Distribution.Data;
using Distribution.Infra.Authorization;
using Distribution.Infra.UoW;
using Microsoft.EntityFrameworkCore;

namespace Distribution.Features.Expense;

public class ExpenseAttachmentService(
    AppDBContext context,
    IConfiguration config,
    IUnitOfWork uow,
    ICurrentUserService currentUser)
{
    private const long MaxBytes = 10 * 1024 * 1024;
    private static readonly string[] AllowedExtensions = [".pdf", ".jpg", ".jpeg", ".png", ".webp"];
    private static readonly string[] AllowedContentTypes =
        ["application/pdf", "image/jpeg", "image/jpg", "image/png", "image/webp"];

    private string AttachmentsRoot =>
        config["Expense:AttachmentsRoot"]
        ?? throw new InvalidOperationException("Expense:AttachmentsRoot is not configured");

    public async Task<ExpenseAttachmentResponse?> UploadAsync(Guid expenseId, IFormFile file, CancellationToken ct)
    {
        var expense = await context.Expenses.FirstOrDefaultAsync(e => e.Id == expenseId && e.IsActive, ct);
        if (expense is null) return null;

        if (file is null || file.Length == 0)
            throw new InvalidOperationException("File is empty");
        if (file.Length > MaxBytes)
            throw new InvalidOperationException($"File exceeds the {MaxBytes / (1024 * 1024)}MB limit");

        var ext = Path.GetExtension(file.FileName).ToLowerInvariant();
        if (!AllowedExtensions.Contains(ext))
            throw new InvalidOperationException($"File type '{ext}' is not allowed");
        if (!AllowedContentTypes.Contains(file.ContentType.ToLowerInvariant()))
            throw new InvalidOperationException($"Content type '{file.ContentType}' is not allowed");

        var userId = currentUser.UserId
            ?? throw new InvalidOperationException("Authenticated user is required");

        var now = DateTime.Now;
        var relativeDir = Path.Combine(now.Year.ToString("D4"), now.Month.ToString("D2"));
        var absoluteDir = Path.Combine(AttachmentsRoot, relativeDir);
        Directory.CreateDirectory(absoluteDir);

        var storedName = $"{Guid.NewGuid()}{ext}";
        var absolutePath = Path.Combine(absoluteDir, storedName);

        await using (var stream = File.Create(absolutePath))
        {
            await file.CopyToAsync(stream, ct);
        }

        var attachment = new Models.ExpenseAttachment
        {
            FK_ExpenseId     = expenseId,
            OriginalFileName = file.FileName,
            StoredPath       = absolutePath,
            ContentType      = file.ContentType,
            SizeBytes        = file.Length,
            UploadedByUserId = userId
        };

        await uow.BeginAsync(ct);
        try
        {
            await context.ExpenseAttachments.AddAsync(attachment, ct);
            await uow.CommitAsync(ct);
        }
        catch
        {
            await uow.RollbackAsync(ct);
            try { File.Delete(absolutePath); } catch { }
            throw;
        }

        return new ExpenseAttachmentResponse(attachment.Id, attachment.OriginalFileName,
            attachment.ContentType, attachment.SizeBytes, attachment.CreatedAt);
    }

    public async Task<(Stream Stream, string ContentType, string FileName)?> DownloadAsync(Guid attachmentId, CancellationToken ct)
    {
        var a = await context.ExpenseAttachments.FirstOrDefaultAsync(x => x.Id == attachmentId && x.IsActive, ct);
        if (a is null) return null;
        if (!File.Exists(a.StoredPath)) return null;

        var stream = File.OpenRead(a.StoredPath);
        return (stream, a.ContentType, a.OriginalFileName);
    }

    public async Task<bool> DeleteAsync(Guid attachmentId, CancellationToken ct)
    {
        var a = await context.ExpenseAttachments.FirstOrDefaultAsync(x => x.Id == attachmentId && x.IsActive, ct);
        if (a is null) return false;

        a.IsActive = false;

        await uow.BeginAsync(ct);
        try { context.ExpenseAttachments.Update(a); await uow.CommitAsync(ct); }
        catch { await uow.RollbackAsync(ct); throw; }

        // Best-effort file removal — keep DB soft-delete even if the file is gone.
        try { File.Delete(a.StoredPath); } catch { }

        return true;
    }
}