using EngineeringSync.Domain.Entities;
using EngineeringSync.Infrastructure;
using Microsoft.EntityFrameworkCore;

namespace EngineeringSync.Service.Services;

public class SyncManager(IDbContextFactory<AppDbContext> dbFactory, ILogger<SyncManager> logger)
{
    public async Task<SyncResult> SyncAsync(IEnumerable<Guid> changeIds, CancellationToken ct = default)
    {
        await using var db = await dbFactory.CreateDbContextAsync(ct);
        var ids = changeIds.ToList();
        var changes = await db.PendingChanges
            .Include(c => c.Project)
            .Where(c => ids.Contains(c.Id) && c.Status == ChangeStatus.Pending)
            .ToListAsync(ct);

        int success = 0, failed = 0;
        foreach (var change in changes)
        {
            try
            {
                await ProcessChangeAsync(change, ct);
                change.Status = ChangeStatus.Synced;
                change.SyncedAt = DateTime.UtcNow;
                success++;
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "Fehler beim Sync von {Path}", change.RelativePath);
                failed++;
            }
        }
        await db.SaveChangesAsync(ct);
        return new SyncResult(success, failed);
    }

    public async Task IgnoreAsync(IEnumerable<Guid> changeIds, CancellationToken ct = default)
    {
        await using var db = await dbFactory.CreateDbContextAsync(ct);
        var ids = changeIds.ToList();
        await db.PendingChanges
            .Where(c => ids.Contains(c.Id) && c.Status == ChangeStatus.Pending)
            .ExecuteUpdateAsync(s => s.SetProperty(c => c.Status, ChangeStatus.Ignored), ct);
    }

    private async Task ProcessChangeAsync(PendingChange change, CancellationToken ct)
    {
        var project = change.Project;
        var sourcePath = SafeCombine(project.EngineeringPath, change.RelativePath);
        var targetPath = SafeCombine(project.SimulationPath, change.RelativePath);

        if (change.ChangeType == ChangeType.Deleted)
        {
            if (File.Exists(targetPath))
            {
                BackupFile(targetPath, project);
                File.Delete(targetPath);
            }
            return;
        }

        if (change.ChangeType == ChangeType.Renamed)
        {
            if (!string.IsNullOrEmpty(change.OldRelativePath))
            {
                var oldTargetPath = SafeCombine(project.SimulationPath, change.OldRelativePath);
                if (File.Exists(oldTargetPath))
                    File.Delete(oldTargetPath);
            }
        }

        if (!File.Exists(sourcePath))
            throw new FileNotFoundException($"Quelldatei nicht gefunden: {sourcePath}");

        Directory.CreateDirectory(Path.GetDirectoryName(targetPath)!);

        if (File.Exists(targetPath))
            BackupFile(targetPath, project);

        await Task.Run(() => File.Copy(sourcePath, targetPath, overwrite: true), ct);
    }

    private void BackupFile(string targetPath, ProjectConfig project)
    {
        if (!project.BackupEnabled)
            return;

        var backupDir = project.BackupPath ?? Path.GetDirectoryName(targetPath)!;
        Directory.CreateDirectory(backupDir);

        var nameWithoutExt = Path.GetFileNameWithoutExtension(targetPath);
        var ext = Path.GetExtension(targetPath);
        var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
        var backupPath = Path.Combine(backupDir, $"{nameWithoutExt}_{timestamp}{ext}.bak");

        try
        {
            File.Move(targetPath, backupPath);
        }
        catch (IOException)
        {
            File.Copy(targetPath, backupPath, overwrite: false);
            File.Delete(targetPath);
        }

        if (project.MaxBackupsPerFile > 0)
            CleanupOldBackups(backupDir, nameWithoutExt, ext, project.MaxBackupsPerFile);
    }

    private void CleanupOldBackups(string backupDir, string baseName, string ext, int max)
    {
        try
        {
            var pattern = $"{baseName}_*{ext}.bak";
            var backups = Directory.GetFiles(backupDir, pattern)
                .OrderBy(f => Path.GetFileName(f))
                .ToList();

            while (backups.Count > max)
            {
                File.Delete(backups[0]);
                backups.RemoveAt(0);
            }
        }
        catch (Exception ex)
        {
            logger.LogWarning(ex, "Cleanup alter Backups fehlgeschlagen in {Dir}", backupDir);
        }
    }

    private static string SafeCombine(string basePath, string relativePath)
    {
        var fullPath = Path.GetFullPath(Path.Combine(basePath, relativePath));
        var normalizedBase = Path.GetFullPath(basePath);
        if (!fullPath.StartsWith(normalizedBase + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase) &&
            !fullPath.Equals(normalizedBase, StringComparison.OrdinalIgnoreCase))
            throw new InvalidOperationException($"Path traversal detected: {relativePath}");
        return fullPath;
    }
}

public record SyncResult(int Success, int Failed);