using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using DysonNetwork.Drive.Data;
using DysonNetwork.Drive.Extensions;
using DysonNetwork.Drive.Interfaces;
using DysonNetwork.Drive.Models;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using NodaTime;

namespace DysonNetwork.Drive.Services;

public class FileService : IFileService, IDisposable
{
    private readonly ILogger<FileService> _logger;
    private readonly AppDatabase _dbContext;
    private readonly IClock _clock;
    private bool _disposed = false;

    public FileService(AppDatabase dbContext, IClock clock, ILogger<FileService> logger)
    {
        _dbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
        _clock = clock ?? throw new ArgumentNullException(nameof(clock));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public async Task<CloudFile> GetFileAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var file = await _dbContext.Files
            .AsNoTracking()
            .FirstOrDefaultAsync(f => f.Id == fileId, cancellationToken);

        if (file == null)
        {
            throw new FileNotFoundException($"File with ID {fileId} not found.");
        }

        return file;
    }

    public async Task<Stream> DownloadFileAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        
        // In a real implementation, this would stream the file from storage (e.g., S3, local filesystem)
        // For now, we'll return a MemoryStream with a placeholder
        var placeholder = $"This is a placeholder for file {fileId} with name {file.Name}";
        var memoryStream = new MemoryStream();
        var writer = new StreamWriter(memoryStream);
        await writer.WriteAsync(placeholder);
        await writer.FlushAsync();
        memoryStream.Position = 0;
        
        return memoryStream;
    }

    public async Task<CloudFile> UploadFileAsync(
        Stream fileStream, 
        string fileName, 
        string contentType, 
        IDictionary<string, string>? metadata = null, 
        CancellationToken cancellationToken = default)
    {
        if (fileStream == null) throw new ArgumentNullException(nameof(fileStream));
        if (string.IsNullOrWhiteSpace(fileName)) throw new ArgumentNullException(nameof(fileName));
        if (string.IsNullOrWhiteSpace(contentType)) throw new ArgumentNullException(nameof(contentType));

        // In a real implementation, this would upload to a storage service
        var now = _clock.GetCurrentInstant();
        var file = new CloudFile
        {
            Id = Guid.NewGuid(),
            Name = Path.GetFileName(fileName),
            OriginalName = fileName,
            MimeType = contentType,
            Size = fileStream.Length,
            StoragePath = $"uploads/{now.ToUnixTimeMilliseconds()}/{Guid.NewGuid()}/{Path.GetFileName(fileName)}",
            StorageProvider = "local", // or "s3", "azure", etc.
            CreatedAt = now.ToDateTimeOffset(),
            IsPublic = false,
            IsTemporary = false,
            IsDeleted = false
        };

        if (metadata != null)
        {
            file.Metadata = System.Text.Json.JsonSerializer.Serialize(metadata);
        }

        _dbContext.Files.Add(file);
        await _dbContext.SaveChangesAsync(cancellationToken);

        _logger.LogInformation("Uploaded file {FileId} with name {FileName}", file.Id, file.Name);
        
        return file;
    }

    public async Task<bool> DeleteFileAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var file = await _dbContext.Files.FindAsync(new object[] { fileId }, cancellationToken);
        if (file == null)
        {
            return false;
        }

        // In a real implementation, this would also delete the file from storage
        file.IsDeleted = true;
        file.DeletedAt = _clock.GetCurrentInstant();
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Soft-deleted file {FileId}", fileId);
        return true;
    }

    public async Task<CloudFile> UpdateFileMetadataAsync(Guid fileId, IDictionary<string, string> metadata, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        
        file.Metadata = System.Text.Json.JsonSerializer.Serialize(metadata);
        var now = _clock.GetCurrentInstant();
        file.UpdatedAt = new DateTimeOffset(now.ToDateTimeUtc(), TimeSpan.Zero);
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Updated metadata for file {FileId}", fileId);
        return file;
    }

    public Task<bool> FileExistsAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        return _dbContext.Files
            .AsNoTracking()
            .AnyAsync(f => f.Id == fileId && !f.IsDeleted, cancellationToken);
    }

    public Task<string> GetFileUrlAsync(Guid fileId, TimeSpan? expiry = null, CancellationToken cancellationToken = default)
    {
        // In a real implementation, this would generate a signed URL with the specified expiry
        return Task.FromResult($"https://storage.dyson.network/files/{fileId}");
    }

    public Task<string> GetFileThumbnailUrlAsync(Guid fileId, int? width = null, int? height = null, TimeSpan? expiry = null, CancellationToken cancellationToken = default)
    {
        // In a real implementation, this would generate a signed thumbnail URL
        var size = width.HasValue || height.HasValue 
            ? $"_{width ?? 0}x{height ?? 0}" 
            : string.Empty;
            
        return Task.FromResult($"https://storage.dyson.network/thumbnails/{fileId}{size}");
    }

    public async Task<CloudFile> CopyFileAsync(Guid sourceFileId, string? newName = null, IDictionary<string, string>? newMetadata = null, CancellationToken cancellationToken = default)
    {
        var sourceFile = await GetFileAsync(sourceFileId, cancellationToken);
        
        var newFile = new CloudFile
        {
            Id = Guid.NewGuid(),
            Name = newName ?? sourceFile.Name,
            OriginalName = sourceFile.OriginalName,
            MimeType = sourceFile.MimeType,
            Size = sourceFile.Size,
            StoragePath = $"copies/{_clock.GetCurrentInstant().ToUnixTimeMilliseconds()}/{Guid.NewGuid()}/{sourceFile.Name}",
            StorageProvider = sourceFile.StorageProvider,
            ContentHash = sourceFile.ContentHash,
            ThumbnailPath = sourceFile.ThumbnailPath,
            PreviewPath = sourceFile.PreviewPath,
            Width = sourceFile.Width,
            Height = sourceFile.Height,
            Duration = sourceFile.Duration,
            Metadata = newMetadata != null 
                ? System.Text.Json.JsonSerializer.Serialize(newMetadata) 
                : sourceFile.Metadata,
            IsPublic = sourceFile.IsPublic,
            IsTemporary = sourceFile.IsTemporary,
            IsDeleted = false,
            ExpiresAt = sourceFile.ExpiresAt,
            UploadedById = sourceFile.UploadedById,
            UploadedByType = sourceFile.UploadedByType,
            CreatedAt = _clock.GetCurrentInstant().ToDateTimeOffset(),
            UpdatedAt = _clock.GetCurrentInstant().ToDateTimeOffset()
        };

        _dbContext.Files.Add(newFile);
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Copied file {SourceFileId} to {NewFileId}", sourceFileId, newFile.Id);
        
        return newFile;
    }

    public async Task<CloudFile> MoveFileAsync(Guid sourceFileId, string? newName = null, IDictionary<string, string>? newMetadata = null, CancellationToken cancellationToken = default)
    {
        var sourceFile = await GetFileAsync(sourceFileId, cancellationToken);
        
        // In a real implementation, this would move the file in storage
        var newPath = $"moved/{_clock.GetCurrentInstant().ToUnixTimeMilliseconds()}/{Guid.NewGuid()}/{newName ?? sourceFile.Name}";
        
        sourceFile.Name = newName ?? sourceFile.Name;
        sourceFile.StoragePath = newPath;
        sourceFile.UpdatedAt = _clock.GetCurrentInstant();
        
        if (newMetadata != null)
        {
            sourceFile.Metadata = System.Text.Json.JsonSerializer.Serialize(newMetadata);
        }
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Moved file {FileId} to {NewPath}", sourceFileId, newPath);
        
        return sourceFile;
    }

    public async Task<CloudFile> RenameFileAsync(Guid fileId, string newName, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        
        file.Name = newName;
        file.UpdatedAt = _clock.GetCurrentInstant().ToDateTimeOffset();
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Renamed file {FileId} to {NewName}", fileId, newName);
        
        return file;
    }

    public async Task<long> GetFileSizeAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        return file.Size;
    }

    public async Task<string> GetFileHashAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        
        if (string.IsNullOrEmpty(file.ContentHash))
        {
            // In a real implementation, this would compute the hash of the file content
            file.ContentHash = Convert.ToBase64String(Guid.NewGuid().ToByteArray())[..16];
            await _dbContext.SaveChangesAsync(cancellationToken);
        }
        
        return file.ContentHash;
    }

    public async Task<Stream> GetFileThumbnailAsync(Guid fileId, int? width = null, int? height = null, CancellationToken cancellationToken = default)
    {
        // In a real implementation, this would generate or retrieve a thumbnail
        var placeholder = $"This is a thumbnail for file {fileId} with size {width ?? 0}x{height ?? 0}";
        var memoryStream = new MemoryStream();
        var writer = new StreamWriter(memoryStream);
        await writer.WriteAsync(placeholder);
        await writer.FlushAsync();
        memoryStream.Position = 0;
        
        return memoryStream;
    }

    public async Task<CloudFile> SetFileVisibilityAsync(Guid fileId, bool isPublic, CancellationToken cancellationToken = default)
    {
        var file = await GetFileAsync(fileId, cancellationToken);
        
        if (file.IsPublic != isPublic)
        {
            file.IsPublic = isPublic;
            file.UpdatedAt = _clock.GetCurrentInstant().ToDateTimeOffset();
            await _dbContext.SaveChangesAsync(cancellationToken);
            
            _logger.LogInformation("Set visibility of file {FileId} to {Visibility}", fileId, isPublic ? "public" : "private");
        }
        
        return file;
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            if (disposing)
            {
                _dbContext?.Dispose();
            }
            
            _disposed = true;
        }
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}