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

namespace DysonNetwork.Drive.Services;

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

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

    public async Task<CloudFileReference> CreateReferenceAsync(
        Guid fileId,
        string resourceId,
        string resourceType,
        string referenceType,
        string? referenceId = null,
        string? referenceName = null,
        string? referenceMimeType = null,
        long? referenceSize = null,
        string? referenceUrl = null,
        string? referenceThumbnailUrl = null,
        string? referencePreviewUrl = null,
        string? referenceMetadata = null,
        IDictionary<string, object>? metadata = null,
        CancellationToken cancellationToken = default)
    {
        // Verify file exists
        var fileExists = await _fileService.FileExistsAsync(fileId, cancellationToken);
        if (!fileExists)
        {
            throw new FileNotFoundException($"File with ID {fileId} not found.");
        }

        var reference = new CloudFileReference
        {
            Id = Guid.NewGuid(),
            FileId = fileId,
            ResourceId = resourceId,
            ResourceType = resourceType,
            ReferenceType = referenceType,
            ReferenceId = referenceId,
            ReferenceName = referenceName,
            ReferenceMimeType = referenceMimeType,
            ReferenceSize = referenceSize,
            ReferenceUrl = referenceUrl,
            ReferenceThumbnailUrl = referenceThumbnailUrl,
            ReferencePreviewUrl = referencePreviewUrl,
            ReferenceMetadata = referenceMetadata,
            IsActive = true,
            CreatedAt = _clock.GetCurrentInstant().ToDateTimeOffset()
        };

        if (metadata != null && metadata.Any())
        {
            var options = new JsonSerializerOptions { WriteIndented = true };
            reference.Metadata = JsonDocument.Parse(JsonSerializer.Serialize(metadata, options));
        }

        _dbContext.FileReferences.Add(reference);
        await _dbContext.SaveChangesAsync(cancellationToken);

        _logger.LogInformation(
            "Created reference {ReferenceId} for file {FileId} to resource {ResourceType}/{ResourceId}",
            reference.Id, fileId, resourceType, resourceId);

        return reference;
    }

    public async Task<CloudFileReference> GetReferenceAsync(Guid referenceId, CancellationToken cancellationToken = default)
    {
        var reference = await _dbContext.FileReferences
            .AsNoTracking()
            .Include(r => r.File)
            .FirstOrDefaultAsync(r => r.Id == referenceId, cancellationToken);

        if (reference == null)
        {
            throw new KeyNotFoundException($"Reference with ID {referenceId} not found.");
        }

        return reference;
    }

    public async Task<IEnumerable<CloudFileReference>> GetReferencesForFileAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        return await _dbContext.FileReferences
            .AsNoTracking()
            .Where(r => r.FileId == fileId && r.IsActive)
            .ToListAsync(cancellationToken);
    }

    public async Task<IEnumerable<CloudFileReference>> GetReferencesForResourceAsync(
        string resourceId, 
        string resourceType, 
        CancellationToken cancellationToken = default)
    {
        return await _dbContext.FileReferences
            .AsNoTracking()
            .Where(r => r.ResourceId == resourceId && 
                       r.ResourceType == resourceType && 
                       r.IsActive)
            .ToListAsync(cancellationToken);
    }

    public async Task<IEnumerable<CloudFileReference>> GetReferencesOfTypeAsync(
        string referenceType, 
        CancellationToken cancellationToken = default)
    {
        return await _dbContext.FileReferences
            .AsNoTracking()
            .Where(r => r.ReferenceType == referenceType && r.IsActive)
            .ToListAsync(cancellationToken);
    }

    public async Task<bool> DeleteReferenceAsync(Guid referenceId, CancellationToken cancellationToken = default)
    {
        var reference = await _dbContext.FileReferences
            .FirstOrDefaultAsync(r => r.Id == referenceId, cancellationToken);

        if (reference == null)
        {
            return false;
        }

        reference.IsActive = false;
        await _dbContext.SaveChangesAsync(cancellationToken);

        _logger.LogInformation("Deleted reference {ReferenceId}", referenceId);
        return true;
    }

    public async Task<int> DeleteReferencesForFileAsync(Guid fileId, CancellationToken cancellationToken = default)
    {
        var references = await _dbContext.FileReferences
            .Where(r => r.FileId == fileId && r.IsActive)
            .ToListAsync(cancellationToken);

        foreach (var reference in references)
        {
            reference.IsActive = false;
        }

        var count = await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Deleted {Count} references for file {FileId}", count, fileId);
        
        return count;
    }

    public async Task<int> DeleteReferencesForResourceAsync(
        string resourceId, 
        string resourceType, 
        CancellationToken cancellationToken = default)
    {
        var references = await _dbContext.FileReferences
            .Where(r => r.ResourceId == resourceId && 
                       r.ResourceType == resourceType && 
                       r.IsActive)
            .ToListAsync(cancellationToken);

        foreach (var reference in references)
        {
            reference.IsActive = false;
        }

        var count = await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation(
            "Deleted {Count} references for resource {ResourceType}/{ResourceId}", 
            count, resourceType, resourceId);
            
        return count;
    }

    public async Task<CloudFileReference> UpdateReferenceMetadataAsync(
        Guid referenceId, 
        IDictionary<string, object> metadata, 
        CancellationToken cancellationToken = default)
    {
        var reference = await GetReferenceAsync(referenceId, cancellationToken);
        
        var options = new JsonSerializerOptions { WriteIndented = true };
        reference.Metadata = JsonDocument.Parse(JsonSerializer.Serialize(metadata, options));
        reference.UpdatedAt = _clock.GetCurrentInstant().ToDateTimeOffset();
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation("Updated metadata for reference {ReferenceId}", referenceId);
        
        return reference;
    }

    public async Task<bool> ReferenceExistsAsync(Guid referenceId, CancellationToken cancellationToken = default)
    {
        return await _dbContext.FileReferences
            .AsNoTracking()
            .AnyAsync(r => r.Id == referenceId && r.IsActive, cancellationToken);
    }

    public async Task<bool> HasReferenceAsync(
        Guid fileId, 
        string resourceId, 
        string resourceType, 
        string? referenceType = null, 
        CancellationToken cancellationToken = default)
    {
        var query = _dbContext.FileReferences
            .AsNoTracking()
            .Where(r => r.FileId == fileId && 
                       r.ResourceId == resourceId && 
                       r.ResourceType == resourceType && 
                       r.IsActive);

        if (!string.IsNullOrEmpty(referenceType))
        {
            query = query.Where(r => r.ReferenceType == referenceType);
        }

        return await query.AnyAsync(cancellationToken);
    }

    public async Task<CloudFileReference> UpdateReferenceResourceAsync(
        Guid referenceId, 
        string newResourceId, 
        string newResourceType, 
        CancellationToken cancellationToken = default)
    {
        var reference = await GetReferenceAsync(referenceId, cancellationToken);
        
        reference.ResourceId = newResourceId;
        reference.ResourceType = newResourceType;
        reference.UpdatedAt = _clock.GetCurrentInstant().ToDateTimeOffset();
        
        await _dbContext.SaveChangesAsync(cancellationToken);
        
        _logger.LogInformation(
            "Updated reference {ReferenceId} to point to resource {ResourceType}/{ResourceId}",
            referenceId, newResourceType, newResourceId);
            
        return reference;
    }

    public async Task<IEnumerable<CloudFile>> GetFilesForResourceAsync(
        string resourceId, 
        string resourceType, 
        string? referenceType = null, 
        CancellationToken cancellationToken = default)
    {
        var query = _dbContext.FileReferences
            .AsNoTracking()
            .Include(r => r.File)
            .Where(r => r.ResourceId == resourceId && 
                       r.ResourceType == resourceType && 
                       r.IsActive);

        if (!string.IsNullOrEmpty(referenceType))
        {
            query = query.Where(r => r.ReferenceType == referenceType);
        }

        var references = await query.ToListAsync(cancellationToken);
        return references.Select(r => r.File!);
    }

    public async Task<IEnumerable<CloudFile>> GetFilesForReferenceTypeAsync(
        string referenceType, 
        CancellationToken cancellationToken = default)
    {
        var references = await _dbContext.FileReferences
            .AsNoTracking()
            .Include(r => r.File)
            .Where(r => r.ReferenceType == referenceType && r.IsActive)
            .ToListAsync(cancellationToken);

        return references.Select(r => r.File!);
    }

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

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