using System.Diagnostics;
using System.Text.RegularExpressions;
using System.Text.Json;
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.ChatCompletion;
using QuestPDF.Fluent;
using QuestPDF.Helpers;
using QuestPDF.Infrastructure;
using PuppeteerSharp;
using VideoStudy.Shared;
using SkiaSharp;
using System.Linq;
using System.Security.Cryptography; // Added for MD5 hash

namespace VideoStudy.API.Services;

public class AnalysisService
{
    private readonly Kernel _kernel;
    private readonly ILogger<AnalysisService> _logger;
    private readonly List<string> _debugSteps = new();

    public AnalysisService(Kernel kernel, ILogger<AnalysisService> logger)
    {
        _kernel = kernel;
        _logger = logger;
        QuestPDF.Settings.License = LicenseType.Community;
        
        Task.Run(async () => {
            try 
            {
                var browserFetcher = new BrowserFetcher();
                await browserFetcher.DownloadAsync();
                _logger.LogInformation("Chromium ready.");
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Failed to download Chromium.");
            }
        });
    }

    private void AddLog(string message)
    {
        _logger.LogInformation(message);
        _debugSteps.Add($"[{DateTime.Now:HH:mm:ss}] {message}");
    }

    private string GetYtDlpPath()
    {
        if (System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(System.Runtime.InteropServices.OSPlatform.Windows))
        {
            var exeName = "yt-dlp.exe";
            var currentPath = Path.Combine(Directory.GetCurrentDirectory(), exeName);
            if (File.Exists(currentPath)) return currentPath;
            var basePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, exeName);
            if (File.Exists(basePath)) return basePath;
            var binPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Binaries", exeName);
            if (File.Exists(binPath)) return binPath;
            return "yt-dlp";
        }
        else
        {
            var baseDir = AppDomain.CurrentDomain.BaseDirectory;
            var binariesDir = Path.Combine(baseDir, "Binaries");
            string executableName = "yt-dlp_linux"; 
            if (System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(System.Runtime.InteropServices.OSPlatform.OSX))
                executableName = "yt-dlp_macos";
            var fullPath = Path.Combine(binariesDir, executableName);
            if (!File.Exists(fullPath)) return "yt-dlp";
            try { Process.Start("chmod", $"+x \"{fullPath}\"").WaitForExit(); } catch { }
            return fullPath;
        }
    }

    public async Task<VideoInfo> GetVideoInfoAsync(string url)
    {
        var ytDlpPath = GetYtDlpPath();
        var startInfo = new ProcessStartInfo
        {
            FileName = ytDlpPath,
            Arguments = $"--print title --print channel --print duration --print thumbnail \"{url}\"",
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        using var proc = Process.Start(startInfo) ?? throw new Exception("Failed to start yt-dlp");
        var output = await proc.StandardOutput.ReadToEndAsync();
        var error = await proc.StandardError.ReadToEndAsync();
        await proc.WaitForExitAsync();

        if (proc.ExitCode != 0)
            throw new Exception($"yt-dlp error: {error}");

        var lines = output.Trim().Split('\n', StringSplitOptions.RemoveEmptyEntries);
        var title = lines.Length > 0 ? lines[0].Trim() : "Unknown";
        var channel = lines.Length > 1 ? lines[1].Trim() : "Unknown";
        var durationStr = lines.Length > 2 ? lines[2].Trim() : "0";
        var thumbnail = lines.Length > 3 ? lines[3].Trim() : "";

        double.TryParse(durationStr, System.Globalization.NumberStyles.Any,
            System.Globalization.CultureInfo.InvariantCulture, out var durationSeconds);

        return new VideoInfo
        {
            Title = title,
            Author = channel,
            Duration = TimeSpan.FromSeconds(durationSeconds),
            Url = url,
            ThumbnailUrl = thumbnail
        };
    }

    public async Task<AnalysisResponse> AnalyzeVideoAsync(AnalysisRequest request)
    {
        _debugSteps.Clear();
        var tempDir = Path.Combine(Path.GetTempPath(), "VideoStudy", Guid.NewGuid().ToString());
        Directory.CreateDirectory(tempDir);
        AddLog($"📁 Inciando processamento em: {tempDir}");

        string rawLlmResponse = "";

        // Get video info early to use duration for timestamp validation
        AddLog("ℹ️ Obtendo informações do vídeo para validação de timestamps...");
        var videoInfo = await GetVideoInfoAsync(request.VideoUrl);
        AddLog($"✅ Duração do vídeo (via yt-dlp): {videoInfo.Duration:hh\\:mm\\:ss}");

        try
        {
            // --- Step 1: Transcription ---
            AddLog("🌐 Obtendo transcrição via yt-dlp...");
            var (transcript, originalTitle) = await GetTranscriptViaYtDlpAsync(request.VideoUrl, request.Language, tempDir);
            
            if (string.IsNullOrWhiteSpace(transcript))
                throw new Exception("Não foi possível obter a transcrição do vídeo.");

            AddLog($"✅ Transcrição obtida: '{originalTitle}' ({transcript.Length} chars).");

            // --- Step 2: Intelligence ---
            AddLog("🧠 Enviando transcrição para o Groq (LLM)...");
            var (tutorialSections, rawJson, category, docTitle) = await GenerateTutorialContentAsync(transcript, originalTitle, request.Language, request.OutputLanguage, videoInfo.Duration);
            rawLlmResponse = rawJson;
            
            // Save debug MD
            var debugFile = Path.Combine(Directory.GetCurrentDirectory(), "DEBUG_LAST_RESPONSE.md");
            var debugContent = $"# {docTitle} ({category})\n\nSource: {originalTitle}\n\n## Raw JSON\n```json\n{rawJson}\n```\n";
            await File.WriteAllTextAsync(debugFile, debugContent);
            AddLog($"📝 Arquivo de debug gerado: {debugFile}");

            // --- Validate and adjust Image Timestamps ---
            AddLog("⏳ Validando timestamps de imagem gerados pela IA...");
            foreach (var section in tutorialSections)
            {
                if (TimeSpan.TryParse(section.ImageTimestamp, out var imageTs))
                {
                    // Allow for a small buffer (e.g., 5 seconds) just in case, but prefer strict bounds.
                    // If timestamp is more than 5 seconds past video end, consider it invalid.
                    if (imageTs.TotalSeconds > videoInfo.Duration.TotalSeconds + 5) 
                    {
                        AddLog($"  ⚠️ Timestamp de imagem ({section.ImageTimestamp}) para '{section.Title}' excede a duração do vídeo ({videoInfo.Duration:hh\\:mm\\:ss}). Ajustando para null para evitar erros de captura.");
                        section.ImageTimestamp = null; // Set to null to skip screenshot for this section
                    }
                }
            }
            AddLog("✅ Validação de timestamps concluída.");

            // --- Step 3: Image Capture ---
            var sectionsWithImages = tutorialSections.Where(s => !string.IsNullOrEmpty(s.ImageTimestamp)).ToList();
            if (sectionsWithImages.Any())
            {
                AddLog($"📸 Capturando {sectionsWithImages.Count} prints usando Puppeteer (Direct Bypass)...");
                // Pass videoInfo.Duration to the screenshot method
                await CaptureScreenshotsWithPuppeteerAsync(request.VideoUrl, tutorialSections, tempDir, videoInfo.Duration);
            }
            else
            {
                AddLog("⚠️ Nenhuma tag [SCREENSHOT] foi gerada pela IA, ou todas foram invalidadas.");
            }

            // --- Step 4: PDF Generation ---
            AddLog("📄 Gerando PDF final com QuestPDF...");
            var pdfBytes = GeneratePdf(docTitle, request.VideoUrl, tutorialSections, category);

            AddLog("🎉 Processamento concluído com sucesso!");

            return new AnalysisResponse
            {
                Status = "success",
                VideoTitle = originalTitle,
                DocumentTitle = docTitle,
                Category = category,
                Transcript = transcript,
                TutorialSections = tutorialSections,
                PdfData = pdfBytes,
                DebugSteps = new List<string>(_debugSteps),
                RawLlmResponse = rawLlmResponse,
                Analysis = "Tutorial gerado com sucesso!"
            };
        }
        catch (Exception ex)
        {
            AddLog($"❌ ERRO: {ex.Message}");
            return new AnalysisResponse 
            { 
                Status = "error", 
                ErrorMessage = ex.Message,
                DebugSteps = new List<string>(_debugSteps),
                RawLlmResponse = rawLlmResponse
            };
        }
        finally
        {
            if (Directory.Exists(tempDir))
            {
                try { Directory.Delete(tempDir, true); } catch { }
            }
        }
    }

    private async Task<(string transcript, string title)> GetTranscriptViaYtDlpAsync(string url, string language, string outputDir)
    {
        var ytDlpPath = GetYtDlpPath();
        // Use a safe output template to avoid filesystem issues, but we want the title.
        // Better: Fetch title separately or read metadata json.
        // Let's stick to filename trick but ensure safe chars. 
        // Actually, just fetch title with --print title
        
        // 1. Fetch Title
        var titleStartInfo = new ProcessStartInfo
        {
            FileName = ytDlpPath,
            Arguments = $"--print title \"{url}\"",
            RedirectStandardOutput = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };
        var pTitle = Process.Start(titleStartInfo);
        var title = (await pTitle!.StandardOutput.ReadToEndAsync()).Trim();
        await pTitle.WaitForExitAsync();
        if (string.IsNullOrEmpty(title)) title = "Video Analysis";

        // 2. Fetch Subs
        var arguments = $"--skip-download --write-sub --write-auto-sub --sub-lang {language},en --sub-format vtt --output \"%(id)s\" \"{url}\"";
        
        var startInfo = new ProcessStartInfo
        {
            FileName = ytDlpPath,
            Arguments = arguments,
            WorkingDirectory = outputDir,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        using var proc = Process.Start(startInfo);
        await proc.WaitForExitAsync();

        var vttFile = Directory.GetFiles(outputDir, "*.vtt").FirstOrDefault();
        if (vttFile == null) return (string.Empty, title);

        return (ParseVttToText(await File.ReadAllTextAsync(vttFile)), title);
    }

    private string ParseVttToText(string vttContent)
    {
        var lines = vttContent.Split('\n');
        var textLines = new List<string>();
        var seen = new HashSet<string>();

        foreach (var line in lines)
        {
            var l = line.Trim();
            if (string.IsNullOrWhiteSpace(l) || l.StartsWith("WEBVTT") || l.StartsWith("NOTE") || l.Contains("-->")) continue;
            l = Regex.Replace(l, @"<[^>]*>", "");
            if (!seen.Contains(l)) { textLines.Add(l); seen.Add(l); }
        }
        return string.Join(" ", textLines);
    }

    private async Task<(List<TutorialSection> sections, string rawJson, string category, string docTitle)> GenerateTutorialContentAsync(string transcript, string originalTitle, string inputLanguage, string? outputLanguage, TimeSpan videoDuration)
    {
        var langMap = new Dictionary<string, string>
        {
            {"en", "English"}, {"pt", "Portuguese (Brazilian)"}, {"es", "Spanish"},
            {"fr", "French"}, {"de", "German"}, {"it", "Italian"},
            {"ja", "Japanese"}, {"ko", "Korean"}, {"zh", "Chinese"}
        };
        var outputLang = string.IsNullOrWhiteSpace(outputLanguage) ? inputLanguage : outputLanguage;
        var outputLangName = langMap.GetValueOrDefault(outputLang, outputLang);

        var chatService = _kernel.GetRequiredService<IChatCompletionService>();

        // Pre-format video duration strings to avoid potential issues in interpolated string
        string formattedVideoDuration = videoDuration.ToString("hh\\:mm\\:ss", System.Globalization.CultureInfo.InvariantCulture);
        string totalSecondsVideoDuration = videoDuration.TotalSeconds.ToString(System.Globalization.CultureInfo.InvariantCulture);


        var prompt = $@"
Você é um Editor Chefe e Analista de Conteúdo Sênior.
Receberá:
A) TÍTULO ORIGINAL: {originalTitle}
B) TRANSCRIÇÃO: {transcript[..Math.Min(transcript.Length, 20000)]}
C) DURAÇÃO TOTAL DO VÍDEO: {formattedVideoDuration} ({totalSecondsVideoDuration} segundos)

SUA MISSÃO:
1. **Classificar** o vídeo em: 'TUTORIAL', 'MEETING', 'LECTURE' ou 'OTHER'.
2. **Criar um Título Profissional**:
    - Use o TÍTULO ORIGINAL como base.
    - Remova clickbaits, emojis e CAPS LOCK excessivo.
    - O título deve parecer o de um documento técnico ou ata oficial.
3. **Estruturar o Conteúdo**:
    - Converta o conteúdo em um texto educativo e denso.
    - Identifique momentos visuais críticos e insira `[SCREENSHOT: HH:MM:SS]` no final do parágrafo correspondente.
    - **IMPORTANTE:** Os timestamps `HH:MM:SS` para os `[SCREENSHOT]` **NÃO DEVEM, EM HIPÓTESE ALGUMA, EXCEDER A DURAÇÃO TOTAL DO VÍDEO** ({formattedVideoDuration}). Se um momento visual crítico ocorrer perto do final do vídeo, use um timestamp que esteja dentro da duração total.

**IMPORTANTE: Todo o texto de saída (documentTitle, títulos das seções e conteúdo) DEVE ser escrito em {outputLangName}.**

SAÍDA JSON OBRIGATÓRIA:
{{
  ""category"": ""TUTORIAL | MEETING | LECTURE | OTHER"",
  ""documentTitle"": ""Título Profissional Gerado"",
  ""sections"": [
    {{
       ""title"": ""Título da Seção"",
       ""content"": ""Texto explicativo detalhado... [SCREENSHOT: 00:05:30]""
    }}
  ]
}}";

        var result = await chatService.GetChatMessageContentAsync(prompt);
        var json = result.Content?.Trim() ?? "{}";
        // Extract JSON from LLM response — handles text before/after the JSON block
        var jsonMatch = Regex.Match(json, @"\{[\s\S]*\}", RegexOptions.Singleline);
        if (jsonMatch.Success)
            json = jsonMatch.Value;

        var sections = new List<TutorialSection>();
        string category = "OTHER";
        string docTitle = originalTitle;

        try {
            using var doc = JsonDocument.Parse(json);
            var root = doc.RootElement;
            
            if (root.TryGetProperty("category", out var catEl)) category = catEl.GetString() ?? "OTHER";
            if (root.TryGetProperty("documentTitle", out var titleEl)) docTitle = titleEl.GetString() ?? originalTitle;

            foreach (var el in root.GetProperty("sections").EnumerateArray()) {
                var content = el.GetProperty("content").GetString() ?? "";
                var ts = ExtractTimestamp(content);
                sections.Add(new TutorialSection { 
                    Title = el.GetProperty("title").GetString() ?? "", 
                    Content = content.Replace($"[SCREENSHOT: {ts}]", "").Trim(), 
                    ImageTimestamp = ts 
                });
            }
        } catch { }
        return (sections, json, category, docTitle);
    }

    private string? ExtractTimestamp(string text)
    {
        var match = Regex.Match(text, @"\[SCREENSHOT:\s*(\d{2}:\d{2}:\d{2})\]");
        return match.Success ? match.Groups[1].Value : null;
    }

    private async Task<string?> GetRawVideoStreamUrl(string videoUrl)
    {
        var ytDlpPath = GetYtDlpPath();
        var startInfo = new ProcessStartInfo
        {
            FileName = ytDlpPath,
            Arguments = $"-g -f b \"{videoUrl}\"",
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        using var proc = Process.Start(startInfo);
        if (proc == null) return null;
        var url = await proc.StandardOutput.ReadLineAsync();
        await proc.WaitForExitAsync();
        return url?.Trim();
    }

    private async Task CaptureScreenshotsWithPuppeteerAsync(string videoUrl, List<TutorialSection> sections, string outputDir, TimeSpan videoDuration)
    {
        var sectionsWithImages = sections.Where(s => !string.IsNullOrEmpty(s.ImageTimestamp)).ToList();
        if (!sectionsWithImages.Any()) return;

        AddLog("🔍 Obtendo link direto do vídeo (Bypass YouTube Player)...");
        var rawVideoUrl = await GetRawVideoStreamUrl(videoUrl);
        if (string.IsNullOrEmpty(rawVideoUrl))
        {
            AddLog("❌ Falha ao obter link direto. As capturas de tela serão ignoradas.");
            return;
        }

        try
        {
            using var browser = await Puppeteer.LaunchAsync(new LaunchOptions { Headless = true, Args = new[] { "--no-sandbox", "--window-size=1280,720" } });
            using var page = await browser.NewPageAsync();
            await page.SetViewportAsync(new ViewPortOptions { Width = 1280, Height = 720 });

            var htmlContent = $@"
                <html>
                <body style='margin:0; background:black; overflow:hidden;'>
                    <video id='raw-player' width='1280' height='720' muted preload='auto'>
                        <source src='{rawVideoUrl}' type='video/mp4'>
                    </video>
                </body>
                </html>";
            await page.SetContentAsync(htmlContent);
            await page.WaitForSelectorAsync("#raw-player");

            // Use the passed videoDuration instead of evaluating it from the page
            AddLog($"🎥 Duração total do vídeo (passada): {videoDuration:hh\\:mm\\:ss}");

            // Loop with index for unique identifiers
            for (int i = 0; i < sectionsWithImages.Count; i++)
            {
                var section = sectionsWithImages[i];
                // ImageTimestamp might be null due to earlier validation
                if (string.IsNullOrEmpty(section.ImageTimestamp))
                {
                    AddLog($"📸 Pulando captura para seção '{section.Title}' pois o timestamp foi invalidado.");
                    continue;
                }

                if (TimeSpan.TryParse(section.ImageTimestamp, out var ts))
                {
                    AddLog($"📸 Processando captura para {section.ImageTimestamp} ('{section.Title}')");
                    var targetSeconds = (int)ts.TotalSeconds;
                    
                    var candidates = new List<(byte[] ImageData, double Score, int Time, string Hash, int Size)>();
                    
                    // "Best of 3" capture window: T-1, T, T+1 seconds
                    var timeOffsets = new[] { -1, 0, 1 };

                    foreach (var offset in timeOffsets)
                    {
                        var captureTime = Math.Max(0, targetSeconds + offset);
                        
                        // Ensure captureTime does not exceed video duration
                        if (captureTime > videoDuration.TotalSeconds + 5) // Add a small buffer for safety
                        {
                            AddLog($"  - ⚠️ Tempo de captura {captureTime}s excede a duração do vídeo ({videoDuration.TotalSeconds:F2}s). Ignorando este candidato.");
                            continue;
                        }

                        try
                        {
                            AddLog($"  - Solicitando seek para {captureTime}s (candidato para {section.ImageTimestamp}).");
                            // 1. Seek to the target time
                            await page.EvaluateFunctionAsync(@"(s) => {{
                                const video = document.getElementById('raw-player');
                                video.currentTime = s;
                            }}", captureTime);
                            
                            // 2. Intelligent Wait: Wait for the video to have enough data to play
                            await page.WaitForFunctionAsync("() => document.getElementById('raw-player').readyState >= 3", new WaitForFunctionOptions { Timeout = 10000 });
                            
                            var actualCurrentTime = await page.EvaluateFunctionAsync<double>("() => document.getElementById('raw-player').currentTime");
                            AddLog($"    -> Buscado para {captureTime}s. CurrentTime real pós-seek: {actualCurrentTime:F2}s.");

                            // 3. Capture screenshot into memory
                            var screenshotData = await page.ScreenshotDataAsync(new ScreenshotOptions { Type = ScreenshotType.Jpeg, Quality = 90 });
                            
                            // Calculate MD5 hash
                            string hash;
                            using (var md5 = MD5.Create())
                            {
                                var hashBytes = md5.ComputeHash(screenshotData);
                                hash = BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant();
                            }
                            AddLog($"    -> Imagem Candidata ({captureTime}s): {screenshotData.Length} bytes, Hash MD5: {hash}");

                            // 4. Score the image
                            var score = CalculateImageClarityScore(screenshotData);
                            AddLog($"  - Candidato {captureTime}s: Score de claridade = {score:F2}");

                            if (score > 0)
                            {
                                candidates.Add((screenshotData, score, captureTime, hash, screenshotData.Length));
                            }
                        }
                        catch (WaitTaskTimeoutException)
                        {
                            AddLog($"  - ⚠️ Timeout esperando pelo frame em {captureTime}s. Ignorando.");
                        }
                        catch (Exception ex)
                        {
                            AddLog($"  - ❌ Erro ao capturar frame em {captureTime}s: {ex.Message}");
                        }
                    }

                    if (candidates.Any())
                    {
                        // Select the best image based on the highest score
                        var bestCandidate = candidates.OrderByDescending(c => c.Score).First();
                        section.ImageData = bestCandidate.ImageData;
                        AddLog($"  => ✅ Selecionado frame de {bestCandidate.Time}s (Score: {bestCandidate.Score:F2}, Hash: {bestCandidate.Hash}) para o timestamp {section.ImageTimestamp}.");
                    }
                    else
                    {
                        AddLog($"  => ❌ Falha ao capturar um frame válido para {section.ImageTimestamp}. O PDF usará um placeholder.");
                        section.ImageData = null; // Ensure it's null if all attempts fail
                    }
                }
            }
        }
        catch (Exception ex)
        {
            AddLog($"❌ Erro irrecuperável no Puppeteer: {ex.Message}. As capturas de tela restantes serão abortadas.");
        }
    }

    private double CalculateImageClarityScore(byte[] imageBytes)
    {
        if (imageBytes == null || imageBytes.Length == 0)
            return -1.0;

        try
        {
            // Use SKBitmap.Decode for robust image format handling
            using var image = SKBitmap.Decode(imageBytes);
            if (image == null || image.Width == 0 || image.Height == 0)
            {
                _logger.LogWarning("SkiaSharp failed to decode image or image is empty.");
                return -1.0;
            }

            var brightnessValues = new List<float>(image.Width * image.Height);
            
            // Using GetPixel is simpler than handling Pixels array for this use case
            for (int y = 0; y < image.Height; y++)
            {
                for (int x = 0; x < image.Width; x++)
                {
                    var p = image.GetPixel(x, y);
                    // Luma calculation (standard formula for perceived brightness)
                    var brightness = (p.Red * 0.299f) + (p.Green * 0.587f) + (p.Blue * 0.114f);
                    brightnessValues.Add(brightness);
                }
            }
            
            if (!brightnessValues.Any()) return 0.0;

            var avg = brightnessValues.Average();
            var sumOfSquares = brightnessValues.Sum(b => Math.Pow(b - avg, 2));
            var stdDev = Math.Sqrt(sumOfSquares / brightnessValues.Count);

            // A very low standard deviation indicates a uniform image (likely black, white, or single color)
            return stdDev;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error calculating image clarity score.");
            // If SkiaSharp throws an exception, it's a bad image.
            return -1.0;
        }
    }

    private byte[] GeneratePdf(string docTitle, string videoUrl, List<TutorialSection> sections, string category)
    {
        var categoryColor = category switch 
        {
            "TUTORIAL" => Colors.Green.Medium,
            "MEETING" => Colors.Orange.Medium,
            "LECTURE" => Colors.Purple.Medium,
            _ => Colors.Blue.Medium
        };

        var document = Document.Create(container =>
        {
            container.Page(page =>
            {
                page.Margin(2, Unit.Centimetre);
                page.DefaultTextStyle(x => x.FontSize(11).FontFamily("Segoe UI").Fallback(f => f.FontFamily("Microsoft YaHei")));

                page.Header().Column(c => 
                {
                    c.Item().Row(row => 
                    {
                        row.RelativeItem().Text(docTitle).SemiBold().FontSize(20).FontColor(Colors.Black);
                        row.ConstantItem(100).AlignRight().Text(category).Bold().FontSize(10).FontColor(categoryColor);
                    });
                    c.Item().PaddingTop(5).LineHorizontal(1).LineColor(Colors.Grey.Lighten2);
                });

                page.Content().PaddingVertical(1, Unit.Centimetre).Column(column =>
                {
                    column.Item().Text($"Fonte: {videoUrl}").Italic().FontSize(9).FontColor(Colors.Grey.Medium);
                    column.Item().PaddingBottom(20);

                    foreach (var section in sections)
                    {
                        column.Item().Text(section.Title).Bold().FontSize(14).FontColor(categoryColor);
                        column.Item().Text(text => { text.Span(section.Content); });
                        
                        if (section.ImageData != null)
                        {
                            column.Item().PaddingVertical(10).Image(section.ImageData).FitWidth();
                        }
                        else if (!string.IsNullOrEmpty(section.ImageTimestamp))
                        {
                            // Placeholder for missing image (Graceful Degradation)
                            column.Item().PaddingVertical(10)
                                  .Background(Colors.Grey.Lighten3)
                                  .Height(100)
                                  .AlignCenter()
                                  .AlignMiddle()
                                  .Text($"[Imagem Indisponível: {section.ImageTimestamp}]")
                                  .FontSize(10)
                                  .FontColor(Colors.Grey.Darken2);
                        }

                        column.Item().PaddingBottom(15);
                    }
                });

                page.Footer().AlignCenter().Text(x => { x.Span("Gerado por VideoStudy.app - "); x.CurrentPageNumber(); });
            });
        });
        return document.GeneratePdf();
    }
}