using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text.Json;
using System.Text.RegularExpressions;
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.ChatCompletion;
using QuestPDF.Fluent;
using QuestPDF.Helpers;
using QuestPDF.Infrastructure;
using VideoStudy.Shared;

namespace VideoStudy.API.Services;

public class AnalysisService
{
    private readonly Kernel _kernel;
    private readonly ILogger<AnalysisService> _logger;
    private readonly IConfiguration _configuration;

    public AnalysisService(Kernel kernel, ILogger<AnalysisService> logger, IConfiguration configuration)
    {
        _kernel = kernel;
        _logger = logger;
        _configuration = configuration;
        QuestPDF.Settings.License = LicenseType.Community;
    }

    private string GetYtDlpPath()
    {
        string exeName = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "yt-dlp.exe" :
                         RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "yt-dlp_macos" : "yt-dlp_linux";

        // Walk up from base directory looking for yt-dlp
        var dir = new DirectoryInfo(AppDomain.CurrentDomain.BaseDirectory);
        for (int i = 0; i < 7; i++)
        {
            var path = Path.Combine(dir.FullName, exeName);
            if (File.Exists(path)) return path;
            var binPath = Path.Combine(dir.FullName, "Binaries", exeName);
            if (File.Exists(binPath)) return binPath;
            if (dir.Parent == null) break;
            dir = dir.Parent;
        }
        return "yt-dlp"; // fallback to PATH
    }

    private string GetCookiesArg()
    {
        var browser = _configuration["YtDlp:CookiesBrowser"];
        return string.IsNullOrWhiteSpace(browser) ? "" : $"--cookies-from-browser {browser}";
    }

    public async IAsyncEnumerable<AnalysisEvent> AnalyzeVideoAsync(AnalysisRequest request, [EnumeratorCancellation] CancellationToken cancellationToken = default)
    {
        var tempDir = Path.Combine(Path.GetTempPath(), "VideoStudy", Guid.NewGuid().ToString());
        Directory.CreateDirectory(tempDir);

        string? errorMessage = null;
        AnalysisResult? finalResult = null;

        yield return new AnalysisEvent { ProgressPercentage = 5, Message = "Obtendo informações do vídeo..." };
        VideoInfo? videoInfo = null;
        try {
            videoInfo = await GetVideoInfoAsync(request.VideoUrl, cancellationToken);
        } catch (Exception ex) {
            errorMessage = $"Erro ao acessar o YouTube: {ex.Message}";
        }

        if (errorMessage == null && videoInfo != null)
        {
            yield return new AnalysisEvent { ProgressPercentage = 10, Message = $"Analisando: {videoInfo.Title}" };

            yield return new AnalysisEvent { ProgressPercentage = 15, Message = "Obtendo transcrição..." };
            string? transcript = null;
            string? transcriptReadable = null;
            try {
                (transcript, transcriptReadable) = await GetTranscriptViaYtDlpAsync(request.VideoUrl, request.Language, tempDir);
                if (string.IsNullOrWhiteSpace(transcript)) errorMessage = "O vídeo não possui transcrição disponível.";
            } catch (Exception ex) {
                errorMessage = $"Erro na transcrição: {ex.Message}";
            }

            if (errorMessage == null && transcript != null)
            {
                yield return new AnalysisEvent { ProgressPercentage = 40, Message = "IA estruturando conteúdo..." };
                List<TutorialSection>? sections = null;
                string? rawJson = null, category = null, docTitle = null, summary = null;

                try {
                    var aiResult = await GenerateTutorialContentAsync(transcript, videoInfo, request.Language, request.OutputLanguage, request.UserContext, cancellationToken);
                    sections = aiResult.sections;
                    rawJson = aiResult.rawJson;
                    category = aiResult.category;
                    docTitle = aiResult.docTitle;
                    summary = aiResult.summary;
                } catch (Exception ex) {
                    errorMessage = $"IA Indisponível: {ex.Message}. Verifique a chave do Groq.";
                }

                if (errorMessage == null && sections != null)
                {
                    var sectionsWithImages = sections.Where(s => !string.IsNullOrEmpty(s.ImageTimestamp)).ToList();
                    if (sectionsWithImages.Any())
                    {
                        yield return new AnalysisEvent { ProgressPercentage = 70, Message = $"Capturando {sectionsWithImages.Count} imagens com FFmpeg..." };
                        try {
                            await CaptureScreenshotsAsync(request.VideoUrl, sectionsWithImages, videoInfo.Duration, cancellationToken);
                        } catch (Exception ex) {
                            _logger.LogWarning(ex, "Falha na captura de screenshots — continuando sem imagens.");
                        }
                    }

                    yield return new AnalysisEvent { ProgressPercentage = 90, Message = "Gerando documento PDF..." };
                    try {
                        var pdfBytes = GeneratePdf(docTitle!, summary!, request.VideoUrl, sections, category!, transcriptReadable);
                        finalResult = new AnalysisResult {
                            VideoTitle = videoInfo.Title,
                            DocumentTitle = docTitle!,
                            Summary = summary!,
                            Category = category!,
                            Transcript = transcript,
                            TutorialSections = sections,
                            PdfData = pdfBytes,
                            RawLlmResponse = rawJson
                        };
                    } catch (Exception ex) {
                        errorMessage = $"Erro ao gerar PDF: {ex.Message}";
                    }
                }
            }
        }

        try { if (Directory.Exists(tempDir)) Directory.Delete(tempDir, true); } catch { }

        if (errorMessage != null) {
            yield return new AnalysisEvent { IsError = true, Message = errorMessage, ProgressPercentage = 100 };
        } else if (finalResult != null) {
            yield return new AnalysisEvent { ProgressPercentage = 100, Message = "Concluído!", Result = finalResult };
        }
    }

    private async Task CaptureScreenshotsAsync(string videoUrl, List<TutorialSection> sections, TimeSpan videoDuration, CancellationToken ct)
    {
        var streamUrl = await GetRawVideoStreamUrl(videoUrl);
        if (string.IsNullOrEmpty(streamUrl)) return;

        using var sem = new SemaphoreSlim(2);
        await Task.WhenAll(sections.Select(s => CaptureFrameAsync(s, streamUrl, videoDuration, sem, ct)));
    }

    private async Task CaptureFrameAsync(TutorialSection section, string streamUrl, TimeSpan duration, SemaphoreSlim sem, CancellationToken ct)
    {
        await sem.WaitAsync(ct);
        var outputFile = Path.Combine(Path.GetTempPath(), $"vs_frame_{Guid.NewGuid()}.jpg");
        try
        {
            if (!TimeSpan.TryParse(section.ImageTimestamp, out var ts) || ts > duration) return;

            var args = $"-ss {ts:hh\\:mm\\:ss} -i \"{streamUrl}\" -frames:v 1 -q:v 2 -y \"{outputFile}\"";
            var psi = new ProcessStartInfo
            {
                FileName = "ffmpeg",
                Arguments = args,
                RedirectStandardError = false,
                UseShellExecute = false,
                CreateNoWindow = true
            };
            using var p = Process.Start(psi)!;
            await p.WaitForExitAsync(ct);

            if (p.ExitCode == 0 && File.Exists(outputFile))
                section.ImageData = await File.ReadAllBytesAsync(outputFile, ct);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Screenshot falhou em {Timestamp}", section.ImageTimestamp);
        }
        finally
        {
            if (File.Exists(outputFile)) File.Delete(outputFile);
            sem.Release();
        }
    }

    public async Task<VideoInfo> GetVideoInfoAsync(string url, CancellationToken ct)
    {
        var ytdlp = GetYtDlpPath();
        var cookies = GetCookiesArg();
        var psi = new ProcessStartInfo
        {
            FileName = ytdlp,
            Arguments = $"{cookies} --print title --print channel --print duration --print thumbnail \"{url}\"",
            RedirectStandardOutput = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };
        using var proc = Process.Start(psi)!;
        await proc.WaitForExitAsync(ct);
        var output = await proc.StandardOutput.ReadToEndAsync(ct);
        var lines = output.Split('\n', StringSplitOptions.RemoveEmptyEntries);
        if (lines.Length < 1) throw new Exception("Falha ao ler dados do vídeo via yt-dlp.");

        double.TryParse(lines.Length > 2 ? lines[2] : "0", System.Globalization.NumberStyles.Any, System.Globalization.CultureInfo.InvariantCulture, out var sec);
        return new VideoInfo
        {
            Title = lines[0].Trim(),
            Author = lines.Length > 1 ? lines[1].Trim() : "",
            Duration = TimeSpan.FromSeconds(sec),
            ThumbnailUrl = lines.Length > 3 ? lines[3].Trim() : "",
            Url = url
        };
    }

    private async Task<(string flat, string readable)> GetTranscriptViaYtDlpAsync(string url, string lang, string dir)
    {
        var ytdlp = GetYtDlpPath();
        var cookies = GetCookiesArg();
        var psi = new ProcessStartInfo
        {
            FileName = ytdlp,
            Arguments = $"{cookies} --skip-download --write-auto-sub --sub-lang {lang},en --sub-format vtt --output \"%(id)s\" \"{url}\"",
            WorkingDirectory = dir,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };
        using var p = Process.Start(psi)!;
        await p.WaitForExitAsync();
        var file = Directory.GetFiles(dir, "*.vtt").FirstOrDefault();
        if (file == null) return ("", "");
        var vtt = await File.ReadAllTextAsync(file);
        return (ParseVttToFlat(vtt), ParseVttToReadable(vtt));
    }

    private string ParseVttToFlat(string vtt)
    {
        var lines = vtt.Split('\n')
            .Select(l => l.Trim())
            .Where(l => !string.IsNullOrEmpty(l) && !l.StartsWith("WEBVTT") && !l.StartsWith("NOTE") && !l.Contains("-->"));
        return string.Join(" ", lines.Select(l => Regex.Replace(l, @"<[^>]*>", ""))).Replace("  ", " ");
    }

    private string ParseVttToReadable(string vtt)
    {
        // Parse cues: timestamp line + text lines
        var cues = new List<(TimeSpan time, string text)>();
        var lines = vtt.Split('\n').Select(l => l.Trim()).ToArray();

        for (int i = 0; i < lines.Length; i++)
        {
            var line = lines[i];
            if (!line.Contains("-->")) continue;

            // Parse start time from "HH:MM:SS.mmm --> HH:MM:SS.mmm"
            var timePart = line.Split("-->")[0].Trim().Replace(',', '.');
            if (!TimeSpan.TryParse(timePart, out var ts)) continue;

            // Collect text lines until blank
            var textLines = new List<string>();
            i++;
            while (i < lines.Length && !string.IsNullOrEmpty(lines[i]) && !lines[i].Contains("-->"))
            {
                var t = Regex.Replace(lines[i], @"<[^>]*>", "").Trim();
                if (!string.IsNullOrEmpty(t)) textLines.Add(t);
                i++;
            }
            i--; // step back, outer loop will increment

            if (textLines.Count > 0)
                cues.Add((ts, string.Join(" ", textLines)));
        }

        if (cues.Count == 0) return ParseVttToFlat(vtt);

        // Merge consecutive cues with same/similar text (VTT often duplicates lines)
        var merged = new List<(TimeSpan time, string text)>();
        foreach (var cue in cues)
        {
            if (merged.Count > 0 && merged[^1].text == cue.text) continue;
            merged.Add(cue);
        }

        // Group into paragraphs every ~60 seconds
        var sb = new System.Text.StringBuilder();
        TimeSpan? paraStart = null;
        var paraWords = new List<string>();

        void FlushParagraph()
        {
            if (paraWords.Count == 0) return;
            sb.AppendLine($"[{paraStart!.Value:hh\\:mm\\:ss}]  {string.Join(" ", paraWords)}");
            sb.AppendLine();
            paraWords.Clear();
            paraStart = null;
        }

        foreach (var (time, text) in merged)
        {
            if (paraStart == null) paraStart = time;
            paraWords.Add(text);
            if ((time - paraStart.Value).TotalSeconds >= 60)
                FlushParagraph();
        }
        FlushParagraph();

        return sb.ToString().TrimEnd();
    }

    private async Task<(List<TutorialSection> sections, string rawJson, string category, string docTitle, string summary)>
        GenerateTutorialContentAsync(string transcript, VideoInfo video, string inLang, string? outLang, string? userContext, CancellationToken ct)
    {
        var langMap = new Dictionary<string, string> { { "en", "English" }, { "pt", "Portuguese (Brazilian)" }, { "es", "Spanish" }, { "fr", "French" } };
        var outName = langMap.GetValueOrDefault(outLang ?? inLang, "Portuguese (Brazilian)");
        var dur = video.Duration.ToString(@"hh\:mm\:ss");
        var contextSection = string.IsNullOrWhiteSpace(userContext)
            ? ""
            : $"\n### CONTEXTO DO USUÁRIO:\n{userContext}\nUse este contexto para ajustar o nível de detalhe, linguagem e foco da análise.\n";

        var prompt = $@"Você é um ANALISTA TÉCNICO DE CONTEÚDO especializado em converter vídeos em documentação estruturada.
{contextSection}
### REGRAS:
1. Transforme cada explicação em um tópico técnico detalhado — NÃO resuma demais.
2. Dedique o mesmo nível de profundidade a todos os tópicos.
3. Garanta que o tema ""{video.Title}"" seja a seção de maior clareza.
4. Insira `[SCREENSHOT: HH:MM:SS]` ao final de parágrafos com algo visualmente importante. (Limite: {dur})

### DADOS:
- Título: {video.Title}
- Transcrição: {transcript[..Math.Min(transcript.Length, 25000)]}

### FORMATO DE SAÍDA (JSON):
{{
  ""category"": ""TUTORIAL | LECTURE | OTHER"",
  ""shortTitle"": ""Título Curto e Limpo"",
  ""summary"": ""Um parágrafo de até 4 linhas resumindo o valor principal do vídeo."",
  ""sections"": [
    {{ ""title"": ""Título do Tópico"", ""content"": ""Explicação densa... [SCREENSHOT: HH:MM:SS]"" }}
  ]
}}
Escreva tudo em {outName}.";

        var chatService = _kernel.GetRequiredService<IChatCompletionService>();
        var result = await chatService.GetChatMessageContentAsync(prompt, cancellationToken: ct);

        string rawContent = result.Content ?? "{}";
        _logger.LogInformation("Resposta bruta da IA: {RawContent}", rawContent);

        var jsonMatch = Regex.Match(rawContent, @"\{[\s\S]*\}");
        if (!jsonMatch.Success) throw new Exception("A IA não retornou um JSON válido.");

        string json = jsonMatch.Value;
        using var doc = JsonDocument.Parse(json);
        var root = doc.RootElement;

        var sections = root.GetProperty("sections").EnumerateArray().Select(el =>
        {
            var content = el.GetProperty("content").GetString() ?? "";
            var tsMatch = Regex.Match(content, @"\[SCREENSHOT:\s*(\d{2}:\d{2}:\d{2})\]");
            return new TutorialSection
            {
                Title = el.GetProperty("title").GetString() ?? "",
                Content = Regex.Replace(content, @"\[SCREENSHOT: \d{2}:\d{2}:\d{2}\]", "").Trim(),
                ImageTimestamp = tsMatch.Success ? tsMatch.Groups[1].Value : null
            };
        }).ToList();

        return (sections, json,
            root.GetProperty("category").GetString() ?? "OTHER",
            root.GetProperty("shortTitle").GetString() ?? video.Title,
            root.GetProperty("summary").GetString() ?? "");
    }

    private async Task<string?> GetRawVideoStreamUrl(string url)
    {
        var ytdlp = GetYtDlpPath();
        var cookies = GetCookiesArg();
        var psi = new ProcessStartInfo
        {
            FileName = ytdlp,
            Arguments = $"{cookies} -g -f \"bv*[height<=720][ext=mp4]/bv*[height<=720]/b\" \"{url}\"",
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };
        using var proc = Process.Start(psi)!;
        var line = await proc.StandardOutput.ReadLineAsync();
        await proc.WaitForExitAsync();
        return line?.Trim();
    }

    private byte[] GeneratePdf(string title, string summary, string url, List<TutorialSection> sections, string category, string? transcriptReadable = null)
    {
        var color = category switch { "TUTORIAL" => Colors.Green.Medium, "LECTURE" => Colors.Orange.Medium, _ => Colors.Blue.Medium };
        return Document.Create(container =>
        {
            // Main content page
            container.Page(page =>
            {
                page.Margin(2, Unit.Centimetre);
                page.DefaultTextStyle(x => x.FontSize(11).FontFamily("Segoe UI"));
                page.Header().Column(c =>
                {
                    c.Item().Row(r =>
                    {
                        r.RelativeItem().Text(title).SemiBold().FontSize(22).FontColor(Colors.Blue.Darken3);
                        r.ConstantItem(80).AlignRight().Text(category).Bold().FontSize(10).FontColor(color);
                    });
                    c.Item().PaddingTop(5).LineHorizontal(1).LineColor(Colors.Grey.Lighten2);
                });
                page.Content().PaddingVertical(1, Unit.Centimetre).Column(col =>
                {
                    col.Item().Background(Colors.Grey.Lighten4).Padding(10).Column(rc =>
                    {
                        rc.Item().Text("Resumo").Bold().FontSize(12).FontColor(Colors.Blue.Medium);
                        rc.Item().PaddingTop(2).Text(summary).Italic();
                    });
                    col.Item().PaddingTop(10).Text(t => { t.Span("Fonte: ").SemiBold(); t.Span(url).Italic().FontSize(9); });

                    foreach (var s in sections)
                    {
                        col.Item().PaddingTop(20).Text(s.Title).Bold().FontSize(16).FontColor(color);
                        col.Item().PaddingTop(5).Text(s.Content).LineHeight(1.5f);
                        if (s.ImageData != null) col.Item().PaddingVertical(10).Image(s.ImageData).FitWidth();
                    }
                });
                page.Footer().AlignCenter().Text(x => { x.Span("VideoStudy.app — "); x.CurrentPageNumber(); });
            });

            // Transcript appendix page
            if (!string.IsNullOrWhiteSpace(transcriptReadable))
            {
                container.Page(page =>
                {
                    page.Margin(2, Unit.Centimetre);
                    page.DefaultTextStyle(x => x.FontSize(10).FontFamily("Segoe UI"));
                    page.Header().Column(c =>
                    {
                        c.Item().Row(r =>
                        {
                            r.RelativeItem().Text("Apêndice — Transcrição").SemiBold().FontSize(18).FontColor(Colors.Grey.Darken2);
                            r.ConstantItem(80).AlignRight().Text(title).FontSize(8).FontColor(Colors.Grey.Medium).Italic();
                        });
                        c.Item().PaddingTop(5).LineHorizontal(1).LineColor(Colors.Grey.Lighten2);
                        c.Item().PaddingTop(4).Text("Cada parágrafo representa aproximadamente 60 segundos. O timestamp indica o início do trecho.")
                            .FontSize(8).Italic().FontColor(Colors.Grey.Medium);
                    });
                    page.Content().PaddingVertical(1, Unit.Centimetre).Column(col =>
                    {
                        foreach (var paragraph in transcriptReadable.Split("\n\n", StringSplitOptions.RemoveEmptyEntries))
                        {
                            var trimmed = paragraph.Trim();
                            if (string.IsNullOrEmpty(trimmed)) continue;

                            // Split timestamp from text: "[HH:MM:SS]  rest of text"
                            var bracketEnd = trimmed.IndexOf(']');
                            if (bracketEnd > 0 && trimmed.StartsWith('['))
                            {
                                var timestamp = trimmed[..(bracketEnd + 1)];
                                var text = trimmed[(bracketEnd + 1)..].Trim();
                                col.Item().PaddingBottom(8).Column(p =>
                                {
                                    p.Item().Text(timestamp).Bold().FontSize(9).FontColor(Colors.Blue.Medium);
                                    p.Item().PaddingTop(2).Text(text).LineHeight(1.5f);
                                });
                            }
                            else
                            {
                                col.Item().PaddingBottom(8).Text(trimmed).LineHeight(1.5f);
                            }
                        }
                    });
                    page.Footer().AlignCenter().Text(x => { x.Span("VideoStudy.app — "); x.CurrentPageNumber(); });
                });
            }
        }).GeneratePdf();
    }
}