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

namespace VideoStudy.API.Services;

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

    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();
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Failed to download Chromium.");
            }
        });
    }

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

        try
        {
            yield return new AnalysisEvent { ProgressPercentage = 5, Message = "Iniciando análise técnica..." };

            var videoInfo = await GetVideoInfoAsync(request.VideoUrl, cancellationToken);
            yield return new AnalysisEvent { ProgressPercentage = 10, Message = $"Processando: {videoInfo.Title}" };

            yield return new AnalysisEvent { ProgressPercentage = 15, Message = "Obtendo transcrição..." };
            var (transcript, _) = await GetTranscriptViaYtDlpAsync(request.VideoUrl, request.Language, tempDir);
            if (string.IsNullOrWhiteSpace(transcript)) throw new Exception("Transcrição indisponível.");

            yield return new AnalysisEvent { ProgressPercentage = 40, Message = "IA estruturando conteúdo e gerando resumo..." };
            var (sections, rawJson, category, docTitle, summary) = await GenerateTutorialContentAsync(transcript, videoInfo, request.Language, request.OutputLanguage, cancellationToken);

            var sectionsToCapture = sections.Where(s => !string.IsNullOrEmpty(s.ImageTimestamp)).ToList();
            if (sectionsToCapture.Any())
            {
                yield return new AnalysisEvent { ProgressPercentage = 70, Message = $"Capturando {sectionsToCapture.Count} imagens críticas..." };
                await CaptureScreenshotsInParallelAsync(request.VideoUrl, sectionsToCapture, videoInfo.Duration, cancellationToken);
            }

            yield return new AnalysisEvent { ProgressPercentage = 90, Message = "Gerando PDF..." };
            var pdfBytes = GeneratePdf(docTitle, summary, request.VideoUrl, sections, category);

            var result = new AnalysisResult
            {
                VideoTitle = videoInfo.Title,
                DocumentTitle = docTitle,
                Summary = summary,
                Category = category,
                Transcript = transcript,
                TutorialSections = sections,
                PdfData = pdfBytes,
                RawLlmResponse = rawJson
            };

            yield return new AnalysisEvent { ProgressPercentage = 100, Message = "Concluído!", Result = result };
        }
        finally
        {
            if (Directory.Exists(tempDir)) try { Directory.Delete(tempDir, true); } catch { }
        }
    }

    private async Task CaptureScreenshotsInParallelAsync(string videoUrl, List<TutorialSection> sections, TimeSpan videoDuration, CancellationToken ct)
    {
        var rawUrl = await GetRawVideoStreamUrl(videoUrl);
        if (string.IsNullOrEmpty(rawUrl)) return;
        using var sem = new SemaphoreSlim(3);
        await Task.WhenAll(sections.Select(s => ProcessSingleSection(s, rawUrl, videoDuration, sem, ct)));
    }

    private async Task ProcessSingleSection(TutorialSection section, string rawUrl, TimeSpan duration, SemaphoreSlim sem, CancellationToken ct)
    {
        await sem.WaitAsync(ct);
        try
        {
            using var browser = await Puppeteer.LaunchAsync(new LaunchOptions { Headless = true, Args = new[] { "--no-sandbox" } });
            using var page = await browser.NewPageAsync();
            await page.SetViewportAsync(new ViewPortOptions { Width = 1280, Height = 720 });
            await page.SetContentAsync($"<html><body style='margin:0;background:black;'><video id='v' width='1280' height='720' src='{rawUrl}'></video></body></html>");
            await page.WaitForSelectorAsync("#v");
            
            if (!TimeSpan.TryParse(section.ImageTimestamp, out var ts)) return;
            int target = (int)ts.TotalSeconds;
            var candidates = new List<(byte[] Data, double Score)>();

            foreach (var offset in new[] { 0, -1, 1 })
            {
                ct.ThrowIfCancellationRequested();
                int time = Math.Max(0, target + offset);
                if (time > duration.TotalSeconds) continue;
                try {
                    await page.EvaluateFunctionAsync($"(s) => document.getElementById('v').currentTime = s", time);
                    await page.WaitForFunctionAsync("() => document.getElementById('v').readyState >= 3", new WaitForFunctionOptions { Timeout = 5000 });
                    var data = await page.ScreenshotDataAsync(new ScreenshotOptions { Type = ScreenshotType.Jpeg, Quality = 85 });
                    var score = CalculateImageClarityScore(data);
                    if (score > 10) candidates.Add((data, score));
                } catch { }
            }
            if (candidates.Any()) section.ImageData = candidates.OrderByDescending(c => c.Score).First().Data;
        }
        finally { sem.Release(); }
    }

    public async Task<VideoInfo> GetVideoInfoAsync(string url, CancellationToken ct)
    {
        var path = GetYtDlpPath();
        var proc = Process.Start(new ProcessStartInfo { FileName = path, Arguments = $"--print title --print channel --print duration --print thumbnail --print description \"{url}\"", RedirectStandardOutput = true, UseShellExecute = false, CreateNoWindow = true });
        await proc!.WaitForExitAsync(ct);
        var lines = (await proc.StandardOutput.ReadToEndAsync()).Split('\n', StringSplitOptions.RemoveEmptyEntries);
        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[1].Trim(), Duration = TimeSpan.FromSeconds(sec), ThumbnailUrl = lines[3].Trim(), Description = lines.Length > 4 ? string.Join("\n", lines.Skip(4)).Trim() : "", Url = url };
    }

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

    private string ParseVttToText(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 async Task<(List<TutorialSection> sections, string rawJson, string category, string docTitle, string summary)> GenerateTutorialContentAsync(string transcript, VideoInfo video, string inLang, string? outLang, CancellationToken ct)
    {
        var langMap = new Dictionary<string, string> { {"en", "English"}, {"pt", "Portuguese (Brazilian)"}, {"es", "Spanish"} };
        var outName = langMap.GetValueOrDefault(outLang ?? inLang, "Portuguese (Brazilian)");
        var dur = video.Duration.ToString(@"hh\:mm\:ss");

        var prompt = $@"
Você é um ANALISTA TÉCNICO DE CONTEÚDO especializado em converter vídeos em documentação estruturada.

### REGRAS DE OURO:
1. NÃO RESUMA: Transforme cada explicação do vídeo em um tópico técnico detalhado e denso.
2. ISONOMIA: Dedique o mesmo nível de profundidade a todos os tópicos. Se o vídeo explica 5 curiosidades, gere 5 seções extensas.
3. FOCO NO TÍTULO: Garanta que o tema ""{video.Title}"" seja a seção de maior clareza e detalhamento.
4. SCREENSHOTS: Insira `[SCREENSHOT: HH:MM:SS]` ao final de parágrafos que descrevam algo visualmente importante. (Limite: {dur}).

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

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

        var result = await _kernel.GetRequiredService<IChatCompletionService>().GetChatMessageContentAsync(prompt, cancellationToken: ct);
        var json = Regex.Match(result.Content ?? "{}", @"\{[\s\S]*\}").Value;
        using var doc = JsonDocument.Parse(json);
        var root = doc.RootElement;
        
        var sections = root.GetProperty("sections").EnumerateArray().Select(el => new TutorialSection {
            Title = el.GetProperty("title").GetString() ?? "",
            Content = Regex.Replace(el.GetProperty("content").GetString() ?? "", @"\[SCREENSHOT: \d{2}:\d{2}:\d{2}\]", "").Trim(),
            ImageTimestamp = Regex.Match(el.GetProperty("content").GetString() ?? "", @"\[SCREENSHOT:\s*(\d{2}:\d{2}:\d{2})\]").Groups[1].Value
        }).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 proc = Process.Start(new ProcessStartInfo { FileName = GetYtDlpPath(), Arguments = $"-g -f b \"{url}\"", RedirectStandardOutput = true, UseShellExecute = false, CreateNoWindow = true });
        return (await proc!.StandardOutput.ReadLineAsync())?.Trim();
    }

    private double CalculateImageClarityScore(byte[] bytes)
    {
        try {
            using var img = SKBitmap.Decode(bytes);
            var lumas = new List<float>();
            for (int y = 0; y < img.Height; y += 20) for (int x = 0; x < img.Width; x += 20) {
                var p = img.GetPixel(x,y);
                lumas.Add(p.Red * 0.299f + p.Green * 0.587f + p.Blue * 0.114f);
            }
            var avg = lumas.Average();
            return Math.Sqrt(lumas.Sum(v => Math.Pow(v - avg, 2)) / lumas.Count);
        } catch { return -1; }
    }

    private byte[] GeneratePdf(string title, string summary, string url, List<TutorialSection> sections, string category)
    {
        var color = category switch { "TUTORIAL" => Colors.Green.Medium, "MEETING" => Colors.Orange.Medium, _ => Colors.Blue.Medium };
        return Document.Create(container => {
            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 => {
                    // Resumo Section
                    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(); });
            });
        }).GeneratePdf();
    }
}