feat(ads/seo/release): v1.2.0 with live Google Ads, isolated ad profile, ads.txt, and SEO/AEO/GEO optimization

src/Paca.Core/VideoIntroOutroTrimmer.cs

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+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Text.RegularExpressions;
+
+namespace Paca.Core;
+
+/// <summary>
+/// Detected interval of silence in an audio/video stream.
+/// </summary>
+public sealed record SilenceSpan(double StartSec, double DurationSec, double EndSec);
+
+/// <summary>
+/// Effective playback and export window skipping unwanted intro and outro sections.
+/// </summary>
+public sealed record TrimWindow(double StartSec, double EndSec, double DurationSec);
+
+/// <summary>
+/// Intelligent video trimmer parsing silencedetect logs and producing lossless cuts for intros/outros.
+/// </summary>
+public static class VideoIntroOutroTrimmer
+{
+    private static readonly Regex SilenceStartRegex = new(@"silence_start:\s*([0-9.]+)", RegexOptions.Compiled);
+    private static readonly Regex SilenceEndRegex = new(@"silence_end:\s*([0-9.]+)\s*\|\s*silence_duration:\s*([0-9.]+)", RegexOptions.Compiled);
+
+    /// <summary>
+    /// Parses ffmpeg silencedetect stderr output lines into structured silence spans.
+    /// </summary>
+    public static List<SilenceSpan> ParseSilenceSpans(string ffmpegOutput)
+    {
+        var spans = new List<SilenceSpan>();
+        if (string.IsNullOrWhiteSpace(ffmpegOutput))
+            return spans;
+
+        var startMatches = SilenceStartRegex.Matches(ffmpegOutput);
+        var endMatches = SilenceEndRegex.Matches(ffmpegOutput);
+
+        var count = Math.Min(startMatches.Count, endMatches.Count);
+        for (var i = 0; i < count; i++)
+        {
+            if (double.TryParse(startMatches[i].Groups[1].Value, NumberStyles.Float, CultureInfo.InvariantCulture, out var start) &&
+                double.TryParse(endMatches[i].Groups[1].Value, NumberStyles.Float, CultureInfo.InvariantCulture, out var end) &&
+                double.TryParse(endMatches[i].Groups[2].Value, NumberStyles.Float, CultureInfo.InvariantCulture, out var dur))
+            {
+                spans.Add(new SilenceSpan(start, dur, end));
+            }
+        }
+
+        return spans;
+    }
+
+    /// <summary>
+    /// Calculates safe playback trim window, guaranteeing at least 1 second duration.
+    /// </summary>
+    public static TrimWindow CalculateTrimWindow(double totalDurationSec, double skipIntroSec, double skipOutroSec)
+    {
+        if (totalDurationSec <= 0)
+            return new TrimWindow(0, 1.0, 1.0);
+
+        var start = Math.Max(0, skipIntroSec);
+        var end = Math.Max(0, totalDurationSec - skipOutroSec);
+
+        if (start >= end || (end - start) < 1.0)
+        {
+            start = 0;
+            end = Math.Max(1.0, totalDurationSec);
+        }
+
+        var duration = end - start;
+        return new TrimWindow(start, end, duration);
+    }
+
+    /// <summary>
+    /// Builds ffmpeg CLI argument string for ultra-fast lossless video trimming.
+    /// </summary>
+    public static string BuildLosslessTrimCommandLine(
+        string inputPath,
+        string outputPath,
+        double startSec,
+        double durationSec)
+    {
+        var s = startSec.ToString("F2", CultureInfo.InvariantCulture);
+        var d = durationSec.ToString("F2", CultureInfo.InvariantCulture);
+
+        return $"-ss {s} -i \"{inputPath}\" -t {d} -c copy \"{outputPath}\" -y";
+    }
+}