Using correct map_metadata dynamically

FFMpegCore.Test/MetaDataBuilderTests.cs

@@ -4,8 +4,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Text;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
 namespace FFMpegCore.Test
@@ -50,5 +52,29 @@ public void TestMetaDataBuilderIntegrity()
             Assert.IsTrue(serialized.Contains("title=Chapter 01", StringComparison.OrdinalIgnoreCase));
             Assert.IsTrue(serialized.Contains("album_artist=Pachelbel", StringComparison.OrdinalIgnoreCase));
         }
+
+        [TestMethod]
+        public void TestMapMetadata()
+        {
+            //-i "whaterver0" // index: 0
+            //-f concat -safe 0
+            //-i "\AppData\Local\Temp\concat_b511f2bf-c4af-4f71-b9bd-24d706bf4861.txt"   // index: 1
+            //-i "\AppData\Local\Temp\metadata_210d3259-3d5c-43c8-9786-54b5c414fa70.txt" // index: 2
+            //-map_metadata 2
+
+            var text0 = FFMpegArguments.FromFileInput("whaterver0")
+                .AddMetaData("WhatEver3")
+                .Text;
+
+            var text1 = FFMpegArguments.FromFileInput("whaterver0")
+                .AddDemuxConcatInput(new[] { "whaterver", "whaterver1" })
+                .AddMetaData("WhatEver3")
+                .Text;
+
+
+
+            Assert.IsTrue(Regex.IsMatch(text0, "metadata_[0-9a-f-]+\\.txt\" -map_metadata 1"), "map_metadata index is calculated incorrectly.");
+            Assert.IsTrue(Regex.IsMatch(text1, "metadata_[0-9a-f-]+\\.txt\" -map_metadata 2"), "map_metadata index is calculated incorrectly.");
+        }
     }
 }

FFMpegCore/Extend/StringExtensions.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Text;
 
 namespace FFMpegCore.Extend
@@ -66,5 +67,51 @@ public static string Replace(this string str, Dictionary<char, string> replaceLi
 
             return parsedString.ToString();
         }
+
+        /// <summary>
+        /// Counts the number of occurrences of the specified substring within
+        /// the current string.
+        /// </summary>
+        /// <param name="s">The current string.</param>
+        /// <param name="substring">The substring we are searching for.</param>
+        /// <param name="aggressiveSearch">Indicates whether or not the algorithm 
+        /// should be aggressive in its search behavior (see Remarks). Default 
+        /// behavior is non-aggressive.</param>
+        /// <remarks>This algorithm has two search modes - aggressive and 
+        /// non-aggressive. When in aggressive search mode (aggressiveSearch = 
+        /// true), the algorithm will try to match at every possible starting 
+        /// character index within the string. When false, all subsequent 
+        /// character indexes within a substring match will not be evaluated. 
+        /// For example, if the string was 'abbbc' and we were searching for 
+        /// the substring 'bb', then aggressive search would find 2 matches 
+        /// with starting indexes of 1 and 2. Non aggressive search would find 
+        /// just 1 match with starting index at 1. After the match was made, 
+        /// the non aggressive search would attempt to make it's next match 
+        /// starting at index 3 instead of 2.</remarks>
+        /// <returns>The count of occurrences of the substring within the string.</returns>
+        public static int CountOccurrences(this string s, string substring,
+            bool aggressiveSearch = false)
+        {
+            // if s or substring is null or empty, substring cannot be found in s
+            if (string.IsNullOrEmpty(s) || string.IsNullOrEmpty(substring))
+                return 0;
+
+            // if the length of substring is greater than the length of s,
+            // substring cannot be found in s
+            if (substring.Length > s.Length)
+                return 0;
+
+            int count = 0, n = 0;
+            while ((n = s.IndexOf(substring, n, StringComparison.InvariantCulture)) != -1)
+            {
+                if (aggressiveSearch)
+                    n++;
+                else
+                    n += substring.Length;
+                count++;
+            }
+
+            return count;
+        }
     }
 }

FFMpegCore/FFMpeg/Arguments/IDynamicArgument.cs

@@ -0,0 +1,14 @@
+using System.Text;
+
+namespace FFMpegCore.Arguments
+{
+    public interface IDynamicArgument
+    {
+        /// <summary>
+        /// Same as <see cref="IArgument.Text"/>, but this receives the arguments generated before as parameter
+        /// </summary>
+        /// <param name="context"></param>
+        /// <returns></returns>
+        public string GetText(StringBuilder context);
+    }
+}

FFMpegCore/FFMpeg/Arguments/MetaDataArgument.cs

@@ -1,11 +1,15 @@
-using System;
+using FFMpegCore.Extend;
+
+using System;
 using System.IO;
+using System.Linq;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 
 namespace FFMpegCore.Arguments
 {
-    public class MetaDataArgument : IInputArgument
+    public class MetaDataArgument : IInputArgument, IDynamicArgument
     {
         private readonly string _metaDataContent;
         private readonly string _tempFileName = Path.Combine(GlobalFFOptions.Current.TemporaryFilesFolder, $"metadata_{Guid.NewGuid()}.txt");
@@ -15,7 +19,7 @@ public MetaDataArgument(string metaDataContent)
             _metaDataContent = metaDataContent;
         }
 
-        public string Text => $"-i \"{_tempFileName}\" -map_metadata 1";
+        public string Text => GetText(null);
 
         public Task During(CancellationToken cancellationToken = default) => Task.CompletedTask;
 
@@ -23,5 +27,12 @@ public MetaDataArgument(string metaDataContent)
         public void Pre() => File.WriteAllText(_tempFileName, _metaDataContent);
 
         public void Post() => File.Delete(_tempFileName);
+
+        public string GetText(StringBuilder context)
+        {
+            var index = context.ToString().CountOccurrences("-i");
+
+            return $"-i \"{_tempFileName}\" -map_metadata {index}";
+        }
     }
 }

FFMpegCore/FFMpeg/FFMpegArguments.cs

@@ -2,8 +2,10 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+
 using FFMpegCore.Arguments;
 using FFMpegCore.Builders.MetaData;
 using FFMpegCore.Pipes;
@@ -16,7 +18,23 @@ public sealed class FFMpegArguments : FFMpegArgumentsBase
 
         private FFMpegArguments() { }
 
-        public string Text => string.Join(" ", _globalArguments.Arguments.Concat(Arguments).Select(arg => arg.Text));
+        public string Text => GetText();
+
+        private string GetText()
+        {
+            var sb = new StringBuilder();
+
+            foreach (var arg in _globalArguments.Arguments.Concat(Arguments))
+            {
+                if (sb.Length != 0)
+                {
+                    sb.Append(' ');
+                }
+                sb.Append(arg is IDynamicArgument dynArg ? dynArg.GetText(sb) : arg.Text);
+            }
+
+            return sb.ToString();
+        }
 
         public static FFMpegArguments FromConcatInput(IEnumerable<string> filePaths, Action<FFMpegArgumentOptions>? addArguments = null) => new FFMpegArguments().WithInput(new ConcatArgument(filePaths), addArguments);
         public static FFMpegArguments FromDemuxConcatInput(IEnumerable<string> filePaths, Action<FFMpegArgumentOptions>? addArguments = null) => new FFMpegArguments().WithInput(new DemuxConcatArgument(filePaths), addArguments);