Simply formatting of constants and environment variables (implementat…

…ion stays backwards compatible)

Microwalk/YamlConfigurationParser.cs

@@ -2,7 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
-using System.Linq;
+using System.Text.RegularExpressions;
 using Microwalk.FrameworkBase.Configuration;
 using Microwalk.FrameworkBase.Exceptions;
 using YamlDotNet.RepresentationModel;
@@ -99,10 +99,10 @@ private void ParseConfigurationFile(string path)
                             string constantValue = (constantNode.Value as YamlScalarNode)?.Value ?? throw new ConfigurationException("Could not parse constant value.");
 
                             // Apply existing constants to value
-                            constantValue = Constants.Aggregate(constantValue, (current, replacement) => current.Replace(replacement.Key, replacement.Value));
+                            constantValue = ReplaceConstants(constantValue);
 
                             // Store/update constant
-                            Constants[$"$${constantName}$$"] = constantValue;
+                            Constants[$"${constantName}"] = constantValue;
                         }
 
                         break;
@@ -150,9 +150,33 @@ private void ApplyConstants(Node currentNode)
         }
         else if(currentNode is ValueNode valueNode)
         {
-            valueNode.Value = Constants.Aggregate(valueNode.Value, (current, replacement) => current?.Replace(replacement.Key, replacement.Value));
+            valueNode.Value = valueNode.Value != null ? ReplaceConstants(valueNode.Value) : "";
         }
     }
+
+    /// <summary>
+    /// Replaces constant expressions in the given string.
+    /// </summary>
+    /// <param name="value">String to replace constants in.</param>
+    /// <returns>Input string with replaced constants.</returns>
+    private string ReplaceConstants(string value)
+    {
+        // Find and handle constants
+        return Regex.Replace(value, @"(\$+[A-Za-z0-9_]+)\$*", match =>
+        {
+            // If this is a constant with the old format, remove one leading $ from its name
+            //   $$NAME$$ -> $NAME (config variables)
+            //   $$$NAME$$$ -> $$NAME (environment variables)               
+            string constantName = match.Groups[1].Value;
+            if(match.Value.EndsWith('$'))
+                constantName = constantName.Substring(1);
+
+            if(Constants.TryGetValue(constantName, out string? constantValue))
+                return constantValue;
+
+            throw new ConfigurationException($"Can not resolve constant '{constantName}'.");
+        });
+    }
 
     /// <summary>
     /// Recursively merges the source node into the target node.
@@ -201,13 +225,13 @@ public void LoadConfigurationFile(string path)
         RootNodes = new Dictionary<string, Node>();
         Constants = new Dictionary<string, string>
         {
-            { "$$CONFIG_PATH$$", Path.GetDirectoryName(Path.GetFullPath(path)) ?? throw new Exception("Could not resolve configuration directory.") },
-            { "$$CONFIG_FILENAME$$", Path.GetFileNameWithoutExtension(path) }
+            { "$CONFIG_PATH", Path.GetDirectoryName(Path.GetFullPath(path)) ?? throw new Exception("Could not resolve configuration directory.") },
+            { "$CONFIG_FILENAME", Path.GetFileNameWithoutExtension(path) }
         };
 
         // Load environment variables as constants as well
         foreach(DictionaryEntry variable in Environment.GetEnvironmentVariables())
-            Constants.Add($"$$${(string)variable.Key}$$$", (string?)variable.Value ?? "");
+            Constants.Add($"$${(string)variable.Key}", (string?)variable.Value ?? "");
 
         // Load passed configuration file
         ParseConfigurationFile(path);

docs/config.md

@@ -67,7 +67,7 @@ Base configuration file which should be loaded and parsed before the current one
 Keys existing in both the base file and the current file are always superseded by those of the current file.
 
 ### `constants`
-A number of arbitrary string constants, which can be referenced by `$$CONSTANT_NAME$$` in other parts of the file.
+A number of arbitrary string constants, which can be referenced by `$CONSTANT_NAME` in other parts of the file.
 
 Predefined constants:
 - `CONFIG_PATH`<br>
@@ -77,7 +77,7 @@ Predefined constants:
   Name of the main configuration file, without extension (e.g., `target-aes` for `target-aes.yml`).
 
 ### Enviroment variables
-All environment variables of the current process environment are available as `$$$VARIABLE_NAME$$$` and are treated just like constants.
+All environment variables of the current process environment are available as `$$VARIABLE_NAME` (mind the double `$`) and are treated just like constants.
 
 
 ## `general`