Extract java config parser to generic reusable key/value parser

source/mirage/java.d

@@ -11,48 +11,13 @@
 
 module mirage.java;
 
-import mirage.config : ConfigFactory, ConfigDictionary, ConfigNode, ValueNode, ObjectNode, ConfigCreationException;
-
-import std.string : lineSplitter, strip, startsWith, split, indexOf;
-import std.array : array;
-import std.exception : enforce;
-import std.conv : to;
+import mirage.config : ConfigDictionary;
+import mirage.keyvalue : KeyValueConfigFactory;
 
 /** 
  * Creates configuration files from Java properties.
  */
-class JavaPropertiesFactory : ConfigFactory {
-    /**
-     * Parse configuration from the given Java properties string.
-     *
-     * Params:
-     *   contents = Text contents of the config to be parsed.
-     * Returns: The parsed configuration.
-     */
-    override ConfigDictionary parseConfig(string contents) {
-        enforce!ConfigCreationException(contents !is null, "Contents cannot be null.");
-        auto lines = contents.lineSplitter().array;
-        auto properties = new ConfigDictionary();
-        foreach (size_t index, string line; lines) {
-            auto normalizedLine = line.strip;
-            if (normalizedLine.length == 0 || normalizedLine.startsWith('#')) {
-                continue;
-            }
-
-            auto commentPosition = normalizedLine.indexOf('#');
-            if (commentPosition >= 0) {
-                normalizedLine = normalizedLine[0 .. commentPosition];
-            }
-
-            auto parts = normalizedLine.split('=');
-            enforce!ConfigCreationException(parts.length <= 2, "Line has too many equals signs and cannot be parsed (L" ~ index
-                    .to!string ~ "): " ~ normalizedLine);
-            enforce!ConfigCreationException(parts.length == 2, "Missing value assignment (L" ~ index.to!string ~ "): " ~ normalizedLine);
-            properties.set(parts[0].strip, parts[1].strip);
-        }
-
-        return properties;
-    }
+class JavaPropertiesFactory : KeyValueConfigFactory {
 }
 
 /** 
@@ -80,6 +45,7 @@ ConfigDictionary loadJavaProperties(const string filePath) {
 version (unittest) {
     import std.exception : assertThrown;
     import std.process : environment;
+    import mirage.config : ConfigCreationException;
 
     @("Parse java properties")
     unittest {

source/mirage/keyvalue.d

@@ -0,0 +1,122 @@
+/**
+ * Utilities for loading generic configuration files consisting of key/value pairs.
+ *
+ * Authors:
+ *  Mike Bierlee, m.bierlee@lostmoment.com
+ * Copyright: 2022 Mike Bierlee
+ * License:
+ *  This software is licensed under the terms of the MIT license.
+ *  The full terms of the license can be found in the LICENSE file.
+ */
+
+module mirage.keyvalue;
+
+import mirage.config : ConfigFactory, ConfigDictionary, ConfigNode, ValueNode, ObjectNode, ConfigCreationException;
+
+import std.string : lineSplitter, strip, startsWith, split, indexOf;
+import std.array : array;
+import std.exception : enforce;
+import std.conv : to;
+
+/** 
+ * A generic reusable key/value config factory that can be configured to parse
+ * the specifics of certain key/value formats.
+ */
+class KeyValueConfigFactory : ConfigFactory {
+    /**
+     * Parse a configuration file following the configured key/value conventions.
+     *
+     * Params:
+     *   contents = Text contents of the config to be parsed.
+     * Returns: The parsed configuration.
+     */
+    override ConfigDictionary parseConfig(string contents) {
+        enforce!ConfigCreationException(contents !is null, "Contents cannot be null.");
+        auto lines = contents.lineSplitter().array;
+        auto properties = new ConfigDictionary();
+        foreach (size_t index, string line; lines) {
+            auto normalizedLine = line.strip;
+            if (normalizedLine.length == 0 || normalizedLine.startsWith('#')) {
+                continue;
+            }
+
+            auto commentPosition = normalizedLine.indexOf('#');
+            if (commentPosition >= 0) {
+                normalizedLine = normalizedLine[0 .. commentPosition];
+            }
+
+            auto parts = normalizedLine.split('=');
+            enforce!ConfigCreationException(parts.length <= 2, "Line has too many equals signs and cannot be parsed (L" ~ index
+                    .to!string ~ "): " ~ normalizedLine);
+            enforce!ConfigCreationException(parts.length == 2, "Missing value assignment (L" ~ index.to!string ~ "): " ~ normalizedLine);
+            properties.set(parts[0].strip, parts[1].strip);
+        }
+
+        return properties;
+    }
+}
+
+version (unittest) {
+    import std.exception : assertThrown;
+    import std.process : environment;
+
+    @("Parse standard key/value config")
+    unittest {
+        auto config = new KeyValueConfigFactory().parseConfig("
+            # I have a comment
+            bla=one
+            di.bla=two
+        ");
+
+        assert(config.get("bla") == "one");
+        assert(config.get("di.bla") == "two");
+    }
+
+    @("Fail to parse when there are too many equals signs")
+    unittest {
+        assertThrown!ConfigCreationException(new KeyValueConfigFactory()
+                .parseConfig("one=two=three"));
+    }
+
+    @("Fail to parse when value assignment is missing")
+    unittest {
+        assertThrown!ConfigCreationException(new KeyValueConfigFactory().parseConfig(
+                "answertolife"));
+    }
+
+    @("Substitute env vars")
+    unittest {
+        environment["MIRAGE_TEST_ENVY"] = "Much";
+        auto config = new KeyValueConfigFactory().parseConfig("envy=$MIRAGE_TEST_ENVY");
+
+        assert(config.get("envy") == "Much");
+    }
+
+    @("Use value from other key")
+    unittest {
+        auto config = new KeyValueConfigFactory().parseConfig("
+            one=money
+            two=${one}
+        ");
+
+        assert(config.get("two") == "money");
+    }
+
+    @("Values and keys are trimmed")
+    unittest {
+        auto config = new KeyValueConfigFactory().parseConfig("
+            one    =       money
+        ");
+
+        assert(config.get("one") == "money");
+    }
+
+    @("Remove end-of-line comments")
+    unittest {
+        auto config = new KeyValueConfigFactory().parseConfig("
+            server=localhost #todo: change me. default=localhost when not set.
+        ");
+
+        assert(config.get("server") == "localhost");
+    }
+}