Implement singleton class MacroProcessor #420

lphy/src/main/java/lphy/core/io/MacroProcessor.java

@@ -0,0 +1,82 @@
+package lphy.core.io;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Inspired by templating languages e.g. Mustache.
+ * Only support {{identifier = default_value}}
+ */
+public class MacroProcessor {
+
+    // {{n = 10}}
+    public static final String CONST_MACRO = "\\{\\{\\s*(\\w+)\\s*=\\s*(.*?)\\s*\\}\\}";
+    private final Pattern pattern;
+
+    public MacroProcessor(String regex) {
+        this.pattern = Pattern.compile(regex);
+    }
+
+    public MacroProcessor() {
+        this(CONST_MACRO);
+    }
+
+    // Singleton
+    private static MacroProcessor INSTANCE;
+    public static MacroProcessor getInstance() {
+        if(INSTANCE == null) {
+            INSTANCE = new MacroProcessor();
+        }
+        return INSTANCE;
+    }
+
+    public static String process(String input) {
+        Map<String, String> macroMap = getInstance().getMacroMap(input);
+        // TODO modify the macroMap based on user input?
+        return getInstance().getResult(input, macroMap);
+    }
+
+    public Map<String, String> getMacroMap(String input) {
+        Map<String, String> macroMap = new HashMap<>();
+
+        // Populate the macroMap based on the initial matches
+        Matcher matcher = pattern.matcher(input);
+
+        while (matcher.find()) {
+            String identifier = matcher.group(1);
+            String literal = matcher.group(2);
+            macroMap.put(identifier, literal);
+        }
+        return macroMap;
+    }
+
+    public String getResult(String input, Map<String, String> macroMap) {
+        Matcher replaceMatcher = pattern.matcher(input);
+        StringBuilder stringBuffer = new StringBuilder();
+
+        while (replaceMatcher.find()) {
+            String replacement = macroMap.get(replaceMatcher.group(1));
+            if (replacement != null) {
+                // The String produced will match the sequence of characters in s treated as a literal sequence.
+                // Slashes ('\') and dollar signs ('$') will be given no special meaning.
+                replacement = Matcher.quoteReplacement(replacement);
+                replaceMatcher.appendReplacement(stringBuffer, replacement);
+            }
+        }
+        replaceMatcher.appendTail(stringBuffer);
+        // Result contains the modified string
+        return stringBuffer.toString();
+    }
+
+    public static void main(String[] args) {
+        String input = "{{identifier1 = value1}} some text {{identifier2 = value2}}";
+
+        String result = MacroProcessor.process(input);
+
+        System.out.println(result);
+    }
+
+}
+