serene-simple/src/main/java/serene/simple/BaseScope.java

package serene.simple;

import java.util.HashMap;
import java.util.Map;

public abstract class BaseScope {
  private final Map<String, Object> symbolsMapping = new HashMap<String, Object>();
  private final BaseScope parent;

  public BaseScope() {
    this(null);
  }

  public BaseScope(BaseScope parent) {
    this.parent = parent;
  }

  public Object lookupSymbol(String symbolName) {
    if (this.symbolsMapping.containsKey(symbolName)) {
      return this.symbolsMapping.get(symbolName);
    }
    else if (this.parent != null) {
      return this.parent.lookupSymbol(symbolName);
    }
    else {
      throw new RuntimeException(String.format("Symbol '%s' is not defined in this scope.",
                                               symbolName));
    }
  }

  public void insertSymbol(String symbolName, Object symbolValue) {
    this.symbolsMapping.put(symbolName, symbolValue);
  }
}