package serene.simple;

import java.util.HashMap;

public class Scope {
    private final HashMap<String, Object> symbolsMapping = new HashMap<String, Object>();
    private final Scope parent;
    private static final Scope root = new Scope(null);

    public Scope() {
        this(null);
    }

    public Scope(Scope 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("Variable '%s' is not defined in this scope.",
                                                     symbolName));
        }
    }

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

    public static Scope getRootScope() {
        return Scope.root;
    }
}