package org.apache.tuscany.container.rhino.rhino;

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

import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.UniqueTag;

/**
 * An invokeable instance of a JavaScript script.
 */
public class RhinoScriptInstance {

    private Scriptable scriptScope;

    private Scriptable instanceScope;

    private Map<String, Class> responseClasses;

    public RhinoScriptInstance(Scriptable scriptScope, Scriptable instanceScope, Map<String, Object> context, Map<String, Class> responseClasses) {
        this.scriptScope = scriptScope;
        this.instanceScope = instanceScope;
        this.responseClasses = responseClasses;
        if (this.responseClasses == null) {
            this.responseClasses = new HashMap<String, Class>();
        }
        addContexts(instanceScope, context);
    }

    public Object invokeFunction(String functionName, Object[] args) {
        RhinoFunctionInvoker invoker = createRhinoFunctionInvoker(functionName);
        return invoker.invoke(args);
    }

    public RhinoFunctionInvoker createRhinoFunctionInvoker(String functionName) {
        Function function = getFunction(functionName);
        Class responseClass = responseClasses.get(functionName);
        RhinoFunctionInvoker invoker = new RhinoFunctionInvoker(instanceScope, function, responseClass);
        return invoker;
    }

    /**
     * Add the context to the scope. This will make the objects available to a script by using the name it was added with.
     */
    protected void addContexts(Scriptable scope, Map contexts) {
        if (contexts != null) {
            Context.enter();
            try {
                for (Iterator i = contexts.keySet().iterator(); i.hasNext();) {
                    String name = (String) i.next();
                    Object value = contexts.get(name);
                    if (value != null) {
                        scope.put(name, scope, Context.toObject(value, scope));
                    }
                }
            } finally {
                Context.exit();
            }
        }
    }

    /**
     * Get the Rhino Function object for the named script function
     */
    protected Function getFunction(String functionName) {

        Object handleObj = scriptScope.get(functionName, instanceScope);
        if (UniqueTag.NOT_FOUND.equals(handleObj)) {
            // Bit of a hack so E4X scripts don't need to define a function for every operation 
            handleObj = scriptScope.get("process", instanceScope);
        }
        if (!(handleObj instanceof Function)) {
            throw new RuntimeException("script function '" + functionName + "' is undefined or not a function");
        }

        return (Function) handleObj;
    }

}