ScriptInterface.h

Go to the documentation of this file.

/* Copyright (C) 2022 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_SCRIPTINTERFACE
#define INCLUDED_SCRIPTINTERFACE

#include "ps/Errors.h"
#include "scriptinterface/ScriptConversions.h"
#include "scriptinterface/ScriptExceptions.h"
#include "scriptinterface/ScriptRequest.h"
#include "scriptinterface/ScriptTypes.h"

#include <map>

ERROR_GROUP(Scripting);
ERROR_TYPE(Scripting, SetupFailed);

ERROR_SUBGROUP(Scripting, LoadFile);
ERROR_TYPE(Scripting_LoadFile, OpenFailed);
ERROR_TYPE(Scripting_LoadFile, EvalErrors);

ERROR_TYPE(Scripting, CallFunctionFailed);
ERROR_TYPE(Scripting, DefineConstantFailed);
ERROR_TYPE(Scripting, CreateObjectFailed);
ERROR_TYPE(Scripting, TypeDoesNotExist);

ERROR_SUBGROUP(Scripting, DefineType);
ERROR_TYPE(Scripting_DefineType, AlreadyExists);
ERROR_TYPE(Scripting_DefineType, CreationFailed);

// Set the maximum number of function arguments that can be handled
// (This should be as small as possible (for compiler efficiency),
// but as large as necessary for all wrapped functions)
#define SCRIPT_INTERFACE_MAX_ARGS 8

class ScriptInterface;
struct ScriptInterface_impl;

class ScriptContext;
// Using a global object for the context is a workaround until Simulation, AI, etc,
// use their own threads and also their own contexts.
extern thread_local std::shared_ptr<ScriptContext> g_ScriptContext;

namespace boost { namespace random { class rand48; } }

class Path;
using VfsPath = Path;

/**
 * Abstraction around a SpiderMonkey JS::Realm.
 *
 * Thread-safety:
 * - May be used in non-main threads.
 * - Each ScriptInterface must be created, used, and destroyed, all in a single thread
 *   (it must never be shared between threads).
 */
class ScriptInterface
{
    NONCOPYABLE(ScriptInterface);

    friend class ScriptRequest;

public:

    /**
     * Constructor.
     * @param nativeScopeName Name of global object that functions (via ScriptFunction::Register) will
     *   be placed into, as a scoping mechanism; typically "Engine"
     * @param debugName Name of this interface for CScriptStats purposes.
     * @param context ScriptContext to use when initializing this interface.
     */
    ScriptInterface(const char* nativeScopeName, const char* debugName, const std::shared_ptr<ScriptContext>& context);

    /**
     * Alternate constructor. This creates the new Realm in the same Compartment as the neighbor scriptInterface.
     * This means that data can be freely exchanged between these two script interfaces without cloning.
     * @param nativeScopeName Name of global object that functions (via ScriptFunction::Register) will
     *   be placed into, as a scoping mechanism; typically "Engine"
     * @param debugName Name of this interface for CScriptStats purposes.
     * @param scriptInterface 'Neighbor' scriptInterface to share a compartment with.
     */
    ScriptInterface(const char* nativeScopeName, const char* debugName, const ScriptInterface& neighbor);

    ~ScriptInterface();

    struct CmptPrivate
    {
        friend class ScriptInterface;
    public:
        static const ScriptInterface& GetScriptInterface(JSContext* cx);
        static void* GetCBData(JSContext* cx);
    protected:
        ScriptInterface* pScriptInterface; // the ScriptInterface object the compartment belongs to
        void* pCBData; // meant to be used as the "this" object for callback functions
    };

    void SetCallbackData(void* pCBData);

    /**
     * Convert the CmptPrivate callback data to T*
     */
    template <typename T>
    static T* ObjectFromCBData(const ScriptRequest& rq)
    {
        static_assert(!std::is_same_v<void, T>);
        ScriptInterface::CmptPrivate::GetCBData(rq.cx);
        return static_cast<T*>(ObjectFromCBData<void>(rq));
    }

    /**
     * Variant for the function wrapper.
     */
    template <typename T>
    static T* ObjectFromCBData(const ScriptRequest& rq, JS::CallArgs&)
    {
        return ObjectFromCBData<T>(rq);
    }

    /**
     * GetGeneralJSContext returns the context without starting a GC request and without
     * entering the ScriptInterface compartment. It should only be used in specific situations,
     * for instance when initializing a persistent rooted.
     * If you need the compartmented context of the ScriptInterface, you should create a
     * ScriptInterface::Request and use the context from that.
     */
    JSContext* GetGeneralJSContext() const;
    std::shared_ptr<ScriptContext> GetContext() const;

    /**
     * Load global scripts that most script interfaces need,
     * located in the /globalscripts directory. VFS must be initialized.
     */
    bool LoadGlobalScripts();

    /**
     * Replace the default JS random number generator with a seeded, network-synced one.
     */
    bool ReplaceNondeterministicRNG(boost::random::rand48& rng);

    /**
     * Call a constructor function, equivalent to JS "new ctor(arg)".
     * @param ctor An object that can be used as constructor
     * @param argv Constructor arguments
     * @param out The new object; On error an error message gets logged and out is Null (out.isNull() == true).
     */
    void CallConstructor(JS::HandleValue ctor, JS::HandleValueArray argv, JS::MutableHandleValue out) const;

    JSObject* CreateCustomObject(const std::string & typeName) const;
    void DefineCustomObjectType(JSClass *clasp, JSNative constructor, uint minArgs, JSPropertySpec *ps, JSFunctionSpec *fs, JSPropertySpec *static_ps, JSFunctionSpec *static_fs);

    /**
     * Set the named property on the global object.
     * Optionally makes it {ReadOnly, DontEnum}. We do not allow to make it DontDelete, so that it can be hotloaded
     * by deleting it and re-creating it, which is done by setting @p replace to true.
     */
    template<typename T>
    bool SetGlobal(const char* name, const T& value, bool replace = false, bool constant = true, bool enumerate = true);

    /**
     * Get an object from the global scope or any lexical scope.
     * This can return globally accessible objects even if they are not properties
     * of the global object (e.g. ES6 class definitions).
     * @param name - Name of the property.
     * @param out The object or null.
     */
    static bool GetGlobalProperty(const ScriptRequest& rq, const std::string& name, JS::MutableHandleValue out);

    bool SetPrototype(JS::HandleValue obj, JS::HandleValue proto);

    /**
     * Load and execute the given script in a new function scope.
     * @param filename Name for debugging purposes (not used to load the file)
     * @param code JS code to execute
     * @return true on successful compilation and execution; false otherwise
     */
    bool LoadScript(const VfsPath& filename, const std::string& code) const;

    /**
     * Load and execute the given script in the global scope.
     * @param filename Name for debugging purposes (not used to load the file)
     * @param code JS code to execute
     * @return true on successful compilation and execution; false otherwise
     */
    bool LoadGlobalScript(const VfsPath& filename, const std::string& code) const;

    /**
     * Load and execute the given script in the global scope.
     * @return true on successful compilation and execution; false otherwise
     */
    bool LoadGlobalScriptFile(const VfsPath& path) const;

    /**
     * Evaluate some JS code in the global scope.
     * @return true on successful compilation and execution; false otherwise
     */
    bool Eval(const char* code) const;
    bool Eval(const char* code, JS::MutableHandleValue out) const;
    template<typename T> bool Eval(const char* code, T& out) const;

    /**
     * Calls the random number generator assigned to this ScriptInterface instance and returns the generated number.
     */
    bool MathRandom(double& nbr) const;

    /**
     * JSNative wrapper of the above.
     */
    static bool Math_random(JSContext* cx, uint argc, JS::Value* vp);

    /**
     * Retrieve the private data field of a JSObject that is an instance of the given JSClass.
     */
    template <typename T>
    static T* GetPrivate(const ScriptRequest& rq, JS::HandleObject thisobj, JSClass* jsClass)
    {
        T* value = static_cast<T*>(JS_GetInstancePrivate(rq.cx, thisobj, jsClass, nullptr));

        if (value == nullptr)
            ScriptException::Raise(rq, "Private data of the given object is null!");

        return value;
    }

    /**
     * Retrieve the private data field of a JS Object that is an instance of the given JSClass.
     * If an error occurs, GetPrivate will report it with the according stack.
     */
    template <typename T>
    static T* GetPrivate(const ScriptRequest& rq, JS::CallArgs& callArgs, JSClass* jsClass)
    {
        if (!callArgs.thisv().isObject())
        {
            ScriptException::Raise(rq, "Cannot retrieve private JS class data because from a non-object value!");
            return nullptr;
        }

        JS::RootedObject thisObj(rq.cx, &callArgs.thisv().toObject());
        T* value = static_cast<T*>(JS_GetInstancePrivate(rq.cx, thisObj, jsClass, &callArgs));

        if (value == nullptr)
            ScriptException::Raise(rq, "Private data of the given object is null!");

        return value;
    }

private:
    bool SetGlobal_(const char* name, JS::HandleValue value, bool replace, bool constant, bool enumerate);

    struct CustomType
    {
        JS::PersistentRootedObject m_Prototype;
        JSClass* m_Class;
        JSNative m_Constructor;
    };

    CmptPrivate m_CmptPrivate;

    // Take care to keep this declaration before heap rooted members. Destructors of heap rooted
    // members have to be called before the custom destructor of ScriptInterface_impl.
    std::unique_ptr<ScriptInterface_impl> m;

    std::map<std::string, CustomType> m_CustomObjectTypes;
};

// Explicitly instantiate void* as that is used for the generic template,
// and we want to define it in the .cpp file.
template <> void* ScriptInterface::ObjectFromCBData(const ScriptRequest& rq);

template<typename T>
bool ScriptInterface::SetGlobal(const char* name, const T& value, bool replace, bool constant, bool enumerate)
{
    ScriptRequest rq(this);
    JS::RootedValue val(rq.cx);
    Script::ToJSVal(rq, &val, value);
    return SetGlobal_(name, val, replace, constant, enumerate);
}

template<typename T>
bool ScriptInterface::Eval(const char* code, T& ret) const
{
    ScriptRequest rq(this);
    JS::RootedValue rval(rq.cx);
    if (!Eval(code, &rval))
        return false;
    return Script::FromJSVal(rq, rval, ret);
}

#endif // INCLUDED_SCRIPTINTERFACE