/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_DOMJSProxyHandler_h

#define mozilla_dom_DOMJSProxyHandler_h

#include "mozilla/Attributes.h"

#include "mozilla/Likely.h"

#include "jsapi.h"

#include "js/Proxy.h"

#include "nsString.h"

namespace mozilla {

namespace dom {

/**

 * DOM proxies store the expando object in the private slot.

 *

 * The expando object is a plain JSObject whose properties correspond to

 * "expandos" (custom properties set by the script author).

 *

 * The exact value stored in the proxy's private slot depends on whether the

 * interface is annotated with the [OverrideBuiltins] extended attribute.

 *

 * If it is, the proxy is initialized with a PrivateValue, which contains a

 * pointer to a js::ExpandoAndGeneration object; this contains a pointer to

 * the actual expando object as well as the "generation" of the object.  The

 * proxy handler will trace the expando object stored in the

 * js::ExpandoAndGeneration while the proxy itself is alive.

 *

 * If it is not, the proxy is initialized with an UndefinedValue. In

 * EnsureExpandoObject, it is set to an ObjectValue that points to the

 * expando object directly. (It is set back to an UndefinedValue only when

 * the object is about to die.)

 */

template<typename T> struct Prefable;

class BaseDOMProxyHandler : public js::BaseProxyHandler

{

public:

  explicit constexpr BaseDOMProxyHandler(const void* aProxyFamily, bool aHasPrototype = false)

    : js::BaseProxyHandler(aProxyFamily, aHasPrototype)

  {}

  // Implementations of methods that can be implemented in terms of

  // other lower-level methods.

  bool getOwnPropertyDescriptor(JSContext* cx, JS::Handle<JSObject*> proxy,

                                JS::Handle<jsid> id,

                                JS::MutableHandle<JS::PropertyDescriptor> desc) const override;

  virtual bool ownPropertyKeys(JSContext* cx, JS::Handle<JSObject*> proxy,

                               JS::AutoIdVector &props) const override;

  virtual bool getPrototypeIfOrdinary(JSContext* cx, JS::Handle<JSObject*> proxy,

                                      bool* isOrdinary,

                                      JS::MutableHandle<JSObject*> proto) const override;

  // We override getOwnEnumerablePropertyKeys() and implement it directly

  // instead of using the default implementation, which would call

  // ownPropertyKeys and then filter out the non-enumerable ones. This avoids

  // unnecessary work during enumeration.

  virtual bool getOwnEnumerablePropertyKeys(JSContext* cx, JS::Handle<JSObject*> proxy,

                                            JS::AutoIdVector &props) const override;

protected:

  // Hook for subclasses to implement shared ownPropertyKeys()/keys()

  // functionality.  The "flags" argument is either JSITER_OWNONLY (for keys())

  // or JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS (for

  // ownPropertyKeys()).

  virtual bool ownPropNames(JSContext* cx, JS::Handle<JSObject*> proxy,

                            unsigned flags,

                            JS::AutoIdVector& props) const = 0;

  // Hook for subclasses to allow set() to ignore named props while other things

  // that look at property descriptors see them.  This is intentionally not

  // named getOwnPropertyDescriptor to avoid subclasses that override it hiding

  // our public getOwnPropertyDescriptor.

  virtual bool getOwnPropDescriptor(JSContext* cx,

                                    JS::Handle<JSObject*> proxy,

                                    JS::Handle<jsid> id,

                                    bool ignoreNamedProps,

                                    JS::MutableHandle<JS::PropertyDescriptor> desc) const = 0;

};

class DOMProxyHandler : public BaseDOMProxyHandler

{

public:

  constexpr DOMProxyHandler()

    : BaseDOMProxyHandler(&family)

  {}

  bool defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,

                      JS::Handle<JS::PropertyDescriptor> desc,

                      JS::ObjectOpResult &result) const override

  {

    bool unused;

    return defineProperty(cx, proxy, id, desc, result, &unused);

  }

  virtual bool defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,

                              JS::Handle<JS::PropertyDescriptor> desc,

                              JS::ObjectOpResult &result, bool *defined) const;

  bool delete_(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,

               JS::ObjectOpResult &result) const override;

  bool preventExtensions(JSContext* cx, JS::Handle<JSObject*> proxy,

                         JS::ObjectOpResult& result) const override;

  bool isExtensible(JSContext *cx, JS::Handle<JSObject*> proxy, bool *extensible)

                    const override;

  bool set(JSContext *cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,

           JS::Handle<JS::Value> v, JS::Handle<JS::Value> receiver, JS::ObjectOpResult &result)

           const override;

  /*

   * If assigning to proxy[id] hits a named setter with OverrideBuiltins or

   * an indexed setter, call it and set *done to true on success. Otherwise, set

   * *done to false.

   */

  virtual bool setCustom(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,

                         JS::Handle<JS::Value> v, bool *done) const;

  /*

   * Get the expando object for the given DOM proxy.

   */

  static JSObject* GetExpandoObject(JSObject* obj);

  /*

   * Clear the expando object for the given DOM proxy and return it.  This

   * function will ensure that the returned object is exposed to active JS if

   * the given object is exposed.

   *

   * GetAndClearExpandoObject does not DROP or clear the preserving wrapper

   * flag.

   */

  static JSObject* GetAndClearExpandoObject(JSObject* obj);

  /*

   * Ensure that the given proxy (obj) has an expando object, and return it.

   * Returns null on failure.

   */

  static JSObject* EnsureExpandoObject(JSContext* cx,

                                       JS::Handle<JSObject*> obj);

  static const char family;

};

// Class used by shadowing handlers (the ones that have [OverrideBuiltins].

// This handles tracing the expando in ExpandoAndGeneration.

class ShadowingDOMProxyHandler : public DOMProxyHandler

{

  virtual void trace(JSTracer* trc, JSObject* proxy) const override;

};

inline bool IsDOMProxy(JSObject *obj)

{

    const js::Class* clasp = js::GetObjectClass(obj);

    return clasp->isProxy() &&

           js::GetProxyHandler(obj)->family() == &DOMProxyHandler::family;

}

inline const DOMProxyHandler*

GetDOMProxyHandler(JSObject* obj)

{

  MOZ_ASSERT(IsDOMProxy(obj));

  return static_cast<const DOMProxyHandler*>(js::GetProxyHandler(obj));

}

extern jsid s_length_id;

// A return value of UINT32_MAX indicates "not an array index".  Note, in

// particular, that UINT32_MAX itself is not a valid array index in general.

inline uint32_t

GetArrayIndexFromId(JSContext* cx, JS::Handle<jsid> id)

{

  // Much like js::IdIsIndex, except with a fast path for "length" and another

  // fast path for starting with a lowercase ascii char.  Is that second one

  // really needed?  I guess it is because StringIsArrayIndex is out of line...

  if (MOZ_LIKELY(JSID_IS_INT(id))) {

    return JSID_TO_INT(id);

  }

  if (MOZ_LIKELY(id == s_length_id)) {

    return UINT32_MAX;

  }

  if (MOZ_UNLIKELY(!JSID_IS_ATOM(id))) {

    return UINT32_MAX;

  }

  JSLinearString* str = js::AtomToLinearString(JSID_TO_ATOM(id));

  char16_t s;

  {

    JS::AutoCheckCannotGC nogc;

    if (js::LinearStringHasLatin1Chars(str)) {

      s = *js::GetLatin1LinearStringChars(nogc, str);

    } else {

      s = *js::GetTwoByteLinearStringChars(nogc, str);

    }

  }

  if (MOZ_LIKELY((unsigned)s >= 'a' && (unsigned)s <= 'z'))

    return UINT32_MAX;

  uint32_t i;

  return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;

}

inline bool

IsArrayIndex(uint32_t index)

{

  return index < UINT32_MAX;

}

inline void

FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,

                       JSObject* obj, bool readonly, bool enumerable = true)

{

  desc.object().set(obj);

  desc.setAttributes((readonly ? JSPROP_READONLY : 0) |

                     (enumerable ? JSPROP_ENUMERATE : 0));

  desc.setGetter(nullptr);

  desc.setSetter(nullptr);

}

inline void

FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,

                       JSObject* obj, const JS::Value& v,

                       bool readonly, bool enumerable = true)

{

  desc.value().set(v);

  FillPropertyDescriptor(desc, obj, readonly, enumerable);

}

inline void

FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,

                       JSObject* obj, unsigned attributes, const JS::Value& v)

{

  desc.object().set(obj);

  desc.value().set(v);

  desc.setAttributes(attributes);

  desc.setGetter(nullptr);

  desc.setSetter(nullptr);

}

} // namespace dom

} // namespace mozilla

#endif /* mozilla_dom_DOMProxyHandler_h */