// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

library _interceptors;

import 'dart:collection';
import 'dart:_internal' hide Symbol;
import "dart:_internal" as _symbol_dev show Symbol;
import 'dart:_js_helper' show allMatchesInStringUnchecked,
                              Null,
                              JSSyntaxRegExp,
                              Primitives,
                              checkInt,
                              checkNull,
                              checkNum,
                              checkString,
                              defineProperty,
                              getRuntimeType,
                              initNativeDispatch,
                              initNativeDispatchFlag,
                              regExpGetNative,
                              stringContainsUnchecked,
                              stringLastIndexOfUnchecked,
                              stringReplaceAllFuncUnchecked,
                              stringReplaceAllUnchecked,
                              stringReplaceFirstUnchecked,
                              lookupAndCacheInterceptor,
                              lookupDispatchRecord,
                              StringMatch,
                              firstMatchAfter,
                              NoInline;
import 'dart:_foreign_helper' show
    JS, JS_EFFECT, JS_INTERCEPTOR_CONSTANT, JS_STRING_CONCAT;
import 'dart:math' show Random;

part 'js_array.dart';
part 'js_number.dart';
part 'js_string.dart';

String _symbolToString(Symbol symbol) => _symbol_dev.Symbol.getName(symbol);

_symbolMapToStringMap(Map<Symbol, dynamic> map) {
  if (map == null) return null;
  var result = new Map<String, dynamic>();
  map.forEach((Symbol key, value) {
    result[_symbolToString(key)] = value;
  });
  return result;
}

/**
 * Get the interceptor for [object]. Called by the compiler when it needs
 * to emit a call to an intercepted method, that is a method that is
 * defined in an interceptor class.
 */
getInterceptor(object) {
  // This is a magic method: the compiler does specialization of it
  // depending on the uses of intercepted methods and instantiated
  // primitive types.

  // The [JS] call prevents the type analyzer from making assumptions about the
  // return type.
  return JS('', 'void 0');
}

getDispatchProperty(object) {
  return JS('', '#[#]', object, JS('String', 'init.dispatchPropertyName'));
}

setDispatchProperty(object, value) {
  defineProperty(object, JS('String', 'init.dispatchPropertyName'), value);
}

makeDispatchRecord(interceptor, proto, extension, indexability) {
  // Dispatch records are stored in the prototype chain, and in some cases, on
  // instances.
  //
  // The record layout and field usage is designed to minimize the number of
  // operations on the common paths.
  //
  // [interceptor] is the interceptor - a holder of methods for the object,
  // i.e. the prototype of the interceptor class.
  //
  // [proto] is usually the prototype, used to check that the dispatch record
  // matches the object and is not the dispatch record of a superclass.  Other
  // values:
  //  - `false` for leaf classes that need no check.
  //  - `true` for Dart classes where the object is its own interceptor (unused)
  //  - a function used to continue matching.
  //
  // [extension] is used for irregular cases.
  //
  // [indexability] is used to cache whether or not the object
  // implements JavaScriptIndexingBehavior.
  //
  //     proto  interceptor extension action
  //     -----  ----------- --------- ------
  //     false  I                     use interceptor I
  //     true   -                     use object
  //     P      I                     if object's prototype is P, use I
  //     F      -           P         if object's prototype is P, call F

  // BUG(10903): Remove this hack. It is needed to avoid inlining this
  // method because inlining gives us multiple allocation points for
  // records which is bad because it leads to polymorphic access.
  if (false) return null;
  return JS('', '{i: #, p: #, e: #, x: #}',
            interceptor, proto, extension, indexability);
}

dispatchRecordInterceptor(record) => JS('', '#.i', record);
dispatchRecordProto(record) => JS('', '#.p', record);
dispatchRecordExtension(record) => JS('', '#.e', record);
dispatchRecordIndexability(record) => JS('bool|Null', '#.x', record);

/**
 * Returns the interceptor for a native class instance. Used by
 * [getInterceptor].
 */
getNativeInterceptor(object) {
  var record = getDispatchProperty(object);

  if (record == null) {
    if (initNativeDispatchFlag == null) {
      initNativeDispatch();
      record = getDispatchProperty(object);
    }
  }

  if (record != null) {
    var proto = dispatchRecordProto(record);
    if (false == proto) return dispatchRecordInterceptor(record);
    if (true == proto) return object;
    var objectProto = JS('', 'Object.getPrototypeOf(#)', object);
    if (JS('bool', '# === #', proto, objectProto)) {
      return dispatchRecordInterceptor(record);
    }

    var extension = dispatchRecordExtension(record);
    if (JS('bool', '# === #', extension, objectProto)) {
      // TODO(sra): The discriminator returns a tag.  The tag is an uncached or
      // instance-cached tag, defaulting to instance-cached if caching
      // unspecified.
      var discriminatedTag = JS('', '(#)(#, #)', proto, object, record);
      throw new UnimplementedError('Return interceptor for $discriminatedTag');
    }
  }

  var interceptor = lookupAndCacheInterceptor(object);
  if (interceptor == null) {
    // JavaScript Objects created via object literals and `Object.create(null)`
    // are 'plain' Objects.  This test could be simplified and the dispatch path
    // be faster if Object.prototype was pre-patched with a non-leaf dispatch
    // record.
    var proto = JS('', 'Object.getPrototypeOf(#)', object);
    if (JS('bool', '# == null || # === Object.prototype', proto, proto)) {
      return JS_INTERCEPTOR_CONSTANT(PlainJavaScriptObject);
    } else {
      return JS_INTERCEPTOR_CONSTANT(UnknownJavaScriptObject);
    }
  }

  return interceptor;
}

/**
 * If [JSInvocationMirror._invokeOn] is being used, this variable
 * contains a JavaScript array with the names of methods that are
 * intercepted.
 */
var interceptedNames;


/**
 * Data structure used to map a [Type] to the [Interceptor] and constructors for
 * that type.  It is JavaScript array of 3N entries of adjacent slots containing
 * a [Type], followed by an [Interceptor] class for the type, followed by a
 * JavaScript object map for the constructors.
 *
 * The value of this variable is set by the compiler and contains only types
 * that are user extensions of native classes where the type occurs as a
 * constant in the program.
 *
 * The compiler, in CustomElementsAnalysis, assumes that [mapTypeToInterceptor]
 * is accessed only by code that also calls [findIndexForWebComponentType].  If
 * this assumption is invalidated, the compiler will have to be updated.
 */
// TODO(sra): Mark this as initialized to a constant with unknown value.
var mapTypeToInterceptor;

int findIndexForNativeSubclassType(Type type) {
  if (JS('bool', '# == null', mapTypeToInterceptor)) return null;
  List map = JS('JSFixedArray', '#', mapTypeToInterceptor);
  for (int i = 0; i + 1 < map.length; i += 3) {
    if (type == map[i]) {
      return i;
    }
  }
  return null;
}

findInterceptorConstructorForType(Type type) {
  var index = findIndexForNativeSubclassType(type);
  if (index == null) return null;
  List map = JS('JSFixedArray', '#', mapTypeToInterceptor);
  return map[index + 1];
}

/**
 * Returns a JavaScript function that runs the constructor on its argument, or
 * `null` if there is no such constructor.
 *
 * The returned function takes one argument, the web component object.
 */
findConstructorForNativeSubclassType(Type type, String name) {
  var index = findIndexForNativeSubclassType(type);
  if (index == null) return null;
  List map = JS('JSFixedArray', '#', mapTypeToInterceptor);
  var constructorMap = map[index + 2];
  var constructorFn = JS('', '#[#]', constructorMap, name);
  return constructorFn;
}

findInterceptorForType(Type type) {
  var constructor = findInterceptorConstructorForType(type);
  if (constructor == null) return null;
  return JS('', '#.prototype', constructor);
}

/**
 * The base interceptor class.
 *
 * The code `r.foo(a)` is compiled to `getInterceptor(r).foo$1(r, a)`.  The
 * value returned by [getInterceptor] holds the methods separately from the
 * state of the instance.  The compiler converts the methods on an interceptor
 * to take the Dart `this` argument as an explicit `receiver` argument.  The
 * JavaScript `this` parameter is bound to the interceptor.
 *
 * In order to have uniform call sites, if a method is defined on an
 * interceptor, methods of that name on plain unintercepted classes also use the
 * interceptor calling convention.  The plain classes are _self-interceptors_,
 * and for them, `getInterceptor(r)` returns `r`.  Methods on plain
 * unintercepted classes have a redundant `receiver` argument and should ignore
 * it in favour of `this`.
 *
 * In the case of mixins, a method may be placed on both an intercepted class
 * and an unintercepted class.  In this case, the method must use the `receiver`
 * parameter.
 *
 *
 * There are various optimizations of the general call pattern.
 *
 * When the interceptor can be statically determined, it can be used directly:
 *
 *     CONSTANT_INTERCEPTOR.foo$1(r, a)
 *
 * If there are only a few classes, [getInterceptor] can be specialized with a
 * more efficient dispatch:
 *
 *     getInterceptor$specialized(r).foo$1(r, a)
 *
 * If it can be determined that the receiver is an unintercepted class, it can
 * be called directly:
 *
 *     r.foo$1(r, a)
 *
 * If, further, it is known that the call site cannot call a foo that is
 * mixed-in to a native class, then it is known that the explicit receiver is
 * ignored, and space-saving dummy value can be passed instead:
 *
 *     r.foo$1(0, a)
 *
 * This class defines implementations of *all* methods on [Object] so no
 * interceptor inherits an implementation from [Object].  This enables the
 * implementations on Object to ignore the explicit receiver argument, which
 * allows dummy receiver optimization.
 */
abstract class Interceptor {
  const Interceptor();

  bool operator ==(other) => identical(this, other);

  int get hashCode => Primitives.objectHashCode(this);

  String toString() => Primitives.objectToString(this);

  dynamic noSuchMethod(Invocation invocation) {
    throw new NoSuchMethodError(
        this,
        invocation.memberName,
        invocation.positionalArguments,
        invocation.namedArguments);
  }

  Type get runtimeType => getRuntimeType(this);
}

/**
 * The interceptor class for [bool].
 */
class JSBool extends Interceptor implements bool {
  const JSBool();

  // Note: if you change this, also change the function [S].
  String toString() => JS('String', r'String(#)', this);

  // The values here are SMIs, co-prime and differ about half of the bit
  // positions, including the low bit, so they are different mod 2^k.
  int get hashCode => this ? (2 * 3 * 23 * 3761) : (269 * 811);

  Type get runtimeType => bool;
}

/**
 * The interceptor class for [Null].
 *
 * This class defines implementations for *all* methods on [Object] since
 * the methods on Object assume the receiver is non-null.  This means that
 * JSNull will always be in the interceptor set for methods defined on Object.
 */
class JSNull extends Interceptor implements Null {
  const JSNull();

  bool operator ==(other) => identical(null, other);

  // Note: if you change this, also change the function [S].
  String toString() => 'null';

  int get hashCode => 0;

  // The spec guarantees that `null` is the singleton instance of the `Null`
  // class. In the mirrors library we also have to patch the `type` getter to
  // special case `null`.
  Type get runtimeType => Null;

  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
}

/**
 * The supertype for JSString and JSArray. Used by the backend as to
 * have a type mask that contains the objects that we can use the
 * native JS [] operator and length on.
 */
abstract class JSIndexable {
  int get length;
  operator[](int index);
}

/**
 * The supertype for JSMutableArray and
 * JavaScriptIndexingBehavior. Used by the backend to have a type mask
 * that contains the objects we can use the JS []= operator on.
 */
abstract class JSMutableIndexable extends JSIndexable {
  operator[]=(int index, var value);
}

/**
 * The interface implemented by JavaScript objects.  These are methods in
 * addition to the regular Dart Object methods like [Object.hashCode].
 *
 * This is the type that should be exported by a JavaScript interop library.
 */
abstract class JSObject {
}


/**
 * Interceptor base class for JavaScript objects not recognized as some more
 * specific native type.
 */
abstract class JavaScriptObject extends Interceptor implements JSObject {
  const JavaScriptObject();

  // It would be impolite to stash a property on the object.
  int get hashCode => 0;

  Type get runtimeType => JSObject;
}


/**
 * Interceptor for plain JavaScript objects created as JavaScript object
 * literals or `new Object()`.
 */
class PlainJavaScriptObject extends JavaScriptObject {
  const PlainJavaScriptObject();
}


/**
 * Interceptor for unclassified JavaScript objects, typically objects with a
 * non-trivial prototype chain.
 */
class UnknownJavaScriptObject extends JavaScriptObject {
  const UnknownJavaScriptObject();
}