/*

 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.nashorn.internal.runtime;

import static jdk.nashorn.internal.codegen.CompilerConstants.staticCall;

import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;

import static jdk.nashorn.internal.runtime.ECMAErrors.referenceError;

import static jdk.nashorn.internal.runtime.ECMAErrors.syntaxError;

import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

import static jdk.nashorn.internal.runtime.JSType.isRepresentableAsInt;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.reflect.Array;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.Locale;

import java.util.Map;

import java.util.NoSuchElementException;

import java.util.Objects;

import jdk.internal.dynalink.beans.StaticClass;

import jdk.nashorn.api.scripting.ScriptObjectMirror;

import jdk.nashorn.internal.codegen.CompilerConstants.Call;

import jdk.nashorn.internal.ir.debug.JSONWriter;

import jdk.nashorn.internal.parser.Lexer;

import jdk.nashorn.internal.runtime.linker.Bootstrap;

/**

 * Utilities to be called by JavaScript runtime API and generated classes.

 */

public final class ScriptRuntime {

    private ScriptRuntime() {

    }

    /** Singleton representing the empty array object '[]' */

    public static final Object[] EMPTY_ARRAY = new Object[0];

    /** Unique instance of undefined. */

    public static final Undefined UNDEFINED = Undefined.getUndefined();

    /**

     * Unique instance of undefined used to mark empty array slots.

     * Can't escape the array.

     */

    public static final Undefined EMPTY = Undefined.getEmpty();

    /** Method handle to generic + operator, operating on objects */

    public static final Call ADD = staticCallNoLookup(ScriptRuntime.class, "ADD", Object.class, Object.class, Object.class);

    /** Method handle to generic === operator, operating on objects */

    public static final Call EQ_STRICT = staticCallNoLookup(ScriptRuntime.class, "EQ_STRICT", boolean.class, Object.class, Object.class);

    /** Method handle used to enter a {@code with} scope at runtime. */

    public static final Call OPEN_WITH = staticCallNoLookup(ScriptRuntime.class, "openWith", ScriptObject.class, ScriptObject.class, Object.class);

    /** Method handle used to exit a {@code with} scope at runtime. */

    public static final Call CLOSE_WITH = staticCallNoLookup(ScriptRuntime.class, "closeWith", ScriptObject.class, ScriptObject.class);

    /**

     * Method used to place a scope's variable into the Global scope, which has to be done for the

     * properties declared at outermost script level.

     */

    public static final Call MERGE_SCOPE = staticCallNoLookup(ScriptRuntime.class, "mergeScope", ScriptObject.class, ScriptObject.class);

    /**

     * Return an appropriate iterator for the elements in a for-in construct

     */

    public static final Call TO_PROPERTY_ITERATOR = staticCallNoLookup(ScriptRuntime.class, "toPropertyIterator", Iterator.class, Object.class);

    /**

     * Return an appropriate iterator for the elements in a for-each construct

     */

    public static final Call TO_VALUE_ITERATOR = staticCallNoLookup(ScriptRuntime.class, "toValueIterator", Iterator.class, Object.class);

    /**

      * Method handle for apply. Used from {@link ScriptFunction} for looking up calls to

      * call sites that are known to be megamorphic. Using an invoke dynamic here would

      * lead to the JVM deoptimizing itself to death

      */

    public static final Call APPLY = staticCall(MethodHandles.lookup(), ScriptRuntime.class, "apply", Object.class, ScriptFunction.class, Object.class, Object[].class);

    /**

     * Converts a switch tag value to a simple integer. deflt value if it can't.

     *

     * @param tag   Switch statement tag value.

     * @param deflt default to use if not convertible.

     * @return int tag value (or deflt.)

     */

    public static int switchTagAsInt(final Object tag, final int deflt) {

        if (tag instanceof Number) {

            final double d = ((Number)tag).doubleValue();

            if (isRepresentableAsInt(d)) {

                return (int)d;

            }

        }

        return deflt;

    }

    /**

     * Converts a switch tag value to a simple integer. deflt value if it can't.

     *

     * @param tag   Switch statement tag value.

     * @param deflt default to use if not convertible.

     * @return int tag value (or deflt.)

     */

    public static int switchTagAsInt(final boolean tag, final int deflt) {

        return deflt;

    }

    /**

     * Converts a switch tag value to a simple integer. deflt value if it can't.

     *

     * @param tag   Switch statement tag value.

     * @param deflt default to use if not convertible.

     * @return int tag value (or deflt.)

     */

    public static int switchTagAsInt(final long tag, final int deflt) {

        return isRepresentableAsInt(tag) ? (int)tag : deflt;

    }

    /**

     * Converts a switch tag value to a simple integer. deflt value if it can't.

     *

     * @param tag   Switch statement tag value.

     * @param deflt default to use if not convertible.

     * @return int tag value (or deflt.)

     */

    public static int switchTagAsInt(final double tag, final int deflt) {

        return isRepresentableAsInt(tag) ? (int)tag : deflt;

    }

    /**

     * This is the builtin implementation of {@code Object.prototype.toString}

     * @param self reference

     * @return string representation as object

     */

    public static String builtinObjectToString(final Object self) {

        String className;

        // Spec tells us to convert primitives by ToObject..

        // But we don't need to -- all we need is the right class name

        // of the corresponding primitive wrapper type.

        final JSType type = JSType.of(self);

        switch (type) {

        case BOOLEAN:

            className = "Boolean";

            break;

        case NUMBER:

            className = "Number";

            break;

        case STRING:

            className = "String";

            break;

        // special case of null and undefined

        case NULL:

            className = "Null";

            break;

        case UNDEFINED:

            className = "Undefined";

            break;

        case OBJECT:

        case FUNCTION:

            if (self instanceof ScriptObject) {

                className = ((ScriptObject)self).getClassName();

            } else if (self instanceof ScriptObjectMirror) {

                className = ((ScriptObjectMirror)self).getClassName();

            } else {

                className = self.getClass().getName();

            }

            break;

        default:

            // Nashorn extension: use Java class name

            className = self.getClass().getName();

            break;

        }

        final StringBuilder sb = new StringBuilder();

        sb.append("[object ");

        sb.append(className);

        sb.append(']');

        return sb.toString();

    }

    /**

     * This is called whenever runtime wants to throw an error and wants to provide

     * meaningful information about an object. We don't want to call toString which

     * ends up calling "toString" from script world which may itself throw error.

     * When we want to throw an error, we don't additional error from script land

     * -- which may sometimes lead to infinite recursion.

     *

     * @param obj Object to converted to String safely (without calling user script)

     * @return safe String representation of the given object

     */

    public static String safeToString(final Object obj) {

        return JSType.toStringImpl(obj, true);

    }

    /**

     * Returns an iterator over property identifiers used in the {@code for...in} statement. Note that the ECMAScript

     * 5.1 specification, chapter 12.6.4. uses the terminology "property names", which seems to imply that the property

     * identifiers are expected to be strings, but this is not actually spelled out anywhere, and Nashorn will in some

     * cases deviate from this. Namely, we guarantee to always return an iterator over {@link String} values for any

     * built-in JavaScript object. We will however return an iterator over {@link Integer} objects for native Java

     * arrays and {@link List} objects, as well as arbitrary objects representing keys of a {@link Map}. Therefore, the

     * expression {@code typeof i} within a {@code for(i in obj)} statement can return something other than

     * {@code string} when iterating over native Java arrays, {@code List}, and {@code Map} objects.

     * @param obj object to iterate on.

     * @return iterator over the object's property names.

     */

    public static Iterator<?> toPropertyIterator(final Object obj) {

        if (obj instanceof ScriptObject) {

            return ((ScriptObject)obj).propertyIterator();

        }

        if (obj != null && obj.getClass().isArray()) {

            return new RangeIterator(Array.getLength(obj));

        }

        if (obj instanceof ScriptObjectMirror) {

            return ((ScriptObjectMirror)obj).keySet().iterator();

        }

        if (obj instanceof List) {

            return new RangeIterator(((List<?>)obj).size());

        }

        if (obj instanceof Map) {

            return ((Map<?,?>)obj).keySet().iterator();

        }

        return Collections.emptyIterator();

    }

    private static final class RangeIterator implements Iterator<Integer> {

        private final int length;

        private int index;

        RangeIterator(int length) {

            this.length = length;

        }

        @Override

        public boolean hasNext() {

            return index < length;

        }

        @Override

        public Integer next() {

            return index++;

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

    /**

     * Returns an iterator over property values used in the {@code for each...in} statement. Aside from built-in JS

     * objects, it also operates on Java arrays, any {@link Iterable}, as well as on {@link Map} objects, iterating over

     * map values.

     * @param obj object to iterate on.

     * @return iterator over the object's property values.

     */

    public static Iterator<?> toValueIterator(final Object obj) {

        if (obj instanceof ScriptObject) {

            return ((ScriptObject)obj).valueIterator();

        }

        if (obj != null && obj.getClass().isArray()) {

            final Object array  = obj;

            final int    length = Array.getLength(obj);

            return new Iterator<Object>() {

                private int index = 0;

                @Override

                public boolean hasNext() {

                    return index < length;

                }

                @Override

                public Object next() {

                    if (index >= length) {

                        throw new NoSuchElementException();

                    }

                    return Array.get(array, index++);

                }

                @Override

                public void remove() {

                    throw new UnsupportedOperationException();

                }

            };

        }

        if (obj instanceof ScriptObjectMirror) {

            return ((ScriptObjectMirror)obj).values().iterator();

        }

        if (obj instanceof Map) {

            return ((Map<?,?>)obj).values().iterator();

        }

        if (obj instanceof Iterable) {

            return ((Iterable<?>)obj).iterator();

        }

        return Collections.emptyIterator();

    }

    /**

     * Merge a scope into its prototype's map.

     * Merge a scope into its prototype.

     *

     * @param scope Scope to merge.

     * @return prototype object after merge

     */

    public static ScriptObject mergeScope(final ScriptObject scope) {

        final ScriptObject global = scope.getProto();

        global.addBoundProperties(scope);

        return global;

    }

    /**

     * Call a function given self and args. If the number of the arguments is known in advance, you can likely achieve

     * better performance by {@link Bootstrap#createDynamicInvoker(String, Class, Class...) creating a dynamic invoker}

     * for operation {@code "dyn:call"}, then using its {@link MethodHandle#invokeExact(Object...)} method instead.

     *

     * @param target ScriptFunction object.

     * @param self   Receiver in call.

     * @param args   Call arguments.

     * @return Call result.

     */

    public static Object apply(final ScriptFunction target, final Object self, final Object... args) {

        try {

            return target.invoke(self, args);

        } catch (final RuntimeException | Error e) {

            throw e;

        } catch (final Throwable t) {

            throw new RuntimeException(t);

        }

    }

    /**

     * Call a script function as a constructor with given args.

     *

     * @param target ScriptFunction object.

     * @param args   Call arguments.

     * @return Constructor call result.

     */

    public static Object construct(final ScriptFunction target, final Object... args) {

        try {

            return target.construct(args);

        } catch (final RuntimeException | Error e) {

            throw e;

        } catch (final Throwable t) {

            throw new RuntimeException(t);

        }

    }

    /**

     * Generic implementation of ECMA 9.12 - SameValue algorithm

     *

     * @param x first value to compare

     * @param y second value to compare

     *

     * @return true if both objects have the same value

     */

    public static boolean sameValue(final Object x, final Object y) {

        final JSType xType = JSType.of(x);

        final JSType yType = JSType.of(y);

        if (xType != yType) {

            return false;

        }

        if (xType == JSType.UNDEFINED || xType == JSType.NULL) {

            return true;

        }

        if (xType == JSType.NUMBER) {

            final double xVal = ((Number)x).doubleValue();

            final double yVal = ((Number)y).doubleValue();

            if (Double.isNaN(xVal) && Double.isNaN(yVal)) {

                return true;

            }

            // checking for xVal == -0.0 and yVal == +0.0 or vice versa

            if (xVal == 0.0 && (Double.doubleToLongBits(xVal) != Double.doubleToLongBits(yVal))) {

                return false;

            }

            return xVal == yVal;

        }

        if (xType == JSType.STRING || yType == JSType.BOOLEAN) {

            return x.equals(y);

        }

        return (x == y);

    }

    /**

     * Returns AST as JSON compatible string. This is used to

     * implement "parse" function in resources/parse.js script.

     *

     * @param code code to be parsed

     * @param name name of the code source (used for location)

     * @param includeLoc tells whether to include location information for nodes or not

     * @return JSON string representation of AST of the supplied code

     */

    public static String parse(final String code, final String name, final boolean includeLoc) {

        return JSONWriter.parse(Context.getContextTrusted().getEnv(), code, name, includeLoc);

    }

    /**

     * Test whether a char is valid JavaScript whitespace

     * @param ch a char

     * @return true if valid JavaScript whitespace

     */

    public static boolean isJSWhitespace(final char ch) {

        return Lexer.isJSWhitespace(ch);

    }

    /**

     * Entering a {@code with} node requires new scope. This is the implementation

     *

     * @param scope      existing scope

     * @param expression expression in with

     *

     * @return {@link WithObject} that is the new scope

     */

    public static ScriptObject openWith(final ScriptObject scope, final Object expression) {

        final ScriptObject global = Context.getGlobalTrusted();

        if (expression == UNDEFINED) {

            throw typeError(global, "cant.apply.with.to.undefined");

        } else if (expression == null) {

            throw typeError(global, "cant.apply.with.to.null");

        }

    }

    /**

     * Exiting a {@code with} node requires restoring scope. This is the implementation

     *

     * @param scope existing scope

     *

     * @return restored scope

     */

    public static ScriptObject closeWith(final ScriptObject scope) {

        if (scope instanceof WithObject) {

        }

        return scope;

    }

    /**

     * ECMA 11.6.1 - The addition operator (+) - generic implementation

     * Compiler specializes using {@link jdk.nashorn.internal.codegen.RuntimeCallSite}

     * if any type information is available for any of the operands

     *

     * @param x  first term

     * @param y  second term

     *

     * @return result of addition

     */

    public static Object ADD(final Object x, final Object y) {

        // This prefix code to handle Number special is for optimization.

        final boolean xIsNumber = x instanceof Number;

        final boolean yIsNumber = y instanceof Number;

        if (xIsNumber && yIsNumber) {

             return ((Number)x).doubleValue() + ((Number)y).doubleValue();

        }

        final boolean xIsUndefined = x == UNDEFINED;

        final boolean yIsUndefined = y == UNDEFINED;