/*
 * 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.ir;

import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_PROFILE;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_STRICT;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_TRACE;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_TRACE_ENTEREXIT;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_TRACE_MISSES;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_TRACE_VALUES;

import java.util.Collections;
import java.util.EnumSet;
import java.util.Iterator;
import java.util.List;
import java.util.function.Function;
import jdk.nashorn.internal.AssertsEnabled;
import jdk.nashorn.internal.codegen.CompileUnit;
import jdk.nashorn.internal.codegen.Compiler;
import jdk.nashorn.internal.codegen.CompilerConstants;
import jdk.nashorn.internal.codegen.Namespace;
import jdk.nashorn.internal.codegen.types.Type;
import jdk.nashorn.internal.ir.annotations.Ignore;
import jdk.nashorn.internal.ir.annotations.Immutable;
import jdk.nashorn.internal.ir.visitor.NodeVisitor;
import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.Source;
import jdk.nashorn.internal.runtime.UserAccessorProperty;
import jdk.nashorn.internal.runtime.linker.LinkerCallSite;

/**
 * IR representation for function (or script.)
 */
@Immutable
public final class FunctionNode extends LexicalContextExpression implements Flags<FunctionNode>, CompileUnitHolder {
    private static final long serialVersionUID = 1L;

    /** Type used for all FunctionNodes */
    public static final Type FUNCTION_TYPE = Type.typeFor(ScriptFunction.class);

    /** Function kinds */
    public enum Kind {
        /** a normal function - nothing special */
        NORMAL,
        /** a script function */
        SCRIPT,
        /** a getter, @see {@link UserAccessorProperty} */
        GETTER,
        /** a setter, @see {@link UserAccessorProperty} */
        SETTER
    }

    /** Compilation states available */
    public enum CompilationState {
        /** compiler is ready */
        INITIALIZED,
        /** method has been parsed */
        PARSED,
        /** method has been parsed */
        PARSE_ERROR,
        /** constant folding pass */
        CONSTANT_FOLDED,
        /** method has been lowered */
        LOWERED,
        /** program points have been assigned to unique locations */
        PROGRAM_POINTS_ASSIGNED,
        /** any transformations of builtins have taken place, e.g. apply=&gt;call */
        BUILTINS_TRANSFORMED,
        /** method has been split */
        SPLIT,
        /** method has had symbols assigned */
        SYMBOLS_ASSIGNED,
        /** computed scope depths for symbols */
        SCOPE_DEPTHS_COMPUTED,
        /** method has had types calculated*/
        OPTIMISTIC_TYPES_ASSIGNED,
        /** method has had types calculated */
        LOCAL_VARIABLE_TYPES_CALCULATED,
        /** compile units reused (optional) */
        COMPILE_UNITS_REUSED,
        /** method has been emitted to bytecode */
        BYTECODE_GENERATED,
        /** method has been installed */
        BYTECODE_INSTALLED
    }

    /** Source of entity. */
    private transient final Source source;

    /**
     * Opaque object representing parser state at the end of the function. Used when reparsing outer functions
     * to skip parsing inner functions.
     */
    private final Object endParserState;

    /** External function identifier. */
    @Ignore
    private final IdentNode ident;

    /** The body of the function node */
    private final Block body;

    /** Internal function name. */
    private final String name;

    /** Compilation unit. */
    private final CompileUnit compileUnit;

    /** Function kind. */
    private final Kind kind;

    /** List of parameters. */
    private final List<IdentNode> parameters;

    /** First token of function. **/
    private final long firstToken;

    /** Last token of function. **/
    private final long lastToken;

    /** Method's namespace. */
    private transient final Namespace namespace;

    /** Current compilation state */
    @Ignore
    private final EnumSet<CompilationState> compilationState;

    /** Number of properties of "this" object assigned in this function */
    @Ignore
    private final int thisProperties;

    /** Function flags. */
    private final int flags;

    /** Line number of function start */
    private final int lineNumber;

    /** Root class for function */
    private final Class<?> rootClass;

    /** Is anonymous function flag. */
    public static final int IS_ANONYMOUS                = 1 << 0;

    /** Is the function created in a function declaration (as opposed to a function expression) */
    public static final int IS_DECLARED                 = 1 << 1;

    /** is this a strict mode function? */
    public static final int IS_STRICT                   = 1 << 2;

    /** Does the function use the "arguments" identifier ? */
    public static final int USES_ARGUMENTS              = 1 << 3;

    /** Has this function been split because it was too large? */
    public static final int IS_SPLIT                    = 1 << 4;

    /** Does the function call eval? If it does, then all variables in this function might be get/set by it and it can
     * introduce new variables into this function's scope too.*/
    public static final int HAS_EVAL                    = 1 << 5;

    /** Does a nested function contain eval? If it does, then all variables in this function might be get/set by it. */
    public static final int HAS_NESTED_EVAL             = 1 << 6;

    /** Does this function have any blocks that create a scope? This is used to determine if the function needs to
     * have a local variable slot for the scope symbol. */
    public static final int HAS_SCOPE_BLOCK             = 1 << 7;

    /**
     * Flag this function as one that defines the identifier "arguments" as a function parameter or nested function
     * name. This precludes it from needing to have an Arguments object defined as "arguments" local variable. Note that
     * defining a local variable named "arguments" still requires construction of the Arguments object (see
     * ECMAScript 5.1 Chapter 10.5).
     * @see #needsArguments()
     */
    public static final int DEFINES_ARGUMENTS           = 1 << 8;

    /** Does this function or any of its descendants use variables from an ancestor function's scope (incl. globals)? */
    public static final int USES_ANCESTOR_SCOPE         = 1 << 9;

    /** Does this function have nested declarations? */
    public static final int HAS_FUNCTION_DECLARATIONS   = 1 << 10;

    /** Does this function have optimistic expressions? (If it does, it can undergo deoptimizing recompilation.) */
    public static final int IS_DEOPTIMIZABLE            = 1 << 11;

    /** Are we vararg, but do we just pass the arguments along to apply or call */
    public static final int HAS_APPLY_TO_CALL_SPECIALIZATION = 1 << 12;

    /**
     * Is this function the top-level program?
     */
    public static final int IS_PROGRAM = 1 << 13;

    /**
     * Flag indicating whether this function uses the local variable symbol for itself. Only named function expressions
     * can have this flag set if they reference themselves (e.g. "(function f() { return f })". Declared functions will
     * use the symbol in their parent scope instead when they reference themselves by name.
     */
    public static final int USES_SELF_SYMBOL = 1 << 14;

    /** Does this function use the "this" keyword? */
    public static final int USES_THIS = 1 << 15;

    /** Is this declared in a dynamic context */
    public static final int IN_DYNAMIC_CONTEXT = 1 << 16;

    /**
     * The following flags are derived from directive comments within this function.
     * Note that even IS_STRICT is one such flag but that requires special handling.
     */

    /** parser, print parse tree */
    public static final int IS_PRINT_PARSE       = 1 << 17;
    /** parser, print lower parse tree */
    public static final int IS_PRINT_LOWER_PARSE = 1 << 18;
    /** parser, print AST */
    public static final int IS_PRINT_AST         = 1 << 19;
    /** parser, print lower AST */
    public static final int IS_PRINT_LOWER_AST   = 1 << 20;
    /** parser, print symbols */
    public static final int IS_PRINT_SYMBOLS     = 1 << 21;

    // callsite tracing, profiling within this function
    /** profile callsites in this function? */
    public static final int IS_PROFILE         = 1 << 22;

    /** trace callsite enterexit in this function? */
    public static final int IS_TRACE_ENTEREXIT = 1 << 23;

    /** trace callsite misses in this function? */
    public static final int IS_TRACE_MISSES    = 1 << 24;

    /** trace callsite values in this function? */
    public static final int IS_TRACE_VALUES    = 1 << 25;

    /**
     * Whether this function needs the callee {@link ScriptFunction} instance passed to its code as a
     * parameter on invocation. Note that we aren't, in fact using this flag in function nodes.
     * Rather, it is always calculated (see {@link #needsCallee()}). {@link RecompilableScriptFunctionData}
     * will, however, cache the value of this flag.
     */
    public static final int NEEDS_CALLEE       = 1 << 26;

    /** extension callsite flags mask */
    public static final int EXTENSION_CALLSITE_FLAGS = IS_PRINT_PARSE |
        IS_PRINT_LOWER_PARSE | IS_PRINT_AST | IS_PRINT_LOWER_AST |
        IS_PRINT_SYMBOLS | IS_PROFILE | IS_TRACE_ENTEREXIT |
        IS_TRACE_MISSES | IS_TRACE_VALUES;

    /** Does this function or any nested functions contain an eval? */
    private static final int HAS_DEEP_EVAL = HAS_EVAL | HAS_NESTED_EVAL;

    /** Does this function need to store all its variables in scope? */
    private static final int HAS_ALL_VARS_IN_SCOPE = HAS_DEEP_EVAL;

    /** Does this function potentially need "arguments"? Note that this is not a full test, as further negative check of REDEFINES_ARGS is needed. */
    private static final int MAYBE_NEEDS_ARGUMENTS = USES_ARGUMENTS | HAS_EVAL;

    /** Does this function need the parent scope? It needs it if either it or its descendants use variables from it, or have a deep eval, or it's the program. */
    public static final int NEEDS_PARENT_SCOPE = USES_ANCESTOR_SCOPE | HAS_DEEP_EVAL | IS_PROGRAM;

    /** What is the return type of this function? */
    private Type returnType = Type.UNKNOWN;

    /**
     * Constructor
     *
     * @param source     the source
     * @param lineNumber line number
     * @param token      token
     * @param finish     finish
     * @param firstToken first token of the function node (including the function declaration)
     * @param namespace  the namespace
     * @param ident      the identifier
     * @param name       the name of the function
     * @param parameters parameter list
     * @param kind       kind of function as in {@link FunctionNode.Kind}
     * @param flags      initial flags
     */
    public FunctionNode(
        final Source source,
        final int lineNumber,
        final long token,
        final int finish,
        final long firstToken,
        final Namespace namespace,
        final IdentNode ident,
        final String name,
        final List<IdentNode> parameters,
        final FunctionNode.Kind kind,
        final int flags) {
        super(token, finish);

        this.source           = source;
        this.lineNumber       = lineNumber;
        this.ident            = ident;
        this.name             = name;
        this.kind             = kind;
        this.parameters       = parameters;
        this.firstToken       = firstToken;
        this.lastToken        = token;
        this.namespace        = namespace;
        this.compilationState = EnumSet.of(CompilationState.INITIALIZED);
        this.flags            = flags;
        this.compileUnit      = null;
        this.body             = null;
        this.thisProperties   = 0;
        this.rootClass        = null;
        this.endParserState    = null;
    }

    private FunctionNode(
        final FunctionNode functionNode,
        final long lastToken,
        final Object endParserState,
        final int flags,
        final String name,
        final Type returnType,
        final CompileUnit compileUnit,
        final EnumSet<CompilationState> compilationState,
        final Block body,
        final List<IdentNode> parameters,
        final int thisProperties,
        final Class<?> rootClass,
        final Source source, Namespace namespace) {
        super(functionNode);

        this.endParserState    = endParserState;
        this.lineNumber       = functionNode.lineNumber;
        this.flags            = flags;
        this.name             = name;
        this.returnType       = returnType;
        this.compileUnit      = compileUnit;
        this.lastToken        = lastToken;
        this.compilationState = compilationState;
        this.body             = body;
        this.parameters       = parameters;
        this.thisProperties   = thisProperties;
        this.rootClass        = rootClass;
        this.source           = source;
        this.namespace        = namespace;

        // the fields below never change - they are final and assigned in constructor
        this.ident           = functionNode.ident;
        this.kind            = functionNode.kind;
        this.firstToken      = functionNode.firstToken;
    }

    @Override
    public Node accept(final LexicalContext lc, final NodeVisitor<? extends LexicalContext> visitor) {
        if (visitor.enterFunctionNode(this)) {
            return visitor.leaveFunctionNode(setBody(lc, (Block)body.accept(visitor)));
        }
        return this;
    }

    /**
     * Visits the parameter nodes of this function. Parameters are normally not visited automatically.
     * @param visitor the visitor to apply to the nodes.
     * @return a list of parameter nodes, potentially modified from original ones by the visitor.
     */
    public List<IdentNode> visitParameters(final NodeVisitor<? extends LexicalContext> visitor) {
        return Node.accept(visitor, parameters);
    }

    /**
     * Get additional callsite flags to be used specific to this function.
     *
     * @return callsite flags
     */
    public int getCallSiteFlags() {
        int callsiteFlags = 0;
        if (getFlag(IS_STRICT)) {
            callsiteFlags |= CALLSITE_STRICT;
        }

        // quick check for extension callsite flags turned on by directives.
        if ((flags & EXTENSION_CALLSITE_FLAGS) == 0) {
            return callsiteFlags;
        }

        if (getFlag(IS_PROFILE)) {
            callsiteFlags |= CALLSITE_PROFILE;
        }

        if (getFlag(IS_TRACE_MISSES)) {
            callsiteFlags |= CALLSITE_TRACE | CALLSITE_TRACE_MISSES;
        }

        if (getFlag(IS_TRACE_VALUES)) {
            callsiteFlags |= CALLSITE_TRACE | CALLSITE_TRACE_ENTEREXIT | CALLSITE_TRACE_VALUES;
        }

        if (getFlag(IS_TRACE_ENTEREXIT)) {
            callsiteFlags |= CALLSITE_TRACE | CALLSITE_TRACE_ENTEREXIT;
        }

        return callsiteFlags;
    }

    /**
     * Get the source for this function
     * @return the source
     */
    public Source getSource() {
        return source;
    }

    /**
     * Sets the source and namespace for this function. It can only set a non-null source and namespace for a function
     * that currently has both a null source and a null namespace. This is used to re-set the source and namespace for
     * a deserialized function node.
     * @param source the source for the function.
     * @param namespace the namespace for the function
     * @return a new function node with the set source and namespace
     * @throws IllegalArgumentException if the specified source or namespace is null
     * @throws IllegalStateException if the function already has either a source or namespace set.
     */
    public FunctionNode initializeDeserialized(final Source source, final Namespace namespace) {
        if (source == null || namespace == null) {
            throw new IllegalArgumentException();
        } else if (this.source == source && this.namespace == namespace) {
            return this;
        } else if (this.source != null || this.namespace != null) {
            throw new IllegalStateException();
        }
        return new FunctionNode(
            this,
            lastToken,
            endParserState,
            flags,
            name,
            returnType,
            compileUnit,
            compilationState,
            body,
            parameters,
            thisProperties,
            rootClass, source, namespace);
    }

    /**
     * Get the unique ID for this function within the script file.
     * @return the id
     */
    public int getId() {
        return position();
    }

    /**
     * get source name - sourceURL or name derived from Source.
     *
     * @return name for the script source
     */
    public String getSourceName() {
        return getSourceName(source);
    }

    /**
     * Static source name getter
     *
     * @param source the source
     * @return source name
     */
    public static String getSourceName(final Source source) {
        final String explicitURL = source.getExplicitURL();
        return explicitURL != null ? explicitURL : source.getName();
    }

    /**
     * Function to parse nashorn per-function extension directive comments.
     *
     * @param directive nashorn extension directive string
     * @return integer flag for the given directive.
     */
    public static int getDirectiveFlag(final String directive) {
        switch (directive) {
            case "nashorn callsite trace enterexit":
                return IS_TRACE_ENTEREXIT;
            case "nashorn callsite trace misses":
                return IS_TRACE_MISSES;
            case "nashorn callsite trace objects":
                return IS_TRACE_VALUES;
            case "nashorn callsite profile":
                return IS_PROFILE;
            case "nashorn print parse":
                return IS_PRINT_PARSE;
            case "nashorn print lower parse":
                return IS_PRINT_LOWER_PARSE;
            case "nashorn print ast":
                return IS_PRINT_AST;
            case "nashorn print lower ast":
                return IS_PRINT_LOWER_AST;
            case "nashorn print symbols":
                return IS_PRINT_SYMBOLS;
            default:
                // unknown/unsupported directive
                return 0;
        }
    }

    /**
     * Returns the line number.
     * @return the line number.
     */
    public int getLineNumber() {
        return lineNumber;
    }

    /**
     * Get the compilation state of this function
     * @return the compilation state
     */
    public EnumSet<CompilationState> getState() {
        return compilationState;
    }

    /**
     * Check whether this FunctionNode has reached a give CompilationState.
     *
     * @param state the state to check for
     * @return true of the node is in the given state
     */
    public boolean hasState(final EnumSet<CompilationState> state) {
        return !AssertsEnabled.assertsEnabled() || compilationState.containsAll(state);
    }

    /**
     * Add a state to the total CompilationState of this node, e.g. if
     * FunctionNode has been lowered, the compiler will add
     * {@code CompilationState#LOWERED} to the state vector
     *
     * @param lc lexical context
     * @param state {@link CompilationState} to add
     * @return function node or a new one if state was changed
     */
    public FunctionNode setState(final LexicalContext lc, final CompilationState state) {
        if (!AssertsEnabled.assertsEnabled() || this.compilationState.contains(state)) {
            return this;
        }
        final EnumSet<CompilationState> newState = EnumSet.copyOf(this.compilationState);
        newState.add(state);
        return setCompilationState(lc, newState);
    }

    /**
     * Copy a compilation state from an original function to this function. Used when creating synthetic
     * function nodes by the splitter.
     *
     * @param lc lexical context
     * @param original the original function node to copy compilation state from
     * @return function node or a new one if state was changed
     */
    public FunctionNode copyCompilationState(final LexicalContext lc, final FunctionNode original) {
        final EnumSet<CompilationState> origState = original.compilationState;
        if (!AssertsEnabled.assertsEnabled() || this.compilationState.containsAll(origState)) {
            return this;
        }
        final EnumSet<CompilationState> newState = EnumSet.copyOf(this.compilationState);
        newState.addAll(origState);
        return setCompilationState(lc, newState);
    }

    private FunctionNode setCompilationState(final LexicalContext lc, final EnumSet<CompilationState> compilationState) {
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }


    /**
     * Create a unique name in the namespace of this FunctionNode
     * @param base prefix for name
     * @return base if no collision exists, otherwise a name prefix with base
     */
    public String uniqueName(final String base) {
        return namespace.uniqueName(base);
    }

    @Override
    public void toString(final StringBuilder sb, final boolean printTypes) {
        sb.append('[').
            append(returnType).
            append(']').
            append(' ');

        sb.append("function");

        if (ident != null) {
            sb.append(' ');
            ident.toString(sb, printTypes);
        }

        sb.append('(');

        for (final Iterator<IdentNode> iter = parameters.iterator(); iter.hasNext(); ) {
            final IdentNode parameter = iter.next();
            if (parameter.getSymbol() != null) {
                sb.append('[').append(parameter.getType()).append(']').append(' ');
            }
            parameter.toString(sb, printTypes);
            if (iter.hasNext()) {
                sb.append(", ");
            }
        }

        sb.append(')');
    }

    @Override
    public int getFlags() {
        return flags;
    }

    @Override
    public boolean getFlag(final int flag) {
        return (flags & flag) != 0;
    }

    @Override
    public FunctionNode setFlags(final LexicalContext lc, final int flags) {
        if (this.flags == flags) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    @Override
    public FunctionNode clearFlag(final LexicalContext lc, final int flag) {
        return setFlags(lc, flags & ~flag);
    }

    @Override
    public FunctionNode setFlag(final LexicalContext lc, final int flag) {
        return setFlags(lc, flags | flag);
    }

    /**
     * Returns true if the function is the top-level program.
     * @return True if this function node represents the top-level program.
     */
    public boolean isProgram() {
        return getFlag(IS_PROGRAM);
    }

    /**
     * Returns true if the function contains at least one optimistic operation (and thus can be deoptimized).
     * @return true if the function contains at least one optimistic operation (and thus can be deoptimized).
     */
    public boolean canBeDeoptimized() {
        return getFlag(IS_DEOPTIMIZABLE);
    }

    /**
     * Check if this function has a call expression for the identifier "eval" (that is, {@code eval(...)}).
     *
     * @return true if {@code eval} is called.
     */
    public boolean hasEval() {
        return getFlag(HAS_EVAL);
    }

    /**
     * Returns true if a function nested (directly or transitively) within this function {@link #hasEval()}.
     *
     * @return true if a nested function calls {@code eval}.
     */
    public boolean hasNestedEval() {
        return getFlag(HAS_NESTED_EVAL);
    }

    /**
     * Get the first token for this function
     * @return the first token
     */
    public long getFirstToken() {
        return firstToken;
    }

    /**
     * Check whether this function has nested function declarations
     * @return true if nested function declarations exist
     */
    public boolean hasDeclaredFunctions() {
        return getFlag(HAS_FUNCTION_DECLARATIONS);
    }

    /**
     * Check if this function's generated Java method needs a {@code callee} parameter. Functions that need access to
     * their parent scope, functions that reference themselves, and non-strict functions that need an Arguments object
     * (since it exposes {@code arguments.callee} property) will need to have a callee parameter. We also return true
     * for split functions to make sure symbols slots are the same in the main and split methods.
     *
     * A function that has had an apply(this,arguments) turned into a call doesn't need arguments anymore, but still
     * has to fit the old callsite, thus, we require a dummy callee parameter for those functions as well
     *
     * @return true if the function's generated Java method needs a {@code callee} parameter.
     */
    public boolean needsCallee() {
        // NOTE: we only need isSplit() here to ensure that :scope can never drop below slot 2 for splitting array units.
        return needsParentScope() || usesSelfSymbol() || isSplit() || (needsArguments() && !isStrict()) || hasOptimisticApplyToCall();
    }

    /**
     * Return {@code true} if this function makes use of the {@code this} object.
     *
     * @return true if function uses {@code this} object
     */
    public boolean usesThis() {
        return getFlag(USES_THIS);
    }


    /**
     * Return true if function contains an apply to call transform
     * @return true if this function has transformed apply to call
     */
    public boolean hasOptimisticApplyToCall() {
        return getFlag(HAS_APPLY_TO_CALL_SPECIALIZATION);
    }

    /**
     * Get the identifier for this function, this is its symbol.
     * @return the identifier as an IdentityNode
     */
    public IdentNode getIdent() {
        return ident;
    }

    /**
     * Get the function body
     * @return the function body
     */
    public Block getBody() {
        return body;
    }

    /**
     * Reset the function body
     * @param lc lexical context
     * @param body new body
     * @return new function node if body changed, same if not
     */
    public FunctionNode setBody(final LexicalContext lc, final Block body) {
        if (this.body == body) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags |
                            (body.needsScope() ?
                                    FunctionNode.HAS_SCOPE_BLOCK :
                                    0),
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    /**
     * Does this function's method needs to be variable arity (gather all script-declared parameters in a final
     * {@code Object[]} parameter. Functions that need to have the "arguments" object as well as functions that simply
     * declare too many arguments for JVM to handle with fixed arity will need to be variable arity.
     * @return true if the Java method in the generated code that implements this function needs to be variable arity.
     * @see #needsArguments()
     * @see LinkerCallSite#ARGLIMIT
     */
    public boolean isVarArg() {
        return needsArguments() || parameters.size() > LinkerCallSite.ARGLIMIT;
    }

    /**
     * Was this function declared in a dynamic context, i.e. in a with or eval style
     * chain
     * @return true if in dynamic context
     */
    public boolean inDynamicContext() {
        return getFlag(IN_DYNAMIC_CONTEXT);
    }

    /**
     * Check whether a function would need dynamic scope, which is does if it has
     * evals and isn't strict.
     * @return true if dynamic scope is needed
     */
    public boolean needsDynamicScope() {
        // Function has a direct eval in it (so a top-level "var ..." in the eval code can introduce a new
        // variable into the function's scope), and it isn't strict (as evals in strict functions get an
        // isolated scope).
        return hasEval() && !isStrict();
    }

    /**
     * Flag this function as declared in a dynamic context
     * @param lc lexical context
     * @return new function node, or same if unmodified
     */
    public FunctionNode setInDynamicContext(final LexicalContext lc) {
        return setFlag(lc, IN_DYNAMIC_CONTEXT);
    }

    /**
     * Returns true if this function needs to have an Arguments object defined as a local variable named "arguments".
     * Functions that use "arguments" as identifier and don't define it as a name of a parameter or a nested function
     * (see ECMAScript 5.1 Chapter 10.5), as well as any function that uses eval or with, or has a nested function that
     * does the same, will have an "arguments" object. Also, if this function is a script, it will not have an
     * "arguments" object, because it does not have local variables; rather the Global object will have an explicit
     * "arguments" property that provides command-line arguments for the script.
     * @return true if this function needs an arguments object.
     */
    public boolean needsArguments() {
        // uses "arguments" or calls eval, but it does not redefine "arguments", and finally, it's not a script, since
        // for top-level script, "arguments" is picked up from Context by Global.init() instead.
        return getFlag(MAYBE_NEEDS_ARGUMENTS) && !getFlag(DEFINES_ARGUMENTS) && !isProgram();
    }

    /**
     * Returns true if this function needs access to its parent scope. Functions referencing variables outside their
     * scope (including global variables), as well as functions that call eval or have a with block, or have nested
     * functions that call eval or have a with block, will need a parent scope. Top-level script functions also need a
     * parent scope since they might be used from within eval, and eval will need an externally passed scope.
     * @return true if the function needs parent scope.
     */
    public boolean needsParentScope() {
        return getFlag(NEEDS_PARENT_SCOPE);
    }

    /**
     * Set the number of properties assigned to the this object in this function.
     * @param lc the current lexical context.
     * @param thisProperties number of properties
     * @return a potentially modified function node
     */
    public FunctionNode setThisProperties(final LexicalContext lc, final int thisProperties) {
        if (this.thisProperties == thisProperties) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    /**
     * Get the number of properties assigned to the this object in this function.
     * @return number of properties
     */
    public int getThisProperties() {
        return thisProperties;
    }

    /**
     * Returns true if any of the blocks in this function create their own scope.
     * @return true if any of the blocks in this function create their own scope.
     */
    public boolean hasScopeBlock() {
        return getFlag(HAS_SCOPE_BLOCK);
    }

    /**
     * Return the kind of this function
     * @see FunctionNode.Kind
     * @return the kind
     */
    public Kind getKind() {
        return kind;
    }

    /**
     * Return the last token for this function's code
     * @return last token
     */
    public long getLastToken() {
        return lastToken;
    }

    /**
     * Set the last token for this function's code
     * @param lc lexical context
     * @param lastToken the last token
     * @return function node or a new one if state was changed
     */
    public FunctionNode setLastToken(final LexicalContext lc, final long lastToken) {
        if (this.lastToken == lastToken) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    /**
     * Returns the end parser state for this function.
     * @return the end parser state for this function.
     */
    public Object getEndParserState() {
        return endParserState;
    }

    /**
     * Set the end parser state for this function.
     * @param lc lexical context
     * @param endParserState the parser state to set
     * @return function node or a new one if state was changed
     */
    public FunctionNode setEndParserState(final LexicalContext lc, final Object endParserState) {
        if (this.endParserState == endParserState) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass,
                        source,
                        namespace));
    }

    /**
     * Get the name of this function
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * Set the internal name for this function
     * @param lc    lexical context
     * @param name new name
     * @return new function node if changed, otherwise the same
     */
    public FunctionNode setName(final LexicalContext lc, final String name) {
        if (this.name.equals(name)) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass,
                        source,
                        namespace));
    }

    /**
     * Check if this function should have all its variables in its own scope. Split sub-functions, and
     * functions having with and/or eval blocks are such.
     *
     * @return true if all variables should be in scope
     */
    public boolean allVarsInScope() {
        return getFlag(HAS_ALL_VARS_IN_SCOPE);
    }

    /**
     * Checks if this function is split into several smaller fragments.
     *
     * @return true if this function is split into several smaller fragments.
     */
    public boolean isSplit() {
        return getFlag(IS_SPLIT);
    }

    /**
     * Get the parameters to this function
     * @return a list of IdentNodes which represent the function parameters, in order
     */
    public List<IdentNode> getParameters() {
        return Collections.unmodifiableList(parameters);
    }

    /**
     * Returns the identifier for a named parameter at the specified position in this function's parameter list.
     * @param index the parameter's position.
     * @return the identifier for the requested named parameter.
     * @throws IndexOutOfBoundsException if the index is invalid.
     */
    public IdentNode getParameter(final int index) {
        return parameters.get(index);
    }

    /**
     * Reset the compile unit used to compile this function
     * @see Compiler
     * @param  lc lexical context
     * @param  parameters the compile unit
     * @return function node or a new one if state was changed
     */
    public FunctionNode setParameters(final LexicalContext lc, final List<IdentNode> parameters) {
        if (this.parameters == parameters) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    /**
     * Check if this function is created as a function declaration (as opposed to function expression)
     * @return true if function is declared.
     */
    public boolean isDeclared() {
        return getFlag(IS_DECLARED);
    }

    /**
     * Check if this function is anonymous
     * @return true if function is anonymous
     */
    public boolean isAnonymous() {
        return getFlag(IS_ANONYMOUS);
    }

    /**
     * Does this function use its self symbol - this is needed only for self-referencing named function expressions.
     * Self-referencing declared functions won't have this flag set, as they can access their own symbol through the
     * scope (since they're bound to the symbol with their name in their enclosing scope).
     * @return true if this function node is a named function expression that uses the symbol for itself.
     */
    public boolean usesSelfSymbol() {
        return getFlag(USES_SELF_SYMBOL);
    }

    @Override
    public Type getType(final Function<Symbol, Type> localVariableTypes) {
        return FUNCTION_TYPE;
    }

    @Override
    public Type getWidestOperationType() {
        return FUNCTION_TYPE;
    }

    /**
     * Get the return type for this function. Return types can be specialized
     * if the compiler knows them, but parameters cannot, as they need to go through
     * appropriate object conversion
     *
     * @return the return type
     */
    public Type getReturnType() {
        return returnType;
    }

    /**
     * Set the function return type
     * @param lc lexical context
     * @param returnType new return type
     * @return function node or a new one if state was changed
     */
    public FunctionNode setReturnType(final LexicalContext lc, final Type returnType) {
        //we never bother with object types narrower than objects, that will lead to byte code verification errors
        //as for instance even if we know we are returning a string from a method, the code generator will always
        //treat it as an object, at least for now
        final Type type = returnType.isObject() ? Type.OBJECT : returnType;
        if (this.returnType == type) {
            return this;
        }
        return Node.replaceInLexicalContext(
            lc,
            this,
            new FunctionNode(
                this,
                lastToken,
                endParserState,
                flags,
                name,
                type,
                compileUnit,
                compilationState,
                body,
                parameters,
                thisProperties,
                rootClass, source, namespace
                ));
   }

    /**
     * Check if the function is generated in strict mode
     * @return true if strict mode enabled for function
     */
    public boolean isStrict() {
        return getFlag(IS_STRICT);
    }

    /**
     * Get the compile unit used to compile this function
     * @see Compiler
     * @return the compile unit
     */
    @Override
    public CompileUnit getCompileUnit() {
        return compileUnit;
    }

    /**
     * Reset the compile unit used to compile this function
     * @see Compiler
     * @param lc lexical context
     * @param compileUnit the compile unit
     * @return function node or a new one if state was changed
     */
    public FunctionNode setCompileUnit(final LexicalContext lc, final CompileUnit compileUnit) {
        if (this.compileUnit == compileUnit) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }

    /**
     * Create a temporary variable to the current frame.
     *
     * @param block that needs the temporary
     * @param type  Strong type of symbol.
     * @param node  Primary node to use symbol.
     *
     * @return Symbol used.
     */

    /**
     * Get the symbol for a compiler constant, or null if not available (yet)
     * @param cc compiler constant
     * @return symbol for compiler constant, or null if not defined yet (for example in Lower)
     */
    public Symbol compilerConstant(final CompilerConstants cc) {
        return body.getExistingSymbol(cc.symbolName());
    }

    /**
     * Get the root class that this function node compiles to
     * @return root class
     */
    public Class<?> getRootClass() {
        return rootClass;
    }

    /**
     * Reset the root class that this function is compiled to
     * @see Compiler
     * @param lc lexical context
     * @param rootClass root class
     * @return function node or a new one if state was changed
     */
    public FunctionNode setRootClass(final LexicalContext lc, final Class<?> rootClass) {
        if (this.rootClass == rootClass) {
            return this;
        }
        return Node.replaceInLexicalContext(
                lc,
                this,
                new FunctionNode(
                        this,
                        lastToken,
                        endParserState,
                        flags,
                        name,
                        returnType,
                        compileUnit,
                        compilationState,
                        body,
                        parameters,
                        thisProperties,
                        rootClass, source, namespace));
    }
}