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 * 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,

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 *

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

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package jdk.nashorn.internal.ir;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.Comparator;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import jdk.nashorn.internal.codegen.Label;

import jdk.nashorn.internal.ir.annotations.Immutable;

import jdk.nashorn.internal.ir.visitor.NodeVisitor;

/**

 * IR representation for a list of statements.

 */

@Immutable

public class Block extends Node implements BreakableNode, Terminal, Flags<Block> {

    private static final long serialVersionUID = 1L;

    /** List of statements */

    protected final List<Statement> statements;

    /** Symbol table - keys must be returned in the order they were put in. */

    protected final Map<String, Symbol> symbols;

    /** Entry label. */

    private final Label entryLabel;

    /** Break label. */

    private final Label breakLabel;

    /** Does the block/function need a new scope? Is this synthetic? */

    protected final int flags;

    /**

     * @see JoinPredecessor

     */

    private final LocalVariableConversion conversion;

    /** Flag indicating that this block needs scope */

    public static final int NEEDS_SCOPE        = 1 << 0;

    /**

     * Is this block tagged as terminal based on its contents

     * (usually the last statement)

     */

    public static final int IS_TERMINAL        = 1 << 2;

    /**

     * Is this block the eager global scope - i.e. the original program. This isn't true for the

     * outermost level of recompiles

     */

    public static final int IS_GLOBAL_SCOPE    = 1 << 3;

    /**

     * Is this block a synthetic one introduced by Parser?

     */

    public static final int IS_SYNTHETIC       = 1 << 4;

    /**

     * Is this the function body block? May not be the first, if parameter list contains expressions.

     */

    public static final int IS_BODY            = 1 << 5;

    /**

     * Is this the parameter initialization block? If present, must be the first block, immediately wrapping the function body block.

     */

    public static final int IS_PARAMETER_BLOCK = 1 << 6;

    /**

     * Marks the variable declaration block for case clauses of a switch statement.

     */

    public static final int IS_SWITCH_BLOCK    = 1 << 7;

    /**

     * Is this block tagged as breakable based on its contents

     * (block having labelled break statement)

     */

    public static final int IS_BREAKABLE       = 1 << 8;

    /**

     * Constructor

     *

     * @param token      The first token of the block

     * @param finish     The index of the last character

     * @param flags      The flags of the block

     * @param statements All statements in the block

     */

    public Block(final long token, final int finish, final int flags, final Statement... statements) {

        super(token, finish);

        this.statements = Arrays.asList(statements);

        this.symbols    = new LinkedHashMap<>();

        this.entryLabel = new Label("block_entry");

        this.breakLabel = new Label("block_break");

        final int len = statements.length;

        final int terminalFlags = len > 0 && statements[len - 1].hasTerminalFlags() ? IS_TERMINAL : 0;

        this.flags = terminalFlags | flags;

        this.conversion = null;

    }

    /**

     * Constructs a new block

     *

     * @param token The first token of the block

     * @param finish The index of the last character

     * @param statements All statements in the block

     */

    public Block(final long token, final int finish, final Statement...statements){

        this(token, finish, IS_SYNTHETIC, statements);

    }

    /**

     * Constructs a new block

     *

     * @param token The first token of the block

     * @param finish The index of the last character

     * @param statements All statements in the block

     */

    public Block(final long token, final int finish, final List<Statement> statements){

        this(token, finish, IS_SYNTHETIC, statements);

    }

    /**

     * Constructor

     *

     * @param token      The first token of the block

     * @param finish     The index of the last character

     * @param flags      The flags of the block

     * @param statements All statements in the block

     */

    public Block(final long token, final int finish, final int flags, final List<Statement> statements) {

        this(token, finish, flags, statements.toArray(new Statement[0]));

    }

    private Block(final Block block, final int finish, final List<Statement> statements, final int flags, final Map<String, Symbol> symbols, final LocalVariableConversion conversion) {

        super(block, finish);

        this.statements = statements;

        this.flags      = flags;

        this.symbols    = new LinkedHashMap<>(symbols); //todo - symbols have no dependencies on any IR node and can as far as we understand it be shallow copied now

        this.entryLabel = new Label(block.entryLabel);

        this.breakLabel = new Label(block.breakLabel);

        this.conversion = conversion;

    }

    /**

     * Is this block the outermost eager global scope - i.e. the primordial program?

     * Used for global anchor point for scope depth computation for recompilation code

     * @return true if outermost eager global scope

     */

    public boolean isGlobalScope() {

        return getFlag(IS_GLOBAL_SCOPE);

    }

    /**

     * Returns true if this block defines any symbols.

     * @return true if this block defines any symbols.

     */

    public boolean hasSymbols() {

        return !symbols.isEmpty();

    }

    /**

     * Replaces symbols defined in this block with different symbols. Used to ensure symbol tables are

     * immutable upon construction and have copy-on-write semantics. Note that this method only replaces the

     * symbols in the symbol table, it does not act on any contained AST nodes that might reference the symbols.

     * Those should be updated separately as this method is meant to be used as part of such an update pass.

     * @param lc the current lexical context

     * @param replacements the map of symbol replacements

     * @return a new block with replaced symbols, or this block if none of the replacements modified the symbol

     * table.

     */

    public Block replaceSymbols(final LexicalContext lc, final Map<Symbol, Symbol> replacements) {

        if (symbols.isEmpty()) {

            return this;

        }

        final LinkedHashMap<String, Symbol> newSymbols = new LinkedHashMap<>(symbols);

        for (final Map.Entry<String, Symbol> entry: newSymbols.entrySet()) {

            final Symbol newSymbol = replacements.get(entry.getValue());

            assert newSymbol != null : "Missing replacement for " + entry.getKey();

            entry.setValue(newSymbol);

        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags, newSymbols, conversion));

    }

    /**

     * Returns a copy of this block with a shallow copy of the symbol table.

     * @return a copy of this block with a shallow copy of the symbol table.

     */

    public Block copyWithNewSymbols() {

        return new Block(this, finish, statements, flags, new LinkedHashMap<>(symbols), conversion);

    }

    @Override

    public Node ensureUniqueLabels(final LexicalContext lc) {

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags, symbols, conversion));

    }

    /**

     * Assist in IR navigation.

     *

     * @param visitor IR navigating visitor.

     * @return new or same node

     */

    @Override

    public Node accept(final LexicalContext lc, final NodeVisitor<? extends LexicalContext> visitor) {

        if (visitor.enterBlock(this)) {

            return visitor.leaveBlock(setStatements(lc, Node.accept(visitor, statements)));

        }

        return this;

    }

    /**

     * Get a copy of the list for all the symbols defined in this block

     * @return symbol iterator

     */

    public List<Symbol> getSymbols() {

        return symbols.isEmpty() ? Collections.emptyList() : Collections.unmodifiableList(new ArrayList<>(symbols.values()));

    }

    /**

     * Retrieves an existing symbol defined in the current block.

     * @param name the name of the symbol

     * @return an existing symbol with the specified name defined in the current block, or null if this block doesn't

     * define a symbol with this name.T

     */

    public Symbol getExistingSymbol(final String name) {

        return symbols.get(name);

    }

    /**

     * This is used by the Splitter as catch blocks are not be subject to splitting.

     *

     * @return true if this block represents a catch block in a try statement.

     */

    public boolean isCatchBlock() {

        return statements.size() == 1 && statements.get(0) instanceof CatchNode;

    }

    @Override

    public void toString(final StringBuilder sb, final boolean printType) {

        for (final Node statement : statements) {

            statement.toString(sb, printType);

            sb.append(';');

        }

    }

    /**

     * Print symbols in block in alphabetical order, sorted on name

     * Used for debugging, see the --print-symbols flag

     *

     * @param stream print writer to output symbols to

     *

     * @return true if symbols were found

     */

    public boolean printSymbols(final PrintWriter stream) {

        final List<Symbol> values = new ArrayList<>(symbols.values());

        Collections.sort(values, new Comparator<Symbol>() {

            @Override

            public int compare(final Symbol s0, final Symbol s1) {

                return s0.getName().compareTo(s1.getName());

            }

        });

        for (final Symbol symbol : values) {

            symbol.print(stream);

        }

        return !values.isEmpty();

    }

    /**

     * Tag block as terminal or non terminal

     * @param lc          lexical context

     * @param isTerminal is block terminal

     * @return same block, or new if flag changed

     */

    public Block setIsTerminal(final LexicalContext lc, final boolean isTerminal) {

        return isTerminal ? setFlag(lc, IS_TERMINAL) : clearFlag(lc, IS_TERMINAL);

    }

    @Override

    public int getFlags() {

        return flags;

    }

    /**

     * Is this a terminal block, i.e. does it end control flow like ending with a throw or return?

     *

     * @return true if this node statement is terminal

     */

    @Override

    public boolean isTerminal() {

        return getFlag(IS_TERMINAL) && !getFlag(IS_BREAKABLE);

    }

    /**

     * Get the entry label for this block

     * @return the entry label

     */

    public Label getEntryLabel() {

        return entryLabel;

    }

    @Override

    public Label getBreakLabel() {

        return breakLabel;

    }

    @Override

    public Block setLocalVariableConversion(final LexicalContext lc, final LocalVariableConversion conversion) {

        if(this.conversion == conversion) {

            return this;

        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags, symbols, conversion));

    }

    @Override

    public LocalVariableConversion getLocalVariableConversion() {

        return conversion;

    }

    /**

     * Get the list of statements in this block

     *

     * @return a list of statements

     */

    public List<Statement> getStatements() {

        return Collections.unmodifiableList(statements);

    }

    /**

     * Returns the number of statements in the block.

     * @return the number of statements in the block.

     */

    public int getStatementCount() {

        return statements.size();

    }

    /**

     * Returns the line number of the first statement in the block.

     * @return the line number of the first statement in the block, or -1 if the block has no statements.

     */

    public int getFirstStatementLineNumber() {

        if(statements == null || statements.isEmpty()) {

            return -1;

        }

        return statements.get(0).getLineNumber();

    }

    /**

     * Returns the last statement in the block.

     * @return the last statement in the block, or null if the block has no statements.

     */

    public Statement getLastStatement() {

        return statements.isEmpty() ? null : statements.get(statements.size() - 1);

    }

    /**

     * Reset the statement list for this block

     *

     * @param lc lexical context

     * @param statements new statement list

     * @return new block if statements changed, identity of statements == block.statements

     */

    public Block setStatements(final LexicalContext lc, final List<Statement> statements) {

        if (this.statements == statements) {

            return this;

        }

        int lastFinish = 0;

        if (!statements.isEmpty()) {

            lastFinish = statements.get(statements.size() - 1).getFinish();

        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, Math.max(finish, lastFinish), statements, flags, symbols, conversion));

    }

    /**

     * Add or overwrite an existing symbol in the block

     *

     * @param symbol symbol

     */

    public void putSymbol(final Symbol symbol) {

        symbols.put(symbol.getName(), symbol);

    }

    /**

     * Check whether scope is necessary for this Block

     *

     * @return true if this function needs a scope

     */

    public boolean needsScope() {

        return (flags & NEEDS_SCOPE) == NEEDS_SCOPE;

    }

    /**

     * Check whether this block is synthetic or not.

     *

     * @return true if this is a synthetic block

     */

    public boolean isSynthetic() {

        return (flags & IS_SYNTHETIC) == IS_SYNTHETIC;

    }

    @Override

    public Block setFlags(final LexicalContext lc, final int flags) {

        if (this.flags == flags) {

            return this;

        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags, symbols, conversion));

    }

    @Override

    public Block clearFlag(final LexicalContext lc, final int flag) {

        return setFlags(lc, flags & ~flag);

    }

    @Override

    public Block setFlag(final LexicalContext lc, final int flag) {

        return setFlags(lc, flags | flag);

    }

    @Override

    public boolean getFlag(final int flag) {

        return (flags & flag) == flag;

    }

    /**

     * Set the needs scope flag.

     * @param lc lexicalContext

     * @return new block if state changed, otherwise this

     */

    public Block setNeedsScope(final LexicalContext lc) {

        if (needsScope()) {

            return this;

        }

        return Node.replaceInLexicalContext(lc, this, new Block(this, finish, statements, flags | NEEDS_SCOPE, symbols, conversion));

    }

    /**

     * Computationally determine the next slot for this block,

     * indexed from 0. Use this as a relative base when computing

     * frames

     * @return next slot

     */

    public int nextSlot() {

        int next = 0;

        for (final Symbol symbol : getSymbols()) {

            if (symbol.hasSlot()) {

                next += symbol.slotCount();

            }

        }

        return next;

    }

    /**

     * Determine whether this block needs to provide its scope object creator for use by its child nodes.

     * This is only necessary for synthetic parent blocks of for-in loops with lexical declarations.

     *

     * @see ForNode#needsScopeCreator()

     * @return true if child nodes need access to this block's scope creator

     */

    public boolean providesScopeCreator() {

        return needsScope() && isSynthetic()

                && (getLastStatement() instanceof ForNode)