////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2020 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
////////////////////////////////////////////////////////////////////////////////

package com.puppycrawl.tools.checkstyle.checks.sizes;

import java.util.ArrayDeque;
import java.util.Deque;

import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;

/**
 * <p>
 * Restricts the number of executable statements to a specified limit.
 * </p>
 * <ul>
 * <li>
 * Property {@code max} - Specify the maximum threshold allowed.
 * Default value is {@code 30}.
 * </li>
 * <li>
 * Property {@code tokens} - tokens to check
 * Default value is:
 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">
 * CTOR_DEF</a>,
 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
 * METHOD_DEF</a>,
 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INSTANCE_INIT">
 * INSTANCE_INIT</a>,
 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#STATIC_INIT">
 * STATIC_INIT</a>.
 * </li>
 * </ul>
 * <p>
 * To configure the check:
 * </p>
 * <pre>
 * &lt;module name="ExecutableStatementCount"/&gt;
 * </pre>
 * <p>
 * To configure the check with a threshold of 20 for constructor and method definitions:
 * </p>
 * <pre>
 * &lt;module name="ExecutableStatementCount"&gt;
 *   &lt;property name="max" value="20"/&gt;
 *   &lt;property name="tokens" value="CTOR_DEF,METHOD_DEF"/&gt;
 * &lt;/module&gt;
 * </pre>
 *
 * @since 3.2
 */
@FileStatefulCheck
public final class ExecutableStatementCountCheck
    extends AbstractCheck {

    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_KEY = "executableStatementCount";

    /** Default threshold. */
    private static final int DEFAULT_MAX = 30;

    /** Stack of method contexts. */
    private final Deque<Context> contextStack = new ArrayDeque<>();

    /** Specify the maximum threshold allowed. */
    private int max;

    /** Current method context. */
    private Context context;

    /** Constructs a {@code ExecutableStatementCountCheck}. */
    public ExecutableStatementCountCheck() {
        max = DEFAULT_MAX;
    }

    @Override
    public int[] getDefaultTokens() {
        return new int[] {
            TokenTypes.CTOR_DEF,
            TokenTypes.METHOD_DEF,
            TokenTypes.INSTANCE_INIT,
            TokenTypes.STATIC_INIT,
            TokenTypes.SLIST,
        };
    }

    @Override
    public int[] getRequiredTokens() {
        return new int[] {TokenTypes.SLIST};
    }

    @Override
    public int[] getAcceptableTokens() {
        return new int[] {
            TokenTypes.CTOR_DEF,
            TokenTypes.METHOD_DEF,
            TokenTypes.INSTANCE_INIT,
            TokenTypes.STATIC_INIT,
            TokenTypes.SLIST,
        };
    }

    /**
     * Setter to specify the maximum threshold allowed.
     *
     * @param max the maximum threshold.
     */
    public void setMax(int max) {
        this.max = max;
    }

    @Override
    public void beginTree(DetailAST rootAST) {
        context = new Context(null);
        contextStack.clear();
    }

    @Override
    public void visitToken(DetailAST ast) {
        switch (ast.getType()) {
            case TokenTypes.CTOR_DEF:
            case TokenTypes.METHOD_DEF:
            case TokenTypes.INSTANCE_INIT:
            case TokenTypes.STATIC_INIT:
                visitMemberDef(ast);
                break;
            case TokenTypes.SLIST:
                visitSlist(ast);
                break;
            default:
                throw new IllegalStateException(ast.toString());
        }
    }

    @Override
    public void leaveToken(DetailAST ast) {
        switch (ast.getType()) {
            case TokenTypes.CTOR_DEF:
            case TokenTypes.METHOD_DEF:
            case TokenTypes.INSTANCE_INIT:
            case TokenTypes.STATIC_INIT:
                leaveMemberDef(ast);
                break;
            case TokenTypes.SLIST:
                // Do nothing
                break;
            default:
                throw new IllegalStateException(ast.toString());
        }
    }

    /**
     * Process the start of the member definition.
     *
     * @param ast the token representing the member definition.
     */
    private void visitMemberDef(DetailAST ast) {
        contextStack.push(context);
        context = new Context(ast);
    }

    /**
     * Process the end of a member definition.
     *
     * @param ast the token representing the member definition.
     */
    private void leaveMemberDef(DetailAST ast) {
        final int count = context.getCount();
        if (count > max) {
            log(ast, MSG_KEY, count, max);
        }
        context = contextStack.pop();
    }

    /**
     * Process the end of a statement list.
     *
     * @param ast the token representing the statement list.
     */
    private void visitSlist(DetailAST ast) {
        if (context.getAST() != null) {
            // find member AST for the statement list
            final DetailAST contextAST = context.getAST();
            DetailAST parent = ast.getParent();
            int type = parent.getType();
            while (type != TokenTypes.CTOR_DEF
                && type != TokenTypes.METHOD_DEF
                && type != TokenTypes.INSTANCE_INIT
                && type != TokenTypes.STATIC_INIT) {
                parent = parent.getParent();
                type = parent.getType();
            }
            if (parent == contextAST) {
                context.addCount(ast.getChildCount() / 2);
            }
        }
    }

    /**
     * Class to encapsulate counting information about one member.
     */
    private static class Context {

        /** Member AST node. */
        private final DetailAST ast;

        /** Counter for context elements. */
        private int count;

        /**
         * Creates new member context.
         *
         * @param ast member AST node.
         */
        /* package */ Context(DetailAST ast) {
            this.ast = ast;
            count = 0;
        }

        /**
         * Increase count.
         *
         * @param addition the count increment.
         */
        public void addCount(int addition) {
            count += addition;
        }

        /**
         * Gets the member AST node.
         *
         * @return the member AST node.
         */
        public DetailAST getAST() {
            return ast;
        }

        /**
         * Gets the count.
         *
         * @return the count.
         */
        public int getCount() {
            return count;
        }

    }

}