/*
 * Copyright 2016 Open Networking Laboratory
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.onosproject.yangutils.parser.impl.listeners;

import org.onosproject.yangutils.datamodel.YangModule;
import org.onosproject.yangutils.datamodel.YangSubModule;
import org.onosproject.yangutils.parser.Parsable;
import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
import org.onosproject.yangutils.parser.exceptions.ParserException;
import org.onosproject.yangutils.parser.impl.TreeWalkListener;

import static org.onosproject.yangutils.utils.YangConstructType.VERSION_DATA;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;

/*
 * Reference: RFC6020 and YANG ANTLR Grammar
 *
 * ABNF grammar as per RFC6020
 * module-header-stmts = ;; these stmts can appear in any order
 *                       [yang-version-stmt stmtsep]
 *                        namespace-stmt stmtsep
 *                        prefix-stmt stmtsep
 *
 * submodule-header-stmts =
 *                            ;; these stmts can appear in any order
 *                            [yang-version-stmt stmtsep]
 *                             belongs-to-stmt stmtsep
 *
 * yang-version-stmt   = yang-version-keyword sep yang-version-arg-str
 *                       optsep stmtend
 *
 *
 * ANTLR grammar rule
 * module_header_statement : yang_version_stmt? namespace_stmt prefix_stmt
 *                         | yang_version_stmt? prefix_stmt namespace_stmt
 *                         | namespace_stmt yang_version_stmt? prefix_stmt
 *                         | namespace_stmt prefix_stmt yang_version_stmt?
 *                         | prefix_stmt namespace_stmt yang_version_stmt?
 *                         | prefix_stmt yang_version_stmt? namespace_stmt?
 *                         ;
 * submodule_header_statement : yang_version_stmt? belongs_to_stmt
 *                            | belongs_to_stmt yang_version_stmt?
 *                            ;
 * yang_version_stmt :   YANG_VERSION_KEYWORD INTEGER STMTEND;
 */

/**
 * Implements listener based call back function corresponding to the "version"
 * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
 */
public final class VersionListener {

    /**
     * Creates a new version listener.
     */
    private VersionListener() {
    }

    /**
     * It is called when parser receives an input matching the grammar rule
     * (version), perform validations and update the data model tree.
     *
     * @param listener Listener's object
     * @param ctx context object of the grammar rule
     */
    public static void processVersionEntry(TreeWalkListener listener,
                                           GeneratedYangParser.YangVersionStatementContext ctx) {

        // Check for stack to be non empty.
        checkStackIsNotEmpty(listener, MISSING_HOLDER, VERSION_DATA, ctx.INTEGER().getText(), ENTRY);

        Integer version = Integer.valueOf(ctx.INTEGER().getText());
        if (!isVersionValid(version)) {
            ParserException parserException = new ParserException("YANG file error: Input version not supported");
            parserException.setLine(ctx.INTEGER().getSymbol().getLine());
            parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
            throw parserException;
        }

        // Obtain the node of the stack.
        Parsable tmpNode = listener.getParsedDataStack().peek();
        switch (tmpNode.getYangConstructType()) {
        case MODULE_DATA: {
            YangModule module = (YangModule) tmpNode;
            module.setVersion((byte) 1);
            break;
        }
        case SUB_MODULE_DATA: {
            YangSubModule subModule = (YangSubModule) tmpNode;
            subModule.setVersion((byte) 1);
            break;
        }
        default:
            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, VERSION_DATA,
                                                                    ctx.INTEGER().getText(), ENTRY));
        }
    }

    /**
     * Validates whether the value of YANG version.
     *
     * @param version input yang version
     * @return validation result
     */
    private static boolean isVersionValid(Integer version) {
        return version == 1;
    }
}