/*
 * 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.
 */

/**
 * Implements listener based call back function corresponding to the "leaf"
 * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
 */
package org.onosproject.yangutils.parser.impl.listeners;

import org.onosproject.yangutils.datamodel.YangLeaf;
import org.onosproject.yangutils.parser.Parsable;
import org.onosproject.yangutils.parser.ParsableDataType;
import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
import org.onosproject.yangutils.parser.exceptions.ParserException;
import org.onosproject.yangutils.parser.impl.TreeWalkListener;
import org.onosproject.yangutils.datamodel.YangLeavesHolder;
import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;

import static org.onosproject.yangutils.parser.ParsableDataType.LEAF_DATA;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
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.ListenerErrorType.INVALID_CARDINALITY;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;

/*
 * Reference: RFC6020 and YANG ANTLR Grammar
 *
 * ABNF grammar as per RFC6020
 *  leaf-stmt           = leaf-keyword sep identifier-arg-str optsep
 *                        "{" stmtsep
 *                            ;; these stmts can appear in any order
 *                            [when-stmt stmtsep]
 *                            *(if-feature-stmt stmtsep)
 *                            type-stmt stmtsep
 *                            [units-stmt stmtsep]
 *                            *(must-stmt stmtsep)
 *                            [default-stmt stmtsep]
 *                            [config-stmt stmtsep]
 *                            [mandatory-stmt stmtsep]
 *                            [status-stmt stmtsep]
 *                            [description-stmt stmtsep]
 *                            [reference-stmt stmtsep]
 *                         "}"
 *
 * ANTLR grammar rule
 *  leafStatement : LEAF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement |
 *  unitsStatement | mustStatement | defaultStatement | configStatement | mandatoryStatement | statusStatement  |
 *  descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
 */

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

    private static ParsableDataType yangConstruct;

    /**
     * Creates a new leaf listener.
     */
    private LeafListener() {
    }

    /**
     * It is called when parser receives an input matching the grammar
     * rule (leaf), performs validation and updates the data model
     * tree.
     *
     * @param listener listener's object.
     * @param ctx context object of the grammar rule.
     */
    public static void processLeafEntry(TreeWalkListener listener,
                                        GeneratedYangParser.LeafStatementContext ctx) {

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

        boolean result = validateSubStatementsCardinality(ctx);
        if (!result) {
            throw new ParserException(constructListenerErrorMessage(INVALID_CARDINALITY, yangConstruct, "", ENTRY));
        }

        YangLeaf leaf = new YangLeaf();
        leaf.setLeafName(ctx.IDENTIFIER().getText());

        Parsable tmpData = listener.getParsedDataStack().peek();
        YangLeavesHolder leaves;

        if (tmpData instanceof YangLeavesHolder) {
            leaves = (YangLeavesHolder) tmpData;
            leaves.addLeaf(leaf);
        } else {
            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, LEAF_DATA,
                    ctx.IDENTIFIER().getText(), ENTRY));
        }

        listener.getParsedDataStack().push(leaf);
    }

    /**
     * It is called when parser exits from grammar rule (leaf), performs
     * validation and updates the data model tree.
     *
     * @param listener listener's object.
     * @param ctx context object of the grammar rule.
     */
    public static void processLeafExit(TreeWalkListener listener,
                                       GeneratedYangParser.LeafStatementContext ctx) {

        // Check for stack to be non empty.
        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_DATA, ctx.IDENTIFIER().getText(), EXIT);

        if (listener.getParsedDataStack().peek() instanceof YangLeaf) {
            listener.getParsedDataStack().pop();
        } else {
            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, LEAF_DATA,
                            ctx.IDENTIFIER().getText(), EXIT));
        }
    }

    /**
     * Validates the cardinality of leaf sub-statements as per grammar.
     *
     * @param ctx context object of the grammar rule.
     * @return true/false validation success or failure.
     */
    private static boolean validateSubStatementsCardinality(GeneratedYangParser
            .LeafStatementContext ctx) {

        if (ctx.typeStatement().isEmpty()
                || (ctx.typeStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.TYPE_DATA;
            return false;
        }

        if ((!ctx.unitsStatement().isEmpty())
                && (ctx.unitsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.UNITS_DATA;
            return false;
        }

        if ((!ctx.configStatement().isEmpty())
                && (ctx.configStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.CONFIG_DATA;
            return false;
        }

        if ((!ctx.mandatoryStatement().isEmpty())
                && (ctx.mandatoryStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.MANDATORY_DATA;
            return false;
        }

        if ((!ctx.descriptionStatement().isEmpty())
                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.DESCRIPTION_DATA;
            return false;
        }

        if ((!ctx.referenceStatement().isEmpty())
                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.REFERENCE_DATA;
            return false;
        }

        if ((!ctx.statusStatement().isEmpty())
                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
            yangConstruct = ParsableDataType.STATUS_DATA;
            return false;
        }

        return true;
    }
}