/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.nifi.attribute.expression.language.evaluation.literals;

import org.apache.nifi.attribute.expression.language.EvaluationContext;
import org.apache.nifi.attribute.expression.language.evaluation.Evaluator;
import org.apache.nifi.attribute.expression.language.evaluation.QueryResult;
import org.apache.nifi.attribute.expression.language.evaluation.StringEvaluator;
import org.apache.nifi.attribute.expression.language.evaluation.StringQueryResult;

public class StringLiteralEvaluator extends StringEvaluator {

    private final String value;

    public StringLiteralEvaluator(final String value) {
        if(value == null) {
            this.value = null;
        } else {
            // need to escape characters after backslashes
            final StringBuilder sb = new StringBuilder();
            boolean lastCharIsBackslash = false;
            for (int i = 0; i < value.length(); i++) {
                final char c = value.charAt(i);

                if (lastCharIsBackslash) {
                    switch (c) {
                        case 'n':
                            sb.append("\n");
                            break;
                        case 'r':
                            sb.append("\r");
                            break;
                        case '\\':
                            sb.append("\\");
                            break;
                        case 't':
                            sb.append("\\t");
                            break;
                        default:
                            sb.append("\\").append(c);
                            break;
                    }

                    lastCharIsBackslash = false;
                } else if (c == '\\') {
                    lastCharIsBackslash = true;
                } else {
                    sb.append(c);
                }
            }

            this.value = sb.toString();
        }
    }

    @Override
    public QueryResult<String> evaluate(final EvaluationContext evaluationContext) {
        return new StringQueryResult(value);
    }

    @Override
    public Evaluator<?> getSubjectEvaluator() {
        return null;
    }

}
