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/*
 * Copyright 2015 Ryan Svihla
 *
 * 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 pro.foundev.cassandra.commons.migrations.script_parser;

import com.datastax.driver.core.SimpleStatement;
import com.datastax.driver.core.Statement;

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;

/**
 * Generates a list of statements from a file
 */
public class ScriptParser {
    private boolean isDoubleSlashComment(char newChar, char lastChar){
        return newChar=='/' && lastChar=='/';
    }
    private boolean isDoubleDashComment(char newChar, char lastChar){
        return newChar=='-' && lastChar=='-';
    }
    private boolean isMultiLineStart(char newChar, char lastChar){
        return newChar=='*'&&lastChar=='/';
    }
    private boolean isMultilineEnd(char newChar, char lastChar){
       return newChar=='/'&&lastChar=='*';
    }

    public List parse(Path file) {
        List statements = new ArrayList<>();
        StringBuffer cqlStatementBuffer = new StringBuffer();

        //FIXME: detect charset
        Charset charset = Charset.forName("UTF-8");

        try (BufferedReader reader = Files.newBufferedReader(file, charset)) {
            int c;
            char lastChar = '\0';
            boolean commentOn = false;
            boolean multiLineCommentOn = false;
            while ((c = reader.read()) != -1) {
                char converted = (char)c;
                if(isMultiLineStart(converted, lastChar)){
                    multiLineCommentOn = true;
                    cqlStatementBuffer = new StringBuffer();
                }else if(isMultilineEnd(converted, lastChar)){
                    multiLineCommentOn = false;
                }else {
                    if (isDoubleDashComment(converted, lastChar) || isDoubleSlashComment(converted, lastChar)) {
                        commentOn = true;
                        cqlStatementBuffer = new StringBuffer();//need to blank out previously stored -
                    } else if (commentOn && converted == '\n') {
                        commentOn = false;
                    }
                    lastChar = converted;
                    if (!commentOn && !multiLineCommentOn) {
                        cqlStatementBuffer.append(converted);
                        if (converted == ';') {
                            statements.add(new SimpleStatement(cqlStatementBuffer.toString()));
                            cqlStatementBuffer = new StringBuffer();
                        }
                    }
                }
            }
            if(statements.size()==0&&cqlStatementBuffer.length()>0){
               statements.add(new SimpleStatement(cqlStatementBuffer.toString()));
            }
        } catch (IOException x) {
            throw new RuntimeException(x);
        }
        return statements;
    }
}