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 * Copyright (C) 2014-2019 Appsicle
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 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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package com.questdb.griffin;

import com.questdb.griffin.model.ExpressionNode;
import com.questdb.griffin.model.QueryColumn;
import com.questdb.std.*;

public class SqlUtil {

    static final CharSequenceHashSet disallowedAliases = new CharSequenceHashSet();

    static {
        for (int i = 0, n = OperatorExpression.operators.size(); i < n; i++) {
            SqlUtil.disallowedAliases.add(OperatorExpression.operators.getQuick(i).token);
        }
    }

    public static CharSequence fetchNext(GenericLexer lexer) {
        int blockCount = 0;
        boolean lineComment = false;
        while (lexer.hasNext()) {
            CharSequence cs = lexer.next();

            if (lineComment) {
                if (Chars.equals(cs, '\n') || Chars.equals(cs, '\r')) {
                    lineComment = false;
                }
                continue;
            }

            if (Chars.equals("--", cs)) {
                lineComment = true;
                continue;
            }

            if (Chars.equals("/*", cs)) {
                blockCount++;
                continue;
            }

            if (Chars.equals("*/", cs) && blockCount > 0) {
                blockCount--;
                continue;
            }

            if (blockCount == 0 && GenericLexer.WHITESPACE.excludes(cs)) {
                return cs;
            }
        }
        return null;
    }

    static ExpressionNode nextLiteral(ObjectPool pool, CharSequence token, int position) {
        return pool.next().of(ExpressionNode.LITERAL, token, 0, position);
    }

    static CharSequence createColumnAlias(CharacterStore store, CharSequence base, int indexOfDot, CharSequenceIntHashMap nameTypeMap) {
        final boolean disallowed = disallowedAliases.contains(base);

        // short and sweet version
        if (indexOfDot == -1 && !disallowed && nameTypeMap.excludes(base)) {
            return base;
        }

        final CharacterStoreEntry characterStoreEntry = store.newEntry();

        if (indexOfDot == -1) {
            if (disallowed) {
                characterStoreEntry.put("column");
            } else {
                characterStoreEntry.put(base);
            }
        } else {
            characterStoreEntry.put(base, indexOfDot + 1, base.length());
        }


        int len = characterStoreEntry.length();
        int sequence = 0;
        while (true) {
            if (sequence > 0) {
                characterStoreEntry.trimTo(len);
                characterStoreEntry.put(sequence);
            }
            sequence++;
            CharSequence alias = characterStoreEntry.toImmutable();
            if (nameTypeMap.excludes(alias)) {
                return alias;
            }
        }
    }

    static QueryColumn nextColumn(
            ObjectPool queryColumnPool,
            ObjectPool sqlNodePool,
            CharSequence alias,
            CharSequence column
    ) {
        return queryColumnPool.next().of(alias, nextLiteral(sqlNodePool, column, 0));
    }
}