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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2020 QuestDB
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 *  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,
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package io.questdb.griffin.engine.functions.rnd;

import io.questdb.cairo.CairoConfiguration;
import io.questdb.cairo.sql.Function;
import io.questdb.cairo.sql.Record;
import io.questdb.cairo.sql.SymbolTableSource;
import io.questdb.griffin.FunctionFactory;
import io.questdb.griffin.SqlExecutionContext;
import io.questdb.griffin.engine.functions.ByteFunction;
import io.questdb.std.ObjList;
import io.questdb.std.Rnd;

public class RndByteFunctionFactory implements FunctionFactory {

    @Override
    public String getSignature() {
        return "rnd_byte()";
    }

    @Override
    public Function newInstance(ObjList args, int position, CairoConfiguration configuration, SqlExecutionContext sqlExecutionContext) {

        return new RndFunction(position);

    }

    private static class RndFunction extends ByteFunction implements Function {
        private final byte lo;
        private final byte range;
        private Rnd rnd;

        public RndFunction(int position) {
            super(position);
            this.lo = 20;
            this.range = (byte) (127 - lo + 1);
        }

        @Override
        public byte getByte(Record rec) {
            short s = rnd.nextShort();
            if (s < 0) {
                return (byte) (lo - s % range);
            }
            return (byte) (lo + s % range);
        }

        @Override
        public void init(SymbolTableSource symbolTableSource, SqlExecutionContext executionContext) {
            this.rnd = executionContext.getRandom();
        }
    }
}