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/*
 * Copyright 2018-2020 the original author or authors.
 *
 * 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 dev.miku.r2dbc.mysql.codec;

import dev.miku.r2dbc.mysql.Parameter;
import dev.miku.r2dbc.mysql.ParameterWriter;
import dev.miku.r2dbc.mysql.constant.DataTypes;
import dev.miku.r2dbc.mysql.util.VarIntUtils;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import reactor.core.publisher.Mono;

import java.math.BigDecimal;
import java.nio.charset.StandardCharsets;

/**
 * Codec for {@link BigDecimal}.
 */
final class BigDecimalCodec extends AbstractClassedCodec {

    BigDecimalCodec(ByteBufAllocator allocator) {
        super(allocator, BigDecimal.class);
    }

    @Override
    public BigDecimal decode(ByteBuf value, FieldInformation info, Class target, boolean binary, CodecContext context) {
        if (binary) {
            short type = info.getType();

            switch (type) {
                case DataTypes.FLOAT:
                    return BigDecimal.valueOf(value.readFloatLE());
                case DataTypes.DOUBLE:
                    return BigDecimal.valueOf(value.readDoubleLE());
            }
            // Not float or double, is text-encoded yet.
        }

        BigDecimal decimal = new BigDecimal(value.toString(StandardCharsets.US_ASCII));

        // Why Java has not BigDecimal.parseBigDecimal(String)?
        if (BigDecimal.ZERO.equals(decimal)) {
            return BigDecimal.ZERO;
        } else if (BigDecimal.ONE.equals(decimal)) {
            return BigDecimal.ONE;
        } else if (BigDecimal.TEN.equals(decimal)) {
            return BigDecimal.TEN;
        } else {
            return decimal;
        }
    }

    @Override
    public boolean canEncode(Object value) {
        return value instanceof BigDecimal;
    }

    @Override
    public Parameter encode(Object value, CodecContext context) {
        return new BigDecimalParameter(allocator, (BigDecimal) value);
    }

    @Override
    protected boolean doCanDecode(FieldInformation info) {
        short type = info.getType();
        return TypePredicates.isDecimal(type) || DataTypes.FLOAT == type || DataTypes.DOUBLE == type;
    }

    static ByteBuf encodeAscii(ByteBufAllocator alloc, String ascii) {
        // Using ASCII, so byte size is string length.
        int size = ascii.length();

        if (size == 0) {
            // It is zero of var int, not terminal.
            return alloc.buffer(Byte.BYTES).writeByte(0);
        }

        ByteBuf buf = alloc.buffer(VarIntUtils.varIntBytes(size) + size);

        try {
            VarIntUtils.writeVarInt(buf, size);
            buf.writeCharSequence(ascii, StandardCharsets.US_ASCII);
            return buf;
        } catch (Throwable e) {
            buf.release();
            throw e;
        }
    }

    private static final class BigDecimalParameter extends AbstractParameter {

        private final ByteBufAllocator allocator;

        private final BigDecimal value;

        private BigDecimalParameter(ByteBufAllocator allocator, BigDecimal value) {
            this.allocator = allocator;
            this.value = value;
        }

        @Override
        public Mono publishBinary() {
            return Mono.fromSupplier(() -> encodeAscii(allocator, value.toString()));
        }

        @Override
        public Mono publishText(ParameterWriter writer) {
            return Mono.fromRunnable(() -> writer.writeBigDecimal(value));
        }

        @Override
        public short getType() {
            return DataTypes.NEW_DECIMAL;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof BigDecimalParameter)) {
                return false;
            }

            BigDecimalParameter that = (BigDecimalParameter) o;

            return value.equals(that.value);
        }

        @Override
        public int hashCode() {
            return value.hashCode();
        }
    }
}