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//
// Copyright (c) 2016-2024 Deephaven Data Labs and Patent Pending
//
package io.deephaven.kafka;

import io.deephaven.qst.type.BooleanType;
import io.deephaven.qst.type.ByteType;
import io.deephaven.qst.type.CharType;
import io.deephaven.qst.type.DoubleType;
import io.deephaven.qst.type.FloatType;
import io.deephaven.qst.type.GenericType;
import io.deephaven.qst.type.IntType;
import io.deephaven.qst.type.LongType;
import io.deephaven.qst.type.PrimitiveType;
import io.deephaven.qst.type.ShortType;
import io.deephaven.qst.type.Type;
import io.deephaven.function.ToBooleanFunction;
import io.deephaven.function.ToByteFunction;
import io.deephaven.function.ToCharFunction;
import io.deephaven.function.ToDoubleFunction;
import io.deephaven.function.ToFloatFunction;
import io.deephaven.function.ToIntFunction;
import io.deephaven.function.ToLongFunction;
import io.deephaven.function.ToObjectFunction;
import io.deephaven.function.ToPrimitiveFunction;
import io.deephaven.function.ToShortFunction;
import io.deephaven.function.TypedFunction;
import io.deephaven.util.QueryConstants;

import java.util.Optional;

class NullFunctions {

    public static  Optional> of(Type returnType) {
        // noinspection unchecked
        return Optional.ofNullable((TypedFunction) returnType.walk(NullFunctionVisitor.INSTANCE));
    }

    public static  Optional> of(PrimitiveType returnType) {
        // noinspection unchecked
        return Optional.ofNullable((ToPrimitiveFunction) returnType
                .walk((PrimitiveType.Visitor>) NullFunctionVisitor.INSTANCE));
    }

    public static  ToObjectFunction of(GenericType returnType) {
        return ToObjectFunction.of(x -> null, returnType);
    }

    public static  ToCharFunction nullCharFunction() {
        return x -> QueryConstants.NULL_CHAR;
    }

    public static  ToByteFunction nullByteFunction() {
        return x -> QueryConstants.NULL_BYTE;
    }

    public static  ToShortFunction nullShortFunction() {
        return x -> QueryConstants.NULL_SHORT;
    }

    public static  ToIntFunction nullIntFunction() {
        return x -> QueryConstants.NULL_INT;
    }

    public static  ToLongFunction nullLongFunction() {
        return x -> QueryConstants.NULL_LONG;
    }

    public static  ToFloatFunction nullFloatFunction() {
        return x -> QueryConstants.NULL_FLOAT;
    }

    public static  ToDoubleFunction nullDoubleFunction() {
        return x -> QueryConstants.NULL_DOUBLE;
    }

    private enum NullFunctionVisitor
            implements Type.Visitor>, PrimitiveType.Visitor> {
        INSTANCE;

        @Override
        public ToPrimitiveFunction visit(PrimitiveType primitiveType) {
            return of(primitiveType).orElse(null);
        }

        @Override
        public TypedFunction visit(GenericType genericType) {
            return of(genericType);
        }

        @Override
        public ToBooleanFunction visit(BooleanType booleanType) {
            return null;
        }

        @Override
        public ToByteFunction visit(ByteType byteType) {
            return nullByteFunction();
        }

        @Override
        public ToPrimitiveFunction visit(CharType charType) {
            return nullCharFunction();
        }

        @Override
        public ToPrimitiveFunction visit(ShortType shortType) {
            return nullShortFunction();
        }

        @Override
        public ToPrimitiveFunction visit(IntType intType) {
            return nullIntFunction();
        }

        @Override
        public ToPrimitiveFunction visit(LongType longType) {
            return nullLongFunction();
        }

        @Override
        public ToPrimitiveFunction visit(FloatType floatType) {
            return nullFloatFunction();
        }

        @Override
        public ToPrimitiveFunction visit(DoubleType doubleType) {
            return nullDoubleFunction();
        }
    }
}