// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.tensor.functions;

import com.google.common.annotations.Beta;
import com.yahoo.tensor.Tensor;
import com.yahoo.tensor.evaluation.EvaluationContext;

import java.util.Collections;
import java.util.List;

/**
 * A function which returns a constant tensor.
 *
 * @author bratseth
 */
@Beta
public class ConstantTensor extends PrimitiveTensorFunction {

    private final Tensor constant;

    public ConstantTensor(String tensorString) {
        this.constant = Tensor.from(tensorString);
    }

    public ConstantTensor(Tensor tensor) {
        this.constant = tensor;
    }

    @Override
    public List<TensorFunction> functionArguments() { return Collections.emptyList(); }

    @Override
    public TensorFunction replaceArguments(List<TensorFunction> arguments) {
        if ( arguments.size() != 1)
            throw new IllegalArgumentException("ConstantTensor must have 0 arguments, got " + arguments.size());
        return this;
    }

    @Override
    public PrimitiveTensorFunction toPrimitive() { return this; }

    @Override
    public Tensor evaluate(EvaluationContext context) { return constant; }

    @Override
    public String toString(ToStringContext context) { return constant.toString(); }

}