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/*
 *  Copyright 2024 Budapest University of Technology and Economics
 *
 *  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 hu.bme.mit.theta.xta.utils;

import hu.bme.mit.theta.core.model.Valuation;
import hu.bme.mit.theta.core.type.LitExpr;
import hu.bme.mit.theta.core.type.NullaryExpr;
import hu.bme.mit.theta.core.type.Type;
import hu.bme.mit.theta.xta.Label;

import java.util.List;

import static com.google.common.base.Preconditions.checkNotNull;
import static hu.bme.mit.theta.common.Utils.head;
import static hu.bme.mit.theta.common.Utils.tail;
import static hu.bme.mit.theta.core.type.arraytype.ArrayExprs.Array;

public final class LabelExpr extends NullaryExpr {

    private static final int HASH_SEED = 4703;

    private volatile int hashCode = 0;
    private volatile Type type = null;

    private final Label label;

    private LabelExpr(final Label label) {
        this.label = checkNotNull(label);
    }

    public static LabelExpr of(final Label label) {
        return new LabelExpr(label);
    }

    public Label getLabel() {
        return label;
    }

    @Override
    public Type getType() {
        Type result = type;
        if (result == null) {
            result = extractType(label.getParamTypes());
            type = result;
        }
        return result;
    }

    @Override
    public LitExpr eval(final Valuation val) {
        throw new UnsupportedOperationException();
    }

    @Override
    public int hashCode() {
        int result = hashCode;
        if (result == 0) {
            result = HASH_SEED;
            result = 31 * result + label.hashCode();
            hashCode = result;
        }
        return result;
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj) {
            return true;
        } else if (obj != null && this.getClass() == obj.getClass()) {
            final LabelExpr that = (LabelExpr) obj;
            return this.label.equals(that.label);
        } else {
            return false;
        }
    }

    @Override
    public String toString() {
        return label.getName();
    }

    private Type extractType(final List types) {
        if (types.isEmpty()) {
            return ChanType.getInstance();
        } else {
            final Type head = head(types);
            final List tail = tail(types);
            return Array(head, extractType(tail));
        }
    }

}