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package org.checkerframework.dataflow.analysis;

/*>>>
import org.checkerframework.checker.nullness.qual.Nullable;
*/

import java.util.Map;
import javax.lang.model.type.TypeMirror;

/**
 * {@code TransferResult} is used as the result type of the individual transfer functions of a
 * {@link TransferFunction}. It always belongs to the result of the individual transfer function for
 * a particular {@link org.checkerframework.dataflow.cfg.node.Node}, even though that {@code
 * org.checkerframework.dataflow.cfg.node.Node} is not explicitly store in {@code TransferResult}.
 *
 * A {@code TransferResult} contains one or two stores (for 'then' and 'else'), and zero or more
 * stores with a cause ({@link TypeMirror}).
 *
 * @author Stefan Heule
 * @param  the {@link Store} used to keep track of intermediate results
 */
public abstract class TransferResult, S extends Store> {

    /**
     * The stores in case the basic block throws an exception (or {@code null} if the corresponding
     * {@link org.checkerframework.dataflow.cfg.node.Node} does not throw any exceptions). Does not
     * necessarily contain a store for every exception, in which case the in-store will be used.
     */
    protected final /*@Nullable*/ Map exceptionalStores;

    /**
     * The abstract value of the {@link org.checkerframework.dataflow.cfg.node.Node} associated with
     * this {@link TransferResult}, or {@code null} if no value has been produced.
     */
    protected /*@Nullable*/ A resultValue;

    public TransferResult(
            /*@Nullable*/ A resultValue, /*@Nullable*/ Map exceptionalStores) {
        this.resultValue = resultValue;
        this.exceptionalStores = exceptionalStores;
    }

    /** @return the abstract value produced by the transfer function */
    public A getResultValue() {
        return resultValue;
    }

    public void setResultValue(A resultValue) {
        this.resultValue = resultValue;
    }

    /**
     * @return the regular result store produced if no exception is thrown by the {@link
     *     org.checkerframework.dataflow.cfg.node.Node} corresponding to this transfer function
     *     result.
     */
    public abstract S getRegularStore();

    /**
     * @return the result store produced if the {@link org.checkerframework.dataflow.cfg.node.Node}
     *     this result belongs to evaluates to {@code true}.
     */
    public abstract S getThenStore();

    /**
     * @return the result store produced if the {@link org.checkerframework.dataflow.cfg.node.Node}
     *     this result belongs to evaluates to {@code false}.
     */
    public abstract S getElseStore();

    /**
     * @return the store that flows along the outgoing exceptional edge labeled with {@code
     *     exception} (or {@code null} if no special handling is required for exceptional edges).
     */
    public /*@Nullable*/ S getExceptionalStore(TypeMirror exception) {
        if (exceptionalStores == null) {
            return null;
        }
        return exceptionalStores.get(exception);
    }

    /**
     * @return a Map of {@link TypeMirror} to {@link Store}
     * @see TransferResult#getExceptionalStore(TypeMirror)
     */
    public Map getExceptionalStores() {
        return exceptionalStores;
    }

    /**
     * @return {@code true} if and only if this transfer result contains two stores that are
     *     potentially not equal. Note that the result {@code true} does not imply that {@code
     *     getRegularStore} cannot be called (or vice versa for {@code false}). Rather, it indicates
     *     that {@code getThenStore} or {@code getElseStore} can be used to give more precise
     *     results. Otherwise, if the result is {@code false}, then all three methods {@code
     *     getRegularStore}, {@code getThenStore}, and {@code getElseStore} return equivalent
     *     stores.
     */
    public abstract boolean containsTwoStores();

    /**
     * @return {@code true} if and only if the transfer function returning this transfer result
     *     changed the regularStore, elseStore, or thenStore.
     */
    public abstract boolean storeChanged();
}