package org.checkerframework.dataflow.analysis;

import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.dataflow.cfg.UnderlyingAST;
import org.checkerframework.dataflow.cfg.node.LocalVariableNode;
import org.checkerframework.dataflow.cfg.node.Node;
import org.checkerframework.dataflow.cfg.node.NodeVisitor;

/**
 * Interface of a transfer function for the abstract interpretation used for the flow analysis.
 *
 * <p>A transfer function consists of the following components:
 *
 * <ul>
 *   <li>A method {@code initialStore} that determines which initial store should be used in the
 *       org.checkerframework.dataflow analysis.
 *   <li>A function for every {@link Node} type that determines the behavior of the
 *       org.checkerframework.dataflow analysis in that case. This method takes a {@link Node} and
 *       an incoming store, and produces a {@link RegularTransferResult}.
 * </ul>
 *
 * <p><em>Important</em>: The individual transfer functions ({@code visit*}) are allowed to use (and
 * modify) the stores contained in the argument passed; the ownership is transfered from the caller
 * to that function.
 *
 * @param <S> the {@link Store} used to keep track of intermediate results
 */
public interface TransferFunction<A extends AbstractValue<A>, S extends Store<S>>
        extends NodeVisitor<TransferResult<A, S>, TransferInput<A, S>> {

    /**
     * @return the initial store to be used by the org.checkerframework.dataflow analysis. {@code
     *     parameters} is only set if the underlying AST is a method.
     */
    S initialStore(UnderlyingAST underlyingAST, @Nullable List<LocalVariableNode> parameters);
}
