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package ninja.soroosh.hashem.lang.nodes;

import com.oracle.truffle.api.dsl.TypeSystemReference;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.instrumentation.GenerateWrapper;
import com.oracle.truffle.api.instrumentation.ProbeNode;
import com.oracle.truffle.api.instrumentation.StandardTags;
import com.oracle.truffle.api.instrumentation.Tag;
import com.oracle.truffle.api.nodes.NodeInfo;
import com.oracle.truffle.api.nodes.UnexpectedResultException;

/**
 * Base class for all Hashem nodes that produce a value and therefore benefit from type specialization.
 * The annotation {@link TypeSystemReference} specifies theHashemitypes. Specifying it here defines the
 * type system for all subclasses.
 */
@TypeSystemReference(HashemTypes.class)
@NodeInfo(description = "The abstract base node for all expressions")
@GenerateWrapper
public abstract class HashemExpressionNode extends HashemStatementNode {

    private boolean hasExpressionTag;

    /**
     * The execute method when no specialization is possible. This is the most general case,
     * therefore it must be provided by all subclasses.
     */
    public abstract Object executeGeneric(VirtualFrame frame);

    /**
     * When we use an expression at places where a {@link HashemStatementNode statement} is already
     * sufficient, the return value is just discarded.
     */
    @Override
    public void executeVoid(VirtualFrame frame) {
        executeGeneric(frame);
    }

    @Override
    public WrapperNode createWrapper(ProbeNode probe) {
        return new HashemExpressionNodeWrapper(this, probe);
    }

    @Override
    public boolean hasTag(Class<? extends Tag> tag) {
        if (tag == StandardTags.ExpressionTag.class) {
            return hasExpressionTag;
        }
        return super.hasTag(tag);
    }

    /**
     * Marks this node as being a {@link StandardTags.ExpressionTag} for instrumentation purposes.
     */
    public final void addExpressionTag() {
        hasExpressionTag = true;
    }

    /*
     * Execute methods for specialized types. They all follow the same pattern: they call the
     * generic execution method and then expect a result of their return type. Type-specialized
     * subclasses overwrite the appropriate methods.
     */

    public long executeLong(VirtualFrame frame) throws UnexpectedResultException {
        return HashemTypesGen.expectLong(executeGeneric(frame));
    }

    public float executeFloat(VirtualFrame frame) throws UnexpectedResultException {
        return HashemTypesGen.expectFloat(executeGeneric(frame));
    }

    public boolean executeBoolean(VirtualFrame frame) throws UnexpectedResultException {
        return HashemTypesGen.expectBoolean(executeGeneric(frame));
    }
}