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package com.oracle.graal.python.nodes.generator;

import com.oracle.graal.python.nodes.expression.ExpressionNode;
import com.oracle.graal.python.nodes.frame.WriteNode;
import com.oracle.graal.python.nodes.statement.StatementNode;
import com.oracle.graal.python.nodes.statement.WithNode;
import com.oracle.graal.python.parser.GeneratorInfo;
import com.oracle.graal.python.runtime.exception.PException;
import com.oracle.graal.python.runtime.exception.YieldException;
import com.oracle.truffle.api.frame.VirtualFrame;

public class GeneratorWithNode extends WithNode implements GeneratorControlNode {
    @Child private GeneratorAccessNode gen = GeneratorAccessNode.create();
    private final int withObjectSlot;
    private final int enterSlot;
    private final int yieldSlot;

    public GeneratorWithNode(WriteNode targetNode, StatementNode body, ExpressionNode withContext, GeneratorInfo.Mutable generatorInfo) {
        super(targetNode, body, withContext);
        this.enterSlot = generatorInfo.nextActiveFlagIndex();
        this.withObjectSlot = generatorInfo.nextIteratorSlotIndex();
        this.yieldSlot = generatorInfo.nextActiveFlagIndex();
    }

    @Override
    public Object returnExecute(VirtualFrame frame) {
        // We do not use returnExecute inside generators
        throw new IllegalStateException();
    }

    @Override
    protected Object getWithObject(VirtualFrame frame) {
        Object withObject = gen.getIterator(frame, withObjectSlot);
        if (withObject == null) {
            withObject = super.getWithObject(frame);
            gen.setIterator(frame, withObjectSlot, withObject);
        }
        return withObject;
    }

    @Override
    protected void doEnter(VirtualFrame frame, Object withObject, Object enterCallable) {
        if (!gen.isActive(frame, enterSlot)) {
            super.doEnter(frame, withObject, enterCallable);
            gen.setActive(frame, enterSlot, true);
        }
    }

    @Override
    protected Object doBody(VirtualFrame frame, boolean isReturn) {
        assert !isReturn; // not supported in generators
        try {
            super.doBody(frame, isReturn);
            return null;
        } catch (YieldException e) {
            gen.setActive(frame, yieldSlot, true);
            throw e;
        }
    }

    @Override
    protected void handleException(VirtualFrame frame, Object withObject, Object exitCallable, PException pException) {
        reset(frame);
        super.handleException(frame, withObject, exitCallable, pException);
    }

    @Override
    protected void doLeave(VirtualFrame frame, Object withObject, Object exitCallable) {
        if (gen.isActive(frame, yieldSlot)) {
            gen.setActive(frame, yieldSlot, false);
        } else {
            reset(frame);
            super.doLeave(frame, withObject, exitCallable);
        }
    }

    public void reset(VirtualFrame frame) {
        gen.setActive(frame, enterSlot, false);
        gen.setActive(frame, yieldSlot, false);
        gen.setIterator(frame, withObjectSlot, null);
    }
}
