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/******************************************************************************/
/* REXX Translator                                                            */
/*                                                                            */
/* When instruction for a SELECT CASE                                         */
/*                                                                            */
/******************************************************************************/
#include "RexxCore.h"
#include "RexxActivation.hpp"
#include "WhenCaseInstruction.hpp"
#include "Token.hpp"


/**
 * Construct a WHEN instructon instance.
 *
 * @param _condition The condition expression to evaluate.
 * @param thenToken  The token for the terminating THEN keyword.
 *                   This is where we mark the end of the
 *                   instruction.
 */
RexxInstructionCaseWhen::RexxInstructionCaseWhen(size_t count, QueueClass *list, RexxToken *thenToken)
{
    expressionCount = count;

    // now copy the expressions from the sub term stack
    // NOTE:  The expressionss are in last-to-first order on the stack.
    initializeObjectArray(count, expressions, RexxInternalObject, list);

    //get the location from the THEN token and use its location to set
    // the end of the instruction.  Note that the THEN is traced on its
    // own, but using the start of the THEN gives a fuller picture of things.
    SourceLocation location = thenToken->getLocation();
    setEnd(location.getLineNumber(), location.getOffset());
}


/**
 * Set the END location for the false branch of an IF
 * instruction.  This will either be an ELSE clause, or
 * the instruction following the instruction on the THEN.
 *
 * @param end_target The new end instruction.
 */
void RexxInstructionCaseWhen::setEndInstruction(RexxInstructionEndIf *end_target)
{
    else_location = end_target;
}


/**
 * Perform garbage collection on a live object.
 *
 * @param liveMark The current live mark.
 */
void RexxInstructionCaseWhen::live(size_t liveMark)
{
    // must be first object marked.
    memory_mark(nextInstruction);
    memory_mark(else_location);
    memory_mark_array(expressionCount, expressions);
}


/**
 * Perform generalized live marking on an object.  This is
 * used when mark-and-sweep processing is needed for purposes
 * other than garbage collection.
 *
 * @param reason The reason for the marking call.
 */
void RexxInstructionCaseWhen::liveGeneral(MarkReason reason)
{
    // must be first object marked.
    memory_mark_general(nextInstruction);
    memory_mark_general(else_location);
    memory_mark_general_array(expressionCount, expressions);
}


/**
 * Flatten a source object.
 *
 * @param envelope The envelope that will hold the flattened object.
 */
void RexxInstructionCaseWhen::flatten(Envelope *envelope)
{
    setUpFlatten(RexxInstructionCaseWhen)

    flattenRef(nextInstruction);
    flattenRef(else_location);
    flattenArrayRefs(expressionCount, expressions);

    cleanUpFlatten
}


/**
 * Execute a WHEN instruction attached to a SELECT CASE.
 *
 * @param context The current execution context.
 * @param stack   The current evaluation stack.
 */
void RexxInstructionCaseWhen::execute(RexxActivation *context, ExpressionStack *stack)
{
    context->traceInstruction(this);

    // This should be us.  It really isn't possible to jump into a middle of a select
    // and get to a WHEN without raising an error.
    DoBlock *doBlock = context->topBlockInstruction();
    // get the case expression
    RexxObject *caseValue = doBlock->getCase();

    for (size_t i = 0; i < expressionCount; i++)
    {
        // and the compare target (which needs tracing, but only as an intermediate
        RexxObject *compareValue = expressions[i]->evaluate(context, stack);
        context->traceResult(compareValue);
        // now perform the compare using the "==" operator method.
        // NOTE that the case value is the left hand side.
        RexxObject *result = caseValue->callOperatorMethod(OPERATOR_STRICT_EQUAL, compareValue);
        context->traceResult(result);

        // Remove the compare object from the stack
        stack->toss();

        // evaluate and decide if we execute this WHEN...we stop with the first true result
        if (result->truthValue(Error_Logical_value_when_case))
        {
            // do a pause and return
            context->pauseInstruction();
            return;
        }
    }

    // we execute the ELSE branch if everything evaluates to false
    context->setNext(else_location->nextInstruction);
    context->pauseInstruction();
}