#include "../config/pathan_config.h"
/*
 * Copyright (c) 2001, DecisionSoft Limited All rights reserved.
 * Please see LICENSE.TXT for more information.
 */

#include <pathan/functions/FunctionSubsequence.hpp>
#include <pathan/ATStringOrDerived.hpp>
#include <pathan/ATDoubleOrDerived.hpp>
#include <pathan/ATDecimalOrDerived.hpp>
#include <pathan/exceptions/FunctionException.hpp>
#include <pathan/DynamicContext.hpp>
#include <xercesc/validators/schema/SchemaSymbols.hpp>
#include <pathan/internal/factory/DatatypeFactory.hpp>

const XMLCh FunctionSubsequence::name[] = {
XERCES_CPP_NAMESPACE_QUALIFIER chLatin_s, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_u, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_b, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_s, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_e, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_q, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_u, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_e, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_n, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_c, XERCES_CPP_NAMESPACE_QUALIFIER chLatin_e, XERCES_CPP_NAMESPACE_QUALIFIER chNull };

/**
 * fn:subsequence($sourceSeq as item()*, $startingLoc as xs:double) as item()*
 * fn:subsequence($sourceSeq as item()*, $startingLoc as xs:double, $length as xs:double) as item()*
**/

FunctionSubsequence::FunctionSubsequence(const VectorOfDataItems &args, XPath2MemoryManager* memMgr)
  : ConstantFoldingFunction(name,2, 3, "item()*, double, double", args, memMgr)
{
}

Sequence FunctionSubsequence::collapseTreeInternal(DynamicContext* context, int flags) const
{
	XPath2MemoryManager* memMgr = context->getMemoryManager();

	Sequence sourceSeq = getParamNumber(1, context);
	if(sourceSeq.isEmpty())
		return Sequence(memMgr);

	Sequence startingLoc=getParamNumber(2,context);

  const ATDecimalOrDerived* zero = DatatypeFactory::POD2AT::createInteger(memMgr, 0, context);
  const ATDecimalOrDerived* one = DatatypeFactory::POD2AT::createInteger(memMgr, 1, context);

	// The first character of a string is located at position 1 (not position 0).
	const Numeric* index = (const ATDoubleOrDerived*)startingLoc.first();
  index = index->subtract(one, context);
  if(index->lessThan(zero, context)) {
    index = zero;
  }

	const Numeric* subSeqLength;
  const ATDecimalOrDerived* seqLength = DatatypeFactory::POD2AT::createDecimal(memMgr, (long)sourceSeq.getLength(), context);
	if(getNumArgs()>2) {
		Sequence length=getParamNumber(3,context);
		subSeqLength = (const ATDoubleOrDerived*)length.first();
	}
	else {
		subSeqLength = seqLength->subtract(index, context);
  }
	const ATDecimalOrDerived* startIndex = (const ATDecimalOrDerived*)index->round(context)->castAs(
      XERCES_CPP_NAMESPACE_QUALIFIER SchemaSymbols::fgURI_SCHEMAFORSCHEMA, 
      XERCES_CPP_NAMESPACE_QUALIFIER SchemaSymbols::fgDT_DECIMAL, context);
	const ATDecimalOrDerived* endIndex = (const ATDecimalOrDerived*)index->add(subSeqLength, context)->round(context)->castAs(
      XERCES_CPP_NAMESPACE_QUALIFIER SchemaSymbols::fgURI_SCHEMAFORSCHEMA,  
      XERCES_CPP_NAMESPACE_QUALIFIER SchemaSymbols::fgDT_DECIMAL, context);

	// More specifically, returns the characters in $sourceSeq whose position $p obeys:
	//    xf:round($startingLoc) <= $p < xf:round($startingLoc + $length)
  if(endIndex->greaterThan(seqLength, context)) {
    endIndex = seqLength;
  }

  if(startIndex->greaterThan(seqLength->subtract(one, context), context) ||
     startIndex->greaterThan(endIndex->subtract(one, context), context) ) {
    return Sequence(memMgr);
  }

	Sequence resultSeq = Sequence(sourceSeq.getLength(), memMgr);
  
	for(const ATDecimalOrDerived* i = startIndex; i->lessThan(endIndex, context); i = (const ATDecimalOrDerived*)i->add(one, context)) {
	  resultSeq.addItem(sourceSeq.item(i));
	}
  
	return resultSeq;
}