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 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /*

   A simple cursor that enumerates the elements of an RDF container

   (RDF:Bag, RDF:Seq, or RDF:Alt).

   Caveats

   -------

   1. This uses an implementation-specific detail to determine the

      index of the last element in the container; specifically, the RDF

      utilities maintain a counter attribute on the container that

      holds the numeric value of the next value that is to be

      assigned. So, this cursor will bust if you use it with a bag that

      hasn't been created using the RDF utility routines.

  */

 #include "nscore.h"

 #include "nsCOMPtr.h"

 #include "nsIRDFContainerUtils.h"

 #include "nsIRDFDataSource.h"

 #include "nsIRDFNode.h"

 #include "nsIRDFService.h"

 #include "nsIServiceManager.h"

 #include "nsRDFCID.h"

 #include "nsString.h"

 #include "nsXPIDLString.h"

 #include "prlog.h"

 #include "rdf.h"

 #include "rdfutil.h"

 ////////////////////////////////////////////////////////////////////////

 class ContainerEnumeratorImpl : public nsISimpleEnumerator {

 private:

     // pseudo-constants

     static nsrefcnt              gRefCnt;

     static nsIRDFResource*       kRDF_nextVal;

     static nsIRDFContainerUtils* gRDFC;

     nsCOMPtr<nsIRDFDataSource>      mDataSource;

     nsCOMPtr<nsIRDFResource>        mContainer;

     nsCOMPtr<nsIRDFResource>        mOrdinalProperty;

     nsCOMPtr<nsISimpleEnumerator>   mCurrent;

     nsCOMPtr<nsIRDFNode>            mResult;

     int32_t mNextIndex;

 public:

     ContainerEnumeratorImpl(nsIRDFDataSource* ds, nsIRDFResource* container);

     virtual ~ContainerEnumeratorImpl();

     nsresult Init();

     NS_DECL_ISUPPORTS

     NS_DECL_NSISIMPLEENUMERATOR

 };

 nsrefcnt              ContainerEnumeratorImpl::gRefCnt;

 nsIRDFResource*       ContainerEnumeratorImpl::kRDF_nextVal;

 nsIRDFContainerUtils* ContainerEnumeratorImpl::gRDFC;

 ContainerEnumeratorImpl::ContainerEnumeratorImpl(nsIRDFDataSource* aDataSource,

                                                  nsIRDFResource* aContainer)

     : mDataSource(aDataSource),

       mContainer(aContainer),

       mNextIndex(1)

 {

 }

 nsresult

 ContainerEnumeratorImpl::Init()

 {

     if (gRefCnt++ == 0) {

         nsresult rv;

         NS_DEFINE_CID(kRDFServiceCID, NS_RDFSERVICE_CID);

         nsCOMPtr<nsIRDFService> rdf = do_GetService(kRDFServiceCID);

         NS_ASSERTION(rdf != nullptr, "unable to acquire resource manager");

         if (! rdf)

             return NS_ERROR_FAILURE;

         rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "nextVal"), &kRDF_nextVal);

         NS_ASSERTION(NS_SUCCEEDED(rv), "unable to get resource");

         if (NS_FAILED(rv)) return rv;

         NS_DEFINE_CID(kRDFContainerUtilsCID, NS_RDFCONTAINERUTILS_CID);

         rv = CallGetService(kRDFContainerUtilsCID, &gRDFC);

         if (NS_FAILED(rv)) return rv;

     }

     return NS_OK;

 }

 ContainerEnumeratorImpl::~ContainerEnumeratorImpl()

 {

     if (--gRefCnt == 0) {

         NS_IF_RELEASE(kRDF_nextVal);

         NS_IF_RELEASE(gRDFC);

     }

 }

 NS_IMPL_ISUPPORTS(ContainerEnumeratorImpl, nsISimpleEnumerator)

 NS_IMETHODIMP

 ContainerEnumeratorImpl::HasMoreElements(bool* aResult)

 {

     NS_PRECONDITION(aResult != nullptr, "null ptr");

     if (! aResult)

         return NS_ERROR_NULL_POINTER;

     nsresult rv;

     // If we've already queued up a next value, then we know there are more elements.

     if (mResult) {

         *aResult = true;

         return NS_OK;

     }

     // Otherwise, we need to grovel

     // Figure out the upper bound so we'll know when we're done. Since it's

     // possible that we're targeting a composite datasource, we'll need to

     // "GetTargets()" and take the maximum value of "nextVal" to know the

     // upper bound.

     //

     // Remember that since nextVal is the next index that we'd assign

     // to an element in a container, it's *one more* than count of

     // elements in the container.

     int32_t max = 0;

     nsCOMPtr<nsISimpleEnumerator> targets;

     rv = mDataSource->GetTargets(mContainer, kRDF_nextVal, true, getter_AddRefs(targets));

     if (NS_FAILED(rv)) return rv;

     while (1) {

         bool hasmore;

         targets->HasMoreElements(&hasmore);

         if (! hasmore)

             break;

         nsCOMPtr<nsISupports> isupports;

         targets->GetNext(getter_AddRefs(isupports));

         nsCOMPtr<nsIRDFLiteral> nextValLiteral = do_QueryInterface(isupports);

         if (! nextValLiteral)

              continue;

          const char16_t *nextValStr;

          nextValLiteral->GetValueConst(&nextValStr);

          nsresult err;

          int32_t nextVal = nsAutoString(nextValStr).ToInteger(&err);

          if (nextVal > max)

              max = nextVal;

     }

     // Now pre-fetch our next value into mResult.

     while (mCurrent || mNextIndex < max) {

         // If mCurrent has been depleted, then conjure up a new one

         if (! mCurrent) {

             rv = gRDFC->IndexToOrdinalResource(mNextIndex, getter_AddRefs(mOrdinalProperty));

             if (NS_FAILED(rv)) return rv;

             rv = mDataSource->GetTargets(mContainer, mOrdinalProperty, true, getter_AddRefs(mCurrent));

             if (NS_FAILED(rv)) return rv;

             ++mNextIndex;

         }

         if (mCurrent) {

             bool hasMore;

             rv = mCurrent->HasMoreElements(&hasMore);

             if (NS_FAILED(rv)) return rv;

             // Is the current enumerator depleted? If so, iterate to

             // the next index.

             if (! hasMore) {

                 mCurrent = nullptr;

                 continue;

             }

             // "Peek" ahead and pull out the next target.

             nsCOMPtr<nsISupports> result;

             rv = mCurrent->GetNext(getter_AddRefs(result));

             if (NS_FAILED(rv)) return rv;

             mResult = do_QueryInterface(result, &rv);

             if (NS_FAILED(rv)) return rv;

             *aResult = true;

             return NS_OK;

         }

     }

     // If we get here, we ran out of elements. The cursor is empty.

     *aResult = false;

     return NS_OK;

 }

 NS_IMETHODIMP

 ContainerEnumeratorImpl::GetNext(nsISupports** aResult)

 {

     nsresult rv;

     bool hasMore;

     rv = HasMoreElements(&hasMore);

     if (NS_FAILED(rv)) return rv;

     if (! hasMore)

         return NS_ERROR_UNEXPECTED;

     NS_ADDREF(*aResult = mResult);

     mResult = nullptr;

     return NS_OK;

 }

 ////////////////////////////////////////////////////////////////////////

 nsresult

 NS_NewContainerEnumerator(nsIRDFDataSource* aDataSource,

                           nsIRDFResource* aContainer,

                           nsISimpleEnumerator** aResult)

 {

     NS_PRECONDITION(aDataSource != nullptr, "null ptr");

     if (! aDataSource)

         return NS_ERROR_NULL_POINTER;

     NS_PRECONDITION(aContainer != nullptr, "null ptr");

     if (! aContainer)

         return NS_ERROR_NULL_POINTER;

     NS_PRECONDITION(aResult != nullptr, "null ptr");

     if (! aResult)

         return NS_ERROR_NULL_POINTER;

     ContainerEnumeratorImpl* result = new ContainerEnumeratorImpl(aDataSource, aContainer);

     if (! result)

         return NS_ERROR_OUT_OF_MEMORY;

     NS_ADDREF(result);

     nsresult rv = result->Init();

     if (NS_FAILED(rv))

         NS_RELEASE(result);

     *aResult = result;

     return rv;

 }