rippled/src/Pathfinder.cpp

#include "Pathfinder.h"
#include "Application.h"
#include "RippleLines.h"
#include "Log.h"
#include <boost/foreach.hpp>

/*
JED: V IIII

we just need to find a succession of the highest quality paths there until we find enough width

Don't do branching within each path

We have a list of paths we are working on but how do we compare the ones that are terminating in a different currency?

Loops

TODO: what is a good way to come up with multiple paths?
	Maybe just change the sort criteria?
	first a low cost one and then a fat short one?


OrderDB:
	getXNSOffers(); 
	
	// return list of all orderbooks that want XNS 
	// return list of all orderbooks that want IssuerID
	// return list of all orderbooks that want this issuerID and currencyID
*/

/*
Test sending to XNS
Test XNS to XNS
Test offer in middle
Test XNS to USD
Test USD to EUR
*/


// we sort the options by:
//    cost of path
//    length of path
//    width of path
//    correct currency at the end



bool sortPathOptions(PathOption::pointer first, PathOption::pointer second)
{
	if(first->mTotalCost<second->mTotalCost) return(true);
	if(first->mTotalCost>second->mTotalCost) return(false);
	
	if(first->mCorrectCurrency && !second->mCorrectCurrency) return(true);
	if(!first->mCorrectCurrency && second->mCorrectCurrency) return(false);

	if(first->mPath.getElementCount()<second->mPath.getElementCount()) return(true);
	if(first->mPath.getElementCount()>second->mPath.getElementCount()) return(false);

	if(first->mMinWidth<second->mMinWidth) return true;
	
	return false;
}

PathOption::PathOption(uint160& srcAccount,uint160& srcCurrencyID,const uint160& dstCurrencyID)
{
	mCurrentAccount=srcAccount;
	mCurrencyID=srcCurrencyID;
	mCorrectCurrency=(srcCurrencyID==dstCurrencyID);
	mQuality=0;
	mMinWidth=STAmount(dstCurrencyID,99999,80);   // this will get lowered when we convert back to the correct currency
}

PathOption::PathOption(PathOption::pointer other)
{
	// TODO:
}


Pathfinder::Pathfinder(NewcoinAddress& srcAccountID, NewcoinAddress& dstAccountID, uint160& srcCurrencyID, STAmount dstAmount) : 
	mSrcAccountID(srcAccountID.getAccountID()) , mDstAccountID(dstAccountID.getAccountID()), mSrcCurrencyID(srcCurrencyID) , mDstAmount(dstAmount), mOrderBook(theApp->getMasterLedger().getCurrentLedger())
{
	mLedger=theApp->getMasterLedger().getCurrentLedger();
}

bool Pathfinder::findPaths(int maxSearchSteps, int maxPay, STPathSet& retPathSet)
{
	if(mLedger)
	{
		PathOption::pointer head(new PathOption(mSrcAccountID,mSrcCurrencyID,mDstAmount.getCurrency()));
		addOptions(head);

		for(int n=0; n<maxSearchSteps; n++)
		{
			std::list<PathOption::pointer> tempPaths=mBuildingPaths;
			mBuildingPaths.clear();
			BOOST_FOREACH(PathOption::pointer path,tempPaths)
			{
				addOptions(path);
			}
			if(checkComplete(retPathSet)) return(true);
		}
		
	}
	
	return(false);
}

bool Pathfinder::checkComplete(STPathSet& retPathSet)
{
	if(mCompletePaths.size())
	{ // TODO: look through these and pick the most promising
		int count=0;
		BOOST_FOREACH(PathOption::pointer pathOption,mCompletePaths)
		{
			retPathSet.addPath(pathOption->mPath);
			count++;
			if(count>2) return(true);
		}
		return(true);
	}
	return(false);
}


// get all the options from this accountID
//   if source is XNS
//		every offer that wants XNS
//   else 
//		every ripple line that starts with the source currency 
//		every offer that we can take that wants the source currency

void Pathfinder::addOptions(PathOption::pointer tail)
{
	if(!tail->mCurrencyID)
	{ // source XNS
		BOOST_FOREACH(OrderBook::pointer book,mOrderBook.getXNSInBooks())
		{
			PathOption::pointer pathOption(new PathOption(tail));

			STPathElement ele(uint160(), book->getCurrencyOut(), book->getIssuerOut());
			pathOption->mPath.addElement(ele);

			pathOption->mCurrentAccount=book->getIssuerOut();
			pathOption->mCurrencyID=book->getCurrencyOut();
			addPathOption(pathOption);
		}
	}else
	{ // ripple
		RippleLines rippleLines(tail->mCurrentAccount);
		BOOST_FOREACH(RippleState::pointer line,rippleLines.getLines())
		{
			// TODO: make sure we can move in the correct direction
			STAmount balance=line->getBalance();  
			if(balance.getCurrency()==tail->mCurrencyID)
			{  // we have a ripple line from the tail to somewhere else
				PathOption::pointer pathOption(new PathOption(tail));

				STPathElement ele(line->getAccountIDPeer().getAccountID(), uint160(),uint160());
				pathOption->mPath.addElement(ele);


				pathOption->mCurrentAccount=line->getAccountIDPeer().getAccountID();
				addPathOption(pathOption);
			}	
		}

		// every offer that wants the source currency
		std::vector<OrderBook::pointer> books;
		mOrderBook.getBooks(tail->mCurrentAccount, tail->mCurrencyID, books);

		BOOST_FOREACH(OrderBook::pointer book,books)
		{
			PathOption::pointer pathOption(new PathOption(tail));

			STPathElement ele(uint160(), book->getCurrencyOut(), book->getIssuerOut());
			pathOption->mPath.addElement(ele);

			pathOption->mCurrentAccount=book->getIssuerOut();
			pathOption->mCurrencyID=book->getCurrencyOut();
			addPathOption(pathOption);
		}
	}
}

void Pathfinder::addPathOption(PathOption::pointer pathOption)
{
	if(pathOption->mCurrencyID==mDstAmount.getCurrency()) 
	{
		pathOption->mCorrectCurrency=true;

		if(pathOption->mCurrentAccount==mDstAccountID)
		{ // this path is complete
			mCompletePaths.push_back(pathOption);
		}else mBuildingPaths.push_back(pathOption);
	}else 
	{
		pathOption->mCorrectCurrency=false;
		mBuildingPaths.push_back(pathOption);
	}
}