//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// TupleAssignment.cc --
//
// Author           : Rodolfo G. Esteves
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Rob Schluntz
// Last Modified On : Wed Nov 9 13:48:42 2016
// Update Count     : 2
//

#include "ResolvExpr/AlternativeFinder.h"
#include "ResolvExpr/Alternative.h"
#include "ResolvExpr/typeops.h"
#include "SynTree/Expression.h"
#include "SynTree/Initializer.h"
#include "Tuples.h"
#include "Explode.h"
#include "Common/SemanticError.h"
#include "InitTweak/InitTweak.h"

#include <functional>
#include <algorithm>
#include <iterator>
#include <iostream>
#include <cassert>
#include <set>
#include <unordered_set>

namespace Tuples {
	class TupleAssignSpotter {
	  public:
		// dispatcher for Tuple (multiple and mass) assignment operations
		TupleAssignSpotter( ResolvExpr::AlternativeFinder & );
		void spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities );

	  private:
		void match();

		struct Matcher {
		  public:
			Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
			virtual ~Matcher() {}
			virtual void match( std::list< Expression * > &out ) = 0;
			ResolvExpr::AltList lhs, rhs;
			TupleAssignSpotter &spotter;
			std::list< ObjectDecl * > tmpDecls;
		};

		struct MassAssignMatcher : public Matcher {
		  public:
			MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
			virtual void match( std::list< Expression * > &out );
		};

		struct MultipleAssignMatcher : public Matcher {
		  public:
			MultipleAssignMatcher( TupleAssignSpotter &spot, const ResolvExpr::AltList & alts );
			virtual void match( std::list< Expression * > &out );
		};

		ResolvExpr::AlternativeFinder &currentFinder;
		std::string fname;
		std::unique_ptr< Matcher > matcher;
	};

	/// true if expr is an expression of tuple type, i.e. a tuple expression, tuple variable, or MRV (multiple-return-value) function
	bool isTuple( Expression *expr ) {
		if ( ! expr ) return false;
		assert( expr->has_result() );
		return dynamic_cast<TupleExpr *>(expr) || expr->get_result()->size() > 1;
	}

	template< typename AltIter >
	bool isMultAssign( AltIter begin, AltIter end ) {
		// multiple assignment if more than one alternative in the range or if
		// the alternative is a tuple
		if ( begin == end ) return false;
		if ( isTuple( begin->expr ) ) return true;
		return ++begin != end;
	}

	bool pointsToTuple( Expression *expr ) {
		// also check for function returning tuple of reference types
		if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
			return pointsToTuple( castExpr->get_arg() );
		} else if ( AddressExpr *addr = dynamic_cast< AddressExpr * >( expr) ) {
			return isTuple( addr->get_arg() );
		}
		return false;
	}

	void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
		TupleAssignSpotter spotter( currentFinder );
		spotter.spot( expr, possibilities );
	}

	TupleAssignSpotter::TupleAssignSpotter( ResolvExpr::AlternativeFinder &f )
		: currentFinder(f) {}

	void TupleAssignSpotter::spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
		if (  NameExpr *op = dynamic_cast< NameExpr * >(expr->get_function()) ) {
			if ( InitTweak::isCtorDtorAssign( op->get_name() ) ) {
				fname = op->get_name();
				for ( std::list<ResolvExpr::AltList>::const_iterator ali = possibilities.begin(); ali != possibilities.end(); ++ali ) {
					if ( ali->size() == 0 ) continue; // AlternativeFinder will natrually handle this case, if it's legal
					if ( ali->size() <= 1 && InitTweak::isAssignment( op->get_name() ) ) {
						// what does it mean if an assignment takes 1 argument? maybe someone defined such a function, in which case AlternativeFinder will naturally handle it
						continue;
					}

					assert( ! ali->empty() );
					// grab args 2-N and group into a TupleExpr
					const ResolvExpr::Alternative & alt1 = ali->front();
					auto begin = std::next(ali->begin(), 1), end = ali->end();
					if ( pointsToTuple(alt1.expr) ) {
						if ( isMultAssign( begin, end ) ) {
							matcher.reset( new MultipleAssignMatcher( *this, *ali ) );
						} else {
							// mass assignment
							matcher.reset( new MassAssignMatcher( *this,  *ali ) );
						}
						match();
					}
				}
			}
		}
	}

	void TupleAssignSpotter::match() {
		assert ( matcher != 0 );

		std::list< Expression * > new_assigns;
		matcher->match( new_assigns );

		if ( new_assigns.empty() ) return;
		ResolvExpr::AltList current;
		// now resolve new assignments
		for ( std::list< Expression * >::iterator i = new_assigns.begin(); i != new_assigns.end(); ++i ) {
			ResolvExpr::AlternativeFinder finder( currentFinder.get_indexer(), currentFinder.get_environ() );
			try {
				finder.findWithAdjustment(*i);
			} catch (...) {
				return; // xxx - no match should not mean failure, it just means this particular tuple assignment isn't valid
			}
			// prune expressions that don't coincide with
			ResolvExpr::AltList alts = finder.get_alternatives();
			assert( alts.size() == 1 );
			assert( alts.front().expr != 0 );
			current.push_back( alts.front() );
		}

		// extract expressions from the assignment alternatives to produce a list of assignments that
		// together form a single alternative
		std::list< Expression *> solved_assigns;
		for ( ResolvExpr::Alternative & alt : current ) {
			solved_assigns.push_back( alt.expr->clone() );
		}
		// xxx - need to do this??
		ResolvExpr::TypeEnvironment compositeEnv;
		simpleCombineEnvironments( current.begin(), current.end(), compositeEnv );
		currentFinder.get_alternatives().push_front( ResolvExpr::Alternative(new TupleAssignExpr(solved_assigns, matcher->tmpDecls), compositeEnv, ResolvExpr::sumCost( current ) ) );
	}

	TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList &alts ) : spotter(spotter) {
		assert( ! alts.empty() );
		ResolvExpr::Alternative lhsAlt = alts.front();
		// peel off the cast that exists on ctor/dtor expressions
		bool isCast = false;
		if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( lhsAlt.expr ) ) {
			lhsAlt.expr = castExpr->get_arg();
			castExpr->set_arg( nullptr );
			delete castExpr;
			isCast = true;
		}

		// explode the lhs so that each field of the tuple-valued-expr is assigned.
		explode( lhsAlt, spotter.currentFinder.get_indexer(), back_inserter(lhs) );

		// and finally, re-add the cast to each lhs expr, so that qualified tuple fields can be constructed
		if ( isCast ) {
			for ( ResolvExpr::Alternative & alt : lhs ) {
				Expression *& expr = alt.expr;
				Type * castType = expr->get_result()->clone();
				Type * type = InitTweak::getPointerBase( castType );
				assert( type );
				type->get_qualifiers() -= Type::Qualifiers(true, true, true, false, true, true);
				type->set_isLvalue( true ); // xxx - might not need this
				expr = new CastExpr( expr, castType );
			}
		}
	}

	TupleAssignSpotter::MassAssignMatcher::MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
		assert( alts.size() == 1 || alts.size() == 2 );
		if ( alts.size() == 2 ) {
			rhs.push_back( alts.back() );
		}
	}

	TupleAssignSpotter::MultipleAssignMatcher::MultipleAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
		// explode the rhs so that each field of the tuple-valued-expr is assigned.
		explode( std::next(alts.begin(), 1), alts.end(), spotter.currentFinder.get_indexer(), back_inserter(rhs) );
	}

	UntypedExpr * createFunc( const std::string &fname, ObjectDecl *left, ObjectDecl *right ) {
		assert( left );
		std::list< Expression * > args;
		args.push_back( new AddressExpr( UntypedExpr::createDeref( new VariableExpr( left ) ) ) );
		// args.push_back( new AddressExpr( new VariableExpr( left ) ) );
		if ( right ) args.push_back( new VariableExpr( right ) );
		return new UntypedExpr( new NameExpr( fname ), args );
	}

	ObjectDecl * newObject( UniqueName & namer, Expression * expr ) {
		assert( expr->has_result() && ! expr->get_result()->isVoid() );
		return new ObjectDecl( namer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, expr->get_result()->clone(), new SingleInit( expr->clone() ) );
	}

	void TupleAssignSpotter::MassAssignMatcher::match( std::list< Expression * > &out ) {
		static UniqueName lhsNamer( "__massassign_L" );
		static UniqueName rhsNamer( "__massassign_R" );
		assert ( ! lhs.empty() && rhs.size() <= 1);

		ObjectDecl * rtmp = rhs.size() == 1 ? newObject( rhsNamer, rhs.front().expr ) : nullptr;
		for ( ResolvExpr::Alternative & lhsAlt : lhs ) {
			ObjectDecl * ltmp = newObject( lhsNamer, lhsAlt.expr );
			out.push_back( createFunc( spotter.fname, ltmp, rtmp ) );
			tmpDecls.push_back( ltmp );
		}
		if ( rtmp ) tmpDecls.push_back( rtmp );
	}

	void TupleAssignSpotter::MultipleAssignMatcher::match( std::list< Expression * > &out ) {
		static UniqueName lhsNamer( "__multassign_L" );
		static UniqueName rhsNamer( "__multassign_R" );

		// xxx - need more complicated matching?
		if ( lhs.size() == rhs.size() ) {
			std::list< ObjectDecl * > ltmp;
			std::list< ObjectDecl * > rtmp;
			std::transform( lhs.begin(), lhs.end(), back_inserter( ltmp ), []( ResolvExpr::Alternative & alt ){
				return newObject( lhsNamer, alt.expr );
			});
			std::transform( rhs.begin(), rhs.end(), back_inserter( rtmp ), []( ResolvExpr::Alternative & alt ){
				return newObject( rhsNamer, alt.expr );
			});
			zipWith( ltmp.begin(), ltmp.end(), rtmp.begin(), rtmp.end(), back_inserter(out), [&](ObjectDecl * obj1, ObjectDecl * obj2 ) { return createFunc(spotter.fname, obj1, obj2); } );
			tmpDecls.splice( tmpDecls.end(), ltmp );
			tmpDecls.splice( tmpDecls.end(), rtmp );
		}
	}
} // namespace Tuples

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// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //