//
// 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.
//
// Explode.h --
//
// Author           : Rob Schluntz
// Created On       : Wed Nov 9 13:12:24 2016
// Last Modified By : Andrew Beach
// Last Modified On : Mon Jun 17 14:36:00 2019
// Update Count     : 4
//

#pragma once

#include <iterator>                     // for back_inserter, back_insert_iterator
#include <utility>                      // for forward

#include "AST/Expr.hpp"
#include "ResolvExpr/Alternative.h"     // for Alternative, AltList
#include "ResolvExpr/Candidate.hpp"     // for Candidate, CandidateList
#include "ResolvExpr/ExplodedActual.h"  // for ExplodedActual
#include "ResolvExpr/ExplodedArg.hpp"   // for ExplodedArg
#include "SynTree/Expression.h"         // for Expression, UniqueExpr, AddressExpr
#include "SynTree/Type.h"               // for TupleType, Type
#include "Tuples.h"                     // for maybeImpure

namespace ast {
	class SymbolTable;
}

namespace SymTab {
class Indexer;
}  // namespace SymTab

namespace Tuples {
	Expression * distributeReference( Expression * );

	static inline CastExpr * isReferenceCast( Expression * expr ) {
		if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
			if ( dynamic_cast< ReferenceType * >( castExpr->result ) ) {
				return castExpr;
			}
		}
		return nullptr;
	}

	/// Append alternative to an OutputIterator of Alternatives
	template<typename OutputIterator>
	void append( OutputIterator out, Expression* expr, const ResolvExpr::TypeEnvironment& env,
			const ResolvExpr::OpenVarSet& openVars, const ResolvExpr::AssertionList& need,
			const ResolvExpr::Cost& cost, const ResolvExpr::Cost& cvtCost ) {
		*out++ = ResolvExpr::Alternative{ expr, env, openVars, need, cost, cvtCost };
	}

	/// Append alternative to an ExplodedActual
	static inline void append( ResolvExpr::ExplodedActual& ea, Expression* expr,
			const ResolvExpr::TypeEnvironment&, const ResolvExpr::OpenVarSet&,
			const ResolvExpr::AssertionList&, const ResolvExpr::Cost&, const ResolvExpr::Cost& ) {
		ea.exprs.emplace_back( expr );
		/// xxx -- merge environment, openVars, need, cost?
	}

	/// helper function used by explode
	template< typename Output >
	void explodeUnique( Expression * expr, const ResolvExpr::Alternative & alt,
			const SymTab::Indexer & indexer, Output&& out, bool isTupleAssign ) {
		if ( isTupleAssign ) {
			// tuple assignment needs CastExprs to be recursively exploded to easily get at all of the components
			if ( CastExpr * castExpr = isReferenceCast( expr ) ) {
				ResolvExpr::AltList alts;
				explodeUnique(
					castExpr->get_arg(), alt, indexer, back_inserter( alts ), isTupleAssign );
				for ( ResolvExpr::Alternative & alt : alts ) {
					// distribute reference cast over all components
					append( std::forward<Output>(out), distributeReference( alt.release_expr() ),
						alt.env, alt.openVars, alt.need, alt.cost, alt.cvtCost );
				}
				// in tuple assignment, still need to handle the other cases, but only if not already handled here (don't want to output too many alternatives)
				return;
			}
		}
		Type * res = expr->get_result()->stripReferences();
		if ( TupleType * tupleType = dynamic_cast< TupleType * > ( res ) ) {
			if ( TupleExpr * tupleExpr = dynamic_cast< TupleExpr * >( expr ) ) {
				// can open tuple expr and dump its exploded components
				for ( Expression * expr : tupleExpr->get_exprs() ) {
					explodeUnique( expr, alt, indexer, std::forward<Output>(out), isTupleAssign );
				}
			} else {
				// tuple type, but not tuple expr - recursively index into its components.
				// if expr type is reference, convert to value type
				Expression * arg = expr->clone();
				if ( Tuples::maybeImpureIgnoreUnique( arg ) ) {
					// expressions which may contain side effects require a single unique instance of the expression.
					arg = new UniqueExpr( arg );
				}
				// cast reference to value type to facilitate further explosion
				if ( dynamic_cast<ReferenceType *>( arg->get_result() ) ) {
					arg = new CastExpr( arg, tupleType->clone() );
				}
				for ( unsigned int i = 0; i < tupleType->size(); i++ ) {
					TupleIndexExpr * idx = new TupleIndexExpr( arg->clone(), i );
					explodeUnique( idx, alt, indexer, std::forward<Output>(out), isTupleAssign );
					delete idx;
				}
				delete arg;
			}
		} else {
			// atomic (non-tuple) type - output a clone of the expression in a new alternative
			append( std::forward<Output>(out), expr->clone(), alt.env, alt.openVars, alt.need,
				alt.cost, alt.cvtCost );
		}
	}

	/// expands a tuple-valued alternative into multiple alternatives, each with a non-tuple-type
	template< typename Output >
	void explode( const ResolvExpr::Alternative &alt, const SymTab::Indexer & indexer,
			Output&& out, bool isTupleAssign = false ) {
		explodeUnique( alt.expr, alt, indexer, std::forward<Output>(out), isTupleAssign );
	}

	// explode list of alternatives
	template< typename AltIterator, typename Output >
	void explode( AltIterator altBegin, AltIterator altEnd, const SymTab::Indexer & indexer,
			Output&& out, bool isTupleAssign = false ) {
		for ( ; altBegin != altEnd; ++altBegin ) {
			explode( *altBegin, indexer, std::forward<Output>(out), isTupleAssign );
		}
	}

	template< typename Output >
	void explode( const ResolvExpr::AltList & alts, const SymTab::Indexer & indexer, Output&& out,
			bool isTupleAssign = false ) {
		explode( alts.begin(), alts.end(), indexer, std::forward<Output>(out), isTupleAssign );
	}

const ast::Expr * distributeReference( const ast::Expr * );

/// Append candidate to an OutputIterator of Candidates.
template<typename OutputIterator>
void append( OutputIterator out, const ast::Expr * expr, const ast::TypeEnvironment & env,
		const ast::OpenVarSet & open, const ast::AssertionList & need,
		const ResolvExpr::Cost & cost, const ResolvExpr::Cost & cvtCost ) {
	ast::TypeEnvironment copyEnv = env;
	ast::OpenVarSet copyOpen = open;
	ast::AssertionSet set;
	mergeAssertionSet( set, need );
	*out++ = std::make_shared<ResolvExpr::Candidate>( expr, std::move( copyEnv ),
		std::move( copyOpen ), std::move( set ), cost, cvtCost );
}

/// Append candidate to an ExplodedArg.
static inline void append( ResolvExpr::ExplodedArg& ea, const ast::Expr * expr,
		const ast::TypeEnvironment&, const ast::OpenVarSet&,
		const ast::AssertionList&, const ResolvExpr::Cost&, const ResolvExpr::Cost& ) {
	// I'm not sure why most of the arguments are unused. But they were in the old version.
	ea.exprs.emplace_back( expr );
}

/// Check if the expression is a cast to a reference type, return it if it is.
static inline const ast::CastExpr * isReferenceCast( const ast::Expr * expr ) {
	if ( const ast::CastExpr * cast = dynamic_cast< const ast::CastExpr * >( expr ) ) {
		if ( dynamic_cast< const ast::ReferenceType * >( cast->result.get() ) ) {
			return cast;
		}
	}
	return nullptr;
}

/// helper function (indirectely) used by explode
template< typename Output >
void explodeRecursive(
	const ast::CastExpr *, const ResolvExpr::Candidate &,
	const ast::SymbolTable &, Output &&
) {
}

/// helper function used by explode
template< typename Output >
void explodeUnique(
	const ast::ptr< ast::Expr > & expr, const ResolvExpr::Candidate & arg,
	const ast::SymbolTable & symtab, Output && out, bool isTupleAssign
) {
	// Tuple assignment can use a faster method if it is cast. Uses recursive exploding.
	if ( isTupleAssign ) if ( const ast::CastExpr * castExpr = isReferenceCast( expr ) ) {
		ResolvExpr::CandidateList candidates;
		explodeUnique( castExpr->arg, arg, symtab, back_inserter( candidates ), true );
		for ( ResolvExpr::CandidateRef & cand : candidates ) {
			// Distribute the reference cast over all components of the candidate.
			append( std::forward<Output>(out), distributeReference( cand->expr ), cand->env,
				cand->open, cand->need, cand->cost, cand->cvtCost );
		}
		return;
	}
	const ast::Type * res = expr->result->stripReferences();
	if ( const ast::TupleType * tupleType = dynamic_cast< const ast::TupleType * >( res ) ) {
		if ( const ast::ptr< ast::TupleExpr > & tupleExpr = expr.as< ast::TupleExpr >() ) {
			// Open the tuple expr and continue on its components.
			for ( const ast::Expr * expr : tupleExpr->exprs ) {
				explodeUnique( expr, arg, symtab, std::forward<Output>(out), isTupleAssign );
			}
		} else {
			ast::ptr< ast::Expr > local = expr;
			// Expressions which may have side effects require a single unique instance.
			if ( Tuples::maybeImpureIgnoreUnique( local ) ) {
				local = new ast::UniqueExpr( local->location, local );
			}
			// Cast a reference away to a value-type to allow further explosion.
			if ( dynamic_cast< const ast::ReferenceType *>( local->result.get() ) ) {
				local = new ast::CastExpr{ local, tupleType };
			}
			// Now we have to go across the tuple via indexing.
			for ( unsigned int i = 0 ; i < tupleType->size() ; ++i ) {
				ast::TupleIndexExpr * idx = new ast::TupleIndexExpr( local->location, local, i );
				explodeUnique( idx, arg, symtab, std::forward<Output>(out), isTupleAssign );
				// TODO: We need more input to figure out the exact lifetimes of these types.
				// delete idx;
			}
			// delete local;
		}
	} else {
		// For atomic/non-tuple types, no explosion is used.
		append( std::forward<Output>(out), expr, arg.env, arg.open, arg.need, arg.cost,
			arg.cvtCost );
	}
}

/// expands a tuple-valued candidate into multiple candidates, each with a non-tuple type
template< typename Output >
void explode(
	const ResolvExpr::Candidate & arg, const ast::SymbolTable & symtab, Output && out,
	bool isTupleAssign = false
) {
	explodeUnique( arg.expr, arg, symtab, std::forward< Output >( out ), isTupleAssign );
}

/// explode list of candidates into flattened list of candidates
template< typename Output >
void explode(
	const ResolvExpr::CandidateList & cands, const ast::SymbolTable & symtab, Output && out,
	bool isTupleAssign = false
) {
	for ( const ResolvExpr::CandidateRef & cand : cands ) {
		explode( *cand, symtab, std::forward< Output >( out ), isTupleAssign );
	}
}

} // namespace Tuples

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