//
// 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.
//
// ScopedMap.h --
//
// Author           : Aaron B. Moss
// Created On       : Wed Dec 2 11:37:00 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Sat Jul 22 09:23:24 2017
// Update Count     : 2
//

#pragma once

#include <cassert>
#include <iterator>
#include <map>
#include <utility>
#include <vector>

namespace GenPoly {
	/// A map where the items are placed into nested scopes;
	/// inserted items are placed into the innermost scope, lookup looks from the innermost scope outward;
	/// erasing a key means that find() will no longer report any instance of the key in a scope further
	/// out, but the erasure itself is scoped. Key erasure works by inserting a sentinal value into the
	/// value field, and thus only works for Value types where a meaningful sentinal can be chosen.
	template<typename Key, typename Value>
	class ErasableScopedMap {
		typedef std::map< Key, Value > Scope;
		typedef std::vector< Scope > ScopeList;

		ScopeList scopes; ///< scoped list of maps
		Value erased;     ///< sentinal value for erased keys
	public:
		typedef typename Scope::key_type key_type;
		typedef typename Scope::mapped_type mapped_type;
		typedef typename Scope::value_type value_type;
		typedef typename ScopeList::size_type size_type;
		typedef typename ScopeList::difference_type difference_type;
		typedef typename Scope::reference reference;
		typedef typename Scope::const_reference const_reference;
		typedef typename Scope::pointer pointer;
		typedef typename Scope::const_pointer const_pointer;

		class iterator : public std::iterator< std::bidirectional_iterator_tag,
		                                       value_type > {
		friend class ErasableScopedMap;
		friend class const_iterator;
			typedef typename std::map< Key, Value >::iterator wrapped_iterator;
			typedef typename std::vector< std::map< Key, Value > > scope_list;
			typedef typename scope_list::size_type size_type;

			/// Checks if this iterator points to a valid item
			bool is_valid() const {
				return it != map->scopes[i].end() && it->second != map->erased;
			}

			/// Increments on invalid
			iterator& next_valid() {
				if ( ! is_valid() ) { ++(*this); }
				return *this;
			}

			/// Decrements on invalid
			iterator& prev_valid() {
				if ( ! is_valid() ) { --(*this); }
				return *this;
			}
			
			iterator(ErasableScopedMap< Key, Value > const &_map, const wrapped_iterator &_it, size_type _i)
					: map(&_map), it(_it), i(_i) {}
			
		public:
			iterator(const iterator &that) : map(that.map), it(that.it), i(that.i) {}
			iterator& operator= (const iterator &that) {
				map = that.map; i = that.i; it = that.it;
				return *this;
			}

			reference operator* () { return *it; }
			pointer operator-> () { return it.operator->(); }

			iterator& operator++ () {
				if ( it == map->scopes[i].end() ) {
					if ( i == 0 ) return *this;
					--i;
					it = map->scopes[i].begin();
				} else {
					++it;
				}
				return next_valid();
			}
			iterator& operator++ (int) { iterator tmp = *this; ++(*this); return tmp; }

			iterator& operator-- () {
				// may fail if this is the begin iterator; allowed by STL spec
				if ( it == map->scopes[i].begin() ) {
					++i;
					it = map->scopes[i].end();
				}
				--it;
				return prev_valid();
			}
			iterator& operator-- (int) { iterator tmp = *this; --(*this); return tmp; }

			bool operator== (const iterator &that) {
				return map == that.map && i == that.i && it == that.it;
			}
			bool operator!= (const iterator &that) { return !( *this == that ); }

		private:
			ErasableScopedMap< Key, Value > const *map;
			wrapped_iterator it;
			size_type i;
		};

		class const_iterator : public std::iterator< std::bidirectional_iterator_tag,
		                                             value_type > {
		friend class ErasableScopedMap;
			typedef typename std::map< Key, Value >::iterator wrapped_iterator;
			typedef typename std::map< Key, Value >::const_iterator wrapped_const_iterator;
			typedef typename std::vector< std::map< Key, Value > > scope_list;
			typedef typename scope_list::size_type size_type;

			/// Checks if this iterator points to a valid item
			bool is_valid() const {
				return it != map->scopes[i].end() && it->second != map->erased;
			}

			/// Increments on invalid
			const_iterator& next_valid() {
				if ( ! is_valid() ) { ++(*this); }
				return *this;
			}

			/// Decrements on invalid
			const_iterator& prev_valid() {
				if ( ! is_valid() ) { --(*this); }
				return *this;
			}
			
			const_iterator(ErasableScopedMap< Key, Value > const &_map, const wrapped_const_iterator &_it, size_type _i)
					: map(&_map), it(_it), i(_i) {}
		public:
			const_iterator(const iterator &that) : map(that.map), it(that.it), i(that.i) {}
			const_iterator(const const_iterator &that) : map(that.map), it(that.it), i(that.i) {}
			const_iterator& operator= (const iterator &that) {
				map = that.map; i = that.i; it = that.it;
				return *this;
			}
			const_iterator& operator= (const const_iterator &that) {
				map = that.map; i = that.i; it = that.it;
				return *this;
			}

			const_reference operator* () { return *it; }
			const_pointer operator-> () { return it.operator->(); }

			const_iterator& operator++ () {
				if ( it == map->scopes[i].end() ) {
					if ( i == 0 ) return *this;
					--i;
					it = map->scopes[i].begin();
				} else {
					++it;
				}
				return next_valid();
			}
			const_iterator& operator++ (int) { const_iterator tmp = *this; ++(*this); return tmp; }

			const_iterator& operator-- () {
				// may fail if this is the begin iterator; allowed by STL spec
				if ( it == map->scopes[i].begin() ) {
					++i;
					it = map->scopes[i].end();
				}
				--it;
				return prev_valid();
			}
			const_iterator& operator-- (int) { const_iterator tmp = *this; --(*this); return tmp; }

			bool operator== (const const_iterator &that) {
				return map == that.map && i == that.i && it == that.it;
			}
			bool operator!= (const const_iterator &that) { return !( *this == that ); }

		private:
			ErasableScopedMap< Key, Value > const *map;
			wrapped_const_iterator it;
			size_type i;
		};

		/// Starts a new scope
		void beginScope() {
			Scope scope;
			scopes.push_back(scope);
		}

		/// Ends a scope; invalidates any iterators pointing to elements of that scope
		void endScope() {
			scopes.pop_back();
			assert( ! scopes.empty() );
		}

		/// Default constructor initializes with one scope
		ErasableScopedMap( const Value &erased_ ) : erased( erased_ ) { beginScope(); }

		iterator begin() { return iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
		const_iterator begin() const { return const_iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
		const_iterator cbegin() const { return const_iterator(*this, scopes.back().begin(), scopes.size()-1).next_valid(); }
		iterator end() { return iterator(*this, scopes[0].end(), 0); }
		const_iterator end() const { return const_iterator(*this, scopes[0].end(), 0); }
		const_iterator cend() const { return const_iterator(*this, scopes[0].end(), 0); }

		/// Gets the index of the current scope (counted from 1)
		size_type currentScope() const { return scopes.size(); }

		/// Finds the given key in the outermost scope it occurs; returns end() for none such
		iterator find( const Key &key ) {
			for ( size_type i = scopes.size() - 1; ; --i ) {
				typename Scope::iterator val = scopes[i].find( key );
				if ( val != scopes[i].end() ) {
					return val->second == erased ? end() : iterator( *this, val, i );
				}
				if ( i == 0 ) break;
			}
			return end();
		}
		const_iterator find( const Key &key ) const {
				return const_iterator( const_cast< ErasableScopedMap< Key, Value >* >(this)->find( key ) );
		}

		/// Finds the given key in the outermost scope inside the given scope where it occurs
		iterator findNext( const_iterator &it, const Key &key ) {
			if ( it.i == 0 ) return end();
			for ( size_type i = it.i - 1; ; --i ) {
				typename Scope::iterator val = scopes[i].find( key );
				if ( val != scopes[i].end() ) {
					return val->second == erased ? end() : iterator( *this, val, i );
				}
				if ( i == 0 ) break;
			}
			return end();
		}
		const_iterator findNext( const_iterator &it, const Key &key ) const {
				return const_iterator( const_cast< ErasableScopedMap< Key, Value >* >(this)->findNext( it, key ) );
		}

		/// Inserts the given key-value pair into the outermost scope
		std::pair< iterator, bool > insert( const value_type &value ) {
			std::pair< typename Scope::iterator, bool > res = scopes.back().insert( value );
			return std::make_pair( iterator(*this, res.first, scopes.size()-1), res.second );
		}
		std::pair< iterator, bool > insert( const Key &key, const Value &value ) { return insert( std::make_pair( key, value ) ); }

		/// Marks the given element as erased from this scope inward; returns 1 for erased an element, 0 otherwise
		size_type erase( const Key &key ) {
			typename Scope::iterator val = scopes.back().find( key );
			if ( val != scopes.back().end() ) {
				val->second = erased;
				return 1;
			} else {
				scopes.back().insert( val, std::make_pair( key, erased ) );
				return 0;
			}
		}

		Value& operator[] ( const Key &key ) {
			iterator slot = find( key );
			if ( slot != end() ) return slot->second;
			return insert( key, Value() ).first->second;
		}
	};
} // namespace GenPoly

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// compile-command: "make install" //
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