//
// Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// list -- lets a user-defined stuct form intrusive linked lists
//
// Author           : Michael Brooks
// Created On       : Wed Apr 22 18:00:00 2020
// Last Modified By : Peter A. Buhr
// Last Modified On : Thu Apr 24 18:12:59 2025
// Update Count     : 72
//

#pragma once

#include <assert.h>

forall( Decorator &, T & )
struct tytagref {
	inline T &;
};

forall( tOuter &, tMid &, tInner & )
trait embedded {
	tytagref( tMid, tInner ) ?`inner( tOuter & );
};

// embedded is reflexive, with no info (void) as the type tag
forall( T & )
static inline tytagref(void, T) ?`inner ( T & this ) { tytagref( void, T ) ret = {this}; return ret; }


//
// P9_EMBEDDED: Use on every case of plan-9 inheritance, to make "implements embedded" be a closure of plan-9 inheritance.
//
// struct foo {
//	int a, b, c;
//	inline (bar);
// };
// P9_EMBEDDED( foo, bar )
//

// usual version, for structs that are top-level declarations
#define P9_EMBEDDED( derived, immedBase ) P9_EMBEDDED_DECL_( derived, immedBase, static ) P9_EMBEDDED_BDY_( immedBase )

// special version, for structs that are declared in functions
#define P9_EMBEDDED_INFUNC( derived, immedBase ) P9_EMBEDDED_DECL_( derived, immedBase, ) P9_EMBEDDED_BDY_( immedBase )

// forward declarations of both the above; generally not needed
// may help you control where the P9_EMBEEDED cruft goes, in case "right after the stuct" isn't where you want it
#define P9_EMBEDDED_FWD( derived, immedBase ) P9_EMBEDDED_DECL_( derived, immedBase, static ) ;
#define P9_EMBEDDED_FWD_INFUNC( derived, immedBase ) auto P9_EMBEDDED_DECL_( derived, immedBase, ) ;

// private helpers
#define P9_EMBEDDED_DECL_( derived, immedBase, STORAGE ) \
	forall( Tbase &, TdiscardPath & | { tytagref( TdiscardPath, Tbase ) ?`inner( immedBase & ); } ) \
	STORAGE inline tytagref( immedBase, Tbase ) ?`inner( derived & this )

#define P9_EMBEDDED_BDY_( immedBase ) { \
		immedBase & ib = this; \
		Tbase & b = ib`inner; \
		tytagref( immedBase, Tbase ) result = { b }; \
		return result; \
	}

#define EMBEDDED_VIA( OUTER, MID, INNER ) (struct { tytagref( MID, INNER ) ( * ?`inner ) ( OUTER & ); }){ ?`inner }

#define DLINK_VIA( TE, TLINK ) EMBEDDED_VIA( TE, TLINK, dlink( TE ) )


// The origin is the position encountered at the start of iteration, signifying, "need to advance to the first element,"
// and at the end of iteration, signifying, "no more elements."  Normal comsumption of an iterator runs "advance" as
// the first step, and uses the return of "advance" as a guard, before dereferencing the iterator.  So normal
// consumption of an iterator does not dereference an iterator in origin position.  The value of a pointer (underlying a
// refence) that is exposed publicly as an iteraor, and also a pointer stored internally in a link field, is tagged, to
// indicate "is the origin" (internally, is the list-head sentinel node), or untagged, to indicate "is a regular node."
// Intent is to help a user who dereferences an iterator in origin position (which would be an API-use error on their
// part), by failing fast.

#if defined( __x86_64 )
	// Preferred case: tag in the most-significant bit.  Dereference has been shown to segfault consistently.
	// Maintenance should list more architectures as "ok" here, to let them use the preferred case, when valid.
	#define ORIGIN_TAG_BITNO ( 8 * sizeof( size_t ) - 1 )
#else
	// Fallback case: tag in the least-significant bit.  Dereference will often give an alignment error, but may not,
	// e.g. if accessing a char-typed member.  32-bit x86 uses the most- significant bit for real room on the heap.
	#define ORIGIN_TAG_BITNO 0
#endif
#define ORIGIN_TAG_MASK (((size_t)1) << ORIGIN_TAG_BITNO)

#define ORIGIN_TAG_SET( p )   ((p) |  ORIGIN_TAG_MASK)
#define ORIGIN_TAG_CLEAR( p ) ((p) & ~ORIGIN_TAG_MASK)
#define ORIGIN_TAG_QUERY( p ) ((p) &  ORIGIN_TAG_MASK)

forall( tE & ) {
	struct dlink{
		tE * next;
		tE * prev;
	};

	static inline void ?{}( dlink( tE ) & this ) {
		this.next = this.prev = 0p;
	}

	forall( tLinks & = dlink( tE ) )
	struct dlist {
		inline dlink( tE );
	};

	forall( tLinks & | embedded( tE, tLinks, dlink( tE ) ) ) {
		static inline tE * $get_list_origin_addr( dlist( tE, tLinks ) & list ) {
			dlink( tE ) & link_from_null = (*(tE *)0p)`inner;
			ptrdiff_t link_offset = (ptrdiff_t)&link_from_null;
			size_t origin_addr = ((size_t)&list) - link_offset;
			size_t preResult = ORIGIN_TAG_SET( origin_addr );
			return (tE *)preResult;
		}

		static inline void ?{}( dlist( tE, tLinks ) & this ) {
			tE * listOrigin = $get_list_origin_addr( this );
			((dlink( tE ) &)this){ listOrigin, listOrigin };
		}
	}
}


static inline forall( tE &, tLinks & | embedded( tE, tLinks, dlink( tE ) ) ) {
	bool isListed( tE & node ) {
		verify( &node != 0p );
		dlink( tE ) & node_links = node`inner;
		return (node_links.prev != 0p) || (node_links.next != 0p);
	}

	bool isEmpty( dlist( tE, tLinks ) & list ) {
		tE * firstPtr = list.next;
		if ( ORIGIN_TAG_QUERY(( size_t)firstPtr) ) firstPtr = 0p;
		return firstPtr == 0p;
	}

	tE & first( dlist( tE, tLinks ) & list ) {
		tE * firstPtr = list.next;
		if ( ORIGIN_TAG_QUERY( (size_t)firstPtr ) ) firstPtr = 0p;
		return *firstPtr;
	}

	tE & last( dlist( tE, tLinks ) & list ) {
		tE * lastPtr = list.prev;
		if ( ORIGIN_TAG_QUERY( (size_t)lastPtr) ) lastPtr = 0p;
		return *lastPtr;
	}

	tE & insert_before( tE & before, tE & node ) {
		verify( &before != 0p );
		verify( &node != 0p );

		dlink( tE ) & linkToInsert = node`inner;

		verify( linkToInsert.next == 0p );
		verify( linkToInsert.prev == 0p );

		tE & list_pos_elem = *(tE *)ORIGIN_TAG_CLEAR( (size_t)&before );
		dlink( tE ) & list_pos_links = list_pos_elem`inner;
		asm( "" : : : "memory" );
		tE & before_raw = *list_pos_links.prev;
		tE & before_elem = *(tE *) ORIGIN_TAG_CLEAR( (size_t)&before_raw );
		linkToInsert.next = &before;
		linkToInsert.prev = &before_raw;
		dlink( tE ) & beforeLinks = before_elem`inner;
		beforeLinks.next = &node;
		list_pos_links.prev = &node;
		asm( "" : : : "memory" );
		return node;
	}

	tE & insert_after( tE & after, tE & node ) {
		verify( &after != 0p );
		verify( &node != 0p );

		dlink( tE ) & linkToInsert = node`inner;

		verify( linkToInsert.prev == 0p );
		verify( linkToInsert.next == 0p );

		tE & list_pos_elem = *(tE *)ORIGIN_TAG_CLEAR( (size_t)&after );
		dlink( tE ) & list_pos_links = list_pos_elem`inner;
		asm( "" : : : "memory" );
		tE & after_raw = *list_pos_links.next;
		tE & after_elem = *(tE *)ORIGIN_TAG_CLEAR( (size_t)&after_raw );
		linkToInsert.prev = &after;
		linkToInsert.next = &after_raw;
		dlink( tE ) & afterLinks = after_elem`inner;
		afterLinks.prev = &node;
		list_pos_links.next = &node;
		asm( "" : : : "memory" );
		return node;
	}

	tE & remove( tE & node ) {
		verify( &node != 0p );
		verify( ! ORIGIN_TAG_QUERY( (size_t)&node) );

		dlink( tE ) & list_pos_links = node`inner;
		tE & before_raw = *list_pos_links.prev;
		tE & before_elem = *(tE *)ORIGIN_TAG_CLEAR( (size_t)&before_raw );
		dlink( tE ) & before_links = before_elem`inner;
		tE & after_raw = *list_pos_links.next;
		tE & after_elem = *(tE *)ORIGIN_TAG_CLEAR( (size_t)&after_raw );
		dlink( tE ) & after_links = after_elem`inner;
		before_links.next = &after_raw;
		after_links.prev = &before_raw;
		asm( "" : : : "memory" );
		list_pos_links.prev = 0p;
		list_pos_links.next = 0p;
		asm( "" : : : "memory" );
		return node;
	}

	tE & iter( dlist( tE, tLinks ) & list ) {
		tE * origin = $get_list_origin_addr( list );
		return *origin;
	}

	bool recede( tE && refx ) {
		tE && ref_inner = refx;
		tE & oldReferent = *(tE*)ORIGIN_TAG_CLEAR( (size_t)&ref_inner );
		&ref_inner = oldReferent`inner.prev;
		return &ref_inner != 0p && ! ORIGIN_TAG_QUERY( (size_t)&ref_inner );
	}

	bool advance( tE && refx ) {
		tE && ref_inner = refx;
		tE & oldReferent = *(tE*)ORIGIN_TAG_CLEAR( (size_t)&ref_inner );
		&ref_inner = oldReferent`inner.next;
		return &ref_inner != 0p && ! ORIGIN_TAG_QUERY( (size_t)&ref_inner );
	}

    bool isFirst( tE & node ) {
        return recede( node );
    }

    bool isLast( tE & node ) {
        return advance( node );
    }

	tE & prev( tE & node ) {
		if ( recede( node ) ) return node;
		return *0p;
	}

	tE & next( tE & node ) {
		if ( advance( node ) ) return node;
		return *0p;
	}

	tE & insert_first( dlist( tE, tLinks ) & list, tE & node ) {
		insert_after( iter( list ), node );
		return node;
	}

	tE & insert_last( dlist( tE, tLinks ) & list, tE & node ) {
		insert_before( iter( list ), node );
		return node;
	}
	tE & insert( dlist( tE, tLinks ) & list, tE & node ) { // synonym for insert_last
		insert_last( list, node );
		return node;
	}

	tE & remove_first( dlist( tE, tLinks ) & list ) {
		tE & first_node = first( list );
		if ( &first_node ) return remove( first_node );
		return first_node;
	}

	tE & remove_last( dlist( tE, tLinks ) & list ) {
		tE & last_node = last( list );
		if ( &last_node ) return remove( last_node );
		return last_node;
	}

	// Transfer the "from" list to the end of this sequence; the "from" list is empty after the transfer.
//	void transfer( dlist( tE, tLinks ) & to, dlist( tE, tLinks ) & from ) {
//		if ( isEmpty( from ) ) return;					// "from" list empty ?
//		if ( isEmpty( to ) ) {							// "to" list empty ?
//			root = from.root;
//		} else {										// "to" list not empty
//			T * toEnd = (T *)uBack( root );
//			T * fromEnd = (T *)from.uBack( from.root );
//			uBack( root ) = fromEnd;
//			from.uNext( fromEnd ) = root;
//			from.uBack( from.root ) = toEnd;
//			uNext( toEnd ) = from.root;
//		} // if
//		from.root = nullptr;							// mark "from" list empty
//	}

	// Transfer the "from" list up to node "n" to the end of this list; the "from" list becomes the sequence after node "n".
	// Node "n" must be in the "from" list.
//	void split( dlist( tE, tLinks ) & to, dlist( tE, tLinks ) & from, tE & node ) {
//		#ifdef __U_DEBUG__
//		if ( ! n->listed() ) abort( "(uSequence &)%p.split( %p ) : Node is not on a list.", this, n );
//		#endif // __U_DEBUG__
//		uSequence<T> to;
//		to.root = from.root;							// start of "to" list
//		from.root = (T *)uNext( n );					// start of "from" list
//		if ( to.root == from.root ) {					// last node in list ?
//			from.root = nullptr;						// mark "from" list empty
//		} else {
//			uBack( from.root ) = (T *)uBack( to.root );	// fix "from" list
//			uNext( uBack( to.root ) ) = from.root;
//			uNext( n ) = to.root;						// fix "to" list
//			uBack( to.root ) = n;
//		} // if
//		transfer( to );
//	}

	#if ! defined(NDEBUG) && (defined(__CFA_DEBUG__) || defined(__CFA_VERIFY__))
	bool $validate_fwd( dlist( tE, tLinks ) & this ) {
		if ( ! & first( this ) ) return &last( this ) == 0p;

		tE & lagElem = *0p;
		while ( tE & it = iter( this ); advance( it ) ) {
			if ( & lagElem == 0p &&  &it != & first( this ) ) return false;
			&lagElem = &it;
		}

		if ( &lagElem != &last( this ) ) return false;

		// TODO: verify that it is back at iter( this );
		return true;
	}

	bool $validate_rev( dlist( tE, tLinks ) & this ) {
		if ( ! & last( this ) ) return &first( this ) == 0p;

		tE & lagElem = *0p;
		while ( tE & it = iter( this ); recede( it ) ) {
			if ( &lagElem == 0p && &it != & last( this ) ) return false;
			&lagElem = &it;
		}

		if ( &lagElem != &first( this ) ) return false;

		// TODO: verify that it is back at iter( this );
		return true;
	}

	bool validate( dlist( tE, tLinks ) & this ) {
		return $validate_fwd( this ) && $validate_rev( this );
	}
	#endif
}

// TEMPORARY, until foreach statement created.
#define FOREACH( list, index ) for ( typeof(iter( list )) & (index) = iter( list ); advance( index ); )
#define FOREACH_REV( list, index ) for ( typeof(iter( list )) & (index) = iter( list ); recede( index ); )
#define FOREACH_COND( list, index, expr ) for ( typeof(iter( list )) & (index) = iter( list ); advance( index ) && !(expr); )
#define FOREACH_REV_COND( list, index, expr ) for ( typeof(iter( list )) & (index) = iter( list ); recede( index ) && !(expr); )