//
// 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 : Michael Brooks
// Last Modified On : Wed Apr 22 18:00:00 2020
// Update Count     : 1
//

#pragma once

#include <assert.h>

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

trait embedded( tOuter &, tMid &, tInner & ) {
    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; }

// use this on every case of plan-9 inheritance, to make embedded a closure of plan-9 inheritance
#define P9_EMBEDDED( derived, immedBase ) \
forall( Tbase &, TdiscardPath & | { tytagref( TdiscardPath, Tbase ) ?`inner( immedBase & ); } ) \
    static inline tytagref(immedBase, Tbase) ?`inner( derived & this ) { \
        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 ?`moveNext as the first step, and uses the return
// of ?`moveNext 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 = 0p;
        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) & lst ) {
            dlink(tE) & link_from_null = ( * (tE *) 0p )`inner;
            ptrdiff_t link_offset = (ptrdiff_t) & link_from_null;
            size_t origin_addr = ((size_t) & lst) - 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 } ;
        }
    }

}


forall( tE &, tLinks & | embedded( tE, tLinks, dlink(tE) ) ) {

	static inline void insert_after(tE & list_pos, tE &to_insert) {
		verify (&list_pos != 0p);
		verify (&to_insert != 0p);
        dlink(tE) & linkToInsert = to_insert`inner;
		verify(linkToInsert.prev == 0p);
		verify(linkToInsert.next == 0p);
        tE & list_pos_elem = * (tE *) ORIGIN_TAG_CLEAR( (size_t) & list_pos );
        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 = & list_pos;
		linkToInsert.next = & after_raw;
        dlink(tE) & afterLinks = after_elem`inner;
        afterLinks.prev = &to_insert;
		list_pos_links.next = &to_insert;
        asm( "" : : : "memory" );
	}

	static inline void insert_before(tE & list_pos, tE &to_insert) {
		verify (&list_pos != 0p);
		verify (&to_insert != 0p);
        dlink(tE) & linkToInsert = to_insert`inner;
		verify(linkToInsert.next == 0p);
		verify(linkToInsert.prev == 0p);
        tE & list_pos_elem = * (tE *) ORIGIN_TAG_CLEAR( (size_t) & list_pos );
        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 = & list_pos;
		linkToInsert.prev = & before_raw;
        dlink(tE) & beforeLinks = before_elem`inner;
        beforeLinks.next = &to_insert;
		(list_pos_links).prev = &to_insert;
        asm( "" : : : "memory" );
	}

	static inline tE & remove(tE & list_pos) {
		verify (&list_pos != 0p);
        verify( ! ORIGIN_TAG_QUERY((size_t) & list_pos) );
        dlink(tE) & list_pos_links = list_pos`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 list_pos;
	}

    static inline tE & ?`first( dlist(tE, tLinks) &lst ) {
        tE * firstPtr = lst.next;
        if (ORIGIN_TAG_QUERY((size_t)firstPtr)) firstPtr = 0p;
        return *firstPtr;
    }
    static inline tE & ?`last ( dlist(tE, tLinks) &lst ) {
        tE * lastPtr = lst.prev;
        if (ORIGIN_TAG_QUERY((size_t)lastPtr)) lastPtr = 0p;
        return *lastPtr;
    }

    static inline bool ?`isEmpty( dlist(tE, tLinks) & lst ) {
        tE * firstPtr = lst.next;
        if (ORIGIN_TAG_QUERY((size_t)firstPtr)) firstPtr = 0p;
        return firstPtr == 0p;
    }

    static inline bool ?`isListed( tE & e ) {
		verify (&e != 0p);
        dlink(tE) & e_links = e`inner;
		return (e_links.prev != 0p) || (e_links.next != 0p);
    }

    static inline tE & ?`elems( dlist(tE, tLinks) & lst ) {
        tE * origin = $get_list_origin_addr( lst );
        return *origin;
    }

    static inline bool ?`moveNext( 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 );
    }

    static inline bool ?`movePrev( 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 );
    }

    static inline bool ?`hasNext( tE & e ) {
        return e`moveNext;
    }

    static inline bool ?`hasPrev( tE & e ) {
        return e`movePrev;
    }

    static inline tE & ?`next( tE & e ) {
        if( e`moveNext ) return e;
        return * 0p;
    }

    static inline tE & ?`prev( tE & e ) {
        if( e`movePrev ) return e;
        return * 0p;
    }

    static inline void insert_first( dlist(tE, tLinks) &lst, tE & e ) {
        insert_after(lst`elems, e);
    }

    static inline void insert_last( dlist(tE, tLinks) &lst, tE & e ) {
        insert_before(lst`elems, e);
    }

    static inline tE & try_pop_front( dlist(tE, tLinks) &lst ) {
        tE & first_inlist = lst`first;
        tE & first_item = first_inlist;
        if (&first_item) remove(first_inlist);
        return first_item;
    }

    static inline tE & try_pop_back( dlist(tE, tLinks) &lst ) {
        tE & last_inlist = lst`last;
        tE & last_item = last_inlist;
        if (&last_item) remove(last_inlist);
        return last_item;
    }


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

        tE & lagElem = *0p;

        while ( tE & it = this`elems; it`moveNext ) {
            if (& lagElem == 0p &&  &it != & this`first ) return false;
            & lagElem = & it;
        }

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

        // TODO: verify that it is back at this`elems;
        return true;
	}
	static bool $validate_rev( dlist(tE, tLinks) & this ) {
        if ( ! & this`last ) return ( (& this`first) == 0p);

        tE & lagElem = *0p;

        while ( tE & it = this`elems; it`movePrev ) {
            if (& lagElem == 0p &&  &it != & this`last ) return false;
            & lagElem = & it;
        }

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

        // TODO: verify that it is back at this`elems;
        return true;
	}
	static bool validate( dlist(tE, tLinks) & this ) {
		return $validate_fwd(this) && $validate_rev(this);
	}
  #endif

}