(*
    Copyright 2021 Anton Krotov

    This file is part of CEdit.

    CEdit is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    CEdit is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with CEdit. If not, see <http://www.gnu.org/licenses/>.
*)

MODULE List;

TYPE

    tItem* = POINTER TO RECORD
        prev*, next*: tItem
    END;

    tList* = POINTER TO RECORD
        first*, last*: tItem;
        count*: INTEGER
    END;

    PmovInt = PROCEDURE (VAR v: INTEGER; x: INTEGER);
    PmovPtr = PROCEDURE (VAR v: tItem; x: tItem);


VAR

    _movInt: PmovInt;
    _movPtr: PmovPtr;


PROCEDURE create* (list: tList): tList;
BEGIN
    IF list = NIL THEN
        NEW(list)
    END;
    list.first := NIL;
    list.last  := NIL;
    list.count := 0
    RETURN list
END create;


PROCEDURE getItem* (list: tList; idx: INTEGER): tItem;
VAR
    item: tItem;
BEGIN
    IF idx < 0 THEN
        item := NIL
    ELSE
        item := list.first;
        WHILE (idx > 0) & (item # NIL) DO
            item := item.next;
            DEC(idx)
        END
    END
    RETURN item
END getItem;


PROCEDURE delete* (list: tList; item: tItem);
VAR
    prev, next: tItem;
BEGIN
    prev := item.prev;
    next := item.next;
    IF prev # NIL THEN
        prev.next := next;
        IF next # NIL THEN
            next.prev := prev
        ELSE
            list.last := prev
        END
    ELSE
        list.first := next;
        IF next # NIL THEN
           next.prev := NIL
        ELSE
           list.last := NIL
        END
    END;
    DEC(list.count)
END delete;


PROCEDURE movInt (VAR v: INTEGER; x: INTEGER);
BEGIN
    _movInt(v, x);
    v := x
END movInt;


PROCEDURE movPtr (VAR v: tItem; x: tItem);
BEGIN
    _movPtr(v, x);
    v := x
END movPtr;


PROCEDURE _delete* (list: tList; item: tItem);
VAR
    prev, next: tItem;
BEGIN
    prev := item.prev;
    next := item.next;
    IF prev # NIL THEN
        movPtr(prev.next, next);
        IF next # NIL THEN
            movPtr(next.prev, prev)
        ELSE
            movPtr(list.last, prev)
        END
    ELSE
        movPtr(list.first, next);
        IF next # NIL THEN
           movPtr(next.prev, NIL)
        ELSE
           movPtr(list.last, NIL)
        END
    END;
    movInt(list.count, list.count - 1)
END _delete;


PROCEDURE _append* (list: tList; item: tItem);
BEGIN
    movPtr(item.prev, list.last);
    IF list.last # NIL THEN
        movPtr(list.last.next, item)
    ELSE
        movPtr(list.first, item)
    END;
    movPtr(list.last, item);
    movPtr(item.next, NIL);
    movInt(list.count, list.count + 1)
END _append;


PROCEDURE _insert* (list: tList; item, newItem: tItem);
VAR
    next: tItem;
BEGIN
    next := item.next;
    IF next # NIL THEN
        movPtr(next.prev, newItem);
        movPtr(newItem.next, next);
        movPtr(item.next, newItem);
        movPtr(newItem.prev, item);
        movInt(list.count, list.count + 1)
    ELSE
        _append(list, newItem)
    END
END _insert;


PROCEDURE _exchange* (list: tList; a, b: tItem);
VAR
    a0, b0: tItem;
BEGIN
    IF (a # NIL) & (b # NIL) THEN
        ASSERT((a.next = b) & (b.prev = a));
        a0 := a.prev;
        b0 := b.next;
        movPtr(b.prev, a0);
        movPtr(a.next, b0);
        movPtr(b.next, a);
        movPtr(a.prev, b);
        IF (a0 # NIL) & (b0 # NIL) THEN
            movPtr(a0.next, b);
            movPtr(b0.prev, a);
        ELSIF (a0 # NIL) & (b0 = NIL) THEN
            movPtr(a0.next, b);
            movPtr(list.last, a)
        ELSIF (a0 = NIL) & (b0 # NIL) THEN
            movPtr(b0.prev, a);
            movPtr(list.first, b)
        ELSIF (a0 = NIL) & (b0 = NIL) THEN
            movPtr(list.first, b);
            movPtr(list.last, a)
        END
    END
END _exchange;


PROCEDURE append* (list: tList; item: tItem);
BEGIN
    item.prev := list.last;
    IF list.last # NIL THEN
        list.last.next := item
    ELSE
        list.first := item
    END;
    list.last := item;
    item.next := NIL;
    INC(list.count)
END append;


PROCEDURE insert* (list: tList; item, newItem: tItem);
VAR
    next: tItem;
BEGIN
    next := item.next;
    IF next # NIL THEN
        next.prev := newItem;
        newItem.next := next;
        item.next := newItem;
        newItem.prev := item;
        INC(list.count)
    ELSE
        append(list, newItem)
    END
END insert;


PROCEDURE pop* (list: tList): tItem;
VAR
    res: tItem;
BEGIN
    IF list.count # 0 THEN
        res := list.last;
        list.last := res.prev;
        DEC(list.count);
        IF list.count # 0 THEN
            list.last.next := NIL
        ELSE
            list.first := NIL
        END;
        res.prev := NIL;
        res.next := NIL
    ELSE
        res := NIL
    END
    RETURN res
END pop;


PROCEDURE init* (movInt: PmovInt; movPtr: PmovPtr);
BEGIN
    _movInt := movInt;
    _movPtr := movPtr
END init;


END List.