// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Center a child between two named anchors
// Not compiled or tested in-world
// Setup: Use a spare nonphysical rezzed linkset; disable competing scripts and do not edit or relink during the preview. Put this in the root. Name two other children anchor_a and anchor_b. Owner-touch the child to preview; touch again to restore.
// Stop / restore: Owner-touch again to restore before removing, resetting, relinking or transferring. Snapshots are memory-only; deletion/reset does not undo changes. Keep an untouched backup.
// Notes: Copies only their midpoint. Both anchors must be distinct from the selected part; no root or avatar anchors.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Test on a spare copy first.
integer selected;
key identity;
list original;
default
{
    touch_start(integer n)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        if(llGetAttached()||llGetStatus(STATUS_PHYSICS)||llGetLinkNumber()>1)
        {
            llOwnerSay("Use a nonphysical rezzed root.");
            return;
        }
        if(selected)
        {
            if(llGetLinkKey(selected)==identity)llSetLinkPrimitiveParamsFast(selected,[PRIM_POS_LOCAL,llList2Vector(original,0),PRIM_ROT_LOCAL,llList2Rot(original,1),PRIM_SIZE,llList2Vector(original,2)]);
            else llOwnerSay("Topology changed; restore manually from backup.");
            selected=0;
            return;
        }
        integer link=llDetectedLinkNumber(0);
        if(link<2||link>llGetObjectPrimCount(llGetKey()))
        {
            llOwnerSay("Touch a child prim.");
            return;
        }
        list data=llGetLinkPrimitiveParams(link,[PRIM_POS_LOCAL,PRIM_ROT_LOCAL,PRIM_SIZE]);
        vector p=llList2Vector(data,0);
        rotation r=llList2Rot(data,1);
        vector size=llList2Vector(data,2);
        integer i;
        integer a;
        integer b;
        integer ca;
        integer cb;
        integer total=llGetObjectPrimCount(llGetKey());
        if(total>32)return;
        for(i=2;i<=total;++i)
        {
            if(llGetLinkName(i)=="anchor_a")
            {
                a=i;
                ++ca;
            }
            if(llGetLinkName(i)=="anchor_b")
            {
                b=i;
                ++cb;
            }
        }
        if(ca!=1||cb!=1||a==link||b==link)
        {
            llOwnerSay("Need two unique other anchor children.");
            return;
        }
        p=(llList2Vector(llGetLinkPrimitiveParams(a,[PRIM_POS_LOCAL]),0)+llList2Vector(llGetLinkPrimitiveParams(b,[PRIM_POS_LOCAL]),0))*0.5;
        selected=link;
        identity=llGetLinkKey(link);
        original=data;
        llSetLinkPrimitiveParamsFast(link,[PRIM_POS_LOCAL,p,PRIM_ROT_LOCAL,r,PRIM_SIZE,size]);
        llOwnerSay("Preview applied; touch again to restore.");
    }
    changed(integer flags)
    {
        if(flags&CHANGED_OWNER)llResetScript();
    }
}