// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Validate a calendar date
// Not compiled or tested in-world
// Setup: Edit DATE and touch as owner.
// Stop / restore: Remove or disable; results are reported only to the owner.
// Notes: Accepts years 1900-2099. Validates a date only; does not convert to Unix time or enforce whether the date is in the future.
// License: see LICENSE in this distribution.
// Original Incoprea example. MIT.
string DATE="2028-02-29";
integer digitsOK(string value)
{
    integer i;
    if(value=="" || llStringLength(value)>6)return FALSE;
    for(i=0;i<llStringLength(value);++i)if(llSubStringIndex("0123456789",llGetSubString(value,i,i))==-1)return FALSE;
    return TRUE;
}
default
{
    touch_start(integer touches)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        list p=llParseStringKeepNulls(DATE,["-"],[]);
        if(llGetListLength(p)!=3 || llStringLength(DATE)!=10 || llStringLength(llList2String(p,0))!=4 || llStringLength(llList2String(p,1))!=2 || llStringLength(llList2String(p,2))!=2)
        {
            llOwnerSay("Use YYYY-MM-DD.");
            return;
        }
        integer i;
        for(i=0;i<3;++i)if(!digitsOK(llList2String(p,i)))
        {
            llOwnerSay("Digits required.");
            return;
        }
        integer y=llList2Integer(p,0);
        integer m=llList2Integer(p,1);
        integer d=llList2Integer(p,2);
        if(y<1900 || y>2099 || m<1 || m>12)
        {
            llOwnerSay("Year or month out of range.");
            return;
        }
        list lengths=[31,28,31,30,31,30,31,31,30,31,30,31];
        integer limit=llList2Integer(lengths,m-1);
        if(m==2 && (y%400==0 || (y%4==0 && y%100!=0)))limit=29;
        if(d<1 || d>limit)llOwnerSay("Day does not exist in that month.");
        else llOwnerSay("Valid Gregorian date.");
    }
    changed(integer flags)
    {
        if(flags & CHANGED_OWNER)llResetScript();
    }
}