# JavaScript, 77 bytes

    a=>[...a+a].map((_,b)=>a-=-z.substring((b-=n)>0?b:0,b+n),a*=n=(z=a).length)|a

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

    f=a=>[...a+a].map((_,b)=>a-=-z.substring((b-=n)>0?b:0,b+n),a*=n=(z=a).length)|a

    console.log(f('123'));
    console.log(f('101'));
    console.log(f('12'));
    console.log(f('1234567'));

<!-- end snippet -->