How many IF/ELSE/ENDIF can be used in a script?

Question

Besides the 520 bytes consensus rule limit, is there a limit on how many of each OP_IF, OP_ELSE and OP_ENDIF can be used in a single script?

For example, a company that has 3 people in its purchase department would like to make a fast purchase if all people in the department agree and slow it down in case not everybody agrees, but not make it impossible in the final:

• Alice, Bob and Carol store funds in a P2SH address. Initially, all 3/3 of signatures are required initially.

• After some time, (OP_CHECKLOCKTIMEVERIFY) just two of them can spend (2/3 signatures required).

• After more time, (first OP_CHECKLOCKTIMEVERIFY + more time), any one can spend (1/3 signatures required).

How would a script like this look like?

Answer 1

OP_IF
  OP_3 
OP_ELSE
  OP_IF
    lock1 OP_CLTV OP_DROP OP_2
  OP_ELSE
    lock2 OP_CLTV OP_DROP OP_1
  OP_ENDIF
OP_ENDIF
pub1 pub2 pub3 OP_3 OP_CHECKMULTISIG

some pseudocode:

var x = stack.pop ( );  // take the last item from stack and remove it
if ( x != 0 )
{
  stack.push ( 3 );  // push the number '3' to the stack
}
else
{
  var y = stack.pop ( ); // take next item
  if ( y != 0 )
  {
    stack.push ( locktime1 ); // push value
    stack.compare_top_value_with_timestamp_and_abort_if_not_valid ( );
    stack.pop ( ); // remove locktime1 if passed
    stack.push ( 2 );
  }
  else
  {
    stack.push ( locktime2 ); // push value
    stack.compare_top_value_with_timestamp_and_abort_if_not_valid ( );
    stack.pop ( ); // remove locktime2 if passed
    stack.push ( 1 );
  }
}
stack.push ( pub1 );
stack.push ( pub2 );
stack.push ( pub3 );
stack.push ( 3 );
stack.check_multi_sig ( );