1-2-3 pattern - known reversal market pattern.
Down pattern:
After maximum 1 follows minimum 2 and maximum 3 (more low than 1).
Up pattern:
After minimum 1 follows maximum 2 and minimum 3 (more high than 1).
For identification minimums and maximums used advanced fractals (viewtopic.php?f=17&t=724).
Download:
MT4 version
https://fxcodebase.com/code/viewtopic.php?f=38&t=74716