Does one have to perform ghusl if one wakes up from sleep and finds a dry trace, not knowing whether it is semen or madhiy?

After waking up from sleep and noticing a discharge, there are several scenarios:

1. If you are certain that it is manī (seminal fluid, e.g., due to a distinctive odor), then a full ritual bath (ghusl) is required.

2. If you are certain that it is madhī (pre-seminal fluid), then it is sufficient to wash the part of the penis, body, and clothing that it has touched.

3. If you are unsure of the nature of the fluid, whether it is manī or madhī, you have the choice: either consider it manī and perform ghusl, or consider it madhī and wash only its affected area. This is the view of the Shafi'i school and the one generally given as a fatwa.