Thr Fuel signal. The train froze forever. Unexpected result

[Horatio]

Hi, I want to make a train schedule that is resistant to possible errors or possible changes in the refueling part, but the game seems to resist this.
What does the problem look like or maybe I don’t understand something and this will help me figure it out.
If there are several types of fuel on the train, for example during automated refueling, this will bring unpleasant consequences, for example, complete freezing:
1. If you set the condition “Full refueling”, and you do not have one or two of the three types of fuel present on the train, this will lead to the fact that the train will never be refueled.
2. If you set the condition "Fuel in all locomotives 'Special symbol' < 'n'", and the trigger fuel that brought the train to the station is missing, then the condition will never be satisfied.
3. If we set the condition for completion "Fuel in all locomotives 'Special symbol' > 'n'", and the trigger fuel that brought the train to the station is not in the first slot - this will essentially deprive us of one or two slots, which will force the train will have to refuel 2 or 3 times more often, since the interruption will be triggered based on the amount of fuel in the first slot.
4. In the screenshot I showed an example of how I got rid of the problem of “eternal parking”, but here there is still the problem of fuel in a non-first slot, which will reduce the travel time without refueling.
I understand that it is possible to assemble and run a fuel checking system on a train, but I don’t see an elegant solution, but I do not see an elegant solution, and also, in my opinion, the “Fully filled” condition is insufficient, and also it and the special “Fuel” signal are unstable in the face of errors that are errors in fact they are not.
I see the most adequate solution here is to unload the locomotives before refueling and check via OR that they are fully refueled, however, if the trigger fuel is in the first slot, it will trigger the interrupt until the train burns it completely. I'm not sure about the special symbol "Fuel", when it does not allow me to move, even if I fill the train, albeit incompletely, but it is the trigger fuel that activated the interruption that does not allow me to move. And in general, fuels have different stack sizes, so it turns out that it is necessary to check each fuel separately rather than setting a special “Fuel” signal - relatively speaking, It’s better to refuel if: coal <20, solid fuel less than <6, rocket fuel <3, nuclear fuel <1. With nuclear fuel, it is imperative to unload the train; if you charge only 1, the train after the first station will immediately go to refuel, and so on ad infinitum, until the remaining slots are occupied by other fuel.
It turns out that the special “Fuel” signal is useless or at least less profitable than a set of several rules?
There may be a lot of water here, I'm just testing and jotting down thoughts so I don't forget.
What I think... The ideal solution would be to count the total amount of fuel inside, and also have the fuel burn start with the exact fuel that brought the train to the station. Is it possible to add logical if else elements? At a minimum, it would be great to be able to receive information about the train itself in the form of a signal indicating what is in front of us and what is inside it, as implemented in LTN. This will also allow for more flexible stations. I would like to be able to use different combinations of the train. Is there perhaps some solution for the Selecting Combinator? There are specialized conditions that are suitable for rockets, perhaps something can also be invented for trains?
I'd love to hear your thoughts or criticism. Thank you

[Horatio]

I did this, plus I’ll add mandatory fuel unloading before refueling.

[Loewchen]

Post a simple save with the simplest schedule that shows the issue please, explain exactly what to do, what happens and what you expect to happen instead.

[BlueTemplar]

Related :
It's 2.0 space age, but refueling station is still a huge PITA

The issue woth B is the possobly long period where you dont have the logistic chests yet, but have the trains (my case) or want to gain the achievement for not using logi chests.

All of the solutions I found propose "mandatory fuel unloading" which from the factorio standpoint... sounds silly.

Trains only hold 3 stacks of fuel per locomotive, and steel chests hold 48. (Steel is a prerequisite of trains, so I'm assuming you're using those.) If you put 6 chests on one side of your refueling station, you can fully swap out obsolete fuel in 96 locomotives. (Only 64 if you're doing it on the train-station side, with 4 chests.) All insterters can use blacklist filters, so it's trivial to unload everything that's not your best fuel, as in this example:

The only thing you can't handle with a setup like that, is trains that have different lengths. But as long as you've got all your trains using a small number of lengths, you can just build that same small number of refueling stations. For example, one refueling station for 1-1-1 trains, one for 2-4 trains, etc. (I don't think your proposal intends that, but I figured I'd mention it anyways.) It is actually a problem that interrupts read an item count instead of fuel-percentage or total energy, but that's already got other threads.

I'll reply tomorrow, but there are multiple reported issues already with interrupts simply not working roght now. One case is double locomotive bidirectional train where one locomotive has different fuel than the other. The train deadlocks and the fuel interrupts dont work, no matter the combination of wait conditions and wildcards.

What makes you so confident about «no matter» ?
Looks like to me that simply changing that «AND time passed» to an «OR inactive for X seconds» would work ?
(EDIT : double checked, inactivity does work on locos too)

[...]
The issue woth B is the possobly long period where you dont have the logistic chests yet, but have the trains (my case) or want to gain the achievement for not using logi chests.
[...]

Well if it's that early, just use a big enough buffer ? (With maybe some boilers.)

[Tooster]

It would be nice if we could run the compound wait condition for each locomotive and THEN take the "all". Or if not that, read the fuel per locomotive and send it to circuit network. "Fuel (all)" is hardly usable when the trains have mixed fuel. There should be something like a "each/any" scope for a range of conditions.