Add example for irrigation system

[buschco]

Hey I did my best to implement an irrigation homekit service. It is similar to the dynamic_services example.
Feedback is welcome 🙂

[maximkulkin]

Instead of relying on hard coded index, use homekit_service_characteristic_by_type:

homekit_characteristic_t *rd = homekit_service_characteristic_by_type(
    thisGate->service, HOMEKIT_CHARACTERISTIC_REMAINING_DURATION
);

Or even pre-cache it inside gate structure for improved performance.

[buschco]

homekit_service_characteristic_by_type makes it a lot simpler 👍
But I don't quite understand how to implement the pre-cache thing.

[maximkulkin]

It makes sense to have a single task for all valves. All tasks needs to do is to wake up every second and check which valves are active and decrement their remaining duration.

[buschco]

I tried my best here but I still need to store the task state as a variable. I tried to use vTaskGetInfo() to get information about the task state but I got type undefined reference to vTaskGetInfo from the compiler 😕

[maximkulkin]

Not sure what update sequence is there, but it feels that if this value is updated, you need to have a meaningful reaction (like update REMAINING_DURATION).

[maximkulkin]

How about saving some CPU cycles and creating characteristics first. Also, (for future) it is easier to use HOMEKIT_CHARACTERISTIC_<name> (e.g. HOMEKIT_CHARACTERISTIC_ACTIVE) defines instead of hard-coding UUIDs.

gates[i].active = NEW_HOMEKIT_CHARACTERISTIC(
    ACTIVE, 0,
    .callback=HOMEKIT_CHARACTERISTIC_CALLBACK(
        on_update_active, .context=(void*)&gates[i],
    ),
);

// ...

homekit_service_t *nextService = NEW_HOMEKIT_SERVICE(VALVE, .characteristics=(homekit_characteristic_t*[]) {
    // ...
    gates[i].active,
    gates[i].remaining_duration,
    gates[i].set_duration,
    gates[i].in_use,
    NULL
});

[maximkulkin]

valve_t gates[valve_count];

[buschco]

But then the compiler complains: error: variably modified 'gates' at file scope

[buschco]

I improved some points you mentioned.

[buschco]

Over the last weeks I improved my code a lot. As far I can see these points are not fixed right now:

1. Pre-cache characteristics

Or even pre-cache it inside gate structure for improved performance.

I don't quite understand how to implement this.

2. Use vTaskGetInfo() instead of storing task state in a variable

I use task_running to determine if the task is suspended or running. I saw vTaskGetInfo() in the freertos docs, but the compiler warned me:
type undefined reference to vTaskGetInfo

3. Create characteristics first

How about saving some CPU cycles and creating characteristics first.

I don't quite understand how to implement this.

4. Use valve_count instead of hard coding array length

This might be a no-brainer but I am quite lost at this one 🙈