mod-playerbots/src/strategy/druid/FeralDruidStrategy.h
Nicolas Lebacq c9cc4324d3
NextAction refactoring to eliminate sentinel arrays and pointers (#1923)
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# Description

This PR aims to refactor the NextAction declaration to achieve two
goals:

## Eliminate C-style sentinel arrays

Currently, a double pointer (`NextAction**`) approach is being used.
This an old pre-C++11 (< 2011) trick before `std::vector<>` became a
thing.
This approach is painful for developers because they constantly need to
declare their `NextAction` arrays as:
```cpp
NextAction::array(0, new NextAction("foo", 1.0f), nullptr)
```
Instead of:
```cpp
{ new NextAction("foo", 1.0f) }
```
The first argument of `NextAction::array` is actually a hack. It is used
to have a named argument so `va_args` can find the remaining arguments.
It is set to 0 everywhere but in fact does nothing. This is very
confusing to people unfamiliar with this antiquated syntax.
The last argument `nullptr` is what we call a sentinel. It's a `nullptr`
because `va_args` is looking for a `nullptr` to stop iterating. It's
also a hack and also leads to confusion.

## Eliminate unnecessary pointers for `NextAction`

Pointers can be used for several reasons, to cite a few:
- Indicate strong, absolute identity.
- Provide strong but transferable ownership (unlike references).
- When a null value is acceptable (`nullptr`).
- When copy is expensive.

`NextAction` meets none of these criteria:
- It has no identity because it is purely behavioural.
- It is never owned by anything as it is passed around and never fetched
from a registry.
- The only situations where it can be `nullptr` are errors that should
in fact throw an `std::invalid_argument` instead.
- They are extremely small objects that embark a single `std::string`
and a single `float`.

Pointers should be avoided when not strictly necessary because they can
quickly lead to undefined behaviour due to unhandled `nullptr`
situations. They also make the syntax heavier due to the necessity to
constantly check for `nullptr`. Finally, they aren't even good for
performance in that situation because shifting a pointer so many times
is likely more expensive than copying such a trivial object.

# End goal

The end goal is to declare `NextAction` arrays this way:
```cpp
{ NextAction("foo", 1.0f) }
```

> [!NOTE]
> Additional note: `NextAction` is nothing but a hacky proxy to an
`Action` constructor. This should eventually be reworked to use handles
instead of strings. This would make copying `NextAction` even cheaper
and remove the need for the extremely heavy stringly typed current
approach. Stringly typed entities are a known anti-pattern so we need to
move on from those.
2026-01-06 12:37:39 +01:00

87 lines
2.9 KiB
C++

/*
* Copyright (C) 2016+ AzerothCore <www.azerothcore.org>, released under GNU AGPL v3 license, you may redistribute it
* and/or modify it under version 3 of the License, or (at your option), any later version.
*/
#ifndef _PLAYERBOT_FERALRUIDSTRATEGY_H
#define _PLAYERBOT_FERALRUIDSTRATEGY_H
#include "GenericDruidStrategy.h"
class PlayerbotAI;
class ShapeshiftDruidStrategyActionNodeFactory : public NamedObjectFactory<ActionNode>
{
public:
ShapeshiftDruidStrategyActionNodeFactory()
{
creators["rejuvenation"] = &rejuvenation;
creators["regrowth"] = &regrowth;
creators["healing touch"] = &healing_touch;
creators["rejuvenation on party"] = &rejuvenation_on_party;
creators["regrowth on party"] = &regrowth_on_party;
creators["healing touch on party"] = &healing_touch_on_party;
}
private:
static ActionNode* regrowth([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("regrowth",
/*P*/ { NextAction("caster form") },
/*A*/ { NextAction("healing touch") },
/*C*/ { NextAction("melee", 10.0f) });
}
static ActionNode* rejuvenation([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("rejuvenation",
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* healing_touch([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("healing touch",
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* regrowth_on_party([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("regrowth on party",
/*P*/ { NextAction("caster form") },
/*A*/ { NextAction("healing touch on party") },
/*C*/ { NextAction("melee", 10.0f) });
}
static ActionNode* rejuvenation_on_party([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("rejuvenation on party",
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
static ActionNode* healing_touch_on_party([[maybe_unused]] PlayerbotAI* botAI)
{
return new ActionNode("healing touch on party",
/*P*/ { NextAction("caster form") },
/*A*/ {},
/*C*/ {});
}
};
class FeralDruidStrategy : public GenericDruidStrategy
{
protected:
FeralDruidStrategy(PlayerbotAI* botAI);
public:
void InitTriggers(std::vector<TriggerNode*>& triggers) override;
uint32 GetType() const override { return STRATEGY_TYPE_COMBAT | STRATEGY_TYPE_MELEE; }
};
#endif