Files
mod-playerbots/src/strategy/Strategy.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

77 lines
2.1 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_STRATEGY_H
#define _PLAYERBOT_STRATEGY_H
#include "Action.h"
#include "Multiplier.h"
#include "NamedObjectContext.h"
#include "PlayerbotAIAware.h"
#include "Trigger.h"
enum StrategyType : uint32
{
STRATEGY_TYPE_GENERIC = 0,
STRATEGY_TYPE_COMBAT = 1,
STRATEGY_TYPE_NONCOMBAT = 2,
STRATEGY_TYPE_TANK = 4,
STRATEGY_TYPE_DPS = 8,
STRATEGY_TYPE_HEAL = 16,
STRATEGY_TYPE_RANGED = 32,
STRATEGY_TYPE_MELEE = 64
};
// enum ActionPriority
// {
// ACTION_IDLE = 0,
// ACTION_DEFAULT = 5,
// ACTION_NORMAL = 10,
// ACTION_HIGH = 20,
// ACTION_MOVE = 30,
// ACTION_INTERRUPT = 40,
// ACTION_DISPEL = 50,
// ACTION_RAID = 60,
// ACTION_LIGHT_HEAL = 10,
// ACTION_MEDIUM_HEAL = 20,
// ACTION_CRITICAL_HEAL = 30,
// ACTION_EMERGENCY = 90
// };
static float ACTION_IDLE = 0.0f;
static float ACTION_BG = 1.0f;
static float ACTION_DEFAULT = 5.0f;
static float ACTION_NORMAL = 10.0f;
static float ACTION_HIGH = 20.0f;
static float ACTION_MOVE = 30.0f;
static float ACTION_INTERRUPT = 40.0f;
static float ACTION_DISPEL = 50.0f;
static float ACTION_RAID = 60.0f;
static float ACTION_LIGHT_HEAL = 10.0f;
static float ACTION_MEDIUM_HEAL = 20.0f;
static float ACTION_CRITICAL_HEAL = 30.0f;
static float ACTION_EMERGENCY = 90.0f;
class Strategy : public PlayerbotAIAware
{
public:
Strategy(PlayerbotAI* botAI);
virtual ~Strategy() {}
virtual std::vector<NextAction> getDefaultActions() { return {}; }
virtual void InitTriggers([[maybe_unused]] std::vector<TriggerNode*>& triggers) {}
virtual void InitMultipliers([[maybe_unused]] std::vector<Multiplier*>& multipliers) {}
virtual std::string const getName() = 0;
virtual uint32 GetType() const { return STRATEGY_TYPE_GENERIC; }
virtual ActionNode* GetAction(std::string const name);
void Update() {}
void Reset() {}
public:
NamedObjectFactoryList<ActionNode> actionNodeFactories;
};
#endif