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  Copyright (c) 2023 Audiokinetic Inc.
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/// \file
/// Plug-in interface for HashTable

#pragma once

#include <AK/SoundEngine/Common/AkHashTableTypes.h>
#include <AK/SoundEngine/Common/AkHashTableFuncs.h>
#include <AK/SoundEngine/Common/IAkPlugin.h>
#include <AK/Tools/Common/AkMurMurHash.h>

namespace AK
{

/// Interface for an open-addressed hash table (or key-value array).
/// Relatively low-cost (O(1)) lookup, add, and removal by key. Typical use is to add values by key,
/// and then using GetFirstSlotByKey (and GetNextSlotByKey, if keys are not guaranteed to be unique)
/// to get a Slot into the AkHashTableBase, and then indexing AkHashTableBase::pValues by the provided Slot.
/// 
/// Note that the AkHashTableBase referred to is not inherently thread-safe, so appropriate protections
/// will be required if the same hashTable is shared across multiple plug-in instances.
///
/// Some hash functions are provided in AkMurMurHash.h which can be used for key generation.
/// In particular, this can be very useful for storing data on audio objects, or audio object channels,
/// over time. Note that if indexing by object-channel is desired, GetObjectChannelHash is recommended
/// to mitigate key-collisions from multiple channels of data. However, Audio Object IDs themselves are
/// chaotic enough that they can be used directly.

class IAkPluginServiceHashTable : public IAkPluginService
{
protected:
	virtual ~IAkPluginServiceHashTable() {}
public:

	// initializes and preallocates storage for specified number of entries
	// 
	// returns either:
	// AK_InsufficientMemory if a required allocation could not be made
	// AK_Success if the hash table was initialized successfully
	virtual AKRESULT InitBase(AK::AkHashTableBase<AkUInt64>* io_pHashTable, AK::IAkPluginMemAlloc* in_pAllocator, AkUInt32 in_uInitialReserveCount, AkUInt32 
in_uValueElementSize, AkUInt32 in_uValueElementAlign) = 0;

	// helper function for initialization of the hashtable against a specific value type
	template<typename ValueType>
	AkForceInline AKRESULT Init(AkHashTable<AkUInt64, ValueType>* io_pHashTable, AK::IAkPluginMemAlloc* in_pAllocator, AkUInt32 in_uInitialReserveCount)
	{
		return InitBase(io_pHashTable, in_pAllocator, in_uInitialReserveCount, sizeof(ValueType), alignof(ValueType));
	}

	// frees memory allocated for entries
	virtual void Term(AK::AkHashTableBase<AkUInt64>* io_pHashTable, AK::IAkPluginMemAlloc* in_pAllocator) = 0;

	// resets the table, clearing all keys and values to zero, but leaving the memory allocated
	virtual void Reset(AK::AkHashTableBase<AkUInt64>* io_pHashTable) = 0;

	// adds the provided key to the hash table
	// note that a key can be added to the table multiple times
	// and returns a pointer to the value made available, or nullptr if a grow occurred but memory could not be provided
	// Note that this can move many entries in the table around, so previous pointers to elements, etc, should be considered invalidated
	virtual void* AddKey(AK::AkHashTableBase<AkUInt64>* io_pHashTable, AK::IAkPluginMemAlloc* in_pAllocator, AkUInt64 in_uKey) = 0;

	// adds this key to the hash table, and inserts the provided value to the newly reserved space, 
	// note that a key can be added to the table multiple times
	// returns a pointer to the value made available, or nullptr if a grow occurred but memory could not be provided
	// Note that this can move many entries in the table around, so previous pointers to elements, etc, should be considered invalidated.
	template<typename ValueType>
	AkForceInline ValueType* AddKeyValue(AkHashTable<AkUInt64, ValueType>* io_pHashTable, AK::IAkPluginMemAlloc* in_pAllocator, AkUInt64 in_uKey, ValueType* in_pNewValue)
	{
		if (ValueType* pInsertedValue = (ValueType*)AddKey(io_pHashTable, in_pAllocator, in_uKey))
		{
			AKASSERT(sizeof(ValueType) == io_pHashTable->uValueElementSize);
			AKPLATFORM::AkMemCpy(pInsertedValue, in_pNewValue, sizeof(ValueType));
			return pInsertedValue;
		}
		return nullptr;
	}

	// removes the entry at the slot provided
	// Note that this can move many entries in the table around, so previous pointers to elements, etc, should be considered invalidated
	// Returns true when a move of data around the end of the list occurred, e.g. in case iteration over the table needs to be modified
	virtual bool RemoveSlot(AK::AkHashTableBase<AkUInt64>* io_pHashTable, AkInt32 in_iSlot) = 0;

	// finds a slot with the provided key and deletes it from the table
	// Note that this can move many entries in the table around, so previous pointers to elements, etc, should be considered invalidated
	virtual void RemoveKey(AK::AkHashTableBase<AkUInt64>* io_pHashTable, AkUInt64 in_uKey) = 0;

	// returns either:
	// the slot of the first valid entry that in_uKey maps to
	// -1 if there are no valid entries at the table that uKey maps to
	static AkInt32 GetFirstSlotByKey(AK::AkHashTableBase<AkUInt64>* in_pHashTable, AkUInt64 in_uKey) {
		return AK::HashTable::GetFirstSlotForKey(in_pHashTable, in_uKey);
	}

	// returns either:
	// the next slot after iPreviousSlot which contains a valid entry
	// -1 if the next slot after iPreviousSlot doesn't contain a valid entry
	static AkInt32 GetNextSlotByKey(AK::AkHashTableBase<AkUInt64>* in_pHashTable, AkUInt64 in_uKey, AkInt32 in_iPreviousSlot) {
		return AK::HashTable::GetNextSlotForKey(in_pHashTable, in_uKey, in_iPreviousSlot);
	}

	// runs the provided function over every active slot in the hashtable, which is used to determine if the element should be removed
	// Note that this can move many entries in the table around, so previous pointers to elements, etc, should be considered invalidated
	// bool functype(AkUInt32 in_slot)
	template<typename KeyType, typename FuncType>
	void RemoveIf(AkHashTableBase<KeyType>* in_pHashTable, FuncType in_func)
	{
		AkUInt32 uNumReservedEntries = in_pHashTable->uNumReservedEntries;
		bool* pbSlotOccupied = in_pHashTable->pbSlotOccupied;
		AkUInt32 uSlot = 0;
		while (uSlot < uNumReservedEntries)
		{
			if (pbSlotOccupied[uSlot] && in_func(uSlot))
			{
				// if slot is occupied, and the function confirmed removal, remove this slot, but don't advance uSlot
				RemoveSlot(in_pHashTable, (AkInt32)uSlot);
			}
			else
			{
				uSlot++;
			}
		}
	}

};

#define AK_GET_PLUGIN_SERVICE_HASHTABLE(plugin_ctx) static_cast<AK::IAkPluginServiceHashTable*>(plugin_ctx->GetPluginService(AK::PluginServiceType_HashTable))

/// A common hashtable for mapping audioobjectIds to a combination of audio buffers and objects
struct AkAudioObjectBuffer
{
	AkAudioObjectBuffer() : pMetadata(nullptr) {}

	AkAudioBuffer pBuffer;
	AkAudioObject* pMetadata;
};
typedef AK::AkHashTable<AkAudioObjectID, AkAudioObjectBuffer> AkAudioObjectBufferMap;

/// Common hash function for getting a unique hash for a channel on an audio object
AkForceInline AkUInt64 GetObjectChannelHash(AkUInt64 in_uAudioObjectId, AkUInt32 in_uChannelIdx)
{
	return AkHashMurMurMix64(((AkUInt64)in_uChannelIdx << AkAudioObject::kObjectKeyNumBits) | (in_uAudioObjectId & AkAudioObject::kObjectKeyMask));
}

} // namespace AK