#ifdef GEN_INTELLISENSE_DIRECTIVES
#	pragma once
#	include "debug.hpp"
#endif

#pragma region Memory

#define kilobytes( x ) ( ( x ) * ( s64 )( 1024 ) )
#define megabytes( x ) ( kilobytes( x ) * ( s64 )( 1024 ) )
#define gigabytes( x ) ( megabytes( x ) * ( s64 )( 1024 ) )
#define terabytes( x ) ( gigabytes( x ) * ( s64 )( 1024 ) )

#define GEN__ONES          ( zpl_cast( uw ) - 1 / GEN_U8_MAX )
#define GEN__HIGHS         ( GEN__ONES * ( GEN_U8_MAX / 2 + 1 ) )
#define GEN__HAS_ZERO( x ) ( ( ( x )-GEN__ONES ) & ~( x )&GEN__HIGHS )

//! Checks if value is power of 2.
GEN_DEF_INLINE b32 is_power_of_two( sw x );

//! Aligns address to specified alignment.
GEN_DEF_INLINE void* align_forward( void* ptr, sw alignment );

//! Aligns value to a specified alignment.
GEN_DEF_INLINE s64 align_forward_i64( s64 value, sw alignment );

//! Moves pointer forward by bytes.
GEN_DEF_INLINE void* pointer_add( void* ptr, sw bytes );

//! Moves pointer forward by bytes.
GEN_DEF_INLINE void const* pointer_add_const( void const* ptr, sw bytes );

//! Calculates difference between two addresses.
GEN_DEF_INLINE sw pointer_diff( void const* begin, void const* end );

//! Copy non-overlapping memory from source to destination.
void* mem_copy( void* dest, void const* source, sw size );

//! Search for a constant value within the size limit at memory location.
void const* mem_find( void const* data, u8 byte_value, sw size );

//! Copy memory from source to destination.
GEN_DEF_INLINE void* mem_move( void* dest, void const* source, sw size );

//! Set constant value at memory location with specified size.
GEN_DEF_INLINE void* mem_set( void* data, u8 byte_value, sw size );

//! @param ptr Memory location to clear up.
//! @param size The size to clear up with.
GEN_DEF_INLINE void zero_size( void* ptr, sw size );

//! Clears up an item.
#define zero_item( t ) zero_size( ( t ), size_of( *( t ) ) )    // NOTE: Pass pointer of struct

//! Clears up an array.
#define zero_array( a, count ) zero_size( ( a ), size_of( *( a ) ) * count )

enum AllocType : u8
{
	EAllocation_ALLOC,
	EAllocation_FREE,
	EAllocation_FREE_ALL,
	EAllocation_RESIZE,
};

using AllocatorProc = void* ( void* allocator_data, AllocType type
	, sw size, sw alignment
	, void* old_memory, sw old_size
	, u64 flags );

struct AllocatorInfo
{
	AllocatorProc* Proc;
	void*          Data;
};

enum AllocFlag
{
	ALLOCATOR_FLAG_CLEAR_TO_ZERO = bit( 0 ),
};

#ifndef GEN_DEFAULT_MEMORY_ALIGNMENT
#	define GEN_DEFAULT_MEMORY_ALIGNMENT ( 2 * size_of( void* ) )
#endif

#ifndef GEN_DEFAULT_ALLOCATOR_FLAGS
#	define GEN_DEFAULT_ALLOCATOR_FLAGS ( ALLOCATOR_FLAG_CLEAR_TO_ZERO )
#endif

//! Allocate memory with default alignment.
GEN_DEF_INLINE void* alloc( AllocatorInfo a, sw size );

//! Allocate memory with specified alignment.
GEN_DEF_INLINE void* alloc_align( AllocatorInfo a, sw size, sw alignment );

//! Free allocated memory.
GEN_DEF_INLINE void free( AllocatorInfo a, void* ptr );

//! Free all memory allocated by an allocator.
GEN_DEF_INLINE void free_all( AllocatorInfo a );

//! Resize an allocated memory.
GEN_DEF_INLINE void* resize( AllocatorInfo a, void* ptr, sw old_size, sw new_size );

//! Resize an allocated memory with specified alignment.
GEN_DEF_INLINE void* resize_align( AllocatorInfo a, void* ptr, sw old_size, sw new_size, sw alignment );

//! Allocate memory for an item.
#define alloc_item( allocator_, Type ) ( Type* )alloc( allocator_, size_of( Type ) )

//! Allocate memory for an array of items.
#define alloc_array( allocator_, Type, count ) ( Type* )alloc( allocator_, size_of( Type ) * ( count ) )

/* heap memory analysis tools */
/* define GEN_HEAP_ANALYSIS to enable this feature */
/* call zpl_heap_stats_init at the beginning of the entry point */
/* you can call zpl_heap_stats_check near the end of the execution to validate any possible leaks */
void heap_stats_init( void );
sw   heap_stats_used_memory( void );
sw   heap_stats_alloc_count( void );
void heap_stats_check( void );

//! Allocate/Resize memory using default options.

//! Use this if you don't need a "fancy" resize allocation
GEN_DEF_INLINE void* default_resize_align( AllocatorInfo a, void* ptr, sw old_size, sw new_size, sw alignment );

void* heap_allocator_proc( void* allocator_data, AllocType type, sw size, sw alignment, void* old_memory, sw old_size, u64 flags );

//! The heap allocator backed by operating system's memory manager.
constexpr AllocatorInfo heap( void ) { return { heap_allocator_proc, nullptr }; }

//! Helper to allocate memory using heap allocator.
#define malloc( sz ) alloc( heap(), sz )

//! Helper to free memory allocated by heap allocator.
#define mfree( ptr ) free( heap(), ptr )

GEN_IMPL_INLINE b32 is_power_of_two( sw x )
{
	if ( x <= 0 )
		return false;
	return ! ( x & ( x - 1 ) );
}

GEN_IMPL_INLINE void* align_forward( void* ptr, sw alignment )
{
	uptr p;

	GEN_ASSERT( is_power_of_two( alignment ) );

	p = zpl_cast( uptr ) ptr;
	return zpl_cast( void* )( ( p + ( alignment - 1 ) ) & ~( alignment - 1 ) );
}

GEN_IMPL_INLINE s64 align_forward_i64( s64 value, sw alignment )
{
	return value + ( alignment - value % alignment ) % alignment;
}

GEN_IMPL_INLINE void* pointer_add( void* ptr, sw bytes )
{
	return zpl_cast( void* )( zpl_cast( u8* ) ptr + bytes );
}

GEN_IMPL_INLINE void const* pointer_add_const( void const* ptr, sw bytes )
{
	return zpl_cast( void const* )( zpl_cast( u8 const* ) ptr + bytes );
}

GEN_IMPL_INLINE sw pointer_diff( void const* begin, void const* end )
{
	return zpl_cast( sw )( zpl_cast( u8 const* ) end - zpl_cast( u8 const* ) begin );
}

GEN_IMPL_INLINE void* mem_move( void* dest, void const* source, sw n )
{
	if ( dest == NULL )
	{
		return NULL;
	}

	u8*       d = zpl_cast( u8* ) dest;
	u8 const* s = zpl_cast( u8 const* ) source;

	if ( d == s )
		return d;
	if ( s + n <= d || d + n <= s )    // NOTE: Non-overlapping
		return mem_copy( d, s, n );

	if ( d < s )
	{
		if ( zpl_cast( uptr ) s % size_of( sw ) == zpl_cast( uptr ) d % size_of( sw ) )
		{
			while ( zpl_cast( uptr ) d % size_of( sw ) )
			{
				if ( ! n-- )
					return dest;
				*d++ = *s++;
			}
			while ( n >= size_of( sw ) )
			{
				*zpl_cast( sw* ) d  = *zpl_cast( sw* ) s;
				n                  -= size_of( sw );
				d                  += size_of( sw );
				s                  += size_of( sw );
			}
		}
		for ( ; n; n-- )
			*d++ = *s++;
	}
	else
	{
		if ( ( zpl_cast( uptr ) s % size_of( sw ) ) == ( zpl_cast( uptr ) d % size_of( sw ) ) )
		{
			while ( zpl_cast( uptr )( d + n ) % size_of( sw ) )
			{
				if ( ! n-- )
					return dest;
				d[ n ] = s[ n ];
			}
			while ( n >= size_of( sw ) )
			{
				n                         -= size_of( sw );
				*zpl_cast( sw* )( d + n )  = *zpl_cast( sw* )( s + n );
			}
		}
		while ( n )
			n--, d[ n ] = s[ n ];
	}

	return dest;
}

GEN_IMPL_INLINE void* mem_set( void* dest, u8 c, sw n )
{
	if ( dest == NULL )
	{
		return NULL;
	}

	u8* s = zpl_cast( u8* ) dest;
	sw  k;
	u32 c32 = ( ( u32 )-1 ) / 255 * c;

	if ( n == 0 )
		return dest;
	s[ 0 ] = s[ n - 1 ] = c;
	if ( n < 3 )
		return dest;
	s[ 1 ] = s[ n - 2 ] = c;
	s[ 2 ] = s[ n - 3 ] = c;
	if ( n < 7 )
		return dest;
	s[ 3 ] = s[ n - 4 ] = c;
	if ( n < 9 )
		return dest;

	k  = -zpl_cast( sptr ) s & 3;
	s += k;
	n -= k;
	n &= -4;

	*zpl_cast( u32* )( s + 0 )     = c32;
	*zpl_cast( u32* )( s + n - 4 ) = c32;
	if ( n < 9 )
		return dest;
	*zpl_cast( u32* )( s + 4 )      = c32;
	*zpl_cast( u32* )( s + 8 )      = c32;
	*zpl_cast( u32* )( s + n - 12 ) = c32;
	*zpl_cast( u32* )( s + n - 8 )  = c32;
	if ( n < 25 )
		return dest;
	*zpl_cast( u32* )( s + 12 )     = c32;
	*zpl_cast( u32* )( s + 16 )     = c32;
	*zpl_cast( u32* )( s + 20 )     = c32;
	*zpl_cast( u32* )( s + 24 )     = c32;
	*zpl_cast( u32* )( s + n - 28 ) = c32;
	*zpl_cast( u32* )( s + n - 24 ) = c32;
	*zpl_cast( u32* )( s + n - 20 ) = c32;
	*zpl_cast( u32* )( s + n - 16 ) = c32;

	k  = 24 + ( zpl_cast( uptr ) s & 4 );
	s += k;
	n -= k;

	{
		u64 c64 = ( zpl_cast( u64 ) c32 << 32 ) | c32;
		while ( n > 31 )
		{
			*zpl_cast( u64* )( s + 0 )  = c64;
			*zpl_cast( u64* )( s + 8 )  = c64;
			*zpl_cast( u64* )( s + 16 ) = c64;
			*zpl_cast( u64* )( s + 24 ) = c64;

			n -= 32;
			s += 32;
		}
	}

	return dest;
}

GEN_IMPL_INLINE void* alloc_align( AllocatorInfo a, sw size, sw alignment )
{
	return a.Proc( a.Data, EAllocation_ALLOC, size, alignment, nullptr, 0, GEN_DEFAULT_ALLOCATOR_FLAGS );
}

GEN_IMPL_INLINE void* alloc( AllocatorInfo a, sw size )
{
	return alloc_align( a, size, GEN_DEFAULT_MEMORY_ALIGNMENT );
}

GEN_IMPL_INLINE void free( AllocatorInfo a, void* ptr )
{
	if ( ptr != nullptr )
		a.Proc( a.Data, EAllocation_FREE, 0, 0, ptr, 0, GEN_DEFAULT_ALLOCATOR_FLAGS );
}

GEN_IMPL_INLINE void free_all( AllocatorInfo a )
{
	a.Proc( a.Data, EAllocation_FREE_ALL, 0, 0, nullptr, 0, GEN_DEFAULT_ALLOCATOR_FLAGS );
}

GEN_IMPL_INLINE void* resize( AllocatorInfo a, void* ptr, sw old_size, sw new_size )
{
	return resize_align( a, ptr, old_size, new_size, GEN_DEFAULT_MEMORY_ALIGNMENT );
}

GEN_IMPL_INLINE void* resize_align( AllocatorInfo a, void* ptr, sw old_size, sw new_size, sw alignment )
{
	return a.Proc( a.Data, EAllocation_RESIZE, new_size, alignment, ptr, old_size, GEN_DEFAULT_ALLOCATOR_FLAGS );
}

GEN_IMPL_INLINE void* default_resize_align( AllocatorInfo a, void* old_memory, sw old_size, sw new_size, sw alignment )
{
	if ( ! old_memory )
		return alloc_align( a, new_size, alignment );

	if ( new_size == 0 )
	{
		free( a, old_memory );
		return nullptr;
	}

	if ( new_size < old_size )
		new_size = old_size;

	if ( old_size == new_size )
	{
		return old_memory;
	}
	else
	{
		void* new_memory = alloc_align( a, new_size, alignment );
		if ( ! new_memory )
			return nullptr;
		mem_move( new_memory, old_memory, min( new_size, old_size ) );
		free( a, old_memory );
		return new_memory;
	}
}

GEN_IMPL_INLINE void zero_size( void* ptr, sw size )
{
	mem_set( ptr, 0, size );
}

struct VirtualMemory
{
	void*  data;
	sw size;
};

//! Initialize virtual memory from existing data.
VirtualMemory vm_from_memory( void* data, sw size );

//! Allocate virtual memory at address with size.

//! @param addr The starting address of the region to reserve. If NULL, it lets operating system to decide where to allocate it.
//! @param size The size to serve.
VirtualMemory vm_alloc( void* addr, sw size );

//! Release the virtual memory.
b32 vm_free( VirtualMemory vm );

//! Trim virtual memory.
VirtualMemory vm_trim( VirtualMemory vm, sw lead_size, sw size );

//! Purge virtual memory.
b32 gen_vm_purge( VirtualMemory vm );

//! Retrieve VM's page size and alignment.
sw gen_virtual_memory_page_size( sw* alignment_out );

struct Arena
{
	static
	void* allocator_proc( void* allocator_data, AllocType type, sw size, sw alignment, void* old_memory, sw old_size, u64 flags );

	static
	Arena init_from_memory( void* start, sw size )
	{
		return
		{
			{ nullptr, nullptr },
			start,
			size,
			0,
			0
		};
	}

	static
	Arena init_from_allocator( AllocatorInfo backing, sw size )
	{
		Arena result =
		{
		backing,
		alloc( backing, size),
		size,
		0,
		0
		};
		return result;
	}

	static
	Arena init_sub( Arena& parent, sw size )
	{
		return init_from_allocator( parent.Backing, size );
	}

	sw alignment_of( sw alignment )
	{
		sw alignment_offset, result_pointer, mask;
		GEN_ASSERT( is_power_of_two( alignment ) );

		alignment_offset = 0;
		result_pointer   = (sw) PhysicalStart + TotalUsed;
		mask             = alignment - 1;

		if ( result_pointer & mask )
			alignment_offset = alignment - ( result_pointer & mask );

		return alignment_offset;
	}

// This id is defined by Unreal for asserts
#pragma push_macro("check")
#undef check
	void check()
	{
		GEN_ASSERT( TempCount == 0 );
	}
#pragma pop_macro("check")

	void free()
	{
		if ( Backing.Proc )
		{
			gen::free( Backing, PhysicalStart );
			PhysicalStart = nullptr;
		}
	}

	sw size_remaining( sw alignment )
	{
		sw result = TotalSize - ( TotalUsed + alignment_of( alignment ) );
		return result;
	}

	AllocatorInfo Backing;
	void*         PhysicalStart;
	sw            TotalSize;
	sw            TotalUsed;
	sw            TempCount;

	operator AllocatorInfo()
	{
		return { allocator_proc, this };
	}
};

// Just a wrapper around using an arena with memory associated with its scope instead of from an allocator.
// Used for static segment or stack allocations.
template< s32 Size >
struct FixedArena
{
	static
	FixedArena init()
	{
		FixedArena result = { Arena::init_from_memory( result.memory, Size ), {0} };
		return result;
	}

	sw size_remaining( sw alignment )
	{
		return arena.size_remaining( alignment );
	}

	operator AllocatorInfo()
	{
		return { Arena::allocator_proc, &arena };
	}

	Arena arena;
	char  memory[ Size ];
};

using Arena_1KB   = FixedArena< kilobytes( 1 ) >;
using Arena_4KB   = FixedArena< kilobytes( 4 ) >;
using Arena_8KB   = FixedArena< kilobytes( 8 ) >;
using Arena_16KB  = FixedArena< kilobytes( 16 ) >;
using Arena_32KB  = FixedArena< kilobytes( 32 ) >;
using Arena_64KB  = FixedArena< kilobytes( 64 ) >;
using Arena_128KB = FixedArena< kilobytes( 128 ) >;
using Arena_256KB = FixedArena< kilobytes( 256 ) >;
using Arena_512KB = FixedArena< kilobytes( 512 ) >;
using Arena_1MB   = FixedArena< megabytes( 1 ) >;
using Arena_2MB   = FixedArena< megabytes( 2 ) >;
using Arena_4MB   = FixedArena< megabytes( 4 ) >;

struct Pool
{
	static
	void* allocator_proc( void* allocator_data, AllocType type, sw size, sw alignment, void* old_memory, sw old_size, u64 flags );

	static
	Pool init( AllocatorInfo backing, sw num_blocks, sw block_size )
	{
		return init_align( backing, num_blocks, block_size, GEN_DEFAULT_MEMORY_ALIGNMENT );
	}

	static
	Pool init_align( AllocatorInfo backing, sw num_blocks, sw block_size, sw block_align );

	void clear();

	void free()
	{
		if ( Backing.Proc )
		{
			gen::free( Backing, PhysicalStart );
		}
	}

	AllocatorInfo Backing;
	void*         PhysicalStart;
	void*         FreeList;
	sw            BlockSize;
	sw            BlockAlign;
	sw            TotalSize;
	sw            NumBlocks;

	operator AllocatorInfo()
	{
		return { allocator_proc, this };
	}
};

#pragma endregion Memory