#pragma once
#include "base_core.h"


typedef U32 ArenaFlags; // no flags defined yet

typedef struct ArenaParams ArenaParams;
struct ArenaParams {
    U32 size;
    U32 commit_size;
    ArenaFlags flags; // No flags defined yet
};

typedef struct MemoryBlock MemoryBlock;
struct MemoryBlock {
    U8 *base;
    U32 size;           // Block size, page aligned
    U32 pos;            // start of next allocation
    U64 base_pos;       // absolute position of base relative to the first linked arena
    U32 committed_end;  // end of committed region. Will be page aligned
    MemoryBlock *prev;
};

typedef struct Arena Arena;
struct Arena {
    MemoryBlock *current;
    U32 block_size;     // requested block size
    U32 commit_size;    // requested commit size
    U32 page_size;      // cached page size
    ArenaFlags flags;
    S32 checkpoint_level;
};

typedef struct ArenaCheckpoint ArenaCheckpoint;
struct ArenaCheckpoint {
    Arena *arena;
    U64 absolute_pos;
};
#ifndef ArenaParams_Default
#define ArenaParams_Default { .size = MB(32), .commit_size = KB(64) }
#endif

StaticAssert(sizeof(MemoryBlock) <= 64);
// Try keep start of user memory at a cacheline
#define MemoryBlock_Header_Size 64u

void arena_init(Arena *arena, const ArenaParams *params);
void arena_free(Arena *arena);
void *arena_push(Arena *arena, U32 size, U32 align);

#define arena_push_type(arena, type) arena_push(arena, (U32)sizeof(type), alignof(type))
// Invalid for arrays > U32
#define arena_push_array_of(arena, type, len) arena_push(arena, (U32) (sizeof(type) * (len)), alignof(type))

ArenaCheckpoint arena_temp_begin(Arena *arena);
void arena_temp_end(ArenaCheckpoint *checkpoint);
void arena_pop_to(Arena *arena, U64 abs_pos);
void arena_reset(Arena *arena);

static INLINE U32 memoryblock_available(const MemoryBlock *block)
{
    return block->size - block->pos;
}

static INLINE U64 arena_used(const Arena *arena)
{
    const MemoryBlock *block = arena->current;
    return block->base_pos + block->pos;
}