#ifndef BASE_ARENA_H
#define BASE_ARENA_H

//- arena
typedef struct MemArena MemArena;
typedef struct ScratchArena ScratchArena;

// NOTE: used capacity can be calculated so we don't care
struct MemArena {
    u64 current_position;
    u64 previous_position;
    u64 capacity;
    u8 *base_position;
    MemArena *next;
};

struct ScratchArena {
    MemArena *arena;
    u64 start_position;
};

//-

#if defined(PLATFORM_UNIX)

internal MemArena *unix_arena_create(u64 capacity);
internal void unix_arena_destroy(MemArena *arena);

#define ArenaCreate(capacity) unix_arena_create(capacity)
#define ArenaDestroy(arena) unix_arena_destroy(arena)
#elif defined(PLATFORM_WINDOWS)

internal void win32_arena_destroy(MemArena *arena);
internal MemArena *win32_arena_create(u64 capacity);

#define ArenaCreate(capacity) win32_arena_create(capacity)
#define ArenaDestroy(arena) win32_arena_destroy(arena)
#endif

internal void *arena_alloc(MemArena *arena, u64 size, b32 zero);
internal void arena_pop(MemArena *arena, u64 size);
internal void arena_pop_to(MemArena *arena, u64 pos);
internal void arena_clear(MemArena *arena);
internal ScratchArena scratch_start(MemArena *arena);
internal void scratch_end(ScratchArena *scratch);
internal MemArena *arena_resize_block_align(MemArena *arena, void *old_memory, u64 new_size, u64 old_size,
                                            umm alignment);
internal MemArena *arena_resize_block(MemArena *arena, void *old_memory, u64 new_size, u64 old_size);
internal u64 arena_calculate_used_capacity(MemArena *arena);

#define Align(pointer, alignment) align((u64)(pointer), (umm)(alignment))
#define PushStruct(arena, type) (type *)arena_alloc((arena), sizeof(type), 0)
#define PushStructZero(arena, type) (type *)arena_alloc((arena), sizeof(type), 1)
#define PushArray(arena, type, len) (type *)arena_alloc((arena), sizeof(type) * (len), 0)
#define PushArrayZero(arena, type, len) (type *)arena_alloc((arena), sizeof(type) * (len), 1)
#define ArenaResize(arena, old_memory, new_size, old_size) arena_resize_block(arena, old_memory, new_size, old_size) // takes the address of the allocated block in the arena and grows it with a new size
#define ArenaPopLastPush(arena) arena_pop_to(arena, arena->previous_position)


// claude magic HAHHAHAHAH
#define LogArena(arena_expr)                                                                       \
    do {                                                                                           \
        MemArena *_a = (arena_expr);                                                               \
        if (!_a) {                                                                                 \
            Log("[arena] %s = NULL (%s:%d)\n", #arena_expr, __FILE__, __LINE__);                   \
            break;                                                                                 \
        }                                                                                          \
        unsigned long long _cap  = (unsigned long long)_a->capacity;                               \
        unsigned long long _cur  = (unsigned long long)_a->current_position;                       \
        unsigned long long _prev = (unsigned long long)_a->previous_position;                      \
        unsigned long long _free = _cur <= _cap ? _cap - _cur : 0;                                 \
        unsigned long long _last = _cur >= _prev ? _cur - _prev : 0;                               \
        double _pct              = _cap ? (100.0 * (double)_cur / (double)_cap) : 0.0;             \
        u8 *_expected_base       = (u8 *)_a + sizeof(MemArena);                                    \
        Log("[arena] %s @ %p (%s:%d)\n"                                                            \
            "  base_position     : %p .. %p%s\n"                                                   \
            "  capacity          : %llu bytes\n"                                                   \
            "  current_position  : %llu (used %.2f%%)\n"                                           \
            "  previous_position : %llu\n"                                                         \
            "  last alloc size   : %llu bytes (current - previous)\n"                              \
            "  free              : %llu bytes (capacity - current)\n"                              \
            "  next write addr   : %p\n",                                                          \
            #arena_expr, (void *)_a, __FILE__, __LINE__,                                           \
            (void *)_a->base_position, (void *)(_a->base_position + _cap),                         \
            _a->base_position == _expected_base ? "" : "  <-- base != arena + sizeof(MemArena)",   \
            _cap, _cur, _pct, _prev, _last, _free,                                                 \
            (void *)(_a->base_position + _cur));                                                   \
        if (_cur > _cap)                                                                           \
            Log("  !! OVERFLOW: current_position exceeds capacity by %llu bytes\n", _cur - _cap);  \
        if (_prev > _cur)                                                                          \
            Log("  !! previous_position (%llu) > current_position (%llu)\n", _prev, _cur);         \
    } while (0)

#endif /* BASE_ARENA_H */