#include "mem_arena.h"
#include "aliases.h"
#include "mem_utils.h"
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>

#ifndef DEFAULT_ALIGNMENT
// Why 2 * sizeof(void *) instead of sizeof(void *)
// https://handmade.network/forums/t/6860-alignment_arena_allocator
#define DEFAULT_ALIGNMENT (2 * sizeof(void *))
#endif /* ifndef DEFAULT_ALIGNMENT */

#define ARENA_MINIMUM_CAPACITY 1024

struct arena {
  u8 *buf;
  u8 *offset;
  u64 capacity;
};

// PUBLIC API

bool wapp_mem_arena_init(Arena **arena, u64 base_capacity) {
  if (!arena || *arena || base_capacity == 0) {
    return false;
  }

  *arena = (Arena *)calloc(1, sizeof(Arena));
  Arena *arena_ptr = *arena;
  if (!arena_ptr) {
    return false;
  }

  u64 arena_capacity = base_capacity >= ARENA_MINIMUM_CAPACITY
                           ? base_capacity
                           : ARENA_MINIMUM_CAPACITY;

  arena_ptr->buf = (u8 *)calloc(arena_capacity, sizeof(u8));
  if (!(arena_ptr->buf)) {
    wapp_mem_arena_destroy(arena);
    return false;
  }

  arena_ptr->capacity = arena_capacity;
  arena_ptr->offset = arena_ptr->buf;

  return true;
}

void *wapp_mem_arena_alloc(Arena *arena, u64 size) {
  return wapp_mem_arena_alloc_aligned(arena, size, DEFAULT_ALIGNMENT);
}

void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment) {
  if (!arena) {
    return NULL;
  }

  u8 *alloc_start = arena->offset;

  u8 *output = wapp_mem_util_align_forward((void *)alloc_start, alignment);
  if (output + size >= arena->buf + arena->capacity) {
    return NULL;
  }

  arena->offset = output + size;

  memset(output, 0, size);

  return (void *)output;
}

void wapp_mem_arena_clear(Arena *arena) {
  if (!arena) {
    return;
  }

  memset(arena->buf, 0, arena->offset - arena->buf);
  arena->offset = arena->buf;
}

void wapp_mem_arena_destroy(Arena **arena) {
  if (!arena) {
    return;
  }

  Arena *arena_ptr = *arena;
  if (arena_ptr->buf) {
    free(arena_ptr->buf);
  }

  arena_ptr->buf = arena_ptr->offset = NULL;
  arena_ptr->capacity = 0;

  free(*arena);
  *arena = NULL;
}