// #TODO: #Arena_Table #garbage_collection in `release_arena`
// [ ] Garbage collection if we have >> 64 in a particular table for a while.
//     There should be some parameters regarding what the upper limit for idle 
//     committed pages should be and a heuristic for maximum number of arenas waiting

// API in Arena.h
#include <mutex> // #TODO: Replace with Mutex (see OS_Win32.cpp)

global b64 arena_tables_initialized = false;
global std::mutex arena_table_mutex;
global s32 arenas_in_flight_count[6];
global Array<Arena*> arena_free_table[6];
#if BUILD_DEBUG
global Array<Arena*> arenas_in_flight[6];
#endif

void initialize_arena_table () {
  // debug_break();
  for (s32 i = 0; i < 6; i += 1) {
    arena_free_table[i].allocator = GPAllocator();
    array_reserve(arena_free_table[i], 64);
#if BUILD_DEBUG
    arenas_in_flight[i].allocator = GPAllocator();
    array_reserve(arenas_in_flight[i], 64);
#endif
  }
  
  arena_tables_initialized = true;
}

Arena* next_arena (Arena_Reserve reserve_size) {
  Arena* arena;
  std::lock_guard<std::mutex> lock(arena_table_mutex);
  s64 reserve_index = (s64)reserve_size;
  arenas_in_flight_count[reserve_index] += 1;
  if (!arena_free_table[reserve_index].count) {
    arena = bootstrap_arena(reserve_size, ARENA_DEFAULT_COMMIT_PAGE_COUNT);
  } else {
    arena = pop(arena_free_table[reserve_index]);
  }
#if ARENA_DEBUG 
  array_add(arenas_in_flight[reserve_index], arena);
#endif  

  Assert(arena != nullptr);
  
  return arena;
}

void release_arena (Arena* arena, bool delete_extra_pages) {
  std::lock_guard<std::mutex> lock(arena_table_mutex);
  s64 reserve_index = (s64)arena->reserve_size;
#if ARENA_DEBUG 
  array_unordered_remove_by_value(arenas_in_flight[reserve_index], arena, 1);
#endif
  arena_reset_keeping_memory(arena);
  if (delete_extra_pages) {
    free_pages_down_to(arena, arena->initial_commit_page_count);
  }
  array_add(arena_free_table[reserve_index], arena);
  
  arenas_in_flight_count[reserve_index] -= 1;
  
  // #garbage_collection
  if (arena_free_table[reserve_index].count > 64) {
    // s64 arenas_to_delete_count = arena_free_table[reserve_index].count - 64.
    // while (arenas_to_delete_count > 0) {
    //   arena_delete(arena_free_table[arena_free_table.count-1]);
    //   array_unordered_remove_by_index(..);
    //   arenas_to_delete_count -= 1;
    // }
  }
}