#include <stdio.h>
#include <stdlib.h>

#include "scratch.h"

#if __STDC_VERSION__ >= 201112L /* C11 and above */
#define thread_local _Thread_local
#elif defined(__GNUC__)
#define thread_local __thread
#else
#error Unsupported compiler.
#endif

#if defined(__GNUC__)
#define WEAK __attribute__((weak))
#endif

thread_local arena_t *scratch_arena[4] = { 0 };

void scratch_destroy(void)
{
    for (int s = 0; s < sizeof(scratch_arena) / sizeof(scratch_arena[0]); s++)
    {
        if (scratch_arena[s] == NULL) continue;
        arena_del(scratch_arena[s]);
        scratch_arena[s] = NULL;
    }
}

/*
 * Optionally allocate and return a scratch arena. Make sure that the returned
 * arena is not present in the NULL-terminated list `conflicts`
 */
arena_t *__scratch_get(arena_t **conflicts)
{
    int s = 0;

    if (conflicts != NULL)
    {
        for (s = 0; s < sizeof(scratch_arena) / sizeof(scratch_arena[0]); s++)
        {
            arena_t **c = conflicts;
            for (; *c != NULL; c++)
            {
                if (*c == scratch_arena[s]) break;
            }
            /* No conflcits found, break out */
            if (*c == NULL) break;
        }
        if (s >= sizeof(scratch_arena) / sizeof(scratch_arena[0]))
        {
            fprintf(stderr, "Out of scratch arenas.\n");
            return NULL;
        }
    }

    if (scratch_arena[s] == NULL)
    {
        scratch_cleanup_init();
        scratch_arena[s] = arena_new(SCRATCH_DEFAULT_SIZE);
        if (scratch_arena[s] == NULL)
        {
            fprintf(stderr, "Error allocating scratch arena %d.", s);
            return NULL;
        }

        printf("NEW SCRATCH = %p\n", scratch_arena[s]);
    }

    return scratch_arena[s];
}

void WEAK scratch_cleanup_init(void)
{
    static bool init = false;
    for (;!init; init = true)
    {
        printf("Single-threaded mode.\n");
        atexit(scratch_destroy);
    }
}