// tiny_failfast.c - Fail-fast debugging utilities (lightweight stubs)
// Purpose: Provide link-time definitions for instrumentation hooks used across
//          alloc/free/refill paths. Behavior controlled via env variables.

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <stdatomic.h>
#include "hakmem_tiny_superslab.h"  // For SuperSlab/TinySlabMeta and hak_now_ns

// Runtime-configurable fail-fast level
// 0 = disabled, 1 = log only, 2 = log + raise(SIGUSR2), 3 = abort()
int tiny_refill_failfast_level(void)
{
    static _Atomic int lvl = -1;
    int v = atomic_load_explicit(&lvl, memory_order_relaxed);
    if (__builtin_expect(v != -1, 1)) return v;
    const char* e = getenv("HAKMEM_TINY_REFILL_FAILFAST");
    int parsed = (e && *e) ? atoi(e) : 0;
    if (parsed < 0) parsed = 0; if (parsed > 3) parsed = 3;
    atomic_store_explicit(&lvl, parsed, memory_order_relaxed);
    return parsed;
}

void tiny_failfast_log(const char* stage,
                       int class_idx,
                       SuperSlab* ss,
                       TinySlabMeta* meta,
                       void* ptr,
                       void* prev)
{
    if (tiny_refill_failfast_level() < 1) return;
    uint64_t ts = hak_now_ns();
    fprintf(stderr,
            "[FF][%s] ts=%llu cls=%d ss=%p slab_used=%u cap=%u ptr=%p prev=%p\n",
            stage ? stage : "?",
            (unsigned long long)ts,
            class_idx,
            (void*)ss,
            meta ? (unsigned)meta->used : 0u,
            meta ? (unsigned)meta->capacity : 0u,
            ptr,
            prev);
}

void tiny_failfast_abort_ptr(const char* stage,
                             SuperSlab* ss,
                             int slab_idx,
                             void* ptr,
                             const char* reason)
{
    int lvl = tiny_refill_failfast_level();
    if (lvl <= 0) return;
    fprintf(stderr,
            "[FF-ABORT][%s] ss=%p slab=%d ptr=%p reason=%s\n",
            stage ? stage : "?",
            (void*)ss,
            slab_idx,
            ptr,
            reason ? reason : "");
    if (lvl >= 3) {
        abort();
    } else if (lvl >= 2) {
        raise(SIGUSR2);
    }
}