// tiny_mmap_gate.h - Mmap Gate (must-adopt-before-mmap)
#pragma once
#include "hakmem_tiny_superslab.h"
#include "tiny_refill.h"
#include "hakmem_super_registry.h"

// Returns adopted SuperSlab* or NULL
static inline SuperSlab* tiny_must_adopt_gate(int class_idx, TinyTLSSlab* tls) {
    // Env: enable gate
    static int en = -1;
    if (__builtin_expect(en == -1, 0)) {
        const char* s = getenv("HAKMEM_TINY_MUST_ADOPT");
        en = (s && atoi(s) != 0) ? 1 : 0;
    }
    if (!en) return NULL;

    // Try fast adopt once
    SuperSlab* ss = tiny_refill_try_fast(class_idx, tls);
    if (ss) return ss;

    // Optional light remote drain to surface supply
    if (!ss) {
        // If TLS holds an SS, lightly drain its remotes to expose freelist
        SuperSlab* cur = tls->ss;
        if (cur && cur->magic == SUPERSLAB_MAGIC) {
            ss_remote_drain_light(cur);
        }
    }

    // Optional yield between attempts
    static int yv = -1;
    if (__builtin_expect(yv == -1, 0)) {
        const char* y = getenv("HAKMEM_TINY_MMAP_YIELD");
        yv = (y && atoi(y) != 0) ? 1 : 0;
    }
    if (yv) sched_yield();

    // Try again after yield
    ss = tiny_refill_try_fast(class_idx, tls);
    if (ss) return ss;

    // Registry small-window adopt (one pass, limited scan)
    {
        uint32_t self_tid = tiny_self_u32();
        int scanned = 0;
        const int scan_max = tiny_reg_scan_max();
        for (int i = 0; i < SUPER_REG_SIZE && scanned < scan_max; i++) {
            SuperRegEntry* e = &g_super_reg[i];
            uintptr_t base = atomic_load_explicit((_Atomic uintptr_t*)&e->base, memory_order_acquire);
            if (base == 0) continue;
            SuperSlab* cand = atomic_load_explicit(&e->ss, memory_order_acquire);
            if (!cand || cand->magic != SUPERSLAB_MAGIC) continue;
            if ((int)cand->size_class != class_idx) { scanned++; continue; }
            int cap = ss_slabs_capacity(cand);
            for (int s = 0; s < cap; s++) {
                // Box: Try to acquire ownership
                SlabHandle h = slab_try_acquire(cand, s, self_tid);
                if (slab_is_valid(&h)) {
                    // Box: Safe to drain - ownership guaranteed
                    slab_drain_remote_full(&h);

                    if (slab_freelist(&h)) {
                        tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                        return h.ss;
                    }

                    slab_release(&h);
                }
            }
            scanned++;
        }
    }
    return NULL;
}