// tls_sll_box.h - Box TLS-SLL: Single-Linked List API (Unified Box version)
//
// Goal:
//   - Single authoritative Box for TLS SLL operations.
//   - All next pointer layout is decided by tiny_next_ptr_box.h (Box API).
//   - Callers pass BASE pointers only; no local next_offset arithmetic.
//   - Compatible with existing ptr_trace PTR_NEXT_* macros (off is logging-only).
//
// Invariants:
//   - g_tiny_class_sizes[cls] is TOTAL stride (including 1-byte header when enabled).
//   - For HEADER_CLASSIDX != 0, tiny_nextptr.h encodes:
//       class 0: next_off = 0
//       class 1-6: next_off = 1
//       class 7: next_off = 0
//     Callers MUST NOT duplicate this logic.
//   - TLS SLL stores BASE pointers only.
//   - Box provides: push / pop / splice with capacity & integrity checks.

#ifndef TLS_SLL_BOX_H
#define TLS_SLL_BOX_H

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

#include "../hakmem_tiny_config.h"
#include "../hakmem_build_flags.h"
#include "../tiny_remote.h"
#include "../tiny_region_id.h"
#include "../hakmem_tiny_integrity.h"
#include "../ptr_track.h"
#include "../ptr_trace.h"
#include "tiny_next_ptr_box.h"

// External TLS SLL state (defined in hakmem_tiny.c or equivalent)
extern __thread void*    g_tls_sll_head[TINY_NUM_CLASSES];
extern __thread uint32_t g_tls_sll_count[TINY_NUM_CLASSES];
extern int g_tls_sll_class_mask;  // bit i=1 → SLL allowed for class i

// ========== Debug guard ==========

#if !HAKMEM_BUILD_RELEASE
static inline void tls_sll_debug_guard(int class_idx, void* base, const char* where)
{
    (void)class_idx;
    if ((uintptr_t)base < 4096) {
        fprintf(stderr,
                "[TLS_SLL_GUARD] %s: suspicious ptr=%p cls=%d\n",
                where, base, class_idx);
        abort();
    }
}
#else
static inline void tls_sll_debug_guard(int class_idx, void* base, const char* where)
{
    (void)class_idx; (void)base; (void)where;
}
#endif

// Normalize helper: callers are required to pass BASE already.
// Kept as a no-op for documentation / future hardening.
static inline void* tls_sll_normalize_base(int class_idx, void* node)
{
    (void)class_idx;
    return node;
}

// ========== Push ==========
//
// Push BASE pointer into TLS SLL for given class.
// Returns true on success, false if capacity full or input invalid.

static inline bool tls_sll_push(int class_idx, void* ptr, uint32_t capacity)
{
    HAK_CHECK_CLASS_IDX(class_idx, "tls_sll_push");

    // Class mask gate (narrow triage): if disallowed, reject push
    if (__builtin_expect(((g_tls_sll_class_mask & (1u << class_idx)) == 0), 0)) {
        return false;
    }

    // Capacity semantics:
    //  - capacity == 0 → disabled (reject)
    //  - capacity > 1<<20 → treat as "unbounded" sentinel (no limit)
    if (capacity == 0) {
        return false;
    }
    const uint32_t kCapacityHardMax = (1u << 20);
    const int unlimited = (capacity > kCapacityHardMax);

    if (!ptr) {
        return false;
    }

    // Base pointer only (callers must pass BASE; this is a no-op by design).
    ptr = tls_sll_normalize_base(class_idx, ptr);

#if !HAKMEM_BUILD_RELEASE
    // Minimal range guard before we touch memory.
    if (!validate_ptr_range(ptr, "tls_sll_push_base")) {
        fprintf(stderr,
                "[TLS_SLL_PUSH] FATAL invalid BASE ptr cls=%d base=%p\n",
                class_idx, ptr);
        abort();
    }
#endif

    // Capacity check BEFORE any writes.
    uint32_t cur = g_tls_sll_count[class_idx];
    if (!unlimited && cur >= capacity) {
        return false;
    }

#if HAKMEM_TINY_HEADER_CLASSIDX
    // Header handling for header classes (class != 0,7).
    // Safe mode (HAKMEM_TINY_SLL_SAFEHEADER=1): never overwrite header; reject on magic mismatch.
    // Default mode: restore expected header.
    if (class_idx != 0 && class_idx != 7) {
        static int g_sll_safehdr = -1;
        if (__builtin_expect(g_sll_safehdr == -1, 0)) {
            const char* e = getenv("HAKMEM_TINY_SLL_SAFEHEADER");
            g_sll_safehdr = (e && *e && *e != '0') ? 1 : 0;
        }
        uint8_t* b = (uint8_t*)ptr;
        uint8_t expected = (uint8_t)(HEADER_MAGIC | (class_idx & HEADER_CLASS_MASK));
        if (g_sll_safehdr) {
            uint8_t got = *b;
            if ((got & 0xF0u) != HEADER_MAGIC) {
                // Reject push silently (fall back to slow path at caller)
                return false;
            }
        } else {
            PTR_TRACK_TLS_PUSH(ptr, class_idx);
            PTR_TRACK_HEADER_WRITE(ptr, expected);
            *b = expected;
        }
    }
#endif

    tls_sll_debug_guard(class_idx, ptr, "push");

#if !HAKMEM_BUILD_RELEASE
    // Optional double-free detection: scan a bounded prefix of the list.
    {
        void* scan = g_tls_sll_head[class_idx];
        uint32_t scanned = 0;
        const uint32_t limit = (g_tls_sll_count[class_idx] < 64)
                                 ? g_tls_sll_count[class_idx]
                                 : 64;
        while (scan && scanned < limit) {
            if (scan == ptr) {
                fprintf(stderr,
                        "[TLS_SLL_PUSH] FATAL double-free: cls=%d ptr=%p already in SLL\n",
                        class_idx, ptr);
                ptr_trace_dump_now("double_free");
                abort();
            }
            void* next;
            PTR_NEXT_READ("tls_sll_scan", class_idx, scan, 0, next);
            scan = next;
            scanned++;
        }
    }
#endif

    // Link new node to current head via Box API (offset is handled inside tiny_nextptr).
    PTR_NEXT_WRITE("tls_push", class_idx, ptr, 0, g_tls_sll_head[class_idx]);
    g_tls_sll_head[class_idx] = ptr;
    g_tls_sll_count[class_idx] = cur + 1;

    return true;
}

// ========== Pop ==========
//
// Pop BASE pointer from TLS SLL.
// Returns true on success and stores BASE into *out.

static inline bool tls_sll_pop(int class_idx, void** out)
{
    HAK_CHECK_CLASS_IDX(class_idx, "tls_sll_pop");
    // Class mask gate: if disallowed, behave as empty
    if (__builtin_expect(((g_tls_sll_class_mask & (1u << class_idx)) == 0), 0)) {
        return false;
    }
    atomic_fetch_add(&g_integrity_check_class_bounds, 1);

    void* base = g_tls_sll_head[class_idx];
    if (!base) {
        return false;
    }

    // Sentinel guard: remote sentinel must never be in TLS SLL.
    if (__builtin_expect((uintptr_t)base == TINY_REMOTE_SENTINEL, 0)) {
        g_tls_sll_head[class_idx] = NULL;
        g_tls_sll_count[class_idx] = 0;
#if !HAKMEM_BUILD_RELEASE
        fprintf(stderr,
                "[TLS_SLL_POP] Remote sentinel detected at head; SLL reset (cls=%d)\n",
                class_idx);
#endif
        return false;
    }

#if !HAKMEM_BUILD_RELEASE
    if (!validate_ptr_range(base, "tls_sll_pop_base")) {
        fprintf(stderr,
                "[TLS_SLL_POP] FATAL invalid BASE ptr cls=%d base=%p\n",
                class_idx, base);
        abort();
    }
#endif

    tls_sll_debug_guard(class_idx, base, "pop");

#if HAKMEM_TINY_HEADER_CLASSIDX
    // Header validation for header-classes (class != 0,7).
    if (class_idx != 0 && class_idx != 7) {
        uint8_t got = *(uint8_t*)base;
        uint8_t expect = (uint8_t)(HEADER_MAGIC | (class_idx & HEADER_CLASS_MASK));
        PTR_TRACK_TLS_POP(base, class_idx);
        PTR_TRACK_HEADER_READ(base, got);
        if (__builtin_expect(got != expect, 0)) {
#if !HAKMEM_BUILD_RELEASE
            fprintf(stderr,
                    "[TLS_SLL_POP] CORRUPTED HEADER cls=%d base=%p got=0x%02x expect=0x%02x\n",
                    class_idx, base, got, expect);
            ptr_trace_dump_now("header_corruption");
            abort();
#else
            // In release, fail-safe: drop list.
            g_tls_sll_head[class_idx] = NULL;
            g_tls_sll_count[class_idx] = 0;
            return false;
#endif
        }
    }
#endif

    // Read next via Box API.
    void* next;
    PTR_NEXT_READ("tls_pop", class_idx, base, 0, next);

#if !HAKMEM_BUILD_RELEASE
    if (next && !validate_ptr_range(next, "tls_sll_pop_next")) {
        fprintf(stderr,
                "[TLS_SLL_POP] FATAL invalid next ptr cls=%d base=%p next=%p\n",
                class_idx, base, next);
        ptr_trace_dump_now("next_corruption");
        abort();
    }
#endif

    g_tls_sll_head[class_idx] = next;
    if (g_tls_sll_count[class_idx] > 0) {
        g_tls_sll_count[class_idx]--;
    }

    // Clear next inside popped node to avoid stale-chain issues.
    tiny_next_write(class_idx, base, NULL);

    *out = base;
    return true;
}

// ========== Splice ==========
//
// Splice a pre-linked chain of BASE pointers into TLS SLL head.
// chain_head is BASE; links are via Box API-compatible next layout.
// Returns number of nodes actually moved (<= capacity remaining).

static inline uint32_t tls_sll_splice(int class_idx,
                                      void* chain_head,
                                      uint32_t count,
                                      uint32_t capacity)
{
    HAK_CHECK_CLASS_IDX(class_idx, "tls_sll_splice");

    if (!chain_head || count == 0 || capacity == 0) {
        return 0;
    }

    uint32_t cur = g_tls_sll_count[class_idx];
    if (cur >= capacity) {
        return 0;
    }

    uint32_t room = capacity - cur;
    uint32_t to_move = (count < room) ? count : room;

    // Traverse chain up to to_move, validate, and find tail.
    void* tail = chain_head;
    uint32_t moved = 1;

    tls_sll_debug_guard(class_idx, chain_head, "splice_head");

#if HAKMEM_TINY_HEADER_CLASSIDX
    // Restore header defensively on each node we touch.
    {
        uint8_t* b = (uint8_t*)chain_head;
        uint8_t expected = (uint8_t)(HEADER_MAGIC | (class_idx & HEADER_CLASS_MASK));
        *b = expected;
    }
#endif

    while (moved < to_move) {
        tls_sll_debug_guard(class_idx, tail, "splice_traverse");

        void* next;
        PTR_NEXT_READ("tls_splice_trav", class_idx, tail, 0, next);

        if (!next) {
            break;
        }

#if HAKMEM_TINY_HEADER_CLASSIDX
        {
            uint8_t* b = (uint8_t*)next;
            uint8_t expected = (uint8_t)(HEADER_MAGIC | (class_idx & HEADER_CLASS_MASK));
            *b = expected;
        }
#endif

        tail = next;
        moved++;
    }

    // Link tail to existing head and install new head.
    tls_sll_debug_guard(class_idx, tail, "splice_tail");
    PTR_NEXT_WRITE("tls_splice_link", class_idx, tail, 0, g_tls_sll_head[class_idx]);

    g_tls_sll_head[class_idx] = chain_head;
    g_tls_sll_count[class_idx] = cur + moved;

    return moved;
}

#endif // TLS_SLL_BOX_H