#include "tiny_debug_ring.h"
#include "hakmem_tiny.h"
#include <signal.h>
#include <stdatomic.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <ucontext.h>

#define TINY_RING_IGNORE(expr) do { ssize_t _tw_ret = (expr); (void)_tw_ret; } while(0)

#define TINY_RING_CAP 4096u

typedef struct {
    uintptr_t ptr;
    uintptr_t aux;
    uint16_t event;
    uint16_t class_idx;
} TinyRingEntry;

static TinyRingEntry g_tiny_ring[TINY_RING_CAP];
static _Atomic uint32_t g_tiny_ring_head = 0;
static int g_tiny_ring_enabled = 0;

typedef struct {
    const char* name;
    size_t len;
} TinyRingName;

static TinyRingName tiny_ring_event_name(uint16_t event) {
    switch (event) {
        case TINY_RING_EVENT_ALLOC_ENTER: return (TinyRingName){"alloc_enter", 11};
        case TINY_RING_EVENT_ALLOC_SUCCESS: return (TinyRingName){"alloc_ok", 8};
        case TINY_RING_EVENT_ALLOC_NULL: return (TinyRingName){"alloc_null", 10};
        case TINY_RING_EVENT_ALLOC_REFILL_START: return (TinyRingName){"refill_start", 12};
        case TINY_RING_EVENT_ALLOC_REFILL_NULL: return (TinyRingName){"refill_null", 11};
        case TINY_RING_EVENT_ALLOC_BIND: return (TinyRingName){"bind", 4};
        case TINY_RING_EVENT_FREE_ENTER: return (TinyRingName){"free_enter", 10};
        case TINY_RING_EVENT_FREE_FAST: return (TinyRingName){"free_fast", 8};
        case TINY_RING_EVENT_FREE_REMOTE: return (TinyRingName){"free_remote", 11};
        case TINY_RING_EVENT_FREE_LOCAL: return (TinyRingName){"free_local", 10};
        case TINY_RING_EVENT_FREE_RETURN_MAG: return (TinyRingName){"free_mag", 7};
        case TINY_RING_EVENT_SUPERSLAB_ADOPT: return (TinyRingName){"ss_adopt", 8};
        case TINY_RING_EVENT_SUPERSLAB_ALLOC: return (TinyRingName){"ss_alloc", 8};
        case TINY_RING_EVENT_SUPERSLAB_PUBLISH: return (TinyRingName){"ss_publish", 10};
        case TINY_RING_EVENT_SUPERSLAB_ADOPT_FAIL: return (TinyRingName){"ss_adopt_fail", 13};
        case TINY_RING_EVENT_REMOTE_PUSH: return (TinyRingName){"remote_push", 11};
        case TINY_RING_EVENT_REMOTE_INVALID: return (TinyRingName){"remote_invalid", 14};
        case TINY_RING_EVENT_REMOTE_DRAIN: return (TinyRingName){"remote_drain", 12};
        case TINY_RING_EVENT_OWNER_ACQUIRE: return (TinyRingName){"owner_acq", 9};
        case TINY_RING_EVENT_OWNER_RELEASE: return (TinyRingName){"owner_rel", 9};
        case TINY_RING_EVENT_FRONT_BYPASS: return (TinyRingName){"front_bypass", 12};
        case TINY_RING_EVENT_MAILBOX_PUBLISH: return (TinyRingName){"mailbox_publish", 15};
        case TINY_RING_EVENT_MAILBOX_FETCH: return (TinyRingName){"mailbox_fetch", 13};
        case TINY_RING_EVENT_MAILBOX_FETCH_NULL: return (TinyRingName){"mailbox_fetch_null", 18};
        default: return (TinyRingName){"unknown", 7};
    }
}

static void tiny_ring_write_dec(int fd, uint64_t value) {
    char buf[32];
    int pos = 31;
    if (value == 0) {
        buf[pos--] = '0';
    } else {
        while (value > 0 && pos >= 0) {
            buf[pos--] = (char)('0' + (value % 10));
            value /= 10;
        }
    }
    int len = 31 - pos;
    TINY_RING_IGNORE(write(fd, buf + pos + 1, len));
}

static void tiny_ring_write_hex(int fd, uintptr_t value) {
    static const char* hex = "0123456789abcdef";
    char buf[2 + sizeof(uintptr_t) * 2 + 1];
    buf[0] = '0';
    buf[1] = 'x';
    for (int i = (int)(sizeof(uintptr_t) * 2) - 1; i >= 0; --i) {
        buf[2 + i] = hex[value & 0xFu];
        value >>= 4;
    }
    buf[2 + sizeof(uintptr_t) * 2] = '\0';
    TINY_RING_IGNORE(write(fd, buf, 2 + sizeof(uintptr_t) * 2));
}

static void tiny_debug_ring_dump(int fd, uintptr_t fault_addr) {
    const char hdr[] = "\n[Tiny Debug Ring Dump]\n";
    TINY_RING_IGNORE(write(fd, hdr, sizeof(hdr) - 1));
    const char addr_prefix[] = "fault_addr=";
    TINY_RING_IGNORE(write(fd, addr_prefix, sizeof(addr_prefix) - 1));
    tiny_ring_write_hex(fd, fault_addr);
    TINY_RING_IGNORE(write(fd, "\n", 1));

    uint32_t head = atomic_load_explicit(&g_tiny_ring_head, memory_order_relaxed);
    uint32_t count = head < TINY_RING_CAP ? head : TINY_RING_CAP;
    for (uint32_t i = 0; i < count; i++) {
        uint32_t idx = (head - count + i) & (TINY_RING_CAP - 1u);
        TinyRingEntry ent = g_tiny_ring[idx];
        TINY_RING_IGNORE(write(fd, "[", 1));
        tiny_ring_write_dec(fd, idx);
        const char mid[] = "] event=";
        TINY_RING_IGNORE(write(fd, mid, sizeof(mid) - 1));
        TinyRingName name = tiny_ring_event_name(ent.event);
        TINY_RING_IGNORE(write(fd, name.name, name.len));
        const char cls[] = " class=";
        TINY_RING_IGNORE(write(fd, cls, sizeof(cls) - 1));
        tiny_ring_write_dec(fd, ent.class_idx);
        const char ptr_prefix[] = " ptr=";
        TINY_RING_IGNORE(write(fd, ptr_prefix, sizeof(ptr_prefix) - 1));
        tiny_ring_write_hex(fd, ent.ptr);
        const char aux_prefix[] = " aux=";
        TINY_RING_IGNORE(write(fd, aux_prefix, sizeof(aux_prefix) - 1));
        tiny_ring_write_hex(fd, ent.aux);
        TINY_RING_IGNORE(write(fd, "\n", 1));
    }
}

static void tiny_debug_ring_sigsegv(int signo, siginfo_t* info, void* uctx) {
    uintptr_t ip = 0;
#if defined(__x86_64__)
    if (uctx) {
        ucontext_t* uc = (ucontext_t*)uctx;
#ifdef REG_RIP
        ip = (uintptr_t)uc->uc_mcontext.gregs[REG_RIP];
#else
        (void)uc; // REG_RIP not available on this platform
#endif
    }
#endif
    if (g_tiny_ring_enabled) {
        uintptr_t fault = info ? (uintptr_t)info->si_addr : 0;
#if defined(__x86_64__)
#ifdef REG_RIP
        if (ip != 0) {
            const char rip_prefix[] = "rip=";
            TINY_RING_IGNORE(write(STDERR_FILENO, rip_prefix, sizeof(rip_prefix) - 1));
            tiny_ring_write_hex(STDERR_FILENO, ip);
            TINY_RING_IGNORE(write(STDERR_FILENO, "\n", 1));
        }
#endif
#endif
        tiny_debug_ring_dump(STDERR_FILENO, fault);
    }
    const char msg[] = "[Tiny Debug Ring] captured SIGSEGV\n";
    TINY_RING_IGNORE(write(STDERR_FILENO, msg, sizeof(msg) - 1));
#if defined(__x86_64__)
#ifdef REG_RIP
    if (ip != 0) {
        const char rip_prefix[] = "rip=";
        TINY_RING_IGNORE(write(STDERR_FILENO, rip_prefix, sizeof(rip_prefix) - 1));
        tiny_ring_write_hex(STDERR_FILENO, ip);
        TINY_RING_IGNORE(write(STDERR_FILENO, "\n", 1));
    }
#endif
#endif
    _exit(128 + signo);
}

static void tiny_debug_ring_sigusr(int signo, siginfo_t* info, void* uctx) {
    (void)signo;
    (void)info;
    (void)uctx;
    if (g_tiny_ring_enabled) {
        tiny_debug_ring_dump(STDERR_FILENO, 0);
        const char msg[] = "[Tiny Debug Ring] SIGUSR2 dump\n";
        TINY_RING_IGNORE(write(STDERR_FILENO, msg, sizeof(msg) - 1));
    }
}

void tiny_debug_ring_init(void) {
    if (g_tiny_ring_enabled) return;
    const char* env = getenv("HAKMEM_TINY_TRACE_RING");
    if (!(env && *env && env[0] != '0')) {
        return;
    }
    g_tiny_ring_enabled = 1;
    struct sigaction sa;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
    sa.sa_sigaction = tiny_debug_ring_sigsegv;
    sigaction(SIGSEGV, &sa, NULL);

    struct sigaction su;
    sigemptyset(&su.sa_mask);
    su.sa_flags = SA_SIGINFO | SA_RESTART;
    su.sa_sigaction = tiny_debug_ring_sigusr;
    sigaction(SIGUSR2, &su, NULL);
}

void tiny_debug_ring_record(uint16_t event, uint16_t class_idx, void* ptr, uintptr_t aux) {
    if (!g_tiny_ring_enabled) return;
    uint32_t idx = atomic_fetch_add_explicit(&g_tiny_ring_head, 1u, memory_order_relaxed);
    TinyRingEntry entry;
    entry.ptr = (uintptr_t)ptr;
    entry.aux = aux;
    entry.event = event;
    entry.class_idx = class_idx;
    g_tiny_ring[idx & (TINY_RING_CAP - 1u)] = entry;
}

__attribute__((constructor))
static void tiny_debug_ring_ctor(void) {
    tiny_debug_ring_init();
}