// pagefault_telemetry_box.c - Box PageFaultTelemetry implementation

#include "pagefault_telemetry_box.h"

#include "../hakmem_tiny_stats_api.h"  // For macros / flags
#include <stdio.h>
#include <stdlib.h>

// Per-thread state
__thread uint64_t g_pf_bloom[PF_BUCKET_MAX][16] = {{0}};
__thread uint64_t g_pf_touch[PF_BUCKET_MAX] = {0};

// Enable flag (cached)
int pagefault_telemetry_enabled(void) {
    static int g_enabled = -1;
    if (__builtin_expect(g_enabled == -1, 0)) {
        const char* env = getenv("HAKMEM_TINY_PAGEFAULT_TELEMETRY");
        g_enabled = (env && *env && *env != '0') ? 1 : 0;
    }
    return g_enabled;
}

// Dump helper
void pagefault_telemetry_dump(void) {
    if (!pagefault_telemetry_enabled()) {
        return;
    }

    const char* dump_env = getenv("HAKMEM_TINY_PAGEFAULT_DUMP");
    if (!(dump_env && *dump_env && *dump_env != '0')) {
        return;
    }

    fprintf(stderr, "\n========== Box PageFaultTelemetry: Tiny Page Touch Stats ==========\n");
    fprintf(stderr, "Note: pages ~= popcount(1024-bit bloom); collisions → 下限近似値\n\n");
    fprintf(stderr, "%-5s %12s %12s %12s\n", "Bucket", "touches", "approx_pages", "touches/page");
    fprintf(stderr, "------|------------|------------|------------\n");

    for (int b = 0; b < PF_BUCKET_MAX; b++) {
        uint64_t touches = g_pf_touch[b];
        if (touches == 0) {
            continue;
        }

        uint64_t bits = 0;
        for (int w = 0; w < 16; w++) {
            bits += (uint64_t)__builtin_popcountll(g_pf_bloom[b][w]);
        }

        double pages = (double)bits;
        double tpp = pages > 0.0 ? (double)touches / pages : 0.0;

        const char* name = NULL;
        char buf[8];
        if (b < PF_BUCKET_TINY_LIMIT) {
            snprintf(buf, sizeof(buf), "C%d", b);
            name = buf;
        } else if (b == PF_BUCKET_MID) {
            name = "MID";
        } else if (b == PF_BUCKET_L25) {
            name = "L25";
        } else if (b == PF_BUCKET_SS_META) {
            name = "SSM";
        } else {
            snprintf(buf, sizeof(buf), "X%d", b);
            name = buf;
        }

        fprintf(stderr, "%-5s %12llu %12llu %12.1f\n",
                name,
                (unsigned long long)touches,
                (unsigned long long)bits,
                tpp);
    }

    fprintf(stderr, "===============================================================\n\n");
}

// Auto-dump at thread exit (bench系で 1 回だけ実行される想定)
static void pagefault_telemetry_atexit(void) __attribute__((destructor));
static void pagefault_telemetry_atexit(void) {
    pagefault_telemetry_dump();
}