face_sdk/app/src/main/cpp/DebugLog.cpp

#include "DebugLog.h"

#include <android/log.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <unistd.h>

#include <cstdarg>
#include <cstdio>
#include <ctime>
#include <cstring>
#include <mutex>
#include <string>
#include <unordered_map>

namespace {

std::mutex  g_mtx;
FILE*       g_fp = nullptr;
std::string g_path;
constexpr size_t kMaxSize = 2 * 1024 * 1024; // 2 MB before rotation

// Throttle bookkeeping: one slot per distinct key passed to log_throttled().
struct ThrottleSlot {
    int64_t  last_emit_ms = 0; // when we last actually wrote a line for this key
    uint32_t suppressed   = 0; // number of calls swallowed since last_emit_ms
};
std::unordered_map<std::string, ThrottleSlot> g_throttle;
constexpr int64_t kThrottleWindowMs = 2000; // 2 seconds

pid_t currentTid() {
    return static_cast<pid_t>(syscall(SYS_gettid));
}

int64_t nowMs() {
    timespec ts{};
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return static_cast<int64_t>(ts.tv_sec) * 1000 + ts.tv_nsec / 1000000;
}

// Assumes g_mtx is held. Writes a single pre-formatted line to disk + logcat.
void writeLineLocked(const char* body) {
    pid_t tid = currentTid();

    timespec ts{};
    clock_gettime(CLOCK_REALTIME, &ts);
    struct tm tm_info{};
    localtime_r(&ts.tv_sec, &tm_info);
    char timebuf[32];
    strftime(timebuf, sizeof(timebuf), "%H:%M:%S", &tm_info);

    if (g_fp) {
        std::fprintf(g_fp, "[%s.%03ld][tid=%d] %s\n",
                     timebuf, ts.tv_nsec / 1000000, tid, body);
        std::fflush(g_fp);
    }
    __android_log_print(ANDROID_LOG_INFO, "FACE_DBG", "[tid=%d] %s", tid, body);
}

} // namespace

namespace DebugLog {

void init(const char* internalDataPath) {
    std::lock_guard<std::mutex> lk(g_mtx);
    if (g_fp) {
        return; // already initialized
    }

    const char* base = (internalDataPath && *internalDataPath) ? internalDataPath : "/data/local/tmp";
    g_path = std::string(base) + "/face_sdk_debug.log";

    // Rotate once if current file is too large.
    struct stat st{};
    if (stat(g_path.c_str(), &st) == 0 && static_cast<size_t>(st.st_size) > kMaxSize) {
        std::string backup = g_path + ".old";
        std::remove(backup.c_str());
        std::rename(g_path.c_str(), backup.c_str());
    }

    g_fp = std::fopen(g_path.c_str(), "a");
    if (g_fp) {
        time_t now = time(nullptr);
        struct tm tm_info{};
        localtime_r(&now, &tm_info);
        char tbuf[64];
        strftime(tbuf, sizeof(tbuf), "%Y-%m-%d %H:%M:%S", &tm_info);
        std::fprintf(g_fp,
                     "\n========== DebugLog opened @ %s (pid=%d) ==========\n",
                     tbuf, getpid());
        std::fflush(g_fp);
    }

    __android_log_print(ANDROID_LOG_INFO, "FACE_DBG",
                        "DebugLog file path: %s", g_path.c_str());
}

void log(const char* fmt, ...) {
    char buf[1024];
    va_list ap;
    va_start(ap, fmt);
    int n = std::vsnprintf(buf, sizeof(buf), fmt, ap);
    va_end(ap);
    if (n < 0) return;

    std::lock_guard<std::mutex> lk(g_mtx);
    writeLineLocked(buf);
}

void log_throttled(const char* key, const char* fmt, ...) {
    char buf[1024];
    va_list ap;
    va_start(ap, fmt);
    int n = std::vsnprintf(buf, sizeof(buf), fmt, ap);
    va_end(ap);
    if (n < 0) return;

    const char* k = key ? key : "";
    int64_t now = nowMs();

    std::lock_guard<std::mutex> lk(g_mtx);
    auto it = g_throttle.find(k);
    if (it == g_throttle.end()) {
        // First time we see this key -> always log.
        ThrottleSlot slot;
        slot.last_emit_ms = now;
        slot.suppressed   = 0;
        g_throttle.emplace(k, slot);
        writeLineLocked(buf);
        return;
    }

    ThrottleSlot& slot = it->second;
    int64_t elapsed = now - slot.last_emit_ms;
    if (elapsed < kThrottleWindowMs) {
        // Still inside the 2s window -> swallow.
        ++slot.suppressed;
        return;
    }

    // Window elapsed: emit the line, annotated with how many we swallowed.
    if (slot.suppressed > 0) {
        char annotated[1200];
        std::snprintf(annotated, sizeof(annotated),
                      "%s (repeated %u times in last %lldms, key=%s)",
                      buf, slot.suppressed, (long long)elapsed, k);
        writeLineLocked(annotated);
    } else {
        writeLineLocked(buf);
    }
    slot.last_emit_ms = now;
    slot.suppressed   = 0;
}

void flush() {
    std::lock_guard<std::mutex> lk(g_mtx);
    if (g_fp) std::fflush(g_fp);
}

std::string getLogPath() {
    std::lock_guard<std::mutex> lk(g_mtx);
    return g_path;
}

} // namespace DebugLog