#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <ntlite/syscall.h>
#include <ntlite/console_service.h>

static int u64_to_string(uint64_t n, char* buf) {
    int i = 0;
    if (n == 0) {
        buf[i++] = '0';
        buf[i] = '\0';
        return i;
    }
    char rev[24];
    int r_idx = 0;
    while (n > 0) {
        rev[r_idx++] = (char)('0' + (n % 10));
        n /= 10;
    }
    while (r_idx > 0) {
        buf[i++] = rev[--r_idx];
    }
    buf[i] = '\0';
    return i;
}

int main(void) {
    NTL_CONSOLE_INFO console;
    SYS_MEMORY_STATUS mem;
    char metricsBuf[128];
    size_t previousLength = 0;

    while (true) {
        if (NtlConsoleQueryInfo(SYS_HANDLE_INVALID, &console) == NTLSTATUS_SUCCESS &&
            SysGetMemoryStatus(&mem) == NTLSTATUS_SUCCESS) {

            // If the system isn't reporting columns correctly, default to a safe standard width
            int columns = (console.Columns > 0) ? (int)console.Columns : 80;

            char freeStr[24], poolStr[24], heapStr[24];
            u64_to_string(mem.FreePhysicalBytes / 1024u, freeStr);
            u64_to_string(mem.KernelPoolBytes / 1024u, poolStr);
            u64_to_string(mem.UserHeapBytes / 1024u, heapStr);

            metricsBuf[0] = '\0';
            strcat(metricsBuf, "[ Free: ");
            strcat(metricsBuf, freeStr);
            strcat(metricsBuf, "K | Pool: ");
            strcat(metricsBuf, poolStr);
            strcat(metricsBuf, "K | Heap: ");
            strcat(metricsBuf, heapStr);
            strcat(metricsBuf, "K ]");

            size_t textLen = strlen(metricsBuf);
            // Erase any trailing characters left by a longer previous sample.
            if (previousLength > textLen && previousLength < sizeof(metricsBuf)) {
                memset(metricsBuf + textLen, ' ', previousLength - textLen);
                textLen = previousLength;
            }
            int targetX = columns - (int)textLen;
            if (targetX >= 0) {
                size_t written = 0;
                if (NtlConsoleWriteAt(SYS_HANDLE_INVALID, targetX, 0,
                                      metricsBuf, textLen, &written) == NTLSTATUS_SUCCESS &&
                    written == textLen)
                    previousLength = textLen;
            }
        }

        SysSleep(2000);
    }
    return 0;
}