#include "find_usb_serial_port.h"

#include <unistd.h>
#include <dirent.h>

/*---------------------------------------------------------------------*\
|                                                                       |
|   find_usb_serial_port                                                |
|                                                                       |
|   This function returns the name of the first USB serial port matching|
|   the given USB product and vendor ID.                                |
|                                                                       |
|   vid: Vendor ID code                                                 |
|   pid: Product ID code                                                |
|                                                                       |
|   returns: std::string containing port name "COMx" or "/dev/ttyX"     |
|                                                                       |
\*---------------------------------------------------------------------*/

std::string find_usb_serial_port(unsigned short vid, unsigned short pid)
{
    std::string     ret_string              = "";
    DIR*            dir;
    char            symlink_path[1024]      = {0};
    struct dirent*  ent;
    char            vid_pid[10]             = {0}; //Store VID/PID

    /*-----------------------------------------------------------------*\
    | Open /sys/class/tty                                               |
    \*-----------------------------------------------------------------*/
    dir = opendir("/sys/class/tty");

    if(dir == NULL)
    {
        return ret_string;
    }

    /*-----------------------------------------------------------------*\
    | Loop through all symlinks in /sys/class/tty directory to find     |
    | paths with "usb" in them.  These links should have the USB device |
    | index which can be used to find the VID/PID                       |
    \*-----------------------------------------------------------------*/
    ent = readdir(dir);

    while(ent != NULL)
    {
        if(ent->d_type == DT_LNK)
        {
            char tty_path[1024];
            strcpy(tty_path, "/sys/class/tty/");
            strcat(tty_path, ent->d_name);

            readlink(tty_path, symlink_path, 1024);

            char * usb_string = strstr(symlink_path, "usb");

            if(usb_string != NULL)
            {
                char * usb_dev = strstr(usb_string, "/");
                usb_dev++;
                usb_dev = strtok(usb_dev, "/");

                char usb_path[1024];

                strcpy(usb_path, "/sys/bus/usb/devices/");
                strcat(usb_path, usb_dev);

                char vendor_path[1024];
                char product_path[1024];

                strcpy(vendor_path, usb_path);
                strcat(vendor_path, "/idVendor");

                strcpy(product_path, usb_path);
                strcat(product_path, "/idProduct");

                std::ifstream vendor_file;
                std::ifstream product_file;
                std::string vendor_string;
                std::string product_string;

                vendor_file.open(vendor_path);
                product_file.open(product_path);

                std::getline(vendor_file, vendor_string);
                std::getline(product_file, product_string);

                snprintf(vid_pid, 10, "%04x", vid);

                if(strcmp(vid_pid, vendor_string.c_str()) == 0)
                {
                    snprintf(vid_pid, 10, "%04x", pid);
                    if(strcmp(vid_pid, product_string.c_str()) == 0)
                    {
                        char* port_string = NULL;
                        for(int i = strlen(tty_path); i > 0; i--)
                        {
                            if(tty_path[i] == '/')
                            {
                                port_string = &tty_path[i + 1];
                                break;
                            }
                        }
                        ret_string.append("/dev/");
                        ret_string.append(port_string);

                        return ret_string;
                    }
                }
            }
        }

        ent = readdir(dir);
    }

    return ret_string;

}   /* find_usb_serial_port() */