/*
* usbhelper.h
*
* Created 6 Apr 2014 by J. Palermo
* (C) Copyright 2014 J. Palermo, GNU GPLv3
* 
* Based on code from the following project:
*
* Project: AVR ATtiny USB Tutorial at http://codeandlife.com/
* Author: Joonas Pihlajamaa, joonas.pihlajamaa@iki.fi
* Based on V-USB example code by Christian Starkjohann
* Copyright: (C) 2012 by Joonas Pihlajamaa
* License: GNU GPL v3 (see License.txt)
*/

/* Used to get descriptor strings for device identification */
static int usbGetDescriptorString(usb_dev_handle *dev, int index, int langid, 
                                  char *buf, int buflen) {
    char buffer[256];
    int rval, i;

    // make standard request GET_DESCRIPTOR, type string and given index 
    // (e.g. dev->iProduct)
    rval = usb_control_msg(dev, 
        USB_TYPE_STANDARD | USB_RECIP_DEVICE | USB_ENDPOINT_IN, 
        USB_REQ_GET_DESCRIPTOR, (USB_DT_STRING << 8) + index, langid, 
        buffer, sizeof(buffer), 1000);

    if(rval < 0) // error
        return rval;

    // rval should be bytes read, but buffer[0] contains the actual response size
    if((unsigned char)buffer[0] < rval)
        rval = (unsigned char)buffer[0]; // string is shorter than bytes read

    if(buffer[1] != USB_DT_STRING) // second byte is the data type
        return 0; // invalid return type

    // we're dealing with UTF-16LE here so actual chars is half of rval,
    // and index 0 doesn't count
    rval /= 2;

    /* lossy conversion to ISO Latin1 */
    for(i = 1; i < rval && i < buflen; i++) {
        if(buffer[2 * i + 1] == 0)
            buf[i-1] = buffer[2 * i];
        else
            buf[i-1] = '?'; /* outside of ISO Latin1 range */
    }
    buf[i-1] = 0;

    return i-1;
}

/******************************************************************************/
static usb_dev_handle * usbOpenDevice(int vendor, char *vendorName, 
                                      int product, char *productName) {
    struct usb_bus *bus;
    struct usb_device *dev;
    char devVendor[256], devProduct[256];

    usb_dev_handle * handle = NULL;

    usb_init();
    usb_find_busses();
    usb_find_devices();

    for(bus=usb_get_busses(); bus; bus=bus->next) {
        for(dev=bus->devices; dev; dev=dev->next) {                     
            if(dev->descriptor.idVendor != vendor ||
               dev->descriptor.idProduct != product)
                continue;

            /* we need to open the device in order to query strings */
            if(!(handle = usb_open(dev))) {
                fprintf(stderr, "Warning: cannot open USB device: %sn",
                        usb_strerror());
                continue;
            }

            /* get vendor name */
            if(usbGetDescriptorString(handle, dev->descriptor.iManufacturer, 
                                      0x0409, devVendor, sizeof(devVendor)) < 0) {
                fprintf(stderr, 
                        "Warning: cannot query manufacturer for device: %sn", 
                        usb_strerror());
                usb_close(handle);
                continue;
            }

            /* get product name */
            if(usbGetDescriptorString(handle, dev->descriptor.iProduct, 
                                      0x0409, devProduct, sizeof(devVendor)) < 0) {
                fprintf(stderr, 
                        "Warning: cannot query product for device: %sn", 
                        usb_strerror());
                usb_close(handle);
                continue;
            }

            if(strcmp(devVendor, vendorName) == 0 && 
               strcmp(devProduct, productName) == 0)
                return handle;
            else
                usb_close(handle);
        }
    }

    return NULL;
}