/*
 * Loosely based on a mix of:
 *   - xorg-xinput
 *     https://github.com/freedesktop/xorg-xinput/blob/master/src/property.c::print_property_xi2
 *   - xkbcat
 *     https://github.com/anko/xkbcat
*/

#define _GNU_SOURCE

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>

#include <X11/extensions/XInput2.h>
#include <X11/Xatom.h>


char* get_property_xi2(Display* dpy, int deviceid, Atom property, const char* property_name)
{
    Atom act_type;
    char* name;
    int act_format;
    unsigned long nitems, bytes_after;
    unsigned char* data;
    unsigned char* ptr;
    int j, done = False;
    char* ret = NULL;

    name = XGetAtomName(dpy, property);
    bool interested_in_property = (strcmp(name, property_name) == 0);
    XFree(name);
    if (!interested_in_property)
        return ret;

    if (XIGetProperty(dpy, deviceid, property, 0, 1000, False,
                           AnyPropertyType, &act_type, &act_format,
                           &nitems, &bytes_after, &data) == Success)
    {
        ptr = data;
        for (j = 0; j < nitems; j++)
        {
            switch(act_type)
            {
                case XA_STRING:
                    if (act_format != 8)
                    {
                        //Unknown string format
                        done = True;
                        break;
                    }

                    int len = strlen((char*)ptr);
                    ret = strdup((const char*)ptr);

                    j += len;   // The loop's j++ jumps over the terminating 0
                    ptr += len; // ptr += size below jumps over the terminating 0
                    break;

                default:
                    // Unknown type
                    done = True;
                    break;
            }
            ptr += act_format/8;
            if (done == True)
                break;
        }
        XFree(data);
    }
    return ret;
}

int is_xinput2_available(Display* disp)
{
    int xiOpcode;
    int queryEvent, queryError;
    if (! XQueryExtension(disp, "XInputExtension", &xiOpcode, &queryEvent, &queryError))
    {
        fprintf(stderr, "XInput extension not available\n");
        return -1;
    }

    int major = 2, minor = 0;
    int queryResult = XIQueryVersion(disp, &major, &minor);
    if (queryResult == BadRequest)
    {
        fprintf(stderr, "XInput 2.0 support required (got %d.%d)\n", major, minor);
        return -2;
    }
    else if (queryResult != Success)
    {
        fprintf(stderr, "XIQueryVersion failed\n");
        return -3;
    }

    return 0;
}

typedef struct SlaveInfo
{
    char* slave_names;
    char* dev_nodes;
} SlaveInfo;

SlaveInfo new_slave_info()
{
    SlaveInfo si;
    si.slave_names = NULL;
    si.dev_nodes = NULL;
    return si;
}

void free_slave_info(SlaveInfo si)
{
    free(si.slave_names);
    free(si.dev_nodes);
    si.slave_names = NULL;
    si.dev_nodes = NULL;
}

bool is_empty_slave_info(SlaveInfo si)
{
    return (si.slave_names == NULL || si.dev_nodes == NULL);
}

void replace(char* str, char old, char new)
{
    int i = 0;
    while (str[i] != '\0')
    {
        if (str[i] == old)
            str[i] = new;
        i++;
    }
}

int append_as_line(char** dst, char* line)
{
    uint len_newstr = strlen(line) + 2;
    if (*dst != NULL)
        len_newstr += strlen(*dst);

    char* newstr = (char*)malloc(len_newstr);
    if (newstr == NULL)
        return -1;

    newstr[0] = '\0';
    replace(line, '\n', ' ');
    if (*dst != NULL)
        strcat(newstr, *dst);
    strcat(newstr, line);
    strcat(newstr, "\n");

    free(*dst);
    *dst = newstr;
    return 0;
}

SlaveInfo get_slave_info(Display* disp)
{
	int num_slaves;
	XIDeviceInfo* all_slaves = XIQueryDevice(disp, XIAllDevices, &num_slaves);
    SlaveInfo slaveinfo = new_slave_info();
    bool fail = false;

	for (int i = 0; i < num_slaves; i++)
	{
		XIDeviceInfo* current_slave = &all_slaves[i];
        int nprops;
        Atom* props = XIListProperties(disp, current_slave->deviceid, &nprops);

        while(nprops-- && !fail)
        {
            char* devnode = get_property_xi2(disp, current_slave->deviceid, props[nprops], "Device Node");
            if (current_slave->name != NULL && devnode != NULL)
            {
                int append_slave_success = append_as_line(&slaveinfo.slave_names, current_slave->name);
                int append_devnode_success = append_as_line(&slaveinfo.dev_nodes, devnode);
                if (append_slave_success != 0 || append_devnode_success != 0)
                    fail = true;
            }
            free(devnode);
        }
        XFree(props);
        if (fail)
        {
            free_slave_info(slaveinfo);
            break;
        }

	}
	XIFreeDeviceInfo(all_slaves);
    return slaveinfo;
}

Display* connect_to_x(const char* xDisplayName)
{
    Display* disp = XOpenDisplay(xDisplayName);
    if (NULL == disp)
    {
        fprintf(stderr, "Cannot open X display '%s'\n", xDisplayName);
        return NULL;
    }

    if (is_xinput2_available(disp) != 0)
    {
        XCloseDisplay(disp);
        return NULL;
    }

    return disp;
}


int main(int argc, char * argv[])
{
    char* xDisplayName = getenv("DISPLAY");
    if (xDisplayName == NULL)
    {
        fprintf(stderr, "DISPLAY environment variable not found\n");
        exit(1);
    }

    Display* disp = connect_to_x(xDisplayName);
    if (disp == NULL)
        exit(1);

    SlaveInfo si = get_slave_info(disp);
    if (!is_empty_slave_info(si))
    {
        printf("%s", si.slave_names);
        printf("%s", si.dev_nodes);
    }

    free_slave_info(si);
    XCloseDisplay(disp);
    exit(0);
}