/*
Copyright (c) 2012-2016 Ben Croston

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#include "Python.h"
#include "c_gpio.h"
#include "event_gpio.h"
#include "py_pwm.h"
#include "cpuinfo.h"
#include "constants.h"
#include "common.h"

static PyObject *rpi_revision; // deprecated
static PyObject *board_info;
static int gpio_warnings = 1;

struct py_callback
{
   unsigned int gpio;
   PyObject *py_cb;
   struct py_callback *next;
};
static struct py_callback *py_callbacks = NULL;

static int mmap_gpio_mem(void)
{
   int result;

   if (module_setup)
      return 0;

   result = setup();
   if (result == SETUP_DEVMEM_FAIL)
   {
      PyErr_SetString(PyExc_RuntimeError, "No access to /dev/mem.  Try running as root!");
      return 1;
   } else if (result == SETUP_MALLOC_FAIL) {
      PyErr_NoMemory();
      return 2;
   } else if (result == SETUP_MMAP_FAIL) {
      PyErr_SetString(PyExc_RuntimeError, "Mmap of GPIO registers failed");
      return 3;
   } else if (result == SETUP_CPUINFO_FAIL) {
      PyErr_SetString(PyExc_RuntimeError, "Unable to open /proc/cpuinfo");
      return 4;
   } else if (result == SETUP_NOT_RPI_FAIL) {
      PyErr_SetString(PyExc_RuntimeError, "Not running on a RPi!");
      return 5;
   } else { // result == SETUP_OK
      module_setup = 1;
      return 0;
   }
}

// python function cleanup(channel=None)
static PyObject *py_cleanup(PyObject *self, PyObject *args, PyObject *kwargs)
{
   int i;
   int chancount = -666;
   int found = 0;
   int channel = -666;
   unsigned int gpio;
   PyObject *chanlist = NULL;
   PyObject *chantuple = NULL;
   PyObject *tempobj;
   static char *kwlist[] = {"channel", NULL};

   void cleanup_one(void)
   {
      // clean up any /sys/class exports
      event_cleanup(gpio);

      // set everything back to input
      if (gpio_direction[gpio] != -1) {
         setup_gpio(gpio, INPUT, PUD_OFF);
         gpio_direction[gpio] = -1;
         found = 1;
      }
   }

   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", kwlist, &chanlist))
      return NULL;

   if (chanlist == NULL) {  // channel kwarg not set
      // do nothing
#if PY_MAJOR_VERSION > 2
   } else if (PyLong_Check(chanlist)) {
      channel = (int)PyLong_AsLong(chanlist);
#else
   } else if (PyInt_Check(chanlist)) {
      channel = (int)PyInt_AsLong(chanlist);
#endif
      if (PyErr_Occurred())
         return NULL;
      chanlist = NULL;
   } else if (PyList_Check(chanlist)) {
      chancount = PyList_Size(chanlist);
   } else if (PyTuple_Check(chanlist)) {
      chantuple = chanlist;
      chanlist = NULL;
      chancount = PyTuple_Size(chantuple);
   } else {
      // raise exception
      PyErr_SetString(PyExc_ValueError, "Channel must be an integer or list/tuple of integers");
      return NULL;
   }

   if (module_setup && !setup_error) {
      if (channel == -666 && chancount == -666) {   // channel not set - cleanup everything
         // clean up any /sys/class exports
         event_cleanup_all();

         // set everything back to input
         for (i=0; i<54; i++) {
            if (gpio_direction[i] != -1) {
               setup_gpio(i, INPUT, PUD_OFF);
               gpio_direction[i] = -1;
               found = 1;
            }
         }
         gpio_mode = MODE_UNKNOWN;
      } else if (channel != -666) {    // channel was an int indicating single channel
         if (get_gpio_number(channel, &gpio))
            return NULL;
         cleanup_one();
      } else {  // channel was a list/tuple
         for (i=0; i<chancount; i++) {
            if (chanlist) {
               if ((tempobj = PyList_GetItem(chanlist, i)) == NULL) {
                  return NULL;
               }
            } else { // assume chantuple
               if ((tempobj = PyTuple_GetItem(chantuple, i)) == NULL) {
                  return NULL;
               }
            }

#if PY_MAJOR_VERSION > 2
            if (PyLong_Check(tempobj)) {
               channel = (int)PyLong_AsLong(tempobj);
#else
            if (PyInt_Check(tempobj)) {
               channel = (int)PyInt_AsLong(tempobj);
#endif
               if (PyErr_Occurred())
                  return NULL;
            } else {
               PyErr_SetString(PyExc_ValueError, "Channel must be an integer");
               return NULL;
            }

            if (get_gpio_number(channel, &gpio))
               return NULL;
            cleanup_one();
         }
      }
   }

   // check if any channels set up - if not warn about misuse of GPIO.cleanup()
   if (!found && gpio_warnings) {
      PyErr_WarnEx(NULL, "No channels have been set up yet - nothing to clean up!  Try cleaning up at the end of your program instead!", 1);
   }

   Py_RETURN_NONE;
}

// python function setup(channel(s), direction, pull_up_down=PUD_OFF, initial=None)
static PyObject *py_setup_channel(PyObject *self, PyObject *args, PyObject *kwargs)
{
   unsigned int gpio;
   int channel = -1;
   int direction;
   int i, chancount;
   PyObject *chanlist = NULL;
   PyObject *chantuple = NULL;
   PyObject *tempobj;
   int pud = PUD_OFF + PY_PUD_CONST_OFFSET;
   int initial = -1;
   static char *kwlist[] = {"channel", "direction", "pull_up_down", "initial", NULL};
   int func;

   int setup_one(void) {
      if (get_gpio_number(channel, &gpio))
         return 0;

      func = gpio_function(gpio);
      if (gpio_warnings &&                             // warnings enabled and
          ((func != 0 && func != 1) ||                 // (already one of the alt functions or
          (gpio_direction[gpio] == -1 && func == 1)))  // already an output not set from this program)
      {
         PyErr_WarnEx(NULL, "This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.", 1);
      }

      // warn about pull/up down on i2c channels
      if (gpio_warnings) {
         if (rpiinfo.p1_revision == 0) { // compute module - do nothing
         } else if ((rpiinfo.p1_revision == 1 && (gpio == 0 || gpio == 1)) ||
                    (gpio == 2 || gpio == 3)) {
            if (pud == PUD_UP || pud == PUD_DOWN)
               PyErr_WarnEx(NULL, "A physical pull up resistor is fitted on this channel!", 1);
         }
      }

      if (direction == OUTPUT && (initial == LOW || initial == HIGH)) {
         output_gpio(gpio, initial);
      }
      setup_gpio(gpio, direction, pud);
      gpio_direction[gpio] = direction;
      return 1;
   }

   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "Oi|ii", kwlist, &chanlist, &direction, &pud, &initial))
      return NULL;

#if PY_MAJOR_VERSION > 2
   if (PyLong_Check(chanlist)) {
      channel = (int)PyLong_AsLong(chanlist);
#else
   if (PyInt_Check(chanlist)) {
      channel = (int)PyInt_AsLong(chanlist);
#endif
      if (PyErr_Occurred())
         return NULL;
      chanlist = NULL;
   } else if (PyList_Check(chanlist)) {
      // do nothing
   } else if (PyTuple_Check(chanlist)) {
      chantuple = chanlist;
      chanlist = NULL;
   } else {
      // raise exception
      PyErr_SetString(PyExc_ValueError, "Channel must be an integer or list/tuple of integers");
      return NULL;
   }

   // check module has been imported cleanly
   if (setup_error)
   {
      PyErr_SetString(PyExc_RuntimeError, "Module not imported correctly!");
      return NULL;
   }

   if (mmap_gpio_mem())
      return NULL;

   if (direction != INPUT && direction != OUTPUT) {
      PyErr_SetString(PyExc_ValueError, "An invalid direction was passed to setup()");
      return 0;
   }

   if (direction == OUTPUT && pud != PUD_OFF + PY_PUD_CONST_OFFSET) {
      PyErr_SetString(PyExc_ValueError, "pull_up_down parameter is not valid for outputs");
      return 0;
   }

   if (direction == INPUT && initial != -1) {
      PyErr_SetString(PyExc_ValueError, "initial parameter is not valid for inputs");
      return 0;
   }

   if (direction == OUTPUT)
      pud = PUD_OFF + PY_PUD_CONST_OFFSET;

   pud -= PY_PUD_CONST_OFFSET;
   if (pud != PUD_OFF && pud != PUD_DOWN && pud != PUD_UP) {
      PyErr_SetString(PyExc_ValueError, "Invalid value for pull_up_down - should be either PUD_OFF, PUD_UP or PUD_DOWN");
      return NULL;
   }

   if (chanlist) {
       chancount = PyList_Size(chanlist);
   } else if (chantuple) {
       chancount = PyTuple_Size(chantuple);
   } else {
       if (!setup_one())
          return NULL;
       Py_RETURN_NONE;
   }

   for (i=0; i<chancount; i++) {
      if (chanlist) {
         if ((tempobj = PyList_GetItem(chanlist, i)) == NULL) {
            return NULL;
         }
      } else { // assume chantuple
         if ((tempobj = PyTuple_GetItem(chantuple, i)) == NULL) {
            return NULL;
         }
      }

#if PY_MAJOR_VERSION > 2
      if (PyLong_Check(tempobj)) {
         channel = (int)PyLong_AsLong(tempobj);
#else
      if (PyInt_Check(tempobj)) {
         channel = (int)PyInt_AsLong(tempobj);
#endif
         if (PyErr_Occurred())
             return NULL;
      } else {
          PyErr_SetString(PyExc_ValueError, "Channel must be an integer");
          return NULL;
      }

      if (!setup_one())
         return NULL;
   }

   Py_RETURN_NONE;
}

// python function output(channel(s), value(s))
static PyObject *py_output_gpio(PyObject *self, PyObject *args)
{
   unsigned int gpio;
   int channel = -1;
   int value = -1;
   int i;
   PyObject *chanlist = NULL;
   PyObject *valuelist = NULL;
   PyObject *chantuple = NULL;
   PyObject *valuetuple = NULL;
   PyObject *tempobj = NULL;
   int chancount = -1;
   int valuecount = -1;

   int output(void) {
      if (get_gpio_number(channel, &gpio))
          return 0;

      if (gpio_direction[gpio] != OUTPUT)
      {
         PyErr_SetString(PyExc_RuntimeError, "The GPIO channel has not been set up as an OUTPUT");
         return 0;
      }

      if (check_gpio_priv())
         return 0;

      output_gpio(gpio, value);
      return 1;
   }

   if (!PyArg_ParseTuple(args, "OO", &chanlist, &valuelist))
       return NULL;

#if PY_MAJOR_VERSION >= 3
   if (PyLong_Check(chanlist)) {
      channel = (int)PyLong_AsLong(chanlist);
#else
   if (PyInt_Check(chanlist)) {
      channel = (int)PyInt_AsLong(chanlist);
#endif
      if (PyErr_Occurred())
         return NULL;
      chanlist = NULL;
   } else if (PyList_Check(chanlist)) {
      // do nothing
   } else if (PyTuple_Check(chanlist)) {
      chantuple = chanlist;
      chanlist = NULL;
   } else {
       PyErr_SetString(PyExc_ValueError, "Channel must be an integer or list/tuple of integers");
       return NULL;
   }

#if PY_MAJOR_VERSION >= 3
   if (PyLong_Check(valuelist)) {
       value = (int)PyLong_AsLong(valuelist);
#else
   if (PyInt_Check(valuelist)) {
       value = (int)PyInt_AsLong(valuelist);
#endif
      if (PyErr_Occurred())
         return NULL;
       valuelist = NULL;
   } else if (PyList_Check(valuelist)) {
      // do nothing
   } else if (PyTuple_Check(valuelist)) {
      valuetuple = valuelist;
      valuelist = NULL;
   } else {
       PyErr_SetString(PyExc_ValueError, "Value must be an integer/boolean or a list/tuple of integers/booleans");
       return NULL;
   }

   if (chanlist)
       chancount = PyList_Size(chanlist);
   if (chantuple)
       chancount = PyTuple_Size(chantuple);
   if (valuelist)
       valuecount = PyList_Size(valuelist);
   if (valuetuple)
       valuecount = PyTuple_Size(valuetuple);
   if ((chancount != -1 && chancount != valuecount && valuecount != -1) || (chancount == -1 && valuecount != -1)) {
       PyErr_SetString(PyExc_RuntimeError, "Number of channels != number of values");
       return NULL;
   }

   if (chancount == -1) {
      if (!output())
         return NULL;
      Py_RETURN_NONE;
   }

   for (i=0; i<chancount; i++) {
      // get channel number
      if (chanlist) {
         if ((tempobj = PyList_GetItem(chanlist, i)) == NULL) {
            return NULL;
         }
      } else { // assume chantuple
         if ((tempobj = PyTuple_GetItem(chantuple, i)) == NULL) {
            return NULL;
         }
      }

#if PY_MAJOR_VERSION >= 3
      if (PyLong_Check(tempobj)) {
         channel = (int)PyLong_AsLong(tempobj);
#else
      if (PyInt_Check(tempobj)) {
         channel = (int)PyInt_AsLong(tempobj);
#endif
         if (PyErr_Occurred())
             return NULL;
      } else {
          PyErr_SetString(PyExc_ValueError, "Channel must be an integer");
          return NULL;
      }

      // get value
      if (valuecount > 0) {
          if (valuelist) {
             if ((tempobj = PyList_GetItem(valuelist, i)) == NULL) {
                return NULL;
             }
          } else { // assume valuetuple
             if ((tempobj = PyTuple_GetItem(valuetuple, i)) == NULL) {
                return NULL;
             }
          }
#if PY_MAJOR_VERSION >= 3
          if (PyLong_Check(tempobj)) {
             value = (int)PyLong_AsLong(tempobj);
#else
          if (PyInt_Check(tempobj)) {
             value = (int)PyInt_AsLong(tempobj);
#endif
             if (PyErr_Occurred())
                 return NULL;
          } else {
              PyErr_SetString(PyExc_ValueError, "Value must be an integer or boolean");
              return NULL;
          }
      }
      if (!output())
         return NULL;
   }

   Py_RETURN_NONE;
}

// python function value = input(channel)
static PyObject *py_input_gpio(PyObject *self, PyObject *args)
{
   unsigned int gpio;
   int channel;
   PyObject *value;

   if (!PyArg_ParseTuple(args, "i", &channel))
      return NULL;

   if (get_gpio_number(channel, &gpio))
       return NULL;

   // check channel is set up as an input or output
   if (gpio_direction[gpio] != INPUT && gpio_direction[gpio] != OUTPUT)
   {
      PyErr_SetString(PyExc_RuntimeError, "You must setup() the GPIO channel first");
      return NULL;
   }

   if (check_gpio_priv())
      return NULL;

   if (input_gpio(gpio)) {
      value = Py_BuildValue("i", HIGH);
   } else {
      value = Py_BuildValue("i", LOW);
   }
   return value;
}

// python function setmode(mode)
static PyObject *py_setmode(PyObject *self, PyObject *args)
{
   int new_mode;

   if (!PyArg_ParseTuple(args, "i", &new_mode))
      return NULL;

   if (gpio_mode != MODE_UNKNOWN && new_mode != gpio_mode)
   {
      PyErr_SetString(PyExc_ValueError, "A different mode has already been set!");
      return NULL;
   }

   if (setup_error)
   {
      PyErr_SetString(PyExc_RuntimeError, "Module not imported correctly!");
      return NULL;
   }

   if (new_mode != BOARD && new_mode != BCM)
   {
      PyErr_SetString(PyExc_ValueError, "An invalid mode was passed to setmode()");
      return NULL;
   }

   if (rpiinfo.p1_revision == 0 && new_mode == BOARD)
   {
      PyErr_SetString(PyExc_RuntimeError, "BOARD numbering system not applicable on compute module");
      return NULL;
   }

   gpio_mode = new_mode;
   Py_RETURN_NONE;
}

// python function getmode()
static PyObject *py_getmode(PyObject *self, PyObject *args)
{
   PyObject *value;

   if (setup_error)
   {
      PyErr_SetString(PyExc_RuntimeError, "Module not imported correctly!");
      return NULL;
   }

   if (gpio_mode == MODE_UNKNOWN)
      Py_RETURN_NONE;

   value = Py_BuildValue("i", gpio_mode);
   return value;
}

static unsigned int chan_from_gpio(unsigned int gpio)
{
   int chan;
   int chans;

   if (gpio_mode == BCM)
      return gpio;
   if (rpiinfo.p1_revision == 0)   // not applicable for compute module
      return -1;
   else if (rpiinfo.p1_revision == 1 || rpiinfo.p1_revision == 2)
      chans = 26;
   else
      chans = 40;
   for (chan=1; chan<=chans; chan++)
      if (*(*pin_to_gpio+chan) == gpio)
         return chan;
   return -1;
}

static void run_py_callbacks(unsigned int gpio)
{
   PyObject *result;
   PyGILState_STATE gstate;
   struct py_callback *cb = py_callbacks;

   while (cb != NULL)
   {
      if (cb->gpio == gpio) {
         // run callback
         gstate = PyGILState_Ensure();
         result = PyObject_CallFunction(cb->py_cb, "i", chan_from_gpio(gpio));
         if (result == NULL && PyErr_Occurred()){
            PyErr_Print();
            PyErr_Clear();
         }
         Py_XDECREF(result);
         PyGILState_Release(gstate);
      }
      cb = cb->next;
   }
}

static int add_py_callback(unsigned int gpio, PyObject *cb_func)
{
   struct py_callback *new_py_cb;
   struct py_callback *cb = py_callbacks;

   // add callback to py_callbacks list
   new_py_cb = malloc(sizeof(struct py_callback));
   if (new_py_cb == 0)
   {
      PyErr_NoMemory();
      return -1;
   }
   new_py_cb->py_cb = cb_func;
   Py_XINCREF(cb_func);         // Add a reference to new callback
   new_py_cb->gpio = gpio;
   new_py_cb->next = NULL;
   if (py_callbacks == NULL) {
      py_callbacks = new_py_cb;
   } else {
      // add to end of list
      while (cb->next != NULL)
         cb = cb->next;
      cb->next = new_py_cb;
   }
   add_edge_callback(gpio, run_py_callbacks);
   return 0;
}

// python function add_event_callback(gpio, callback)
static PyObject *py_add_event_callback(PyObject *self, PyObject *args, PyObject *kwargs)
{
   unsigned int gpio;
   int channel;
   PyObject *cb_func;
   char *kwlist[] = {"gpio", "callback", NULL};

   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "iO|i", kwlist, &channel, &cb_func))
      return NULL;

   if (!PyCallable_Check(cb_func))
   {
      PyErr_SetString(PyExc_TypeError, "Parameter must be callable");
      return NULL;
   }

   if (get_gpio_number(channel, &gpio))
       return NULL;

   // check channel is set up as an input
   if (gpio_direction[gpio] != INPUT)
   {
      PyErr_SetString(PyExc_RuntimeError, "You must setup() the GPIO channel as an input first");
      return NULL;
   }

   if (!gpio_event_added(gpio))
   {
      PyErr_SetString(PyExc_RuntimeError, "Add event detection using add_event_detect first before adding a callback");
      return NULL;
   }

   if (add_py_callback(gpio, cb_func) != 0)
      return NULL;

   Py_RETURN_NONE;
}

// python function add_event_detect(gpio, edge, callback=None, bouncetime=None)
static PyObject *py_add_event_detect(PyObject *self, PyObject *args, PyObject *kwargs)
{
   unsigned int gpio;
   int channel, edge, result;
   int bouncetime = -666;
   PyObject *cb_func = NULL;
   char *kwlist[] = {"gpio", "edge", "callback", "bouncetime", NULL};

   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "ii|Oi", kwlist, &channel, &edge, &cb_func, &bouncetime))
      return NULL;

   if (cb_func != NULL && !PyCallable_Check(cb_func))
   {
      PyErr_SetString(PyExc_TypeError, "Parameter must be callable");
      return NULL;
   }

   if (get_gpio_number(channel, &gpio))
       return NULL;

   // check channel is set up as an input
   if (gpio_direction[gpio] != INPUT)
   {
      PyErr_SetString(PyExc_RuntimeError, "You must setup() the GPIO channel as an input first");
      return NULL;
   }

   // is edge valid value
   edge -= PY_EVENT_CONST_OFFSET;
   if (edge != RISING_EDGE && edge != FALLING_EDGE && edge != BOTH_EDGE)
   {
      PyErr_SetString(PyExc_ValueError, "The edge must be set to RISING, FALLING or BOTH");
      return NULL;
   }

   if (bouncetime <= 0 && bouncetime != -666)
   {
      PyErr_SetString(PyExc_ValueError, "Bouncetime must be greater than 0");
      return NULL;
   }

   if (check_gpio_priv())
      return NULL;

   if ((result = add_edge_detect(gpio, edge, bouncetime)) != 0)   // starts a thread
   {
      if (result == 1)
      {
         PyErr_SetString(PyExc_RuntimeError, "Conflicting edge detection already enabled for this GPIO channel");
         return NULL;
      } else {
         PyErr_SetString(PyExc_RuntimeError, "Failed to add edge detection");
         return NULL;
      }
   }

   if (cb_func != NULL)
      if (add_py_callback(gpio, cb_func) != 0)
         return NULL;

   Py_RETURN_NONE;
}

// python function remove_event_detect(gpio)
static PyObject *py_remove_event_detect(PyObject *self, PyObject *args)
{
   unsigned int gpio;
   int channel;
   struct py_callback *cb = py_callbacks;
   struct py_callback *temp;
   struct py_callback *prev = NULL;

   if (!PyArg_ParseTuple(args, "i", &channel))
      return NULL;

   if (get_gpio_number(channel, &gpio))
       return NULL;

   // remove all python callbacks for gpio
   while (cb != NULL)
   {
      if (cb->gpio == gpio)
      {
         Py_XDECREF(cb->py_cb);
         if (prev == NULL)
            py_callbacks = cb->next;
         else
            prev->next = cb->next;
         temp = cb;
         cb = cb->next;
         free(temp);
      } else {
         prev = cb;
         cb = cb->next;
      }
   }

   if (check_gpio_priv())
      return NULL;

   remove_edge_detect(gpio);

   Py_RETURN_NONE;
}

// python function value = event_detected(channel)
static PyObject *py_event_detected(PyObject *self, PyObject *args)
{
   unsigned int gpio;
   int channel;

   if (!PyArg_ParseTuple(args, "i", &channel))
      return NULL;

   if (get_gpio_number(channel, &gpio))
       return NULL;

   if (event_detected(gpio))
      Py_RETURN_TRUE;
   else
      Py_RETURN_FALSE;
}

// python function channel = wait_for_edge(channel, edge, bouncetime=None, timeout=None)
static PyObject *py_wait_for_edge(PyObject *self, PyObject *args, PyObject *kwargs)
{
   unsigned int gpio;
   int channel, edge, result;
   int bouncetime = -666; // None
   int timeout = -1; // None

   static char *kwlist[] = {"channel", "edge", "bouncetime", "timeout", NULL};

   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "ii|ii", kwlist, &channel, &edge, &bouncetime, &timeout))
      return NULL;

   if (get_gpio_number(channel, &gpio))
      return NULL;

   // check channel is setup as an input
   if (gpio_direction[gpio] != INPUT)
   {
      PyErr_SetString(PyExc_RuntimeError, "You must setup() the GPIO channel as an input first");
      return NULL;
   }

   // is edge a valid value?
   edge -= PY_EVENT_CONST_OFFSET;
   if (edge != RISING_EDGE && edge != FALLING_EDGE && edge != BOTH_EDGE)
   {
      PyErr_SetString(PyExc_ValueError, "The edge must be set to RISING, FALLING or BOTH");
      return NULL;
   }

   if (bouncetime <= 0 && bouncetime != -666)
   {
      PyErr_SetString(PyExc_ValueError, "Bouncetime must be greater than 0");
      return NULL;
   }

   if (timeout <= 0 && timeout != -1)
   {
      PyErr_SetString(PyExc_ValueError, "Timeout must be greater than 0");
      return NULL;
   }

   if (check_gpio_priv())
      return NULL;

   Py_BEGIN_ALLOW_THREADS // disable GIL
   result = blocking_wait_for_edge(gpio, edge, bouncetime, timeout);
   Py_END_ALLOW_THREADS   // enable GIL

   if (result == 0) {
      Py_RETURN_NONE;
   } else if (result == -1) {
      PyErr_SetString(PyExc_RuntimeError, "Conflicting edge detection events already exist for this GPIO channel");
      return NULL;
   } else if (result == -2) {
      PyErr_SetString(PyExc_RuntimeError, "Error waiting for edge");
      return NULL;
   } else {
      return Py_BuildValue("i", channel);
   }

}

// python function value = gpio_function(channel)
static PyObject *py_gpio_function(PyObject *self, PyObject *args)
{
   unsigned int gpio;
   int channel;
   int f;
   PyObject *func;

   if (!PyArg_ParseTuple(args, "i", &channel))
      return NULL;

   if (get_gpio_number(channel, &gpio))
       return NULL;

   if (mmap_gpio_mem())
      return NULL;

   f = gpio_function(gpio);
   switch (f)
   {
      case 0 : f = INPUT;  break;
      case 1 : f = OUTPUT; break;

      // ALT 0
      case 4 : switch (gpio)
               {
                  case 0 :
                  case 1 :
                  case 2 :
                  case 3 : f = I2C; break;

                  case 7 :
                  case 8 :
                  case 9 :
                  case 10 :
                  case 11 : f = SPI; break;

                  case 12 :
                  case 13 : f = PWM; break;

                  case 14 :
                  case 15 : f = SERIAL; break;

                  case 28 :
                  case 29 : f = I2C; break;

                  default : f = MODE_UNKNOWN; break;
               }
               break;

      // ALT 5
      case 2 : if (gpio == 18 || gpio == 19) f = PWM; else f = MODE_UNKNOWN;
               break;

      // ALT 4
      case 3 : switch (gpio)

               {
                  case 16 :
                  case 17 :
                  case 18 :
                  case 19 :
                  case 20 :
                  case 21 : f = SPI; break;
                  default : f = MODE_UNKNOWN; break;
               }
               break;

      default : f = MODE_UNKNOWN; break;

   }
   func = Py_BuildValue("i", f);
   return func;
}

// python function setwarnings(state)
static PyObject *py_setwarnings(PyObject *self, PyObject *args)
{
   if (!PyArg_ParseTuple(args, "i", &gpio_warnings))
      return NULL;

   if (setup_error)
   {
      PyErr_SetString(PyExc_RuntimeError, "Module not imported correctly!");
      return NULL;
   }

   Py_RETURN_NONE;
}

static const char moduledocstring[] = "GPIO functionality of a Raspberry Pi using Python";

PyMethodDef rpi_gpio_methods[] = {
   {"setup", (PyCFunction)py_setup_channel, METH_VARARGS | METH_KEYWORDS, "Set up a GPIO channel or list of channels with a direction and (optional) pull/up down control\nchannel        - either board pin number or BCM number depending on which mode is set.\ndirection      - IN or OUT\n[pull_up_down] - PUD_OFF (default), PUD_UP or PUD_DOWN\n[initial]      - Initial value for an output channel"},
   {"cleanup", (PyCFunction)py_cleanup, METH_VARARGS | METH_KEYWORDS, "Clean up by resetting all GPIO channels that have been used by this program to INPUT with no pullup/pulldown and no event detection\n[channel] - individual channel or list/tuple of channels to clean up.  Default - clean every channel that has been used."},
   {"output", py_output_gpio, METH_VARARGS, "Output to a GPIO channel or list of channels\nchannel - either board pin number or BCM number depending on which mode is set.\nvalue   - 0/1 or False/True or LOW/HIGH"},
   {"input", py_input_gpio, METH_VARARGS, "Input from a GPIO channel.  Returns HIGH=1=True or LOW=0=False\nchannel - either board pin number or BCM number depending on which mode is set."},
   {"setmode", py_setmode, METH_VARARGS, "Set up numbering mode to use for channels.\nBOARD - Use Raspberry Pi board numbers\nBCM   - Use Broadcom GPIO 00..nn numbers"},
   {"getmode", py_getmode, METH_VARARGS, "Get numbering mode used for channel numbers.\nReturns BOARD, BCM or None"},
   {"add_event_detect", (PyCFunction)py_add_event_detect, METH_VARARGS | METH_KEYWORDS, "Enable edge detection events for a particular GPIO channel.\nchannel      - either board pin number or BCM number depending on which mode is set.\nedge         - RISING, FALLING or BOTH\n[callback]   - A callback function for the event (optional)\n[bouncetime] - Switch bounce timeout in ms for callback"},
   {"remove_event_detect", py_remove_event_detect, METH_VARARGS, "Remove edge detection for a particular GPIO channel\nchannel - either board pin number or BCM number depending on which mode is set."},
   {"event_detected", py_event_detected, METH_VARARGS, "Returns True if an edge has occured on a given GPIO.  You need to enable edge detection using add_event_detect() first.\nchannel - either board pin number or BCM number depending on which mode is set."},
   {"add_event_callback", (PyCFunction)py_add_event_callback, METH_VARARGS | METH_KEYWORDS, "Add a callback for an event already defined using add_event_detect()\nchannel      - either board pin number or BCM number depending on which mode is set.\ncallback     - a callback function"},
   {"wait_for_edge", (PyCFunction)py_wait_for_edge, METH_VARARGS | METH_KEYWORDS, "Wait for an edge.  Returns the channel number or None on timeout.\nchannel      - either board pin number or BCM number depending on which mode is set.\nedge         - RISING, FALLING or BOTH\n[bouncetime] - time allowed between calls to allow for switchbounce\n[timeout]    - timeout in ms"},
   {"gpio_function", py_gpio_function, METH_VARARGS, "Return the current GPIO function (IN, OUT, PWM, SERIAL, I2C, SPI)\nchannel - either board pin number or BCM number depending on which mode is set."},
   {"setwarnings", py_setwarnings, METH_VARARGS, "Enable or disable warning messages"},
   {NULL, NULL, 0, NULL}
};

#if PY_MAJOR_VERSION > 2
static struct PyModuleDef rpigpiomodule = {
   PyModuleDef_HEAD_INIT,
   "RPi._GPIO",      // name of module
   moduledocstring,  // module documentation, may be NULL
   -1,               // size of per-interpreter state of the module, or -1 if the module keeps state in global variables.
   rpi_gpio_methods
};
#endif

#if PY_MAJOR_VERSION > 2
PyMODINIT_FUNC PyInit__GPIO(void)
#else
PyMODINIT_FUNC init_GPIO(void)
#endif
{
   int i;
   PyObject *module = NULL;

#if PY_MAJOR_VERSION > 2
   if ((module = PyModule_Create(&rpigpiomodule)) == NULL)
      return NULL;
#else
   if ((module = Py_InitModule3("RPi._GPIO", rpi_gpio_methods, moduledocstring)) == NULL)
      return;
#endif

   define_constants(module);

   for (i=0; i<54; i++)
      gpio_direction[i] = -1;

   // detect board revision and set up accordingly
   if (get_rpi_info(&rpiinfo))
   {
      PyErr_SetString(PyExc_RuntimeError, "This module can only be run on a Raspberry Pi!");
      setup_error = 1;
#if PY_MAJOR_VERSION > 2
      return NULL;
#else
      return;
#endif
   }
   board_info = Py_BuildValue("{sissssssssss}",
                              "P1_REVISION",rpiinfo.p1_revision,
                              "REVISION",&rpiinfo.revision,
                              "TYPE",rpiinfo.type,
                              "MANUFACTURER",rpiinfo.manufacturer,
                              "PROCESSOR",rpiinfo.processor,
                              "RAM",rpiinfo.ram);
   PyModule_AddObject(module, "RPI_INFO", board_info); 

   if (rpiinfo.p1_revision == 1) {
      pin_to_gpio = &pin_to_gpio_rev1;
   } else if (rpiinfo.p1_revision == 2) {
      pin_to_gpio = &pin_to_gpio_rev2;
   } else { // assume model B+ or A+ or 2B
      pin_to_gpio = &pin_to_gpio_rev3;
   }

   rpi_revision = Py_BuildValue("i", rpiinfo.p1_revision);     // deprecated
   PyModule_AddObject(module, "RPI_REVISION", rpi_revision);   // deprecated

   // Add PWM class
   if (PWM_init_PWMType() == NULL)
#if PY_MAJOR_VERSION > 2
      return NULL;
#else
      return;
#endif
   Py_INCREF(&PWMType);
   PyModule_AddObject(module, "PWM", (PyObject*)&PWMType);

   if (!PyEval_ThreadsInitialized())
      PyEval_InitThreads();

   // register exit functions - last declared is called first
   if (Py_AtExit(cleanup) != 0)
   {
      setup_error = 1;
      cleanup();
#if PY_MAJOR_VERSION > 2
      return NULL;
#else
      return;
#endif
   }

   if (Py_AtExit(event_cleanup_all) != 0)
   {
      setup_error = 1;
      cleanup();
#if PY_MAJOR_VERSION > 2
      return NULL;
#else
      return;
#endif
   }

#if PY_MAJOR_VERSION > 2
   return module;
#else
   return;
#endif
}
