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/* mbed Microcontroller Library
 * Copyright (c) 2006-2014 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef __GPS_PROVIDER_H__
#define __GPS_PROVIDER_H__

class GPSProviderImplBase; /* forward declaration */
extern GPSProviderImplBase *createGPSProviderInstance(void);

//
// Here's a snippet showing how this API can be used. Please note that this is
// an asynchronous API--users can setup an asynchronous handler to receive
// location updates. The handler gets invoked from interrupt context. Users
// *should not* do any long running or blocking operations in the handler.
//
//      void handleGPSData(const LocationUpdateParams_t *newData) {
//          /* Do something with the location update; but please don't make any
//           * blocking calls or invoke long-running operations. */
//      }
//
//      GPSProvider gps;
//
//      gps.setPowerMode(LOW_POWER);
//      gps.onLocationUpdate(handleGPSData);
//
//      gps.reset(); // implicitly calls powerOn().
//      gps.start();
//
//      wait(/* some duration to allow controller to stabilize */);
//      if (gps.haveDeviceInfo()) {
//          printf("%s", gps.getDeviceInfo());
//      }
//
//      ...
//      /* Period where the gps locationHandler gets invoked asynchronously. */
//      ...
//
//      /* at some point in the future, either the following.. */
//      gps.stop();
//      gps.powerOff();
//      /* or simply destroy the gps object to achieve the same. */
//

class GPSProvider {
public:
    /** Power mode selection */
    enum PowerMode_t {
         POWER_FULL,
         POWER_LOW,
    };

    /**
     * GPS time starts from UTC 01/06/1980(MM/DD/YYYY) and includes 2 fields:
     * week and tow. For a given GPS time, week is the passed week number since
     * the GPS start time, and tow(time of week) is the passed seconds since the
     * last Sunday. For example, a given UTC time [10/30/3014
     * 01:10:00](MM/DD/YYYY HH:MM:SS) can be converted into GPS time [1816,
     * 4200](week, seconds).
     *
     * GPS time can be used as a quite accurate time once position is fixed.
     */
    struct GPSTime_t {
        uint16_t gps_week;
        uint32_t tow;       /* time of week (in seconds) */
    };

    typedef float LocationType_t;
    typedef float Altitude_t;
    struct LocationUpdateParams_t {
        uint32_t       version; /* Layout-version for the following structure;
                                 * this is to accommodate changes over time. */
        LocationType_t lat;
        LocationType_t lon;
        Altitude_t     altitude;

        union {
            GPSTime_t gpsTime;
            float     utcTime;
        } u;
    };

public:
    /**
     * Set the operating mode for power. Typically this allows the user to
     * choose between various low-power modes. Entering low-power modes often
     * results in a trade-off between accuracy and power consumption.
     *
     * The new mode takes effect upon calling start().
     *
     * @param power The new power mode.
     * @return      true if the update was successful.
     */
    bool setPowerMode(PowerMode_t power);

    /**
     * HW reset to get location chip into hibernation mode, but in readiness for
     * starting operation. The GPS controller emerges from hibernation when
     * start() is called.
     *
     * The typical initialization sequence is:
     *   reset();
     *   start(); // and thereafter receive location-update callbacks.
     */
    void reset(void);

    /**
     * Start the GPS operation, taking into account the operation mode set
     * previously. Following this call, the user may expect to receive location
     * notifications in interrupt context if a handler has previously been set.
     *
     * @note: calling start repeatedly doesn't hurt.
     */
    void start(void);

    /**
     * Stop active operation of the GPS; and put it to hibernation.
     *
     * @note: You don't need to call reset() afterwards to enter hibernation.
     * @note: Calling stop() repeatedly doesn't hurt.
     */
    void stop(void);

    /**
     * @return  true if the initialization process has received enough
     *     information to determine the hardware's version/device-info.
     */
    bool haveDeviceInfo(void) const {
        return discoveredDeviceInfo;
    }

    /**
     * Fetch the device information string. This is expected to contain the
     * version number or any other device identifier.
     */
    const char *getDeviceInfo(void) const {
        return deviceInfo;
    }

    /**
     * This is a wildcard API for sending controller specific commands. Use of
     * this API will make programs non-portable, but then there may arise a
     * genuine need to access special functionality.
     *
     * @param  command   A controller specific command.
     * @param  arg       Argument to the command; interpreted according to the command.
     * @return           any return from the command.
     */
    uint32_t ioctl(uint32_t command, void *arg);

    /**
     * @return  true if we've obtained at least one valid location since last
     *     calling start().
     *
     * @Note: This is cleared after reset().
     */
    bool locationAvailable(void) const {
        return haveValidLocation;
    }

    /**
     * @return  the last valid location if there is any; else NULL.
     */
    const LocationUpdateParams_t *getLastLocation(void) const {
        return haveValidLocation ? &lastLocation : NULL;
    }

    /**
     * Type declaration for a callback to be invoked from interrupt context upon
     * receiving new location data.
     *
     * @Note: Please note that the handler gets invoked from interrupt context.
     * Users *should not* do any long running or blocking operations in the
     * handler.
     */
    typedef void (* LocationUpdateCallback_t)(const LocationUpdateParams_t *params);

    /**
     * Setup the locationUpdate callback.
     *
     * @Note: Please note that the handler gets invoked from interrupt context.
     * Users *should not* do any long running or blocking operations in the
     * handler.
     */
    void onLocationUpdate(LocationUpdateCallback_t callback);

public:
    /**
     * Default constructor.
     */
    GPSProvider() :
        impl(createGPSProviderInstance()),
        havePoweredOn(false),
        discoveredDeviceInfo(false),
        haveValidLocation(false),
        deviceInfo(NULL),
        updateCallback(NULL) {
        /* empty */
    }

    virtual ~GPSProvider() {
        stop();
    }

private:
    /**
     * We use 'composition' to combine a driver-implementation object to the
     * GPSProvider interface. The implementation object will come to life
     * through the createGPSProviderInstance(), which must be defined by the
     * driver library. The mechanics of the implementation are to be hidden
     * behind the abstract interface provided by GPSProvider.
     */
    GPSProviderImplBase *const impl;

private:
    bool                      havePoweredOn;
    bool                      discoveredDeviceInfo;
    bool                      haveValidLocation;

    const char               *deviceInfo;
    LocationUpdateParams_t    lastLocation;
    LocationUpdateCallback_t *updateCallback;

    /* disallow copy constructor and assignment operators */
private:
    GPSProvider(const GPSProvider&);
    GPSProvider & operator= (const GPSProvider&);
};

#endif /*__GPS_PROVIDER_H__*/