/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
 * Many thanks to members of the UAVCAN project:
 *  Pavel Kirienko <pavel.kirienko@gmail.com>
 *  Ilia Sheremet <illia.sheremet@gmail.com>
 *
 *  license info can be found in the uavcan submodule located:
 *  modules/uavcan/LICENSE
 *  modules/uavcan/libuavcan_drivers/linux/include/uavcan_linux/socketcan.hpp
 */


#pragma once

#include "AP_HAL_Linux.h"

#if HAL_NUM_CAN_IFACES

#include <AP_HAL/CANIface.h>

#include <linux/can.h>

#include <string>
#include <queue>
#include <memory>
#include <map>
#include <unordered_set>
#include <poll.h>

namespace Linux {

enum class SocketCanError
{
    SocketReadFailure,
    SocketWriteFailure,
    TxTimeout
};

#define CAN_MAX_POLL_ITERATIONS_COUNT 100
#define CAN_MAX_INIT_TRIES_COUNT 100
#define CAN_FILTER_NUMBER 8

class CANIface: public AP_HAL::CANIface {
public:
    CANIface(int index)
      : _self_index(index)
      , _max_frames_in_socket_tx_queue(2)
      , _frames_in_socket_tx_queue(0)
    { }

    ~CANIface() { }

    // Initialise CAN Peripheral
    bool init(const uint32_t bitrate, const OperatingMode mode) override;

    // Put frame into Tx FIFO returns negative on error, 0 on buffer full, 
    // 1 on successfully pushing a frame into FIFO
    int16_t send(const AP_HAL::CANFrame& frame, uint64_t tx_deadline,
                 CanIOFlags flags) override;

    // Receive frame from Rx Buffer, returns negative on error, 0 on nothing available, 
    // 1 on successfully poping a frame
    int16_t receive(AP_HAL::CANFrame& out_frame, uint64_t& out_timestamp_us,
                    CanIOFlags& out_flags) override;

    // Set Filters to ignore frames not to be handled by us
    bool configureFilters(const CanFilterConfig* filter_configs,
                          uint16_t num_configs) override;

    // Always return false, there's no busoff condition in Linux CAN
    bool is_busoff() const override
    {
        return false;
    }

    void flush_tx() override;

    void clear_rx() override;

    // Get number of Filter configurations
    uint16_t getNumFilters() const override;

    // Get total number of Errors discovered
    uint32_t getErrorCount() const override;

    // returns true if init was successfully called
    bool is_initialized() const override;

    /******************************************
     * Select Method                          *
     * ****************************************/
    // wait until selected event is available, false when timed out waiting else true
    bool select(bool &read, bool &write,
                const AP_HAL::CANFrame* const pending_tx,
                uint64_t blocking_deadline) override;
    
    // setup event handle for waiting on events
    bool set_event_handle(AP_HAL::BinarySemaphore *handle) override;

    // fetch stats text and return the size of the same,
    // results available via @SYS/can0_stats.txt or @SYS/can1_stats.txt 
    void get_stats(ExpandingString &str) override;

private:
    void _pollWrite();

    bool _pollRead();

    int _write(const AP_HAL::CANFrame& frame) const;

    int _read(AP_HAL::CANFrame& frame, uint64_t& ts_usec, bool& loopback) const;

    void _incrementNumFramesInSocketTxQueue();

    void _confirmSentFrame();

    bool _wasInPendingLoopbackSet(const AP_HAL::CANFrame& frame);

    bool _checkHWFilters(const can_frame& frame) const;

    bool _hasReadyTx();

    bool _hasReadyRx();

    void _poll(bool read, bool write);

    int _openSocket(const std::string& iface_name);

    void _updateDownStatusFromPollResult(const pollfd& pfd);

    uint32_t _bitrate;

    bool _down;
    bool _initialized;

    int _fd;

    const uint8_t _self_index;

    const unsigned _max_frames_in_socket_tx_queue;
    unsigned _frames_in_socket_tx_queue;
    uint32_t _tx_frame_counter;
    AP_HAL::BinarySemaphore *sem_handle;

    pollfd _pollfd;
    std::map<SocketCanError, uint64_t> _errors;
    std::priority_queue<CanTxItem> _tx_queue;
    std::queue<CanRxItem> _rx_queue;
    std::unordered_multiset<uint32_t> _pending_loopback_ids;
    std::vector<can_filter> _hw_filters_container;

    struct bus_stats : public AP_HAL::CANIface::bus_stats_t {
        uint32_t tx_confirmed;
        uint32_t num_downs;
        uint32_t num_rx_poll_req;
        uint32_t num_tx_poll_req;
        uint32_t num_poll_waits;
        uint32_t num_poll_tx_events;
        uint32_t num_poll_rx_events;
    } stats;

protected:
    bool add_to_rx_queue(const CanRxItem &rx_item) override {
        _rx_queue.push(rx_item);
        return true;
    }

    int8_t get_iface_num(void) const override {
        return _self_index;
    }
    HAL_Semaphore sem;
};

}

#endif //#if HAL_NUM_CAN_IFACES