/**
 ******************************************************************************
 * @file       pios_ibus.c
 * @author     dRonin, http://dRonin.org/, Copyright (C) 2016
 * @addtogroup PIOS PIOS Core hardware abstraction layer
 * @{
 * @addtogroup PIOS_IBus PiOS IBus receiver driver
 * @{
 * @brief Receives and decodes IBus protocol reciever packets
 *****************************************************************************/
/*
 * 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, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Additional note on redistribution: The copyright and license notices above
 * must be maintained in each individual source file that is a derivative work
 * of this source file; otherwise redistribution is prohibited.
 */

#include "pios_ibus_priv.h"

#ifdef PIOS_INCLUDE_IBUS

// private
#define PIOS_IBUS_CHANNELS 10
// 1 sync byte, 1 unknown byte, 10x channels (uint16_t), 8 unknown bytes, 2 crc bytes
#define PIOS_IBUS_BUFLEN   (1 + 1 + PIOS_IBUS_CHANNELS * 2 + 8 + 2)
#define PIOS_IBUS_SYNCBYTE 0x20
#define PIOS_IBUS_MAGIC    0x84fd9a39

/**
 * @brief IBus receiver driver internal state data
 */
struct pios_ibus_dev {
    uint32_t magic;
    int      buf_pos;
    int      rx_timer;
    int      failsafe_timer;
    uint16_t checksum;
    uint16_t channel_data[PIOS_IBUS_CHANNELS];
    uint8_t  rx_buf[PIOS_IBUS_BUFLEN];
};

/**
 * @brief Allocates a driver instance
 * @retval pios_ibus_dev pointer on success, NULL on failure
 */
static struct pios_ibus_dev *PIOS_IBUS_Alloc(void);
/**
 * @brief Validate a driver instance
 * @param[in] dev device driver instance pointer
 * @retval true on success, false on failure
 */
static bool PIOS_IBUS_Validate(const struct pios_ibus_dev *ibus_dev);
/**
 * @brief Read a channel from the last received frame
 * @param[in] id Driver instance
 * @param[in] channel 0-based channel index
 * @retval raw channel value, or error value (see pios_rcvr.h)
 */
static int32_t PIOS_IBUS_Read(uint32_t id, uint8_t channel);
/**
 * @brief Set all channels in the last frame buffer to a given value
 * @param[in] dev Driver instance
 * @param[in] value channel value
 */
static void PIOS_IBUS_SetAllChannels(struct pios_ibus_dev *ibus_dev, uint16_t value);
/**
 * @brief Serial receive callback
 * @param[in] context Driver instance handle
 * @param[in] buf Receive buffer
 * @param[in] buf_len Number of bytes available
 * @param[out] headroom Number of bytes remaining in internal buffer
 * @param[out] task_woken Did we awake a task?
 * @retval Number of bytes consumed from the buffer
 */
static uint16_t PIOS_IBUS_Receive(uint32_t context, uint8_t *buf, uint16_t buf_len,
                                  uint16_t *headroom, bool *task_woken);
/**
 * @brief Reset the internal receive buffer state
 * @param[in] ibus_dev device driver instance pointer
 */
static void PIOS_IBUS_ResetBuffer(struct pios_ibus_dev *ibus_dev);
/**
 * @brief Unpack a frame from the internal receive buffer to the channel buffer
 * @param[in] ibus_dev device driver instance pointer
 */
static void PIOS_IBUS_UnpackFrame(struct pios_ibus_dev *ibus_dev);
/**
 * @brief RTC tick callback
 * @param[in] context Driver instance handle
 */
static void PIOS_IBUS_Supervisor(uint32_t context);

// public
const struct pios_rcvr_driver pios_ibus_rcvr_driver = {
    .read = PIOS_IBUS_Read,
};


static struct pios_ibus_dev *PIOS_IBUS_Alloc(void)
{
    struct pios_ibus_dev *ibus_dev;

    ibus_dev = (struct pios_ibus_dev *)pios_malloc(sizeof(*ibus_dev));

    if (!ibus_dev) {
        return NULL;
    }

    memset(ibus_dev, 0, sizeof(*ibus_dev));
    ibus_dev->magic = PIOS_IBUS_MAGIC;

    return ibus_dev;
}

static bool PIOS_IBUS_Validate(const struct pios_ibus_dev *ibus_dev)
{
    return ibus_dev && ibus_dev->magic == PIOS_IBUS_MAGIC;
}

int32_t PIOS_IBUS_Init(uint32_t *ibus_id, const struct pios_com_driver *driver,
                       uint32_t lower_id)
{
    struct pios_ibus_dev *ibus_dev = PIOS_IBUS_Alloc();

    if (!ibus_dev) {
        return -1;
    }

    *ibus_id = (uint32_t)ibus_dev;

    PIOS_IBUS_SetAllChannels(ibus_dev, PIOS_RCVR_INVALID);

    if (!PIOS_RTC_RegisterTickCallback(PIOS_IBUS_Supervisor, *ibus_id)) {
        PIOS_Assert(0);
    }

    (driver->bind_rx_cb)(lower_id, PIOS_IBUS_Receive, *ibus_id);

    return 0;
}

static int32_t PIOS_IBUS_Read(uint32_t context, uint8_t channel)
{
    if (channel > PIOS_IBUS_CHANNELS) {
        return PIOS_RCVR_INVALID;
    }

    struct pios_ibus_dev *ibus_dev = (struct pios_ibus_dev *)context;
    if (!PIOS_IBUS_Validate(ibus_dev)) {
        return PIOS_RCVR_NODRIVER;
    }

    return ibus_dev->channel_data[channel];
}

static void PIOS_IBUS_SetAllChannels(struct pios_ibus_dev *ibus_dev, uint16_t value)
{
    for (int i = 0; i < PIOS_IBUS_CHANNELS; i++) {
        ibus_dev->channel_data[i] = value;
    }
}

static uint16_t PIOS_IBUS_Receive(uint32_t context, uint8_t *buf, uint16_t buf_len,
                                  uint16_t *headroom, bool *task_woken)
{
    struct pios_ibus_dev *ibus_dev = (struct pios_ibus_dev *)context;

    if (!PIOS_IBUS_Validate(ibus_dev)) {
        goto out_fail;
    }

    for (int i = 0; i < buf_len; i++) {
        if (ibus_dev->buf_pos == 0 && buf[i] != PIOS_IBUS_SYNCBYTE) {
            continue;
        }

        ibus_dev->rx_buf[ibus_dev->buf_pos++] = buf[i];
        if (ibus_dev->buf_pos <= PIOS_IBUS_BUFLEN - 2) {
            ibus_dev->checksum -= buf[i];
        } else if (ibus_dev->buf_pos == PIOS_IBUS_BUFLEN) {
            PIOS_IBUS_UnpackFrame(ibus_dev);
        }
    }

    ibus_dev->rx_timer = 0;

    *headroom   = PIOS_IBUS_BUFLEN - ibus_dev->buf_pos;
    *task_woken = false;
    return buf_len;

out_fail:
    *headroom   = 0;
    *task_woken = false;
    return 0;
}

static void PIOS_IBUS_ResetBuffer(struct pios_ibus_dev *ibus_dev)
{
    ibus_dev->checksum = 0xffff;
    ibus_dev->buf_pos  = 0;
}

static void PIOS_IBUS_UnpackFrame(struct pios_ibus_dev *ibus_dev)
{
    uint16_t rxsum = ibus_dev->rx_buf[PIOS_IBUS_BUFLEN - 1] << 8 |
                     ibus_dev->rx_buf[PIOS_IBUS_BUFLEN - 2];

    if (ibus_dev->checksum != rxsum) {
        goto out_fail;
    }

    uint16_t *chan = (uint16_t *)&ibus_dev->rx_buf[2];
    for (int i = 0; i < PIOS_IBUS_CHANNELS; i++) {
        ibus_dev->channel_data[i] = *chan++;
    }

    ibus_dev->failsafe_timer = 0;

out_fail:
    PIOS_IBUS_ResetBuffer(ibus_dev);
}

static void PIOS_IBUS_Supervisor(uint32_t context)
{
    struct pios_ibus_dev *ibus_dev = (struct pios_ibus_dev *)context;

    PIOS_Assert(PIOS_IBUS_Validate(ibus_dev));

    if (++ibus_dev->rx_timer > 3) {
        PIOS_IBUS_ResetBuffer(ibus_dev);
    }

    if (++ibus_dev->failsafe_timer > 32) {
        PIOS_IBUS_SetAllChannels(ibus_dev, PIOS_RCVR_TIMEOUT);
    }
}

#endif // PIOS_INCLUDE_IBUS

/**
 * @}
 * @}
 */