/*
 * Copyright (C) 2016 Kaspar Schleiser <kaspar@schleiser.de>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */

/**
 * @ingroup     drivers_ethos
 * @{
 *
 * @file
 * @brief       Implementation of a simple ethernet-over-serial driver
 *
 * @author      Kaspar Schleiser <kaspar@schleiser.de>
 *
 * @}
 */

#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <string.h>

#include "ethos.h"
#include "periph/uart.h"
#include "tsrb.h"
#include "irq.h"

#include "net/netdev.h"
#include "net/netdev/eth.h"
#include "net/eui64.h"
#include "net/eui_provider.h"
#include "net/ethernet.h"

#ifdef MODULE_ETHOS_STDIO
#include "stdio_uart.h"
#include "isrpipe.h"
extern isrpipe_t ethos_stdio_isrpipe;
#endif

#define ENABLE_DEBUG 0
#include "debug.h"

#define ETHOS_FRAME_TYPE_ERRORED    (0xff)

static void _get_mac_addr(netdev_t *dev, uint8_t* buf);
static void ethos_isr(void *arg, uint8_t c);
static const netdev_driver_t netdev_driver_ethos;

static const uint8_t _esc_esc[] = {ETHOS_ESC_CHAR, (ETHOS_ESC_CHAR ^ 0x20)};
static const uint8_t _esc_delim[] = {ETHOS_ESC_CHAR, (ETHOS_FRAME_DELIMITER ^ 0x20)};

void ethos_setup(ethos_t *dev, const ethos_params_t *params, uint8_t idx,
                 void *inbuf, size_t inbuf_size)
{
    dev->netdev.driver = &netdev_driver_ethos;
    dev->uart = params->uart;
    dev->state = WAIT_FRAMESTART;
    dev->frametype = 0;

    tsrb_init(&dev->inbuf, inbuf, inbuf_size);
    mutex_init(&dev->out_mutex);

    netdev_register(&dev->netdev, NETDEV_ETHOS, idx);
    netdev_eui48_get(&dev->netdev, (eui48_t *)&dev->mac_addr);

    uart_init(params->uart, params->baudrate, ethos_isr, (void*)dev);

    uint8_t frame_delim = ETHOS_FRAME_DELIMITER;
    uart_write(dev->uart, &frame_delim, 1);
    ethos_send_frame(dev, dev->mac_addr, 6, ETHOS_FRAME_TYPE_HELLO);
}

static void _reset_state(ethos_t *dev)
{
    dev->state = WAIT_FRAMESTART;
    dev->frametype = 0;
}

static void _fail_frame(ethos_t *dev)
{
    switch (dev->frametype) {
        case ETHOS_FRAME_TYPE_DATA:
            tsrb_clear(&dev->inbuf);
            /* signal to handler thread that frame is at an end (makes handler thread to
             * truncate frame) */
            tsrb_add_one(&dev->inbuf, ETHOS_FRAME_DELIMITER);
            break;
        case ETHOS_FRAME_TYPE_TEXT:
#ifdef MODULE_ETHOS_STDIO
            tsrb_clear(&ethos_stdio_isrpipe.tsrb);
            /* signal to handler thread that frame is at an end (makes handler thread to
             * truncate frame) */
            isrpipe_write_one(&ethos_stdio_isrpipe, ETHOS_FRAME_DELIMITER);
#endif
            break;
        case ETHOS_FRAME_TYPE_ERRORED:
            return;
        default:
            assert(0);
            break;
    }
    dev->frametype = ETHOS_FRAME_TYPE_ERRORED;
}

static void _handle_char(ethos_t *dev, char c)
{
    switch (dev->frametype) {
        case ETHOS_FRAME_TYPE_DATA:
            if (tsrb_add_one(&dev->inbuf, c) < 0) {
                //puts("lost frame");
                _fail_frame(dev);
            }
            break;
        case ETHOS_FRAME_TYPE_TEXT:
#ifdef MODULE_ETHOS_STDIO
            if (isrpipe_write_one(&ethos_stdio_isrpipe, c) < 0) {
                //puts("lost frame");
                _fail_frame(dev);
            }
            break;
#endif
            break;
        case ETHOS_FRAME_TYPE_ERRORED:
            break;
        default:
            assert(0);
            break;

    }
}

static void _end_of_frame(ethos_t *dev)
{
    switch(dev->frametype) {
        case ETHOS_FRAME_TYPE_DATA:
            netdev_trigger_event_isr(&dev->netdev);
            break;
        case ETHOS_FRAME_TYPE_TEXT:
            break;
        case ETHOS_FRAME_TYPE_ERRORED:
            break;
        default:
            /* Unexpected frametype */
            assert(0);
            break;
    }

    _reset_state(dev);
}

static void ethos_isr(void *arg, uint8_t c)
{
    ethos_t *dev = (ethos_t *) arg;

    switch (dev->state) {
        case WAIT_FRAMESTART:
            if (c == ETHOS_FRAME_DELIMITER) {
                dev->state = IN_FRAME;
                dev->frametype = ETHOS_FRAME_TYPE_DATA;
            }
            break;
        case IN_FRAME:
            _handle_char(dev, c);
            if (c == ETHOS_ESC_CHAR) {
                dev->state = IN_ESCAPE;
            }
            else if (c == ETHOS_FRAME_DELIMITER) {
                _end_of_frame(dev);
            }
            break;
        case IN_ESCAPE:
            switch (c) {
                case (ETHOS_FRAME_DELIMITER ^ 0x20):
                    break;
                case (ETHOS_ESC_CHAR ^ 0x20):
                    break;
                case (ETHOS_FRAME_TYPE_TEXT ^ 0x20):
                    dev->frametype = ETHOS_FRAME_TYPE_TEXT;
                    /* reset tsrb (used for networking) */
                    dev->inbuf.reads = 0;
                    dev->inbuf.writes = 0;
                    dev->state = IN_FRAME;
                    return;
                case (ETHOS_FRAME_TYPE_HELLO ^ 0x20):
                case (ETHOS_FRAME_TYPE_HELLO_REPLY ^ 0x20):
                    dev->frametype = ETHOS_FRAME_TYPE_DATA;
                    break;
                case ETHOS_FRAME_DELIMITER:
                    _handle_char(dev, c);
                    _reset_state(dev);
                    return;
                default:
                    /* unknown escaped character or raw delimiter */
                    _fail_frame(dev);
                    return;
            }
            dev->state = IN_FRAME;
            /* write marker to tsrb for thread layer to handle */
            _handle_char(dev, c);
            break;
        default:
            break;
    }
}

static void _isr(netdev_t *netdev)
{
    netdev->event_callback(netdev, NETDEV_EVENT_RX_COMPLETE);
}

static int _init(netdev_t *netdev)
{
    /* signal link UP */
    netdev->event_callback(netdev, NETDEV_EVENT_LINK_UP);

    return 0;
}

static size_t iolist_count_total(const iolist_t *iolist)
{
    size_t result = 0;
    for (const iolist_t *iol = iolist; iol; iol = iol->iol_next) {
        result += iol->iol_len;
    }
    return result;
}

static void _write_escaped(uart_t uart, uint8_t c)
{
    const uint8_t *out;
    int n;

    switch(c) {
        case ETHOS_FRAME_DELIMITER:
            out = _esc_delim;
            n = 2;
            break;
        case ETHOS_ESC_CHAR:
            out = _esc_esc;
            n = 2;
            break;
        default:
            out = &c;
            n = 1;
    }

    uart_write(uart, out, n);
}

void ethos_send_frame(ethos_t *dev, const uint8_t *data, size_t len, unsigned frame_type)
{
    uint8_t frame_delim = ETHOS_FRAME_DELIMITER;

    mutex_lock(&dev->out_mutex);

    /* send frame delimiter */
    uart_write(dev->uart, &frame_delim, 1);

    /* set frame type */
    if (frame_type) {
        uint8_t out[2] = { ETHOS_ESC_CHAR, (frame_type ^ 0x20) };
        uart_write(dev->uart, out, 2);
    }

    /* send frame content */
    while(len--) {
        _write_escaped(dev->uart, *data++);
    }

    /* end of frame */
    uart_write(dev->uart, &frame_delim, 1);

    mutex_unlock(&dev->out_mutex);
}

static int _send(netdev_t *netdev, const iolist_t *iolist)
{
    ethos_t * dev = (ethos_t *) netdev;
    (void)dev;

    /* count total packet length */
    size_t pktlen = iolist_count_total(iolist);

    /* lock line in order to prevent multiple writes */
    mutex_lock(&dev->out_mutex);

    /* send start-frame-delimiter */
    uint8_t frame_delim = ETHOS_FRAME_DELIMITER;
    uart_write(dev->uart, &frame_delim, 1);

    /* send iolist */
    for (const iolist_t *iol = iolist; iol; iol = iol->iol_next) {
        size_t n = iol->iol_len;
        uint8_t *ptr = iol->iol_base;
        while(n--) {
            _write_escaped(dev->uart, *ptr++);
        }
    }

    uart_write(dev->uart, &frame_delim, 1);

    mutex_unlock(&dev->out_mutex);

    return pktlen;
}

static void _get_mac_addr(netdev_t *encdev, uint8_t* buf)
{
    ethos_t * dev = (ethos_t *) encdev;
    memcpy(buf, dev->mac_addr, 6);
}

static unsigned _copy_byte(uint8_t *buf, uint8_t byte, bool *escaped)
{
    *buf = byte;
    *escaped = false;
    return 1U;
}

unsigned ethos_unstuff_readbyte(uint8_t *buf, uint8_t byte, bool *escaped, uint8_t *frametype)
{
    switch (byte) {
        case ETHOS_ESC_CHAR:
            *escaped = true;
            /* Intentionally falls through */
        case ETHOS_FRAME_DELIMITER:
            break;
        case ETHOS_ESC_CHAR ^ 0x20:
            if (*escaped) {
                return _copy_byte(buf, ETHOS_ESC_CHAR, escaped);
            }
            /* Intentionally falls through */
            /* to default when !(*escaped) */
        case ETHOS_FRAME_DELIMITER ^ 0x20:
            if (*escaped) {
                return _copy_byte(buf, ETHOS_FRAME_DELIMITER, escaped);
            }
            /* Intentionally falls through */
            /* to default when !(*escaped) */
        case ETHOS_FRAME_TYPE_TEXT ^ 0x20:
        case ETHOS_FRAME_TYPE_HELLO ^ 0x20:
        case ETHOS_FRAME_TYPE_HELLO_REPLY ^ 0x20:
            if (*escaped) {
                *frametype = byte ^ 0x20;
                break;
            }
            /* Intentionally falls through */
        default:
            return _copy_byte(buf, byte, escaped);
    }
    return 0U;
}

static int _recv(netdev_t *netdev, void *buf, size_t len, void* info)
{
    (void) info;
    ethos_t * dev = (ethos_t *) netdev;
    int res = 0;

    if (buf) {
        int byte;
        bool escaped = false;
        uint8_t *ptr = buf;
        uint8_t frametype = ETHOS_FRAME_TYPE_DATA;

        do {
            int tmp;

            if ((byte = tsrb_get_one(&dev->inbuf)) < 0) {
                DEBUG("ethos _recv(): inbuf doesn't contain enough bytes.\n");
                return -EIO;
            }
            if ((unsigned)res >= len) {
                while (byte != (int)ETHOS_FRAME_DELIMITER && byte >= 0) {
                    /* clear out unreceived packet */
                    byte = tsrb_get_one(&dev->inbuf);
                }
                return -ENOBUFS;
            }

            tmp = ethos_unstuff_readbyte(ptr, (uint8_t)byte, &escaped, &frametype);
            ptr += tmp;
            res += tmp;
        } while (byte != ETHOS_FRAME_DELIMITER);

        switch (frametype) {
        case ETHOS_FRAME_TYPE_HELLO:
            ethos_send_frame(dev, dev->mac_addr, 6, ETHOS_FRAME_TYPE_HELLO_REPLY);
            /* fall through */
        case ETHOS_FRAME_TYPE_HELLO_REPLY:
            if (res == 6) {
                memcpy(dev->remote_mac_addr, buf, 6);
            }
            return 0;
        default:
            break;
        }
    }
    else {
        if (len) {
            /* remove data */
            for (; len > 0; len--) {
                int byte = tsrb_get_one(&dev->inbuf);
                if ((byte == (int)ETHOS_FRAME_DELIMITER) || (byte < 0)) {
                    /* end early if end of packet or ringbuffer is reached;
                     * len might be larger than the actual packet */
                    break;
                }
            }
        }
        else {
            /* set to 2048 in sys/net/gnrc/netif/init_devs/auto_init_ethos.c so safe to cast
             * unsigned to int */
            res = (int)tsrb_avail(&dev->inbuf);
        }
    }
    return res;
}

static int _get(netdev_t *dev, netopt_t opt, void *value, size_t max_len)
{
    int res = 0;

    switch (opt) {
        case NETOPT_ADDRESS:
            if (max_len < ETHERNET_ADDR_LEN) {
                res = -EINVAL;
            }
            else {
                _get_mac_addr(dev, (uint8_t*)value);
                res = ETHERNET_ADDR_LEN;
            }
            break;
        default:
            res = netdev_eth_get(dev, opt, value, max_len);
            break;
    }

    return res;
}

/* netdev interface */
static const netdev_driver_t netdev_driver_ethos = {
    .send = _send,
    .recv = _recv,
    .init = _init,
    .isr = _isr,
    .get = _get,
    .set = netdev_eth_set
};