/*
 * Copyright © Stéphane Raimbault <stephane.raimbault@gmail.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#include "errno.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "modbus-private.h"
#include <assert.h>

#include "modbus-rtu-private.h"
#include "modbus-rtu.h"
#include "uart_device.h"

#define TIMEROUT_SEND_MSG 1000

/* Table of CRC values for high-order byte */
static const uint8_t table_crc_hi[] = {
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1,
    0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1,
    0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
    0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40};

/* Table of CRC values for low-order byte */
static const uint8_t table_crc_lo[] = {
    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5,
    0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B,
    0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE,
    0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6,
    0xD2, 0x12, 0x13, 0xD3, 0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
    0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
    0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8,
    0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C,
    0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26, 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21,
    0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
    0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A,
    0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
    0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5, 0x77, 0xB7,
    0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91, 0x51,
    0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
    0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98,
    0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D,
    0x4C, 0x8C, 0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
    0x41, 0x81, 0x80, 0x40};

/* Define the slave ID of the remote device to talk in master mode or set the
 * internal slave ID in slave mode */
static int _modbus_set_slave(modbus_t *ctx, int slave)
{
    int max_slave = (ctx->quirks & MODBUS_QUIRK_MAX_SLAVE) ? 255 : 247;

    /* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */
    if (slave >= 0 && slave <= max_slave) {
        ctx->slave = slave;
    } else {
        errno = EINVAL;
        return -1;
    }

    return 0;
}

/* Builds a RTU request header */
static int _modbus_rtu_build_request_basis(
    modbus_t *ctx, int function, int addr, int nb, uint8_t *req)
{
    assert(ctx->slave != -1);
    req[0] = ctx->slave;
    req[1] = function;
    req[2] = addr >> 8;
    req[3] = addr & 0x00ff;
    req[4] = nb >> 8;
    req[5] = nb & 0x00ff;

    return _MODBUS_RTU_PRESET_REQ_LENGTH;
}

/* Builds a RTU response header */
static int _modbus_rtu_build_response_basis(sft_t *sft, uint8_t *rsp)
{
    /* In this case, the slave is certainly valid because a check is already
     * done in _modbus_rtu_listen */
    rsp[0] = sft->slave;
    rsp[1] = sft->function;

    return _MODBUS_RTU_PRESET_RSP_LENGTH;
}

static uint16_t crc16(uint8_t *buffer, uint16_t buffer_length)
{
    uint8_t crc_hi = 0xFF; /* high CRC byte initialized */
    uint8_t crc_lo = 0xFF; /* low CRC byte initialized */
    unsigned int i;        /* will index into CRC lookup */

    /* pass through message buffer */
    while (buffer_length--) {
        i = crc_lo ^ *buffer++; /* calculate the CRC  */
        crc_lo = crc_hi ^ table_crc_hi[i];
        crc_hi = table_crc_lo[i];
    }

    return (crc_hi << 8 | crc_lo);
}

static int _modbus_rtu_prepare_response_tid(const uint8_t *req, int *req_length)
{
    (*req_length) -= _MODBUS_RTU_CHECKSUM_LENGTH;
    /* No TID */
    return 0;
}

static int _modbus_rtu_send_msg_pre(uint8_t *req, int req_length)
{
    uint16_t crc = crc16(req, req_length);

    /* According to the MODBUS specs (p. 14), the low order byte of the CRC comes
     * first in the RTU message */
    req[req_length++] = crc & 0x00FF;
    req[req_length++] = crc >> 8;

    return req_length;
}


static ssize_t _modbus_rtu_send(modbus_t *ctx, const uint8_t *req, int req_length)
{
	/* 使用usb/UART2/UART4的UART_Device来发送数据 */
    modbus_rtu_t *ctx_rtu = ctx->backend_data;
	struct UART_Device *pdev = ctx_rtu->dev;

	if (0 == pdev->Send(pdev, (uint8_t *)req, req_length, TIMEROUT_SEND_MSG))
		return req_length;
    else
    {
		errno = EIO;
		return -1;
    }
}

static int _modbus_rtu_receive(modbus_t *ctx, uint8_t *req)
{
    int rc;
    modbus_rtu_t *ctx_rtu = ctx->backend_data;

    if (ctx_rtu->confirmation_to_ignore) {
        _modbus_receive_msg(ctx, req, MSG_CONFIRMATION);
        /* Ignore errors and reset the flag */
        ctx_rtu->confirmation_to_ignore = FALSE;
        rc = 0;
        if (ctx->debug) {
            debug_printf("Confirmation to ignore\n");
        }
    } else {
        rc = _modbus_receive_msg(ctx, req, MSG_INDICATION);
        if (rc == 0) {
            /* The next expected message is a confirmation to ignore */
            ctx_rtu->confirmation_to_ignore = TRUE;
        }
    }
    return rc;
}

static ssize_t _modbus_rtu_recv(modbus_t *ctx, uint8_t *rsp, int rsp_length, int timeout)
{
	/* 使用usb/UART2/UART4的UART_Device来接收数据 */
    modbus_rtu_t *ctx_rtu = ctx->backend_data;
	struct UART_Device *pdev = ctx_rtu->dev;

	if (0 == pdev->RecvByte(pdev, rsp, timeout))
		return 1;
    else
    {
		errno = EIO;
		return -1;
    }
}

static int _modbus_rtu_flush(modbus_t *);

static int _modbus_rtu_pre_check_confirmation(modbus_t *ctx,
                                              const uint8_t *req,
                                              const uint8_t *rsp,
                                              int rsp_length)
{
    /* Check responding slave is the slave we requested (except for broacast
     * request) */
    if (req[0] != rsp[0] && req[0] != MODBUS_BROADCAST_ADDRESS) {
        if (ctx->debug) {
            debug_fprintf(stderr,
                    "The responding slave %d isn't the requested slave %d\n",
                    rsp[0],
                    req[0]);
        }
        errno = EMBBADSLAVE;
        return -1;
    } else {
        return 0;
    }
}

/* The check_crc16 function shall return 0 if the message is ignored and the
   message length if the CRC is valid. Otherwise it shall return -1 and set
   errno to EMBBADCRC. */
static int _modbus_rtu_check_integrity(modbus_t *ctx, uint8_t *msg, const int msg_length)
{
    uint16_t crc_calculated;
    uint16_t crc_received;
    int slave = msg[0];

    /* Filter on the Modbus unit identifier (slave) in RTU mode to avoid useless
     * CRC computing. */
    if (slave != ctx->slave && slave != MODBUS_BROADCAST_ADDRESS) {
        if (ctx->debug) {
            debug_printf("Request for slave %d ignored (not %d)\n", slave, ctx->slave);
        }
        /* Following call to check_confirmation handles this error */
        return 0;
    }

    crc_calculated = crc16(msg, msg_length - 2);
    crc_received = (msg[msg_length - 1] << 8) | msg[msg_length - 2];

    /* Check CRC of msg */
    if (crc_calculated == crc_received) {
        return msg_length;
    } else {
        if (ctx->debug) {
            debug_fprintf(stderr,
                    "ERROR CRC received 0x%0X != CRC calculated 0x%0X\n",
                    crc_received,
                    crc_calculated);
        }

        if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
            _modbus_rtu_flush(ctx);
        }
        errno = EMBBADCRC;
        return -1;
    }
}

/* Sets up a serial port for RTU communications */

/* POSIX */
static int _modbus_rtu_connect(modbus_t *ctx)
{
	/* 使用usb/UART2/UART4的UART_Device来初始化设备 */
    modbus_rtu_t *ctx_rtu = ctx->backend_data;
	struct UART_Device *pdev = ctx_rtu->dev;

	pdev->Init(pdev, ctx_rtu->baud, ctx_rtu->parity, ctx_rtu->data_bit, ctx_rtu->stop_bit);
	
    ctx->s = 1; //open(ctx_rtu->device, flags);
    return 0;
}

// FIXME Temporary solution before rewriting Windows RTU backend
static unsigned int _modbus_rtu_is_connected(modbus_t *ctx)
{
    return 1;
}


static void _modbus_rtu_close(modbus_t *ctx)
{
}

static int _modbus_rtu_flush(modbus_t *ctx)
{
	/* 使用usb/UART2/UART4的UART_Device来flush数据 */
    modbus_rtu_t *ctx_rtu = ctx->backend_data;
	struct UART_Device *pdev = ctx_rtu->dev;

	return pdev->Flush(pdev);
}

static int
_modbus_rtu_select(modbus_t *ctx, fd_set *rset, struct timeval *tv, int length_to_read)
{
//    int s_rc;
//    while ((s_rc = select(ctx->s + 1, rset, NULL, NULL, tv)) == -1) {
//        if (errno == EINTR) {
//            if (ctx->debug) {
//                debug_fprintf(stderr, "A non blocked signal was caught\n");
//            }
//            /* Necessary after an error */
//            FD_ZERO(rset);
//            FD_SET(ctx->s, rset);
//        } else {
//            return -1;
//        }
//    }

//    if (s_rc == 0) {
//        /* Timeout */
//        errno = ETIMEDOUT;
//        return -1;
//    }

    return 0;
}

static void _modbus_rtu_free(modbus_t *ctx)
{
    if (ctx->backend_data) {
        free(((modbus_rtu_t *) ctx->backend_data)->device);
        free(ctx->backend_data);
    }

    free(ctx);
}


// clang-format off
const modbus_backend_t _modbus_rtu_backend_uart = {
    _MODBUS_BACKEND_TYPE_RTU,
    _MODBUS_RTU_HEADER_LENGTH,
    _MODBUS_RTU_CHECKSUM_LENGTH,
    MODBUS_RTU_MAX_ADU_LENGTH,
    _modbus_set_slave,
    _modbus_rtu_build_request_basis,
    _modbus_rtu_build_response_basis,
    _modbus_rtu_prepare_response_tid,
    _modbus_rtu_send_msg_pre,
    _modbus_rtu_send,
    _modbus_rtu_receive,
    _modbus_rtu_recv,
    _modbus_rtu_check_integrity,
    _modbus_rtu_pre_check_confirmation,
    _modbus_rtu_connect,
    _modbus_rtu_is_connected,
    _modbus_rtu_close,
    _modbus_rtu_flush,
    _modbus_rtu_select,
    _modbus_rtu_free
};


// clang-format on

modbus_t *
modbus_new_st_rtu(const char *device, int baud, char parity, int data_bit, int stop_bit)
{
    modbus_t *ctx;
    modbus_rtu_t *ctx_rtu;
	struct UART_Device *pdev;

    /* Check device argument */
    if (device == NULL || *device == 0) {
        debug_fprintf(stderr, "The device string is empty\n");
        errno = EINVAL;
        return NULL;
    }

    ctx = (modbus_t *) malloc(sizeof(modbus_t));
    if (ctx == NULL) {
        return NULL;
    }

    _modbus_init_common(ctx);

	ctx->backend = &_modbus_rtu_backend_uart;
	pdev = GetUARTDevice((char *)device);
	if (!pdev)
	{
		modbus_free(ctx);
		errno = ENOENT;
		return NULL;
	}

    ctx->backend_data = (modbus_rtu_t *) malloc(sizeof(modbus_rtu_t));
    if (ctx->backend_data == NULL) {
        modbus_free(ctx);
        errno = ENOMEM;
        return NULL;
    }
    ctx_rtu = (modbus_rtu_t *) ctx->backend_data;
	ctx_rtu->dev = pdev;

    /* Device name and \0 */
    ctx_rtu->device = (char *) malloc((strlen(device) + 1) * sizeof(char));
    if (ctx_rtu->device == NULL) {
        modbus_free(ctx);
        errno = ENOMEM;
        return NULL;
    }

    strcpy(ctx_rtu->device, device);

    ctx_rtu->baud = baud;
    if (parity == 'N' || parity == 'E' || parity == 'O') {
        ctx_rtu->parity = parity;
    } else {
        modbus_free(ctx);
        errno = EINVAL;
        return NULL;
    }
    ctx_rtu->data_bit = data_bit;
    ctx_rtu->stop_bit = stop_bit;


    ctx_rtu->confirmation_to_ignore = FALSE;

    return ctx;
}