shellmatta/src/shellmatta.c

/*
 * Copyright (c) 2019 Stefan Strobel <stefan.strobel@shimatta.net>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

/**
 * @file    shellmatta.c
 * @brief   Main implementation of the Shellmatta terminal implementation
 * @author  Stefan Strobel <stefan.strobel@shimatta.net>
 */

/**
 * @addtogroup shellmatta
 * @{
 * @addtogroup shellmatta_private
 * @{
 */

#include "shellmatta.h"
#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include <stdarg.h>


/* defines */

#ifndef SHELLMATTA_OUTPUT_BUFFER_SIZE
#define SHELLMATTA_OUTPUT_BUFFER_SIZE   128u
#endif

#define SHELLMATTA_MIN(a,b) (((a) > (b)) ?  (b) : (a))
#define SHELLMATTA_MAX(a,b) (((a) < (b)) ?  (b) : (a))
#define SHELLMATTA_PRINT_BUFFER(buffer,cnt,fct) \
    while((cnt) > sizeof((buffer)))             \
    {                                           \
        (cnt) -= sizeof((buffer));              \
        (fct)((buffer), sizeof((buffer)));      \
    }                                           \
    if((cnt) != 0u)                             \
    {                                           \
        (fct)((buffer), (cnt));                 \
    }

#define SHELLMATTA_MAGIC    0x5101E110u

/* static functions */

/**
 * @brief       function to write an echo to the output depending on
 *              the echo enabled state of the instance
 * @param[in]   inst    pointer to a shellmatta instance
 * @param[in]   data    pointer to the data so send
 * @param[in]   length  length of the data to send (in byte)
 */
static void writeEcho(  shellmatta_instance_t   *inst,
                        const char              *data,
                        uint32_t                length)
{
    if(true == inst->echoEnabled)
    {
        inst->write(data, length);
    }
}

/**
 * @brief       appends a byte to the history ring stack buffer
 * @param[in]   inst    pointer to a shellmatta instance
 * @param[in]   byte    byte to append to the history buffer
 */
static void appendHistoryByte(shellmatta_instance_t *inst, char byte)
{
    /** -# calculate the new history buffer index */
    inst->historyEnd ++;
    if(inst->historyEnd >= inst->historyBufferSize)
    {
        inst->historyEnd = 0u;
    }

    /** -# append the byte */
    inst->historyBuffer[inst->historyEnd] = byte;

    /** -# check if the we overwrite an existing stored command */
    if(inst->historyEnd == inst->historyStart)
    {
        /** -# move the start pointer to the next termination (0) */
        do
        {
            inst->historyStart ++;

            if(inst->historyStart >= inst->historyBufferSize)
            {
                inst->historyStart = 0u;
            }

        }while(0u != inst->historyBuffer[inst->historyStart]);
    }
}

/**
 * @brief       reads a byte from the history buffer and decreases the read index
 * @param[in]   inst    pointer to a shellmatta instance
 * @param[out]  byte    pointer to a char where the read out byte will be stored
 * @return
 */
static bool getHistoryByte(shellmatta_instance_t *inst, char *byte)
{
    bool ret = false;

    /** -# check if we have reached the end of the buffer already */
    if(inst->historyRead != inst->historyStart)
    {
        /** -# read out one byte and decrease the read index */
        *byte = inst->historyBuffer[inst->historyRead];

        if(0u == inst->historyRead)
        {
            inst->historyRead = inst->historyBufferSize;
        }

        inst->historyRead --;

        ret = true;
    }

    return ret;
}

/**
 * @brief       stores the current command from the instances buffer into the
 *              history buffer
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void storeHistoryCmd(shellmatta_instance_t *inst)
{
    uint32_t i;

    /** -# check if we have enough room for the command in the history buffer
     * and there is a new command to be stored                              */
    if(     (inst->historyBufferSize > inst->inputCount)
        &&  (0u != inst->inputCount)
        &&  (true == inst->dirty))
    {
        /** -# append the command termination */
        appendHistoryByte(inst, 0u);

        /** -# append the command byte wise in reverse direction */
        for(i = inst->inputCount; i > 0u; i --)
        {
            appendHistoryByte(inst, inst->buffer[i - 1u]);
        }
    }

    /** -# remove the dirty flag - everything is nice and saved */
    inst->dirty = false;
}

/**
 * @brief       navigates in the history buffer by the given number of commands
 * @param[in]   inst    pointer to a shellmatta instance
 * @param[in]   cnt     direction and count to navigate
 * @return
 */
static bool navigateHistoryCmd(shellmatta_instance_t *inst, int32_t cnt)
{
    bool ret = true;
    uint32_t tempReadIdx = 0u;

    while((cnt > 0) && (true == ret))
    {
        if(inst->historyRead != inst->historyEnd)
        {
            inst->historyRead ++;
        }
        while(inst->historyRead != inst->historyEnd)
        {
            inst->historyRead ++;
            if(inst->historyRead >= inst->historyBufferSize)
            {
                inst->historyRead = 0u;
            }

            if(     (inst->historyRead != inst->historyEnd)
                &&  (0u == inst->historyBuffer[inst->historyRead]))
            {
                if(0u == inst->historyRead)
                {
                    inst->historyRead = inst->historyBufferSize;
                }
                inst->historyRead --;
                cnt -= 1;
                break;
            }
        }

        if(inst->historyRead == inst->historyEnd)
        {
            ret = false;
        }
    }

    while((cnt < 0) && (true == ret))
    {
        tempReadIdx = inst->historyRead;
        while(inst->historyRead != inst->historyStart)
        {
            if(0u == inst->historyRead)
            {
                inst->historyRead = inst->historyBufferSize;
            }
            inst->historyRead --;

            if(     (inst->historyRead != inst->historyStart)
                &&  (0u == inst->historyBuffer[inst->historyRead]))
            {
                if(0u == inst->historyRead)
                {
                    inst->historyRead = inst->historyBufferSize;
                }
                inst->historyRead --;
                cnt += 1;
                break;
            }
        }
        if(inst->historyRead == inst->historyStart)
        {
            inst->historyRead = tempReadIdx;
            inst->historyReadUp = false;
            ret = false;
        }
    }

    return ret;
}

/**
 * @brief       restores the command from the history buffer where the read
 *              index points on
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void restoreHistoryCmd(shellmatta_instance_t *inst)
{
    char byte;
    bool ret = true;

    ret = getHistoryByte(inst, &byte);
    while((ret == true) && (byte != 0u))
    {
        inst->buffer[inst->inputCount] = byte;
        inst->inputCount    ++;
        inst->cursor        ++;
        ret = getHistoryByte(inst, &byte);
    }

    writeEcho(inst, inst->buffer, inst->inputCount);
    navigateHistoryCmd(inst, 1);
    inst->dirty = false;
}

/**
 * @brief       resets the history buffer pointers to show to the most recent
 *              command again
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void resetHistoryBuffer(shellmatta_instance_t *inst)
{
    inst->historyRead = inst->historyEnd;
    inst->historyReadUp = true;
}

/**
 * @brief       tells the terminal to save the current cursor position
 * @param[in]   inst    pointer to shellmatta instance
 */
static void saveCursorPos(shellmatta_instance_t *inst)
{
    writeEcho(inst, "\e[s", 3u);
}

/**
 * @brief       tells the terminal to restore the saved cursor position
 * @param[in]   inst    pointer to shellmatta instance
 */
static void restoreCursorPos(shellmatta_instance_t *inst)
{
    writeEcho(inst, "\e[u", 3u);
}

/**
 * @brief       tells the terminal to erase the line on the right side of the
 *              cursor
 * @param[in]   inst    pointer to shellmatta instance
 */
static void eraseLine(shellmatta_instance_t *inst)
{
    writeEcho(inst, "\e[K", 3u);
}

/**
 * @brief       moves the cursor back by the given amoung of characters
 * @param[in]   inst    pointer to shellmatta instance
 * @param[in]   length  number of characters to rewind
 */
static void rewindCursor(shellmatta_instance_t *inst, uint32_t length)
{
    char    terminalCmd[16];
    size_t  size;

    length = SHELLMATTA_MIN (length, inst->cursor);
    if(length > 0u)
    {
        size = snprintf(terminalCmd, sizeof(terminalCmd), "\e[%uD", length);
        writeEcho(inst, terminalCmd, size);
        inst->cursor -= length;
    }
}

/**
 * @brief       moves the cursor forward by the given amoung of characters
 * @param[in]   inst    pointer to shellmatta instance
 * @param[in]   length  number of characters to move forward
 */
static void forwardCursor(shellmatta_instance_t *inst, uint32_t length)
{
    char   terminalCmd[16];
    size_t size;

    length = SHELLMATTA_MAX (length, (inst->inputCount - inst->cursor));
    if (length > 0u)
    {
        size = snprintf(terminalCmd, sizeof(terminalCmd), "\e[%uC", length);
        writeEcho(inst, terminalCmd, size);
        inst->cursor += length;
    }
}

/**
 * @brief       inserts the given amount of characters at the cursor position
 * @param[in]   inst    pointer to shellmatta instance
 * @param[in]   data    pointer to the data to be inserted
 * @param[in]   length  length of the data to be inserted
 */
static void insertChars(shellmatta_instance_t   *inst,
                        char                    *data,
                        uint32_t                 length)
{
    if(0u != length)
    {
        /** -# check if we have to move chars in the buffer */
        if(     (inst->cursor     != inst->inputCount)
            &&  (SHELLMATTA_MODE_INSERT == inst->mode))
        {
            /** -# move the existing chars */
            for (   uint32_t i = inst->inputCount;
                    i > inst->cursor;
                    i --)
            {
                inst->buffer[i + length - 1] = inst->buffer[i - 1];
            }

            /** -# store and print the new chars */
            memcpy(&(inst->buffer[inst->cursor]), data, length);
            writeEcho(inst, data, length);

            /** -# print the other chars and restore the cursor to this position */
            eraseLine(inst);
            saveCursorPos(inst);
            writeEcho(  inst,
                        &(inst->buffer[inst->cursor + length]),
                        inst->inputCount - inst->cursor);
            restoreCursorPos(inst);
        }
        /** -# just overwrite/append the chars */
        else
        {
            memcpy(&(inst->buffer[inst->cursor]), data, length);
            writeEcho(inst, data, length);
        }

        inst->inputCount    += length;
        inst->cursor        += length;
    }
}

/**
 * @brief       removes the given amount of characters from the current cursor
 *              position
 * @param[in]   inst        pointer to a shellmatta instance
 * @param[in]   length      number of characters to remove
 * @param[in]   backspace   remove characters left of the cursor
 */
static void removeChars(shellmatta_instance_t   *inst,
                        uint32_t                 length,
                        bool                     backspace)
{
    if(0u != length)
    {
        /** -# rewind the cursor in case of backspace */
        if(true == backspace)
        {
            length = SHELLMATTA_MIN (length, inst->cursor);
            rewindCursor(inst, length);
        }
        else
        {
            length = SHELLMATTA_MIN (length, inst->inputCount - inst->cursor);
        }
        /** -# delete the char at the cursor position */
        for (   uint32_t i = inst->cursor;
                i < (inst->inputCount - length);
                i++)
        {
            inst->buffer[i] = inst->buffer[i + length];
        }

        /** -# print the rest of the line again */
        eraseLine(inst);
        saveCursorPos(inst);
        writeEcho(    inst,
                    &(inst->buffer[inst->cursor]),
                     (inst->inputCount - inst->cursor - length));
        restoreCursorPos(inst);

        inst->inputCount -= length;
    }
}

/**
 * @brief       clears the input buffer and removes the currend command from
 *              the terminal output
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void clearInput(shellmatta_instance_t *inst)
{
    rewindCursor(inst, inst->cursor);
    eraseLine(inst);
    inst->inputCount = 0u;
    inst->dirty = false;
}

/**
 * @brief       processes the excape character stream of the instance and chacks
 *              if an arrow key was pressed
 * @param[in]   inst    pointer to a shellmatta instance
 * @return      #SHELLMATTA_OK if an arrow key was pressed
 */
static shellmatta_retCode_t processArrowKeys(shellmatta_instance_t *inst)
{
    shellmatta_retCode_t ret = SHELLMATTA_USE_FAULT;

    if ('[' == inst->escapeChars[0])
    {
        ret = SHELLMATTA_OK;

        switch (inst->escapeChars[1])
        {
        case 'A': /* arrow up     */
            storeHistoryCmd(inst);
            if(false == inst->historyReadUp)
            {
                navigateHistoryCmd(inst, -1);
            }
            inst->historyReadUp = true;
            clearInput(inst);
            restoreHistoryCmd(inst);
            navigateHistoryCmd(inst, -1);

            break;
        case 'B': /* arrow down   */

            if((inst->historyRead != inst->historyEnd))
            {
                storeHistoryCmd(inst);
                if(true == inst->historyReadUp)
                {
                    navigateHistoryCmd(inst, 1);
                }
                inst->historyReadUp = false;
                navigateHistoryCmd(inst, 1);
                clearInput(inst);
                restoreHistoryCmd(inst);
            }
            break;
        case 'C': /* arrow right  */
            forwardCursor(inst, 1u);
            break;
        case 'D': /* arrow left   */
            rewindCursor(inst, 1u);
            break;
        default:
            /** ignore unknown escape */
            ret = SHELLMATTA_USE_FAULT;
            break;
        }
    }
    return ret;
}

/**
 * @brief       handles a ANSI escape sequence to be able to react to some
 *              special keys
 * @param[in]   inst    pointer to a shellmatta instance
 * @param[in]   data    new received character of the escape sequence
 */
static void handleEscapeSequence(shellmatta_instance_t *inst, char data)
{
    switch (inst->escapeCounter)
    {
    case 1u:
        inst->escapeChars[inst->escapeCounter - 1] = data;
        inst->escapeCounter ++;
        break;
    case 2u:
        inst->escapeChars[inst->escapeCounter - 1] = data;
        /** -# check if an arrow key was pressed */
        if(SHELLMATTA_OK == processArrowKeys(inst))
        {
            inst->escapeCounter = 0u;
        }
        /** -# check if end was pressed */
        else if (   (0x4f == inst->escapeChars[0])
                &&  (0x46 == inst->escapeChars[1]))
        {
            forwardCursor(inst, inst->inputCount - inst->cursor);
            inst->escapeCounter = 0u;
        }
        /** -# if the highest bit is not set this is usually not the end of the
         * sequence - so we go on */
        else if(0u == (0x40 & data))
        {
            inst->escapeCounter ++;
        }
        else
        {
            inst->escapeCounter = 0u;
        }
        break;
    case 3u:
        /** -# check if delete was pressed */
        inst->escapeChars[inst->escapeCounter - 1] = data;
        if(     (0x5b == inst->escapeChars[0])
            &&  (0x33 == inst->escapeChars[1])
            &&  (0x7e == inst->escapeChars[2]))
        {
            removeChars(inst, 1u, false);
            inst->escapeCounter = 0u;
        }
        /** -# check if pos1 was pressed */
        else if (   (0x5bu == inst->escapeChars[0])
                &&  (0x31u == inst->escapeChars[1])
                &&  (0x7eu == inst->escapeChars[2]))
        {
            rewindCursor(inst, inst->cursor);
            inst->escapeCounter = 0u;
        }
        else if(0u == (0x40u & data))
        {
            inst->escapeCounter ++;
        }
        else
        {
            inst->escapeCounter = 0u;
        }
        break;
    default:
        inst->escapeCounter = 0u;
        break;
    }
}

/**
 * @brief       terminates an input and prints the prompt again
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void terminateInput(shellmatta_instance_t *inst)
{
    inst->inputCount    = 0u;
    inst->cursor        = 0u;
    shellmatta_printf(inst, "\r\n%s", inst->prompt);
}

/**
 * @brief       searches the registered commands for matching ones and prints
 *              the common part of all matching commands on the output
 *              if called twice all matching commands are printed
 * @param[in]   inst    pointer to a shellmatta instance
 */
static void doAutocomplete(shellmatta_instance_t *inst)
{
    shellmatta_cmd_t   *cmd         = inst->cmdList;
    char               *tempCmd     = NULL;
    uint32_t            minLen      = 0u;
    uint32_t            sizeDiff    = 0u;
    bool                exactMatch  = true;
    uint32_t            printedLen  = 0u;
    uint32_t            tempCursor  = 0u;

    /** -# increase the tab counter to print all matching commands next time */
    inst->tabCounter++;

    /** -# on douple tab show all matching commands */
    if (1u < inst->tabCounter)
    {
        inst->tabCounter        = 0u;

        /** -# loop through all registered commands */
        while (NULL != cmd)
        {
            /** -# check if command matches the input */
            if(    (strlen(cmd->cmd) >= inst->cursor)
                && (0u == memcmp(cmd->cmd, inst->buffer, inst->cursor)))
            {
                /** -# add newline on first find */
                if(0u == printedLen)
                {
                    inst->write("\r\n", 2u);
                }
                inst->write(cmd->cmd, strlen(cmd->cmd));
                printedLen += strlen(cmd->cmd);
                inst->write("    ", 4u);
                printedLen += 4u;
            }
            /** -# check if command alias matches the input */
            if(    (strlen(cmd->cmdAlias) >= inst->cursor)
                && (0u == memcmp(cmd->cmdAlias, inst->buffer, inst->cursor)))
            {
                /** -# add newline on first find */
                if(0u == printedLen)
                {
                    inst->write("\r\n", 2u);
                }
                inst->write(cmd->cmdAlias, strlen(cmd->cmdAlias));
                printedLen += strlen(cmd->cmdAlias);
                inst->write("    ", 4u);
                printedLen += 4u;
            }
            cmd = cmd->next;
        }
        /** -# print input again if a commands was found */
        if(printedLen > 0u)
        {
            writeEcho(inst, "\r\n", 2u);
            writeEcho(inst, inst->prompt, strlen(inst->prompt));
            writeEcho(inst, inst->buffer, inst->inputCount);
            tempCursor = inst->cursor;
            inst->cursor = inst->inputCount;
            rewindCursor(inst, inst->inputCount - tempCursor);
        }
    }
    /** -# on single tab autocomplete as far as possible */
    else if(0u != inst->cursor)
    {
        /** -# loop through all registered commands */
        while (NULL != cmd)
        {
            /** -# check if command matches the input */
            if(    (strlen(cmd->cmd) >= inst->cursor)
                && (0u == memcmp(cmd->cmd, inst->buffer, inst->cursor)))
            {
                /** -# store first match */
                if(NULL == tempCmd)
                {
                    tempCmd = cmd->cmd;
                    minLen = strlen(cmd->cmd);
                }
                /** -# find common part of the matching commands */
                else
                {
                    exactMatch = false;
                    minLen = SHELLMATTA_MIN(strlen(cmd->cmd), minLen);
                    for(uint32_t i = 0u; i < minLen; i++)
                    {
                        if(cmd->cmd[i] != tempCmd[i])
                        {
                            minLen = i;
                        }
                    }
                }
            }

            /** -# check if command Alias matches the input */
            if(    (strlen(cmd->cmdAlias) >= inst->cursor)
                && (0u == memcmp(cmd->cmdAlias, inst->buffer, inst->cursor)))
            {
                /** -# store first match */
                if(NULL == tempCmd)
                {
                    tempCmd = cmd->cmdAlias;
                    minLen = strlen(cmd->cmdAlias);
                }
                /** -# find common part of the matches */
                else
                {
                    exactMatch = false;
                    minLen = SHELLMATTA_MIN(strlen(cmd->cmdAlias), minLen);
                    for(uint32_t i = 0u; i < minLen; i++)
                    {
                        if(cmd->cmdAlias[i] != tempCmd[i])
                        {
                            minLen = i;
                        }
                    }
                }
            }
            cmd = cmd->next;
        }

        /** -# autocomplete found command */
        if(NULL != tempCmd)
        {
            /** -# calculate the size of the command to be inserted */
            sizeDiff = minLen - inst->cursor;

            /** -# copy the found part into the buffer and display it */
            insertChars(inst, &(tempCmd[inst->cursor]), sizeDiff);

            /** -# on exact match there is no need to double Tab to display all */
            if(true == exactMatch)
            {
                inst->tabCounter = 0u;
            }
        }
    }
    else
    {
        /* nothing to do here */
    }
}

/**
 * @brief       prints all possible commands with description and usage
 * @param[in]   handle      handle  shellmatta instance handle
 * @param[in]   arguments   not used here
 * @param[in]   length      not used here
 * @return      #SHELLMATTA_OK
 *              #SHELLMATTA_ERROR (buffer overflow)
 */
static shellmatta_retCode_t helpCmdFct(shellmatta_handle_t handle, const char *arguments, uint32_t length)
{
    shellmatta_retCode_t    ret = SHELLMATTA_OK;
    shellmatta_instance_t   *inst = (shellmatta_instance_t*) handle;
    shellmatta_cmd_t        *cmd = inst->cmdList;
    size_t                  maxCmdLen       = 0u;
    size_t                  maxCmdAliasLen  = 0u;
    size_t                  maxCmdHelpLen   = 0u;
    size_t                  cmdLen       = 0u;
    size_t                  cmdAliasLen  = 0u;
    size_t                  cmdHelpLen   = 0u;
    uint32_t                tabCnt       = 0u;
    static const char       tabBuffer[] = { ' ', ' ', ' ', ' ',
                                            ' ', ' ', ' ', ' ',
                                            ' ', ' ', ' ', ' ',
                                            ' ', ' ', ' ', ' '};

    /** -# loop through all commands to determine the lengths of each cmd */
    while(NULL != cmd)
    {
        maxCmdLen       = SHELLMATTA_MAX(maxCmdLen,         strlen(cmd->cmd));
        maxCmdAliasLen  = SHELLMATTA_MAX(maxCmdAliasLen,    strlen(cmd->cmdAlias));
        maxCmdHelpLen   = SHELLMATTA_MAX(maxCmdHelpLen,     strlen(cmd->helpText));
        cmd = cmd->next;
    }

    /** -# loop through all commands and print all possible information */
    cmd = inst->cmdList;
    while(NULL != cmd)
    {
        /** -# determine the length of each field to add padding */
        cmdLen       = strlen(cmd->cmd);
        cmdAliasLen  = strlen(cmd->cmdAlias);
        cmdHelpLen   = strlen(cmd->helpText);

        shellmatta_printf(handle, "%s  ", cmd->cmd);
        tabCnt = (maxCmdLen - cmdLen);
        SHELLMATTA_PRINT_BUFFER(tabBuffer, tabCnt, inst->write);
        shellmatta_printf(handle, "%s  ", cmd->cmdAlias);
        tabCnt = (maxCmdAliasLen - cmdAliasLen);
        SHELLMATTA_PRINT_BUFFER(tabBuffer, tabCnt, inst->write);
        shellmatta_printf(handle, "%s  ", cmd->helpText);
        tabCnt = (maxCmdHelpLen - cmdHelpLen);
        SHELLMATTA_PRINT_BUFFER(tabBuffer, tabCnt, inst->write);
        shellmatta_printf(handle, "%s\r\n", cmd->usageText);

        cmd = cmd->next;
    }

    (void)arguments;
    (void)length;

    return ret;
}
shellmatta_cmd_t helpCmd = {"help", "h", "Print this help text", "help", helpCmdFct, NULL};

/* interface functions */

/**
 * @}
 * @addtogroup shellmatta_api
 * @{
 */

/**
 * @brief           initialize the shellmatta terminal and provide all callbacks
 * @param[in,out]   inst                pointer to a shellmatta instance
 * @param[out]      handle              pointer to shellmatta handle -
 *                                      has to be used for all furterh api calls
 * @param[in]       buffer              pointer to the input buffer to use
 * @param[in]       bufferSize          size of the provided input buffer
 * @param[in]       historyBuffer       pointer to the history buffer to use
 *                                      NULL in case of no history buffer
 * @param[in]       historyBufferSize   size of the history buffer
 *                                      0 in case of no history buffer
 * @param[in]       prompt              pointer to prompt string - is printed
 *                                      after each command
 * @param[in]       cmdList             constant command list if no dynamic
 *                                      adding of commands is desired
 * @param[in]       writeFct            function pointer to output function
 */
shellmatta_retCode_t shellmatta_doInit(
        shellmatta_instance_t  *inst,
        shellmatta_handle_t    *handle,
        char                   *buffer,
        uint32_t                bufferSize,
        char                   *historyBuffer,
        uint32_t                historyBufferSize,
        const char             *prompt,
        const shellmatta_cmd_t *cmdList,
        shellmatta_write_t     writeFct)
{
    /** -# check parameters for plausibility  */
    if(     (NULL != inst)
        &&  (NULL != handle)
        &&  (NULL != buffer)
        &&  (0u   != bufferSize)
        &&  (NULL != prompt)
        &&  (NULL != writeFct)
        &&  ((NULL != historyBuffer) || (0u == historyBufferSize)))
    {
        /** -# copy all provided buffers into the shellmatta instance */
        inst->buffer                = buffer;
        inst->bufferSize            = bufferSize;
        inst->inputCount            = 0u;
        inst->cursor                = 0u;
        inst->historyBuffer         = historyBuffer;
        inst->historyBufferSize     = historyBufferSize;
        inst->historyStart          = 0u;
        inst->historyEnd            = 0u;
        inst->historyRead           = 0u;
        inst->historyReadUp         = true;
        inst->write                 = writeFct;
        inst->prompt                = prompt;
        inst->echoEnabled           = true;
        inst->dirty                 = false;
        inst->tabCounter            = 0u;
        inst->escapeCounter         = 0u;
        inst->mode                  = SHELLMATTA_MODE_INSERT;
        inst->cmdList               = &helpCmd;
        inst->cmdListIsConst        = false;

        if(NULL != cmdList)
        {
            helpCmd.next = (shellmatta_cmd_t *) cmdList;
            inst->cmdListIsConst = true;
        }

        inst->magic = SHELLMATTA_MAGIC;
        *handle     = (shellmatta_handle_t)inst;

        /** -# print the first prompt */
        terminateInput(inst);
    }

    return SHELLMATTA_OK;
}

/**
 * @brief       adds a command to the command list alphabetically ordered
 * @param[in]   handle  shellmatta instance handle
 * @param[in]   cmd     pointer to the command to add type #shellmatta_cmd_t
 * @return      errorcode   #SHELLMATTA_OK
 *                          #SHELLMATTA_USE_FAULT (param err)
 *                          SHELLMATTA_DUPLICATE
 */
shellmatta_retCode_t shellmatta_addCmd(shellmatta_handle_t handle, shellmatta_cmd_t *cmd)
{
    shellmatta_instance_t   *inst       = (shellmatta_instance_t*)handle;
    shellmatta_cmd_t       *tempCmd;
    shellmatta_cmd_t       **prevCmd;
    bool                    cmdPlaced   = false;
    shellmatta_retCode_t    ret         = SHELLMATTA_OK;
    int                     cmdDiff     = 0;
    int                     aliasDiff   = 0;

    /** -# check parameters for plausibility  */
    if(     (NULL               != inst)
        &&  (SHELLMATTA_MAGIC   == inst->magic)
        &&  (false              == inst->cmdListIsConst))
    {
        tempCmd     = inst->cmdList;
        prevCmd    = &inst->cmdList;
        /** -# register first command as list entry */
        if (NULL == tempCmd)
        {
            inst->cmdList = cmd;
            cmd->next = NULL;
        }
        /** -# append the new command sorted */
        else
        {
            while ((false == cmdPlaced) && (SHELLMATTA_OK == ret))
            {
                cmdDiff     = strcmp(tempCmd->cmd,      cmd->cmd);
                aliasDiff   = strcmp(tempCmd->cmdAlias, cmd->cmdAlias);
                /** -# check for a duplicate command */
                if((0u == cmdDiff) || (0u == aliasDiff))
                {
                    ret = SHELLMATTA_DUPLICATE;
                }
                else if(0 < cmdDiff)
                {
                    cmd->next   = tempCmd;
                    *prevCmd    = cmd;
                    cmdPlaced   = true;
                }
                else if(NULL == tempCmd->next)
                {
                    tempCmd->next = cmd;
                    cmd->next = NULL;
                    cmdPlaced = true;
                }
                else
                {
                    /* nothing to do */
                }
                prevCmd = &tempCmd;
                tempCmd = tempCmd->next;
            }
        }
    }
    else
    {
        ret = SHELLMATTA_USE_FAULT;
    }

    return ret;
}

/**
 * @brief       processes the passed amount of data
 * @param[in]   handle  shellmatta instance handle
 * @param[in]   data    pointer to input data to process
 * @param[in]   size    length of input data to process
 * @return      errorcode   #SHELLMATTA_OK
 *                          #SHELLMATTA_USE_FAULT
 */
shellmatta_retCode_t shellmatta_processData(shellmatta_handle_t     handle,
                                            char                    *data,
                                            uint32_t                 size)
{
    shellmatta_cmd_t        *cmd;
    uint8_t                 cmdExecuted = 0u;
    shellmatta_retCode_t    ret = SHELLMATTA_OK;
    shellmatta_instance_t   *inst = (shellmatta_instance_t*)handle;

    /** -# check parameters for plausibility  */
    if(     (NULL               != inst)
        &&  (SHELLMATTA_MAGIC   == inst->magic))
    {

        /** -# process byte wise */
        for (uint32_t i = 0u; i < size; i++)
        {
            /** -# handle escape sequences */
            if(inst->escapeCounter != 0u)
            {
                handleEscapeSequence(inst, *data);
            }
            /** -# handle return as start of processing the command */
            else if ('\r' == *data)
            {
                cmd                             = inst->cmdList;
                inst->buffer[inst->inputCount]  = 0u;

                /** -# store the current command and reset the history buffer */
                inst->dirty = true;
                storeHistoryCmd(inst);
                resetHistoryBuffer(inst);

                /** -# search for a matching command */
                while (NULL != cmd)
                {
                    if (    (0 == strcmp(inst->buffer, cmd->cmd))
                        ||  (0 == strcmp(inst->buffer, cmd->cmdAlias)))
                    {
                        inst->write("\r\n", 2u);

                        cmdExecuted = 1u;
                        cmd->cmdFct(inst, inst->buffer, inst->inputCount);
                        cmd = NULL;
                    }
                    else
                    {
                        cmd = cmd->next;
                    }
                }

                if ((cmdExecuted == 0u) && (inst->inputCount > 0))
                {
                    inst->buffer[inst->inputCount] = '\0';
                    shellmatta_printf(  inst,
                                        "\r\nCommand: %s not found",
                                        inst->buffer);
                }
                terminateInput(inst);
            }
            /** -# check for tabulator key - auto complete */
            else if('\t' == *data)
            {
                inst->dirty = true;
                doAutocomplete(inst);
            }
            /** -# check for cancel -
             *      terminate current input and print prompt again */
            else if(3 == *data)
            {
                inst->dirty = false;
                resetHistoryBuffer(inst);
                terminateInput(inst);
            }
            /** -# check for backspace */
            else if('\b' == *data)
            {
                inst->dirty = true;
                removeChars(inst, 1u, true);
            }
            /** -# check for delete key */
            else if(0x7eu == *data)
            {
                inst->dirty = true;
                removeChars(inst, 1u, false);
            }
            /** -# check for start of escape sequence */
            else if('\e' == *data)
            {
                inst->escapeCounter = 1u;
            }
            else
            {
                inst->dirty = true;
                insertChars(inst, data, 1);
            }

            /** -# reset tab counter on not a tab */
            if ('\t' != *data)
            {
                inst->tabCounter = 0u;
            }

            data ++;
        }
    }
    else
    {
        ret = SHELLMATTA_USE_FAULT;
    }
    return ret;
}

/**
 * @brief       printf like function to print output to the instances output
 * @param[in]   handle  shellmatta instance handle
 * @param[in]   fmt     format string and parameters
 * @return      errorcode   #SHELLMATTA_OK
 *                          #SHELLMATTA_USE_FAULT   (no valid instance)
 *                          #SHELLMATTA_ERROR       (buffer overflow or format err)
 */
shellmatta_retCode_t shellmatta_printf( shellmatta_handle_t handle,
                                        const char          *fmt,
                                        ...)
{
    char                    outputBuffer[SHELLMATTA_OUTPUT_BUFFER_SIZE];
    va_list                 arg;
    int                     length;
    shellmatta_retCode_t    ret = SHELLMATTA_OK;
    shellmatta_instance_t   *inst = (shellmatta_instance_t*)handle;

    /** -# check parameters for plausibility  */
    if(     (NULL               != inst)
        &&  (SHELLMATTA_MAGIC   == inst->magic))
    {
        va_start(arg, fmt);
        length = vsnprintf(outputBuffer, SHELLMATTA_OUTPUT_BUFFER_SIZE, fmt, arg);
        va_end(arg);

        if(length < 0)
        {
            ret = SHELLMATTA_ERROR;
        }
        else
        {
            inst->write(outputBuffer, length);
        }
    }
    else
    {
        ret = SHELLMATTA_USE_FAULT;
    }
    return ret;
}

/** @} */
/** @} */