Bitmessage installer

#!/bin/bash
#
# The MIT License (MIT)
#
# Copyright (c) 2013 Thomas Klose
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this software
# and associated documentation files (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
# The above copyright notice and this permission notice shall be included in all copies or substantial
# portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
# LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
# EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
# THE USE OR OTHER DEALINGS IN THE SOFTWARE
#

echo "Welcomme to Bitmessageinstaller"
echo "if this script stops working properly, please install bitmesaage manually"
echo "as descibed in https://bitmessage.org/wiki/Compiling_instructions"
echo " "
echo "setting up environment"

BITMESSAGE_GIT="https://github.com/Bitmessage/PyBitmessage"
EXIT_UNKOWNINSTALLER=1
EXIT_REQUIREMENTSUNRESSOLVED=2
EXIT_BITMESSAGEEXECUTEABLENOTFOUND=3

INSTALLDIR="/home/`id -un`/.bitmessage/"
PY_EXECUTEABLE="/home/`id -un`/.bitmessage/PyBitmessage/bitmessagemain.py"
BM_EXECUTEABLE="/usr/local/bin/bitmessage"

if [ -n $(which sudo) ]
then
    SWITCHTOROOTCOMMAND="sudo"
else
    SWITCHTOROOTCOMMAND="su root"
fi

echo "discovering requirements ..."

REQUIREMENTSTOINSTALL=""

if [ -z $(which python) ]
then
    REQUIREMENTSTOINSTALL="$REQUIREMENTSTOINSTALL python"
fi

if [ -z $(which openssl) ]
then
    REQUIREMENTSTOINSTALL="$REQUIREMENTSTOINSTALL openssl"
fi

if [ -z $(which python-qt4) ]
then
    REQUIREMENTSTOINSTALL="$REQUIREMENTSTOINSTALL python-qt4"
fi
if [ -z $(which git) ]
then
    REQUIREMENTSTOINSTALL="$REQUIREMENTSTOINSTALL git"
fi

if [ -n "$REQUIREMENTSTOINSTALL" ]
then
    if [ -n $(which apt-get) ]
    then
        INSTALLTOOL="apt-get"
    elif [ -n $(which yum) ]
    then
        INSTALLTOOL="yum"
    else
        echo "couldn't find yum or apt-get, please install 'REQUIREMENTSTOINSTALL' and restart this script"
        exit $EXIT_UNKOWNINSTALLER
    fi

    echo "installing requirements ($REQUIREMENTSTOINSTALL)"
    if [ -n $(which sudo) ]
    then
        sudo $INSTALLTOOL -y --force-yes install $REQUIREMENTSTOINSTALL
    else
        su root -c"$INSTALLTOOL -y install $REQUIREMENTSTOINSTALL"
    fi
fi

if [ "`which git openssl python | grep -c /`" != "3" ]
then
    echo "unable to resolve all requirements, please install '$REQUIREMENTSTOINSTALL' and restart this script"
    exit $EXIT_REQUIREMENTSUNRESSOLVED
fi

echo "downloading bitmessage from github"

mkdir "$INSTALLDIR"
cd "$INSTALLDIR"
git clone "$BITMESSAGE_GIT"
if [ -f "$PY_EXECUTEABLE" ]
then
    if [ ! -x "$PY_EXECUTEABLE" ]
    then
        chmod u+x "$PY_EXECUTEABLE"
    fi
else
    echo "Error: Excpected File $PY_EXECUTEABLE does not exist"
    exit $EXIT_BITMESSAGEEXECUTEABLENOTFOUND
fi

if [ ! -x "$BM_EXECUTEABLE" ]
then
    if [ -n $(which sudo) ]
    then
        sudo bash << EOF
        echo "#!/bin/bash" >  $BM_EXECUTEABLE
        echo "python ~/.bitmessage/PyBitmessage/bitmessagemain.py" >>  $BM_EXECUTEABLE
        chmod a+x "$BM_EXECUTEABLE"
EOF

    else
        su root -c"bash" << EOF
        echo "#!/bin/bash" >  $BM_EXECUTEABLE
        echo "python ~/.bitmessage/PyBitmessage/bitmessagemain.py" >>  $BM_EXECUTEABLE
        chmod a+x "$BM_EXECUTEABLE"
EOF

    fi
fi

if [ ! -x "$PY_EXECUTEABLE" ]
then
    echo "File $PY_EXECUTEABLE´ could not be set as executeable."
    echo "set it executeable to use bitmessage"
fi

if [ ! -x "$BM_EXECUTEABLE" ]
then
    echo "Unable to create $BM_EXECUTEABLE. create it with following contents:"
    echo " "
    echo "#!/bin/bash"
    echo "python ~/.bitmessage/PyBitmessage/bitmessagemain.py"
    echo " "
    echo "and set it as executeable"
fi

echo "installation of bitmessage was successfull"
echo "you can find a userguide at bitmessage.org"
echo "start Bitmeassege by 'bitmessage' command"