# Environment variables:
#
# PS1_SHOWHOSTNAME
#       'auto' (default):       Only show hostname over SSH
#       'yes':                  Always show hostname
#       anything else:          Never show hostname


__show-hostname ()
{
    case ${PS1_SHOWHOSTNAME} in
        (''|auto)
            [ "${SSH_CONNECTION}" ];;
        (yes)
            true;;
        (*)
            false;;
    esac
}

__have-gitprompt ()
{
    [ -f /usr/lib/git-core/git-sh-prompt ]
}

__set-title ()
{
    local title=${USER}
    if __show-hostname
    then
        title+="@${HOSTNAME}"
    fi
    title+=:

    local path=${PWD/~/\~}
    local git_root=$(git rev-parse --show-toplevel 2> /dev/null)

    if [ -z "${git_root}" -o "${git_root}" = ~ ]
    then
        title+=${path}
    else
        local project=$(basename "${git_root}")
        path=$(realpath --relative-to "${git_root}" "${PWD}")
        if [ "${path}" = . ]
        then
            title+=${project}
        else
            title+=${project}/${path}
        fi
    fi

    # Cf. console_codes(4):
    #
    #   ESC ] 2 ; txt ST        Set window title to txt.
    #
    # ST is a "string terminator", either "ESC \" or "BEL".

    echo -ne "\E]2;${title}\a"
}

# In order to know how much space PS1 takes, Bash needs us to delimit
# non-printing characters with \[ and \].
__start-nonprinting ()
{
    if [ ${BUILDING_PS1} ]
    then
        echo -en '\['
    fi
}

__end-nonprinting ()
{
    if [ ${BUILDING_PS1} ]
    then
        echo -en '\]'
    fi
}

__fontify ()
{
    local -A codes=(
        [bold]=1
        [dim]=2
        [red]=31
        [green]=32
        [blue]=34
    )

    local text=$1
    shift

    __start-nonprinting

    echo -en '\E['

    local i
    for ((i=1; i<=$#; i++))
    do
        echo -en ${codes[${!i}]}

        if ((i<$#))
        then
            echo -en ';'
        else
            echo -en 'm'
        fi
    done

    __end-nonprinting

    echo -en "${text}"

    __start-nonprinting
    echo -en '\E[0m'
    __end-nonprinting
}

__set-prompt ()
{
    BUILDING_PS1=t

    PS1="$(__write-context)\n$(__fontify '\$' dim) "

    unset BUILDING_PS1
}

__current-column ()
{
    # Cf. console_codes(4) § ECMA-48 Status Report Commands

    local position
    read -sdR -p$'\E[6n' position

    local pattern='\[[0-9]+;([0-9]+)'

    if [[ ${position} =~ ${pattern} ]]
    then
        echo ${BASH_REMATCH[1]}
    else
        echo 0
    fi
}

__signal-no-newline ()
{
    echo $(__fontify ∅ bold red)
}

__draw-rule ()
{
    local i line

    for ((i=$(__current-column); i<COLUMNS; i++))
    do
        line+=─
    done

    # If we do not add a newline, whatever comes after will be shoved
    # offscreen when autowrap is off.
    line+='\n'

    __fontify ${line} $@
}

__write-context ()
{
    __fontify '\u' green

    if __show-hostname
    then
        __fontify @ dim
        __fontify '\H' bold green
    fi

    printf ' '
    __fontify '\w' bold blue

    if [ ${PS1_SHOWGITSTATUS} ]
    then
        printf ' '
        __fontify "$(__git_ps1 '(%s)')" red
    fi
}

__refresh-terminal ()
{
    local last_status=$?

    __set-title

    if [ $(__current-column) -ne 1 ]
    then
        __signal-no-newline
    fi

    if [ ${last_status} -ne 0 ]
    then
        __fontify "${last_status} " bold red
        __draw-rule dim red
    else
        __draw-rule dim
    fi

    __set-prompt
}


PS2='… '

if [ "${TERM}" = dumb ]
then
    PS1='$? \u:\w\$ '
    return
fi

PS2=$(__fontify "${PS2}" dim)

if __have-gitprompt
then
    . /usr/lib/git-core/git-sh-prompt
    GIT_PS1_SHOWDIRTYSTATE=t
    GIT_PS1_SHOWUPSTREAM=auto

    PS1_SHOWGITSTATUS=t
fi

PROMPT_COMMAND=__refresh-terminal