eval_spin9

#!/bin/sh

############################################################ GLOBALS

#
# Global exit status variables
#
export SUCCESS=0
export FAILURE=1

# Status indicator message formats for task_begin/task_end
export FMT_COLS=70
export FMT_HEAD="%-${FMT_COLS}s"
export FMT_STAT=" [$ANSI_BLD%s$ANSI_BLD_OFF]\n"
export MSG_GOOD="${ANSI_GRN}  OK  $ANSI_NRM"
export MSG_FAIL="${ANSI_RED}FAILED$ANSI_NRM"


__cp=0 # reserved for internal use

############################################################ FUNCTIONS

# strip_ansi $text ...
#
# Remove ANSI coloring from string arguments or stdin.
#
strip_ansi()
{
        if [ $# -gt 0 ]; then
                echo "$@" | sed -e 's/^[[^m]*m//g'
        else
                sed -e 's/^[[^m]*m//g'
        fi
}

# task_begin [ $caption ]
#
# Inform the user that you have started a task.
#
task_begin()
{
        local caption="$1"
        local colorless_caption="$( strip_ansi "$caption" )"

        task_end $SUCCESS # end the previous task

        # Padded strings in printf (e.g., "%-70s") do not work properly if the
        # string contains invisibles, such as ANSI color codes. Compensate for
        # ANSI color codes if any.
        #
        local color_gap=$(( ${#caption} - ${#colorless_caption} ))
        local FMT_COLS2=$(( $FMT_COLS + $color_gap ))

        printf "%-${FMT_COLS2}s" "$caption"

        export __task_running=YES
        export __cp=${#colorless_caption}
}

# task_end [ $exit_status ]
#
# End the currently running task (if any) and display the given exit status.
#
task_end()
{
        local status="$1"

        [ "$__task_running" ] || return # nothing to do

        if [ "$status" ]; then
                #
                # If the caption last-used with task_begin is wider than our
                # preset-limit, output a new header with blank caption, vert-
                # ically aligning the cursor to the column where we need to
                # print the status.
                #
                if [ ${__cp:-0} -ge $FMT_COLS ]; then
                        printf "\n$FMT_HEAD"
                        export __cp=0
                fi

                case "$status" in
                $SUCCESS) printf "$FMT_STAT" "$MSG_GOOD";;
                       *) printf "$FMT_STAT" "$MSG_FAIL";;
                esac
        fi

        export __task_running= # clear task state
}

# spinner
#
# Throw up a spinner. Spin spin spin until we receive "EXIT:###:" on stdin.
# Returns the exit status as specified in the "###" portion above.
#
spinner()
{
        local spin="/-\\|"
        local init=${__task_running:+1} n=1 done=
        local line_format="^[[A\n%s^[[K\n${__task_running:+$FMT_HEAD }"

        printf " "
        while [ ! "$DONE" ]; do
                local LINE="$( /bin/sh -c 'IFS=;read -t0 L;echo "$L"' )"
                case "$LINE" in

                *EXIT:*:*)
                        DONE="$( echo "$LINE" | sed -e \
                                "s/.*EXIT:\([[:digit:]]*\):.*/\1/" )"
                        LINE="$( echo "$LINE" | sed -e \
                                "s/EXIT:[[:digit:]]*://g" )"
                esac
                if [ "$LINE" ]; then
                        printf "${init:+\b \n}$line_format" "$LINE"
                        init=
                fi
                printf "\b%s" "$( echo "$spin" | sed -e \
                        "s/.\{0,$(( $n % ${#spin} ))\}\(.\).*/\1/" )"
                n=$(( $n + 1 ))
        done

        printf "\b \b"
        return $DONE
}

# eval_spin $command [ $args ... ]
#
# Execute a command while displaying a rotating spinner.
#
eval_spin()
{
        #
        # Execute the command w/ spinner
        #
        (
                if [ $# -gt 0 ]; then
                        # Take commands from positional arguments
                        ( eval "$@" ) 2>&1
                        echo EXIT:$?:
                else
                        # Take commands from standard input
                        ( eval "$( cat )" ) 2>&1
                        echo EXIT:$?:
                fi
        ) | spinner
}

############################################################ MAIN SOURCE

task_begin "Some task header..."
eval_spin "$@"
task_end $?