setup.sh

#!/bin/sh

if [ -n "${OUTPUT+x}" ]; then
    if [ "$OUTPUT" != color ] && [ "$OUTPUT" != plain ]; then
        echo "OUTPUT: invalid value \"$OUTPUT\" (supported: color, plain)"
        exit 2
    fi
fi

if [ "$OUTPUT" != plain ] && command -v tput >/dev/null; then
    I=$(tput bold)$(tput setaf 2)  # installed - green
    B=$(tput bold)$(tput setaf 6)  # backed up - cyan
    S=$(tput bold)$(tput setaf 3)  # skipped - yellow
    F=$(tput bold)$(tput setaf 1)  # failed - red
    R=$(tput sgr0)                 # reset
else
    I=":) "
    B="B) "
    S="   "
    F=":( "
fi

count_I=0
count_S=0
count_F=0

backup() {
    # copies file at $1 to first suitable filename
    # return: 0 = installed, 1 = failed, 2 = skipped, 3 = doesn't exist
    if [ ! -e "$1" ]; then
        echo >&2 "$S$1: file doesn't exist - skipping backup$R"
        return 3
    elif [ ! -r "$1" ]; then
        echo >&2 "$F$1: can't read file$R"
        return 1
    fi

    day=$(date '+%Y%m%d')
    for n in $(seq -w 0 999); do
        # always start destination name with a dot
        bn="$(basename "$1")"
        dn="$(dirname "$1")"
        case "$bn" in
            .*)  dst="$dn/$bn.$day.$n"   ;;
            *)   dst="$dn/.$bn.$day.$n"  ;;
        esac
        if [ ! -e "$dst" ]; then
            if [ -n "$last" ] && diff -q "$1" "$last" >/dev/null; then
                return 2
            fi
            cp "$1" "$dst"
            echo >&2 "$B$1: backed up to $dst$R"
            return 0
        fi
        last="$dst"
    done
        
    echo >&2 "$F$1: could not backup - exhausted suffixes?$R"
    return 1
}

install() {
    # copies file at $1 to $2
    # return: 0 = installed, 1 = failed, 2 = skipped
    if [ ! -r "$1" ]; then
        echo >&2 "$F$1: can't read file$R"
        count_F=$((count_F+1))
        return 1
    fi

    if [ -r "$2" ] && diff -q "$1" "$2" >/dev/null; then
        echo >&2 "$S$1: destination $2 does not differ - skipping$R"
        count_S=$((count_S+1))
        return 2
    fi

    backup "$2"
    result="$?"
    if [ "$result" -eq 1 ]; then
        echo >&2 "$F$1: failed to backup - aborting$R"
        count_F=$((count_F+1))
        return 1
    elif [ "$result" -eq 2 ]; then
        echo >&2 "$S$1: last backup does not differ - skipping$R"
        count_S=$((count_S+1))
        return 2
    fi

    cp "$1" "$2" || {
        echo >&2 "$F$1: failed to install to $2$R"
        count_F=$((count_F+1))
        return 1
    }
    echo >&2 "$I$1: installed to $2$R"
    count_I=$((count_I+1))
    return 0
}

exists() {
    command -v "$1" >/dev/null
    return $?
}

install_if_exists() {
    # copies file at $2 to $3 if the command at $1 exists
    # return: 2 if not installed, else passed from `install`
    if exists "$1"; then
        install "$2" "$3"
        return "$?"
    else
        echo >&2 "$S$2: $1 is not installed - skipping$R"
        count_S=$((count_S+1))
        return 2
    fi
}

. ./install.sh

echo >&2
[ $count_I -gt 0 ] && echo >&2 "$I$count_I installed$R"
[ $count_S -gt 0 ] && echo >&2 "$S$count_S skipped$R"
[ $count_F -gt 0 ] && echo >&2 "$F$count_F failed$R"

if [ $count_F -gt 0 ]; then
    exit 1
else
    exit 0
fi