setup

#!/bin/bash
function help() {
echo "======================================================================="
echo ".dotfiles/bin/setup"
echo "   by Todd Gamblin, tgamblin@llnl.gov"
echo "======================================================================="
echo "This script links and unlinks dotfiles into your home directory."
echo
echo "The .dotfiles repository is laid out like this:"
echo
echo "  .dotfiles/"
echo "      bin/"
echo "      help"
echo "      home/"
echo "          ... actual dotfiles ..."
echo "      link"
echo "      unlink"
echo
echo "help, link, and unlink are symbolic links to the setup script, which"
echo "does three things, depending on which symlink you call it with."
echo "They are as follows:"
echo
echo "link"
echo "    If you call this command as 'link', it will create symlnks in"
echo "    your home directory to all of the files in .dotfiles/home."
echo "    This can be used to bootstrap a home directory on a new machine,"
echo "    e.g.:"
echo
echo "        git clone git@github.com:tgamblin/dotfiles.git .dotfiles"
echo "        .dotfiles/link"
echo
echo "    If there are files in the way, the script will create a directory"
echo "    called ~/.dotfiles-backup, where it moves the original versions"
echo "    of your files."
echo
echo "    'link' is idempotent if called twice in a row."
echo
echo "unlink"
echo "    Unlink removes symbolic links created by this script and restores"
echo "    any files in ~/.dotfiles-backup to their original locations."
echo "    If you call it without having created symlinks into the .dotfiles"
echo "    repo, it will do nothing (so as not to damage your home directory)."
echo
echo "help"
echo "    Calling this script as '.dotfiles/help' will print this message."
echo
}

#
# Prints an error message and dies.
#
function error() {
    echo "ERROR: $1"
    exit 1
}

#
# Get readlink -f behavior when readlink doesn't support it
#
function readlink_f {
    _target_file=$1

    cd `dirname $_target_file`
    _target_file=`basename $_target_file`

    # Iterate down a (possible) chain of symlinks
    while [ -L "$_target_file" ]; do
	_target_file=`readlink $_target_file`
	cd `dirname $_target_file`
	_target_file=`basename $_target_file`
    done

    # Compute the canonicalized name by finding the physical path
    # for the directory we're in and appending the target file.
    _phys_dir=`pwd -P`
    _result=$_phys_dir/$_target_file
    echo $_result
}

# Directory to link files into
link_dest=$HOME

# Ensure that the script, as called, is a symlink
[[ -L "$0" ]] || error "Something isn't right: $0 is not a link."

# Location of the repository the link script lives in
repository=$(dirname $(dirname $(readlink_f "$0")))

# The directory in the repository where files to be linked
# into the home directory live.
repo_home="$repository/home"

# Default name of directory to store backups in
backup_dir=$link_dest/.dotfiles-backup

# Ensure that the repository home exists.
[[ -d "$repo_home" ]] || error "Couldn't find $repo_home!"

# Check whether we can write to the link destination.
[[ -w "$link_dest" ]] || error "$link_dest is not writable!"

# If the repo is inside link destination, use a relative path.
rel_repo=\
$(echo $repo_home | perl -pe "\$s=quotemeta(\"${link_dest}/\"); s/\$s//;")

# Command is the symlink through which we ran this script.
cmd=$(basename $0)
[[ -n "$cmd" ]] || cmd="help"

case $cmd in
    link | unlink)
        echo "${cmd}ing dotfiles"
        echo "  from: $repo_home"
        echo "  into: $link_dest"

        for file in $(\ls -A $repo_home); do
            dest="$link_dest/$file"
            src="$rel_repo/$file"

            if [ "$cmd" = "link" ]; then
                # If the file already exists, move it.
                if [ -e "$dest" -a \( "$(readlink $dest)" != "$src" \) ]; then
                    [[ -d "$backup_dir" ]] || mkdir "$backup_dir"
                    mv "$dest" "$backup_dir/$file"
                fi

                # Link the file into the destination location, if the link
                # isn't already there.
                if [ ! -e "$dest" ]; then
                    ln -s "$src" "$dest"
                fi

            else
                # Remove our symlink if it exists, then restore backup
                if [ -L "$dest" -a \( "$(readlink $dest)" = "$src" \) ]; then
                    if [ -e "$backup_dir/$file" ]; then
                        # Restrore the backup if it exists
                        rm "$dest"
                        mv "$backup_dir/$file" "$dest"
                    else
                        # Just remove the link if not
                        rm "$dest"
                    fi
                fi
            fi
        done
        ;;
    *)
        help
        ;;
esac