#!/bin/bash -

# File: rm-unneeded-files.sh
# Copyright (c) 2018-2019 Justin Hanekom <justin_hanekom@yahoo.com>
# Licensed under the MIT License

# 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.

# Setup a safe Bash scripting environment

set -o errexit      # Exit immediately if an error occurs
set -o noclobber    # Do not allow files to be overwritten via redirect
set -o nounset      # Do not allow unset variables

# Set the exit code of a pipeline to the rightmost non-zero on error
set -o pipefail
# Set the internal field separator to newline or tab, but not space
IFS=$'\n\t'

# Setup a secure Bash scripting environment by: setting a secure path;
# clearing all aliases; clearing the command path hash; setting the hard limit
# to 0 to turn off core dumps; and setting a secure umask

PATH=$(PATH='/bin:/usr/bin' getconf PATH); export PATH
builtin unalias -a
hash -r
ulimit -H -c 0 --

UMASK=002
umask ${UMASK}

# Global constant definitions

readonly OPTIONS='d:vh'
readonly LONGOPTS='directory:,verbose,help'
# unneeded regexp not using --regexp='...' --regexp='...' etc.
# because this would mean having to eval the grep command
readonly UNNEEDED_REGEXP="\.[#].+|~$|^[#].*[#]$|\.autosave$|\.DS_Store$|\
\.lein_failures$|\.lein-repl-history$|\.lisp-temp$|\.sw.$"
readonly STARTED_AT=$(date '+%s')

# Global variable declarations

DIR=''
IS_VERBOSE=''

################################################################################
# Function:     chomp_slash
# Description:  Removes any trailing slash ("/") from a string
# Arguments:    $1 :- String from which to remove any trailing slashes
# Ouputs:       Prints string with trailing slashes removed
function chomp_slash {
    local dir="$1"
    while [ "${dir:(-1)}" = '/' ]; do
        dir=${dir::-1}
    done
    echo "${dir}"
}

################################################################################
# Function:     trim
# Description:  Trims any/all whitespace from the beginning and end of a string
# Arguments:    $1 :- The string from which to trim whitespace
# Outputs:      Prints string with any leading/trailing whitespace removed
function trim {
    local str="$1"
    str="${str#"${str%%[![:space:]]*}"}"
    str="${str%"${str##*[![:space:]]}"}"
    echo "$1"
}

################################################################################
# Function:     usage_exit
# Description:  Prints the usage message for this script and then exits
# Arguments:    $1 :- Exit code; defaults to 1
# Outputs:      Prints description of how to call this script
function usage_exit {
    local exit_code=1

    if [[ ${1-} =~ ^[0-9]+$ ]]; then
        exit_code="$1"
    fi

    cat << EOT
Usage: $(basename "$0") [options]...
    -d|--directory  <val>   (Required) The dir containing unneccessary files
    -v|--verbose            Displays verbose output
    -h|--help               Displays this message and exits the script

NOTE: The <directory> argument is mandatory and *must* be supplied

EOT
    exit "${exit_code}"
}

################################################################################
# Function:     parse_cmd_line
# Description:  Parses the command-line using the enhanced version of getopt
# Arguments:    $@ :- Command-line arguments (required)
# Requires:     Global variable $DIR
# Outputs:      Sets above-mentioned global variable based on given
#               command-line arguments
function parse_cmd_line {
    # Ensure that the enhanced version of getopt is available

    ! getopt --test > /dev/null
    if (( "${PIPESTATUS[0]}" != 4 )); then
        echo "I'm sorry, the enhanced version of getopt is required. Exiting." >&2
        exit 1
    fi

    # Initialize the global variables

    DIR=''
    IS_VERBOSE=''

    # Parse the command-line options

    if ! readonly PARSED_OPTIONS=$(getopt --options=${OPTIONS} \
                                    --longoptions=${LONGOPTS} \
                                    --name "$(basename "$0")" -- "$@"); then
        echo 'Unknown error parsing getopt options. Exiting.' >&2
        exit 2
    fi

    eval set -- "${PARSED_OPTIONS}"

    # Extract command-line options and their arguments, if any

    while (( $# >= 1 )); do
        case "$1" in
            -d|--directory)
                DIR="$(trim "$2")" ; shift 2
                ;;
            -v|--verbose)
                IS_VERBOSE='true' ; shift
                ;;
            -h|--help)
                usage_exit 0
                ;;
            --)
                shift ; break
                ;;
            *)
                usage_exit 3 >&2
                ;;
        esac
    done

    # Ensure that the required options have been supplied

    if [ -z "${DIR}" ]; then
        usage_exit 4 >&2
    fi
} # parse_cmd_line

################################################################################
# Start of program

parse_cmd_line "$@"

# Determine what should be done when an unneeded file is found

if [ "$IS_VERBOSE" ]; then
    verbose_flag='--verbose'
else
    verbose_flag=''
fi

# Remove unneeded files

set +e  # Temporarily disable error exiting
sudo find "${DIR}" -mount -path '/cdrom' -prune -path '/dev' -prune \
    -path '/media' -prune -path '/root' -prune -path '/proc' -prune -print | \
    grep --extended-regexp  "${UNNEEDED_REGEXP}" | \
    sudo xargs rm --force ${verbose_flag}
set -e  # Reenable error exiting

# Report that we are done, and how long the script took

if [ -n "$IS_VERBOSE" ]; then
    readonly ENDED_AT=$(date '+%s')
    readonly DIFF=$(( ENDED_AT - STARTED_AT ))
    echo "Done, in ${DIFF} seconds"!
fi

# vim: set filetype=sh smartindent autoindent smarttab expandtab tabstop=4 softtabstop=4 shiftwidth=4 autoread