#!/usr/bin/env bash

set -eEuo pipefail

SCRIPT_PATH="${BASH_SOURCE[0]}"
SCRIPT_DIR="$(dirname "$SCRIPT_PATH")"

#######################################
# Print the given message to STDERR
#######################################
err() {
	printf "%s\n" "${*}" >&2
}

#######################################
# End the script with a non-zero exit code and the given message
# Arguments:
#   msg: The message to print to STDERR before exiting
#######################################
die() {
	local msg="${*}"
	err "$msg"
	exit 1
}

#######################################
# Print a usage synopsis for the script to stdout
#######################################
usage() {
	cat <<-__EOS__
		Usage:
		    ${SCRIPT_PATH} <input-files...>
		Args:
		    <input-files...>: One or more paths to files on the system
		Example:
		    ${SCRIPT_PATH} ./some/file/to/handle.txt ./another/file/to/handle.txt
	__EOS__
}

#######################################
# Replace all instances of <dstamp> or <date> with todays date in day/month/year
# format in place for the given file
# Arguments:
#   file: The file to template in the date for
#######################################
replace_date_placeholders_in_file() {
	local file="${1}"
	local current_date
	current_date="$(date +"%d\/%m\/%Y")"
	sed -ri "s/(<dstamp>|<date>)/$current_date/g" "$file"

}

#######################################
# Redact the given file with the included sed script in place for the given file
# Arguments:
#   file: The file to redact
#######################################
redact_file() {
	local file="${1}"
	sed -ri -f "${SCRIPT_DIR}/assign2.sed" "$file"
}

#######################################
# Check that the given file can be used within the script. For example, check
# that the current script/user has read & write permissions for the given file.
# Arguments:
# 	file: The file to check
#######################################
check_file() {
	local file="${1}"
	if ! [[ -r "$file" ]]; then
		err "Unable to read '${file}', the current user lacks read permissions or the file does not exist!"
		return 1
	fi

	if ! [[ -w "$file" ]]; then
		err "Unable to modify '${file}', the current user lacks write permissions!"
		return 1
	fi
}

#######################################
# Check all given files and return a single error code if any given check fails.
# This is done so all errors for the given files are output to the user prior to
# exiting.
# Arguments:
# 	files: an array of files to loop through and validate
#######################################
validate_files() {
	local ret_code=0
	local files=("${@}")
	for file in "${files[@]}"; do
		if ! check_file "$file"; then
			ret_code=1
		fi
	done
	return "$ret_code"
}

main() {
	local files=("${@}")
	if (("${#files[@]}" == 0)); then
		usage
		die "No arguments provided!"
	fi

	validate_files "${files[@]}" || die "File checks failed, refusing to run script!"

	for file in "${files[@]}"; do
		redact_file "$file"
		replace_date_placeholders_in_file "$file"
	done
}

main "${@}"