#!/bin/sh
# Purpose {{{
## Create a temp file (to monitor) if an upgrade is available for Zoom client
## from official website − https://zoom.us/download
## It's based on .deb package installation to check the current version.
## It can also compare the current available version in APT repositories
##   if "repo" is given as first argument.
## If a new version is available, the script will try to download it.
## How-to use {{{
### 1. Create a cron job, eg :
#00 20 * * * root /opt/repos/ipr.scripts/app/check.zoom.update
### 2-1 Create a cron job to compare the version available in an APT repository :
#00 20 * * * root /opt/repos/ipr.scripts/app/check.zoom.update --mode repo
### 2. Monitor the temp file : /tmp/.zoom.upgrade
# Or enable MAILTO in cronjob and edit the script to print a message.
# Or send a mail.
# …
## }}}

## Inspired by https://github.com/pazepaze/zoom-autoupdater/blob/master/autoupdate-zoom.sh
# }}}

# Vars {{{
PROGNAME=$(basename "${0}"); readonly PROGNAME
PROGDIR=$(readlink -m $(dirname "${0}")); readonly PROGDIR
ARGS="${*}"; readonly ARGS
readonly NBARGS="${#}"
[ -z "${DEBUG}" ] && DEBUG=1
## Export DEBUG for sub-script
export DEBUG

## Default values for some vars
CHECK_MODE_DEFAULT="file"

## Colors
readonly PURPLE='\033[1;35m'
readonly RED='\033[0;31m'
readonly RESET='\033[0m'
readonly COLOR_DEBUG="${PURPLE}"
# }}}

usage() {                                                       # {{{

	cat << HELP

usage: $PROGNAME [check_mode] [-m|-d|-h]

Compare current version of an installed Zoom client and the last available.

EXAMPLES :
    - Compare the current version of Zoom installed from a .deb file
        ${PROGNAME}
        ${PROGNAME} --mode file

    - Compare the current version of Zoom available in the APT repo
        ${PROGNAME} repo
        ${PROGNAME} --mode repo

OPTIONS :
    -m,--mode
        Set the check_mode to use to get current version of Zoom client
        Available mode :
          * repo
          * file (default behaviour)

    -d,--debug
        Enable debug messages.

    -h,--help
        Print this help message.
HELP
}
# }}}
debug_message() {                                               # {{{

	local_debug_message="${1}"

	## Print message if DEBUG is enable (=0)
	[ "${DEBUG}" -eq "0" ] && printf '\e[1;35m%-6b\e[m\n' "DEBUG − ${PROGNAME} : ${local_debug_message}"

	unset local_debug_message

	return 0
}
# }}}
error_message() {                                               # {{{

	local_error_message="${1}"
	local_error_code="${2}"

	## Print message
	printf '%b\n' "ERROR − ${PROGNAME} : ${RED}${local_error_message}${RESET}"

	unset local_error_message

	exit "${local_error_code:=66}"
}
# }}}
is_var_empty() {                                                # {{{

	## Return False by default
	return_var_empty="1"
	## Total number of variables to test
	local_total_var_empty="${#}"

	loop_count_var_empty="0"

	## While it remains a variable to test
	while [ "${local_total_var_empty}" -gt "${loop_count_var_empty}" ]; do
		debug_message "is_var_empty − \
Test var: ${1}."
		### Test if this is empty and set return value to True
		[ -z "${1}" ] && return_var_empty="0"

		### Increase the number of tested variables
		loop_count_var_empty=$((loop_count_var_empty+1))

		### Shift to the next variable
		shift
	done

	unset local_total_var_empty
	unset loop_count_var_empty

	return "${return_var_empty}"
}
# }}}
define_vars() {                                                 # {{{

	## If check_mode wasn't defined (argument) {{{
	## Use default value
	is_var_empty "${check_mode}" \
		&& debug_message "define_vars − Use default value (${CHECK_MODE_DEFAULT}) for check_mode variable." \
		&& check_mode="${CHECK_MODE_DEFAULT}"
	## }}}

	## Get zoom_current_version according to the check_mode {{{
	case "${check_mode}" in
		"repo" )               ## Check zoom version from repository
			zoom_current_version=$(apt-cache policy -- zoom | awk '/Candidate:/ {print $2}' | sed 's/.:\(.*\)-.*/\1/')
			;;
		"file" )               ## Check zoom version from installed .deb file
			zoom_current_version=$(dpkg --list -- zoom | awk '/^ii *zoom/ {print $3}' | sed 's/.:\(.*\)-.*/\1/')
			;;
		* )                    ## unknow mode
			error_message "define_vars − Invalid check mode: ${check_mode}" 1
			printf '%b\n' "---"
			usage
			exit 1
			;;
	esac

	## If zoom_current_version is empty
	is_var_empty "${zoom_current_version}" \
		&& error_message "define_vars − Error with zoom_current_version variable (${zoom_current_version})" 2

	## }}}

	## Zoom vars for new version {{{
	temp_zoom_new_version=$(curl --silent 'https://zoom.us/support/download' --header 'User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36' | grep "class=\"linux-ver-text\"" | sed -e 's/.*Version \(.*\)<.*/\1/')
	zoom_new_version_major=$(echo "${temp_zoom_new_version}" | sed -e 's/\(.*\) .*/\1/')
	zoom_new_version_minor=$(echo "${temp_zoom_new_version}" | sed -e 's/.* (\(.*\))/\1/')
	zoom_new_version="${zoom_new_version_major}.${zoom_new_version_minor}"

	is_var_empty "${temp_zoom_new_version}" "${zoom_new_version_major}" "${zoom_new_version_minor}" "${zoom_new_version}" \
		&& error_message "define_vars − Error with new version variables (temp_zoom_new_version: ${temp_zoom_new_version} ; zoom_new_version_major: ${zoom_new_version_major} ; zoom_new_version_minor: ${zoom_new_version_minor} ; zoom_new_version: ${zoom_new_version})." 3
	## }}}

	## Vars for temp files
	zoom_new_version_file="/tmp/.zoom.upgrade"
	zoom_new_pkg_path="/tmp/zoom_${zoom_new_version}_amd64.deb"
	zoom_tmp_pkg_path="/tmp/.zoom_${zoom_new_version}_amd64.deb"
}
# }}}
is_version_greater_than() {                                     # {{{

	first_value="${1}"
	value_to_compare="${2}"

	## Return False by default
	return_is_version_greater_than="1"

	debug_message "is_version_greater_than − \
Is first value (${first_value}) greater than the second value (${value_to_compare})."

	if printf '%s\n' "${first_value}" "${value_to_compare}" | sort --check=quiet --version-sort; then
		debug_message "is_version_greater_than − ${first_value} <= ${value_to_compare} ."
		return_is_version_greater_than="1"
	else
		debug_message "is_version_greater_than − ${first_value} > ${value_to_compare} ."
		return_is_version_greater_than="0"
	fi

	unset first_value
	unset value_to_compare

	return "${return_is_version_greater_than}"
}
# }}}

main() {                                                        # {{{

	define_vars

	# Behaviour can be tested by overriding this variable
	#zoom_current_version="66.11.4.2845"
	#zoom_current_version="${zoom_new_version}"
	#zoom_current_version="1.9.4.2845"

	if is_version_greater_than "${zoom_new_version}" "${zoom_current_version}"; then
		debug_message "Test version − \
New version (${zoom_new_version}) seems more recent than the current one (${zoom_current_version})."

		## If it doesn't already exists, download the package for this new version
		if [ ! -f "${zoom_new_pkg_path}" ]; then
			debug_message "Deb file − \
Download .deb file from zoom.us to ${zoom_new_pkg_path} ."
			wget --quiet https://zoom.us/client/latest/zoom_amd64.deb --output-document="${zoom_new_pkg_path}"
		fi

		# Verify downloaded package
		# Check the version from dpkg info {{{
		zoom_dpkg_version=$(dpkg --info -- "${zoom_new_pkg_path}" | awk '/ Version/ { print $2 }')

		if [ "${zoom_dpkg_version}" = "${zoom_new_version}" ]; then
			debug_message "Check dpkg version − \
New version and .deb file informations are similar."
			## Create a temp file to monitor
			touch -- "${zoom_new_version_file}"
			printf '\e[1;35m%-6s\e[m\n' "An upgrade is available for Zoom client (current : ${zoom_current_version}) : ${zoom_new_version}." >> "${zoom_new_version_file}"

			## Exit
			exit 0
		else
			debug_message "Check dpkg version − \
New version and .deb file informations mismatch, don't need to go further."

		# }}}
		# Remove useless file {{{
			## Ensure to remove the file to monitor
			rm --force -- "${zoom_new_version_file}"

			## Keep a record of the downloaded package because as a new release might come soon
			mv --force -- "${zoom_new_pkg_path}" "${zoom_tmp_pkg_path}"

			## Exit
			exit 0
		fi

		# }}}

	else
		debug_message "Test version − The current version is the same or is more recent than the available one."
		## Ensure to remove any temp file and useless .deb file
		rm --force -- "${zoom_new_version_file}" "${zoom_new_pkg_path}" "${zoom_tmp_pkg_path}"

		## Exit
		exit 0
	fi
	# }}}
}
# }}}

# Manage arguments                                                # {{{
# This code can't be in a function due to arguments

if [ ! "${NBARGS}" -eq "0" ]; then

	manage_arg="0"

	## If the first argument is not an option
	if ! printf -- '%s' "${1}" | grep --quiet --extended-regexp -- "^-+";
	then
		## Consider it as the mode to use to get current zoom version
		check_mode="${1}"
		## Move to the next argument
		shift
		manage_arg=$((manage_arg+1))
	fi

	# Parse all options (start with a "-") one by one
	while printf -- '%s' "${1}" | grep --quiet --extended-regexp -- "^-+"; do

	case "${1}" in
		-m|--mode )            ## Define check_mode
			## Move to the next argument
			shift
			## Define var
			readonly check_mode="${1}"
			;;
		-d|--debug )           ## debug
			DEBUG=0
			;;
		-h|--help )            ## help
			usage
			## Exit after help informations
			exit 0
			;;
		-- )                   ## End of options list
			## End the while loop
			break
			;;
		* )                    ## unknow option
			printf '%b\n' "${RED}Invalid option: ${1}${RESET}"
			printf '%b\n' "---"
			usage
			exit 1
			;;
	esac

	debug_message "Arguments management − \
${RED}${1}${COLOR_DEBUG} option managed."

	## Move to the next argument
	shift
	manage_arg=$((manage_arg+1))

	done

	debug_message "Arguments management − \
${RED}${manage_arg}${COLOR_DEBUG} argument(s) successfully managed."
else
	debug_message "Arguments management − \
No arguments/options to manage."
fi

# }}}

main

exit 255