#!/bin/sh
#
# Purpose {{{
########### Remove me
#  R     This is a template to build a script that
#  E     will try to get the latest version of an app.
#  M M   1. Replace all "A_MAGNIFICIENT_PACKAGE_NAME" by the correct package name.
#  O E   2. Replace APP_AUTHOR by the owner of git repository.
#  V     3. Watch all TODO because some repositories might have differents configurations.
#  E
########### Remove me
# This script will try to get last version of A_MAGNIFICIENT_PACKAGE_NAME .deb file
# from github repository https://github.com/APP_AUTHOR/A_MAGNIFICIENT_PACKAGE_NAME
#   1. Get current version from APT repo (by default).
#   1.b Or use version from manually installed package (with --file option).
#   2. Get latest version from github repository.
#   3. Compare current and new versions.
#   4. Download the .deb file for this new version.
#   5. Create a temp file (to monitor) if an upgrade is available.
#
# TODO: Change the date…
# 1601-01-01
# }}}
# How-to use {{{
## 1. Needs releasetags script, in the same directory
## cf. https://git.ipr.univ-rennes.fr/cellinfo/scripts/src/master/github/releasetags
# wget https://git.ipr.univ-rennes.fr/cellinfo/scripts/raw/master/github/releasetags
## 2. Create a cron job, eg :
#00 20 * * * root /opt/repos/ipr.scripts/github/check.A_MAGNIFICIENT_PACKAGE_NAME.update
## 2-1 Create a cron job to compare the version of manually installed package
#00 20 * * * root /opt/repos/ipr.scripts/github/check.A_MAGNIFICIENT_PACKAGE_NAME.update --file
## 3. Monitor the temp file : /tmp/.github.A_MAGNIFICIENT_PACKAGE_NAME.upgrade
# }}}
# Flags {{{
## Exit on error
set -o errexit
## Exit on unset var
### Use "${VARNAME-}" to test a var that may not have been set
set -o nounset
## Pipeline command is treated as failed
### Not available in POSIX sh − https://github.com/koalaman/shellcheck/wiki/SC3040
#set -o pipefail
## Help with debugging
### Call the script by prefixing it with "TRACE=1 ./script.sh"
if [ "${TRACE-0}" -eq 1 ]; then set -o xtrace; fi
# }}}
# Vars {{{
PROGNAME=$(basename "${0}"); readonly PROGNAME
PROGDIR=$(readlink --canonicalize-missing $(dirname "${0}")); readonly PROGDIR
ARGS="${*}"; readonly ARGS
readonly NBARGS="${#}"
[ -z "${DEBUG-}" ] && DEBUG=1
## Export DEBUG for sub-script
export DEBUG

## Default values for some vars
readonly PACKAGE_NAME_DEFAULT="A_MAGNIFICIENT_PACKAGE_NAME"
readonly CHECK_MODE_DEFAULT="repository"

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

	cat <<- HELP
usage: $PROGNAME [-d|-h|-f|-r]

Try to get last version of ${PACKAGE_NAME_DEFAULT} .deb file.

EXAMPLES :
    - Check ${PACKAGE_NAME_DEFAULT} version (from APT repository or manually installed file).
        ${PROGNAME}

OPTIONS :
    -d,--debug
        Enable debug messages.

    -h,--help
        Print this help message.

    -f,--file,--p,--package
        Use manually installed package.

    -r,--repo,--repository
        Use ${PACKAGE_NAME_DEFAULT} version from APT repository.
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}" >&2

	unset local_error_message

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

	local_var_empty="${1}"
	debug_prefix="${2:-}"
	## Return False by default
	return_var_empty="1"

	debug_message "${debug_prefix}is_var_empty − Test var value (${1})."
	[ -z "${local_var_empty}" ] && return_var_empty="0"

	unset debug_prefix
	unset local_var_empty

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

	debug_message "-- define_vars BEGIN"
	## If repo_url wasn't defined {{{
	## TODO: Verify and fix this URL!
	is_var_empty "${repo_url-}" "|| " \
		&& repo_url="https://github.com/APP_AUTHOR/A_MAGNIFICIENT_PACKAGE_NAME" \
		&& debug_message "| define_vars − Use value (${RED}${repo_url}${COLOR_DEBUG}) for repo_url variable."
	## }}}
	## If package_name wasn't defined (argument) {{{
	## Use default value
	is_var_empty "${package_name-}" "|| " \
		&& debug_message "| define_vars − Use default value (${RED}${PACKAGE_NAME_DEFAULT}${COLOR_DEBUG}) for package_name variable." \
		&& package_name="${PACKAGE_NAME_DEFAULT}"
	## }}}
	## Get new_version from application repository {{{
	## TODO: Verify the pattern ignored by grep. The repository might work with other unwanted release.
	## TODO: Verify the pattern of sed. This command should gave the version number only!
	new_version=$("${PROGDIR}"/releasetags "${repo_url}" | grep --invert-match --extended-regexp -- '(dev|rc)' | head --lines=1 | sed 's/v//g')
	if is_var_empty "${new_version-}" "|| "; then
		error_message "define_vars − Invalid value for ${package_name} new version (${new_version})." 1
	else
		debug_message "| define_vars − Get value (${RED}${new_version}${COLOR_DEBUG}) for new_version variable."
	fi
	## }}}
	## If new_package_filename wasn't defined {{{
	## TODO: Verify and check that filename is correct!
	is_var_empty "${new_package_filename-}" "|| " \
		&& new_package_filename="${package_name}_${new_version}_amd64.deb" \
		&& debug_message "| define_vars − Use value (${RED}${new_package_filename}${COLOR_DEBUG}) for new_package_filename variable."
	## }}}
	## If new_package_url wasn't defined {{{
	## TODO: Verify and fix this URL! Does the repository use a "v" before version number or not.
	is_var_empty "${new_package_url-}" "|| " \
		&& new_package_url="${repo_url}/releases/download/v${new_version}/${new_package_filename}" \
		&& debug_message "| define_vars − Use value (${RED}${new_package_url}${COLOR_DEBUG}) for new_package_url variable."
	## }}}
	## If new_version_file wasn't defined {{{
	is_var_empty "${new_version_file-}" "|| " \
		&& new_version_file="/tmp/.github.${package_name}.upgrade" \
		&& debug_message "| define_vars − Use value (${RED}${new_version_file}${COLOR_DEBUG}) for new_version_file variable."
	## }}}
	## If tmp_package_path wasn't defined {{{
	is_var_empty "${tmp_package_path-}" "|| " \
		&& tmp_package_path="/tmp/.${new_package_filename}" \
		&& debug_message "| define_vars − Use value (${RED}${tmp_package_path}${COLOR_DEBUG}) for tmp_package_path variable."
	## }}}
	## If new_package_path wasn't defined {{{
	is_var_empty "${new_package_path-}" "|| " \
		&& new_package_path="/tmp/${new_package_filename}" \
		&& debug_message "| define_vars − Use value (${RED}${new_package_path}${COLOR_DEBUG}) for new_package_path variable."
	## }}}
	## If check_mode wasn't defined (argument) {{{
	## Use default value
	is_var_empty "${check_mode-}"  "|| " \
		&& debug_message "| define_vars − Use default value (${RED}${CHECK_MODE_DEFAULT}${COLOR_DEBUG}) for check_mode variable." \
		&& check_mode="${CHECK_MODE_DEFAULT}"
	## }}}

	## Get current_version according to the check_mode {{{
	case "${check_mode}" in
		"repo"|"repository" )  ## Check current version from repository
			current_version=$(apt-cache policy -- "${package_name}" | awk '/Candidate:/ {print $2}' | sed 's/.:\(.*\)-.*/\1/')
			;;
		"file" )               ## Check current version from installed .deb file
			current_version=$(dpkg --list -- "${package_name}" | awk -v pattern="${package_name}" '$0~pattern {print $3}' | sed 's/.:\(.*\)-.*/\1/')
			;;
		* )                    ## unknow mode
			error_message "define_vars − Invalid check mode: ${check_mode}. See help message with -h." 2
			;;
	esac

	## If current_version is empty
	is_var_empty "${current_version}"  "|| " \
		&& error_message "define_vars − Error with current_version variable (${current_version}) for package (${package_name})." 2
	## }}}
	debug_message "-- define_vars END"
}
# }}}
is_version_greater_than() {                                     # {{{

	first_value="${1}"
	value_to_compare="${2}"
	debug_prefix="${3:-}"

	## Return False by default
	return_is_version_greater_than="1"

	debug_message "${debug_prefix}is_version_greater_than − \
Is first value (${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 "${debug_prefix}is_version_greater_than − ${first_value} <= ${value_to_compare} ."
		return_is_version_greater_than="1"
	else
		debug_message "${debug_prefix}is_version_greater_than − ${first_value} > ${value_to_compare} ."
		return_is_version_greater_than="0"
	fi

	unset first_value
	unset value_to_compare
	unset debug_prefix

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

main() {                                                        # {{{

	debug_message "--- MAIN BEGIN"

	## Define all vars
	define_vars

	## Uncomment variable(s) to simulate different behaviour
	#current_version="1.0.2"
	#new_version="42.3.1"

	debug_message "-- Test version BEGIN"
	## If new_version is greater than current_version {{{
	if is_version_greater_than "${new_version}" "${current_version}" "|| "; then
		debug_message "| Current version (${current_version}) is older than new one \
(${new_version})."
		### If it doesn't already exists, download the new package {{{
		if [ ! -f "${new_package_path}" ]; then
			debug_message "| Download .deb file from ${package_name} repository on Github to: ${new_package_path} ."
			wget --quiet "${new_package_url}" --output-document="${new_package_path}"
		fi
	### }}}
	## }}}
	## If current version is uptodate {{{
	else
		debug_message "| Current version (${current_version}) seems uptodate \
or newer than available version (${new_version})."
		### Ensure to remove any temp file and useless .deb files
		rm --force -- "${new_version_file}" "${new_package_path}" "${tmp_package_path}"
		### Exit
		debug_message "-- Test version END"
		debug_message "--- MAIN END"
		exit 0
	fi
	## }}}
	debug_message "-- Test version END"

	## Verify downloaded package {{{
	debug_message "-- Verify downloaded package BEGIN"
	## If the downloaded package has a size greater than zero {{{
	if [ -s "${new_package_path}" ]; then
		debug_message "| Downloaded package looks good."
		### Create a temp file to monitor
		touch -- "${new_version_file}"
		printf '\e[1;35m%-6s\e[m\n' "An upgrade is available for ${package_name} terminal (current : ${current_version}) : ${new_version}." >> "${new_version_file}"
	## }}}
	## If the size is null {{{
	else
		debug_message "| Empty file, don't need to go further."
		### Ensure to remove the file to monitor
		rm --force -- "${new_version_file}"

		### Keep a record of the downloaded package because as a new release might come soon
		mv --force -- "${new_package_path}" "${tmp_package_path}"
	fi
	## }}}
	debug_message "-- Verify downloaded package END"
	# }}}

	debug_message "--- MAIN END"

	# Exit
	exit 0
}
# }}}

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

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

	manage_arg="0"

	## If the first argument ask for help (h|help|-h|-help|-*h|-*help) {{{
	if printf -- '%s' "${1-}" | grep --quiet --extended-regexp -- "^-*h(elp)?$"; then
		usage
		exit 0
	fi
	## }}}

	## If the first argument is not an option
	if ! printf -- '%s' "${1}" | grep --quiet --extended-regexp -- "^-+";
	then
		## Print help message and exit
		printf '%b\n' "${RED}Invalid option: ${1}${RESET}"
		printf '%b\n' "---"
		usage

		exit 1
	fi

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

	case "${1}" in
		-d|--debug )                          ## debug
			DEBUG=0
			debug_message "--- Manage argument BEGIN"
			;;
		-f|--file|--files|-p|--package )      ## Define check_mode to file mode
			## Define var
			readonly check_mode="file"
			;;
		-r|--repo|--repository )              ## Define check_mode to repo mode
			## Define var
			readonly check_mode="repo"
			;;
		* )                                   ## unknow option
			printf '%b\n' "${RED}Invalid option: ${1}${RESET}"
			printf '%b\n' "---"
			usage
			exit 1
			;;
	esac

	debug_message "| ${RED}${1}${COLOR_DEBUG} option managed."

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

	done

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

	debug_message "--- Manage argument END"
# }}}

main

# This should never be reach
exit 255