#!/bin/sh
#
# Purpose {{{
# This script will try to start eza
#   1. installed on the system if available
#   2. from a symlink in user's PATH
#
# 2023-09-16
# }}}
# 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 EZA_SYSTEM_PATH="/bin/eza"
readonly EZA_USER_PATH="${HOME}/bin/eza.link"

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

	cat <<- HELP
usage: $PROGNAME [--debug|help|--user|--system]

Tiny script to start existing eza (from the system or from user's PATH)

EXAMPLES :
    - Start eza
        ${PROGNAME}

    - Set different binary for user
        ${PROGNAME} --user "${HOME}/bin/my.eza"

OPTIONS :
    --debug
        Enable debug messages.

    help
        Print this help message.

    --user
        Change the user's binary to use.
        (default: ${EZA_USER_PATH})

    --system
        Change the system's binary to use.
        (default: ${EZA_SYSTEM_PATH})

    ALL OTHER OPTIONS WILL BE PASSED AS EZA's OPTIONS
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}"
}
# }}}
define_vars() {                                                 # {{{

	# If eza_system_path wasn't defined (argument) {{{
	if [ -z "${eza_system_path-}" ]; then
		## Use default value
		readonly eza_system_path="${EZA_SYSTEM_PATH}"
	fi
	# }}}
	# If eza_user_path wasn't defined (argument) {{{
	if [ -z "${eza_user_path-}" ]; then
		## Use default value
		readonly eza_user_path="${EZA_USER_PATH}"
	fi
	# }}}

}
# }}}

is_bin_present() {                                             # {{{

	local_bin_present="${1}"
	debug_prefix="${2:-}"

	## File doesn't exist by default
	return_is_bin_present="1"

	### Check if the file exists with executable perm
	# shellcheck disable=SC2086
	if find ${local_bin_present} -perm -a+x > /dev/null 2>&1; then
		return_is_bin_present="0"
		debug_message "${debug_prefix}is_bin_present − \
The file ${RED}${local_bin_present}${COLOR_DEBUG} exists."
	else
		return_is_bin_present="1"
		debug_message "${debug_prefix}is_bin_present − \
The file ${RED}${local_bin_present}${COLOR_DEBUG} doesn't exist."
	fi

	unset local_bin_present="${1}"
	unset debug_prefix

	return "${return_is_bin_present}"
}
# }}}

main() {                                                        # {{{

	debug_message "--- MAIN BEGIN"

	## Define all vars
	define_vars
	debug_message "| Define vars"

	## If eza system is available {{{
	### Start it
	if is_bin_present "${eza_system_path}" "| "; then
		### If EZA_OPTIONS is defined, call eza with options {{{
		if [ -n "${EZA_OPTIONS-}" ]; then
			debug_message "Use Eza from system (${eza_system_path}) with options (${EZA_OPTIONS})."
			"${eza_system_path}" $(echo "${EZA_OPTIONS}") \
				|| error_message "Error while calling eza from system path (${eza_system_path})" 11
		### }}}
		### If EZA_OPTIONS is NOT defined simply call it {{{
		elif [ -z "${EZA_OPTIONS-}" ]; then
			debug_message "Use Eza from system (${eza_system_path}) without options."
			"${eza_system_path}" \
				|| error_message "Error while calling eza from system path (${eza_system_path})" 12
		### }}}
		### If anything else happens, exit with error {{{
		else
			error_message "This test case is not supposed to happen ! Variable EZA_OPTIONS is defined or not." 13
		fi
		### }}}
		debug_message "--- MAIN END"
		exit 0
	fi
	## }}}
  ## If eza from user path is available {{{
	if is_bin_present "${eza_user_path}" "| "; then
		### If EZA_OPTIONS is defined, call eza with options {{{
		if [ -n "${EZA_OPTIONS-}" ]; then
			debug_message "Use Eza from user's path (${eza_user_path}) with options (${EZA_OPTIONS})."
			"${eza_user_path}" $(echo "${EZA_OPTIONS}") \
				|| error_message "Error while calling eza from system path (${eza_user_path})" 21
		### }}}
		### If EZA_OPTIONS is NOT defined simply call it {{{
		elif [ -z "${EZA_OPTIONS-}" ]; then
			debug_message "Use Eza from user's path (${eza_user_path}) without options."
			"${eza_user_path}" \
				|| error_message "Error while calling eza from user path (${eza_user_path})" 22
		### }}}
		### If anything else happens, exit with error {{{
		else
			error_message "This test case is not supposed to happen ! Variable EZA_OPTIONS is defined or not." 23
		fi
		### }}}
		debug_message "--- MAIN END"
		exit 0
	fi
  ## }}}

	debug_message "--- MAIN END"
}
# }}}

# 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) {{{
	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 "${1}" in
			--debug )                             ## debug
				DEBUG=0
				debug_message "--- Manage argument BEGIN"
				;;
			--user )                              ## Define eza_user_path with given arg
				## Move to the next argument
				shift
				## Define var
				readonly eza_user_path="${1}"
				;;
			--system )                            ## Define eza_system_path with given arg
				## Move to the next argument
				shift
				## Define var
				readonly eza_system_path="${1}"
				;;
			* )                                   ## unknow option
				debug_message "Unknown option (${1}), pass it as eza's option"
				test -n "${EZA_OPTIONS-}" && EZA_OPTIONS="${EZA_OPTIONS} ${1}"
				test -z "${EZA_OPTIONS-}" && EZA_OPTIONS="${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

exit 255