#!/bin/bash

programName="${0##*/}"

defaultArchiveLocation="https://brltty.app/archive/Canute"
defaultArchiveName="canute-controller.tar.gz"

showUsageSummary() {
cat <<END-OF-USAGE-SUMMARY
Install or upgrade the Raspbian Canute Controller software.
Copyright © 2022 by Bristol Braille Technology CIC

Usage: ${programName} [-option ...]
The following options may be specified:
-h       show this command line usage summary, and then exit
-q       quiet mode - don't show the name of each action before it's performed
-t       test mode - show the host commands that would be executed (root not required) - -q ignored
-a file  the name of the archive - default is ${defaultArchiveName}
-l path  the archive's container (URL or local directory) - default is ${defaultArchiveLocation}

This script must be executed as root on a Raspbian system.
END-OF-USAGE-SUMMARY
}

programMessage() {
   local message="${1}"

   echo >&2 "${programName}: ${message}"
}

logTask() {
   local message="${1}"

   "${quietMode}" || programMessage "${message}"
}

syntaxError() {
   local message="${1}"

   programMessage "${message}"
   exit 2
}

semanticError() {
   local message="${1}"

   programMessage "${message}"
   exit 3
}

executeHostCommand() {
   if "${testMode}"
   then
      programMessage "executing host command: ${*}"
   else
      "${@}"
   fi
}

downloadFile() {
   local file="${1}"

   executeHostCommand curl --output "${file}" --silent --show-error --get --location -- "${archiveLocation}/${file}"
}

needTemporaryDirectory() {
   [ -n "${TMPDIR}" -a -d "${TMPDIR}" -a -r "${TMPDIR}" -a -w "${TMPDIR}" -a -x "${TMPDIR}" ] || export TMPDIR="/tmp"
   temporaryDirectory="$(mktemp -d "${TMPDIR}/${programName}.$(date +"%Y%m%d-%H%M%S").XXXXXX")"
}

removeTemporaryDirectory() {
   set +e
   cd /
   rm -f -r -- "${temporaryDirectory}"
}

showUsage=false
quietMode=false
testMode=false
archiveLocation="${defaultArchiveLocation}"
archiveName="${defaultArchiveName}"

while getopts ":hqta:l:" option
do
   case "${option}"
   in
      h) showUsage=true;;
      q) quietMode=true;;
      t) testMode=true;;
      a) archiveName="${OPTARG}";;
      l) archiveLocation="${OPTARG}";;

      :) syntaxError "missing operand: -${OPTARG}";;
     \?) syntaxError "unrecognized option: -${OPTARG}";;
      *) syntaxError "unimplemented option: -${option}";;
   esac
done

shift $((OPTIND - 1))
[ "${#}" -eq 0 ] || syntaxError "too many parameters"

"${showUsage}" && {
   showUsageSummary
   exit 0
}

[ -n "${archiveName}" ] || syntaxError "archive name not specified"
[ -n "${archiveLocation}" ] || archiveLocation="."
tarDecompressionOption=""

case "${archiveName}"
in
   *.tgz) tarDecompressionOption="--gzip";;
   *.tar) tarDecompressionOption="";;
   *.tar.bz2) tarDecompressionOption="--bzip2";;
   *.tar.gz) tarDecompressionOption="--gzip";;
   *.tar.xz) tarDecompressionOption="--xz";;
   *) semanticError "unrecognized archive file extension: ${archiveName}";;
esac

[ -f "/usr/bin/raspi-config" ] || semanticError "not Raspbian"
"${testMode}" || [ "$(id -u)" -eq 0 ] || semanticError "not executing as root"

"${testMode}" && quietMode=false
set -e

archiveScheme="${archiveLocation%%:*}"
[ "${archiveScheme}" = "${archiveLocation}" ] || {
   # the location contains a colon so it might have a scheme

   [ "${archiveScheme}" != "${archiveScheme#*/}" ] || {
      # the scheme doesn't contain a slash
      [ -n "${archiveScheme}" ] || syntaxError "empty archive location sheme: ${archiveLocation}"
      # yes it actually is a scheme

      needTemporaryDirectory
      trap removeTemporaryDirectory exit
      executeHostCommand cd "${temporaryDirectory}"

      logTask "downloading archive"
      downloadFile "${archiveName}"
      archiveLocation="."
   }
}

archivePath="${archiveLocation}/${archiveName}"
"${testMode}" || {
   [ -e "${archiveLocation}" ] || semanticError "directory not found: ${archiveLocation}"
   [ -d "${archiveLocation}" ] || semanticError "not a directory: ${archiveLocation}"
   [ -x "${archiveLocation}" ] || semanticError "directory not searchable: ${archiveLocation}"

   [ -e "${archivePath}" ] || semanticError "archive not found: ${archivePath}"
   [ -f "${archivePath}" ] || semanticError "not a file: ${archivePath}"
   [ -r "${archivePath}" ] || semanticError "archive not readable: ${archivePath}"
}

logTask "unpacking archive"
executeHostCommand tar --extract ${tarDecompressionOption} --absolute-names --file "${archivePath}" --directory "/"

logTask "setting up system"
setupCommand=("/brltty/current/libexec/canute-setup" -A)

if "${testMode}"
then
   setupCommand+=(-t -v -v)
   testMode=false
elif "${quietMode}"
then
   setupCommand+=(-q)
fi

executeHostCommand "${setupCommand[@]}"
exit 0