#!/bin/sh

getTimeStamp() {
  (date -u +"%Y-%m-%dT%H:%M:%SZ")
}

getHostname() {
  (hostname -s)
}

lowercase() {
  echo "$1" | tr '[:upper:]' '[:lower:]'
}

uppercase() {
  echo "$1" | tr '[:lower:] [:upper:]'
}

standardizeLogLevels() {
  LEVEL_TO_TRANSLATE="$1"
  case "$LEVEL_TO_TRANSLATE" in
  "critical" | "crit" | "fatal")
    echo "CRIT"
    ;;
  "error" | "err")
    echo "ERR"
    ;;
  "warning" | "warn")
    echo "WARN"
    ;;
  "information" | "info")
    echo "INFO"
    ;;
  "debug" | "verbose")
    echo "DEBUG"
    ;;
  *)
    echo "INFO"
    ;;
  esac
}

translateLogLevelsToJournalD() {
  LEVEL_TO_TRANSLATE="$(standardizeLogLevels "$1")"
  case "$LEVEL_TO_TRANSLATE" in
  "CRIT")
    return 5
    ;;
  "ERR")
    return 4
    ;;
  "WARN")
    return 3
    ;;
  "INFO")
    return 1
    ;;
  "DEBUG")
    return 0
    ;;
  *)
    return 0
  esac
}

# modified syslog fmt: <ISO-8601 timestamp> <hostname> <tag>[pid]: [LEVEL:$2] [STATUS:$3] <MESSAGE:$1> (<OPERATION:$4>:<CODE:$5>)
writePlainTextLog() {
  # not enough information to generate a meaningful log message
  if [ -z "$1" ] || [ $# -lt 3 ]; then
    return
  fi

  printf "%s %s %s[%s]: [%s] [%s] %s (%s:%s)\n" \
    "$(getTimeStamp)" "$(getHostname)" "$LOG_PROGRAM_NAME" "$$" \
    "$2" "$(standardizeLogLevels "$3")" "$1" "${4:UNSPECIFIED}" "${5:999}"
}

# $1: message, $2: level, $3: status, [$4: operation], [$5: code]
writeJsonLog() {
  # not enough information to generate a meaningful log message
  if [ -z "$1" ] || [ $# -lt 3 ]; then
    return
  fi

  PROPS="$(
    jq --null-input \
      --arg timestamp "$(getTimeStamp)" \
      --arg hostname "$(getHostname)" \
      --arg pName "$LOG_PROGRAM_NAME" \
      --arg pid = "$$" \
      --arg level "$2" \
      --arg status "$(uppercase "$3")" \
      --arg message "$1" \
      --arg operation "${4:UNSPECIFIED}" \
      --arg code "${5:999}" \
      '{"level":$level, "programName":$pName, "status":$status, "operation":$operation, "code":$code, "message":$message}' \
  )"
  fi

  echo "$PROPS" | jq "."
  return
}

# $1: message, $2: level, $3: status, $4: operation, $5: code
writeJournalLog() {
  # translate error levels
  if [ -z "$2" ]; then
    LOG_LEVEL=1
  else
    case "$2" in
    "emergency" | "emerg")
      LOG_LEVEL=7
      ;;
    "alert")
      LOG_LEVEL=6
      ;;
    "critical" | "crit")
      LOG_LEVEL=5
      ;;
    "error" | "err")
      LOG_LEVEL=4
      ;;
    "warning" | "warn")
      LOG_LEVEL=3
      ;;
    "notice")
      LOG_LEVEL=2
      ;;
    "info")
      LOG_LEVEL=1
      ;;
    "debug")
      LOG_LEVEL=0
      ;;
    esac
  fi

  # log the message
  if [ -z "$1" ]; then
    logger --journald <<end
MESSAGE_ID="$(systemd-id128 new)"
SYSLOG_TIMESTAMP="$(getTimeStamp)"
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER="${LOG_PROGRAM_NAME}"
PRIORITY=4
ERRNO="${LOG_DEFAULT_CODE}"
OPERATION="${LOG_DEFAULT_OPERATION}"
MESSAGE="${LOG_DEFAULT_MESSAGE}"
STATUS="${LOG_DEFAULT_STATUS}"
end
  else
    logger --journald <<end
MESSAGE_ID="$(systemd-id128 new)"
SYSLOG_TIMESTAMP="$(getTimeStamp)"
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER="${LOG_PROGRAM_NAME}"
PRIORITY="${LOG_LEVEL}"
ERRNO="${5:-$LOG_DEFAULT_CODE}"
OPERATION="${4:-$LOG_DEFAULT_OPERATION}"
MESSAGE="$1"
STATUS="${3:-$LOG_DEFAULT_STATUS}"
end
  fi

  return
}

LOG_PROGRAM_NAME="cfddns"
LOG_DEFAULT_CODE=99
LOG_DEFAULT_LEVEL="info"
LOG_DEFAULT_MESSAGE="An unspecified error has occurred"
LOG_DEFAULT_OPERATION="unspecified"
LOG_DEFAULT_STATUS="ERR"

if [ "$1" = "json" ]; then
  writeJsonLog # this will generate a generic error message
  writeJsonLog "This is a test message" # generate this message at the default level with the default code
  writeJsonLog "This is a test message" "warning" # generate this message at the 'warning' level with the default code
  writeJsonLog "This is a test message" "error" "testing" # generate this message at the 'error' level, part of a 'test' operation, and with the default code
  writeJsonLog "This is a test message" "alert" "testing" 10 # generate this message at the 'alert' level with all parameters set
elif [ "$1" = "journal" ]; then
  writeJournalLog # this will generate a generic error message
  writeJournalLog "This is a test message" # generate this message at the default level with the default code
  writeJournalLog "This is a test message" "warning" # generate this message at the 'warning' level with the default code
  writeJournalLog "This is a test message" "error" "testing" # generate this message at the 'error' level as part of a 'test' operation, and with the default code
  writeJournalLog "This is a test message" "alert" "testing" 10 # generate this message at the 'alert' level with all parameters set
else
  printf "\nPlease specify either 'json' or 'journal' after the script name. Exiting.\n\n"
  exit 1
fi

exit 0