#!/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_STANDARDIZE="$(lowercase "$1")"
  case "$LEVEL_TO_STANDARDIZE" 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")
    echo 5
    ;;
  "ERR")
    echo 4
    ;;
  "WARN")
    echo 3
    ;;
  "INFO")
    echo 1
    ;;
  "DEBUG")
    echo 0
    ;;
  *)
    echo 1
  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" "$$" \
    "$(standardizeLogLevels "$2")" "$(uppercase "$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 "$(standardizeLogLevels "$2")" \
      --arg status "$(uppercase "$3")" \
      --arg message "$1" \
      --arg operation "${4:-UNSPECIFIED}" \
      --arg code "${5:-999}" \
      '{"timestamp":$timestamp, "hostname":$hostname, "programName":$pName, "pid":$pid, "level":$level, "status":$status, "message":$message, "operation":$operation, "code":$code}' \
  )"

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

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

  J_TIMESTAMP="$(getTimeStamp)"
  J_PID="$$"
  J_PRIO="$(translateLogLevelsToJournalD "$2")"
  J_STAT="$(uppercase "$3")"

  logger --journald <<end
SYSLOG_TIMESTAMP=${J_TIMESTAMP}
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER=${LOG_PROGRAM_NAME}
SYSLOG_PID=${J_PID}
PRIORITY=${J_PRIO}
STATUS=${J_STAT}
MESSAGE=$1
OPERATION=${4:-UNSPECIFIED}
ERRNO=${5:-999}
end

  return
}

LOG_PROGRAM_NAME="cfddns"

if [ "$1" = "text" ]; then
  writePlainTextLog # this will do nothing
  writePlainTextLog "Testing plain-text logging output" # this will also do nothing
  writePlainTextLog "Informational plain-text log message" "information" "ok" # info message
  writePlainTextLog "Plain-text message forced to info level" "whoops" "ok" # level translated to default
  writePlainTextLog "Warning! This is plain-text." "warning" "flagged" # warning level with 'flagged' status
  writePlainTextLog "Error sample! This is plain-text." "err" "error" # error level message
  writePlainTextLog "Unable to continue, critical failure. (This is plain-text)" "fatal" "exit" "startup" "2" # critical level error with operation and error code
elif [ "$1" = "json" ]; then
  writeJsonLog # this will do nothing
  writeJsonLog "This is a test message" # this will also do nothing
  writeJsonLog "Informational JSON log message" "information" "ok" # info message
  writeJsonLog "JSON message forced to info level" "whoops" "ok" # level translated to default
  writeJsonLog "Warning! This is JSON." "warning" "flagged" # warning level with 'flagged' status
  writeJsonLog "Error sample! This is JSON." "err" "error" # error level message
  writeJsonLog "Unable to continue, critical failure. (This is JSON)" "fatal" "exit" "startup" "2" # critical level error with operation and error code
elif [ "$1" = "journal" ]; then
  writeJournalDLog # this will do nothing
  writeJournalDLog "This is a test message" # this will also do nothing
  writeJournalDLog "Informational JOURNALD log message" "information" "ok" # info message
  writeJournalDLog "JOURNALD message forced to info level" "whoops" "ok" # level translated to default
  writeJournalDLog "Warning! This is a JOURNALD message." "warning" "flagged" # warning level with 'flagged' status
  writeJournalDLog "Error sample! This is a JOURNALD." "err" "error" # error level message
  writeJournalDLog "Unable to continue, critical failure. (This is JOURNALD message)" "fatal" "exit" "startup" "2" # critical level error with operation and error code
else
  printf "\nPlease specify either 'text', 'json', or 'journal' after the script name. Exiting.\n\n"
  exit 1
fi

exit 0