ircmsg.sh

#!/bin/bash

declare -A tags

clear_message() {
  start=0
  source=""
  fragment=""

  tags=()
  prefix=""
  command=""
  params=()
}

extract_fragment() {
  local end=${1:-"-1"}
  local prefix=${2:-""}
  
  # Try to set find the end of the space-delimited fragment
  if [ "$end" == "-1" ]; then
      local tmp=${source:$start}
      local tmp=${tmp%% *}
      end=$(($start + ${#tmp}))
  fi
  # If no space comes after this point, use the remainder of the string
  if [ "$end" == "-1" ]; then
    end=${#source}
  fi

  fragment=""
  # If a prefix is set
  if [ "$prefix" != "" ]; then
    # And the fragment starts with the prefix
    if [ "$start" -lt "${#source}" ] && [ "${source:$start:1}" == "$prefix" ]; then
      # return the fragment without the prefix, advancing the string
      fragment=${source:$(($start + 1)):$(($end - $start - 1))}
      start=$end
    fi
  else
    # otherwise return the entire fragment
    fragment=${source:$start:$(($end - $start))}
    start=$end
  fi
}

skip_empty_parts() {
  while [ "$start" -lt "${#source}" ] && [ "${source:$start:1}" == " " ]; do
    start=$((start + 1))
  done
}

parse_tag_value() {
  local value=${1}
  local result=""
  local escaped=0
  for (( i=0; i<${#value}; i++ )); do
    c=${value:$i:1}
    if [ $escaped -ne 0 ]; then
      if [ "$c" == "\\" ]; then
        result+="\\"
      elif [ "$c" == "s" ]; then
        result+=" "
      elif [ "$c" == ":" ]; then
        result+=";"
      elif [ "$c" == "r" ]; then
        result+="\r"
      elif [ "$c" == "n" ]; then
        result+="\n"
      else
        result+="$c"
      fi
      escaped=0
    elif [ $c == "\\" ]; then
      escaped=1
    else
      result+="$c"
    fi
  done
  echo $result
}

parse_tags() {
  extract_fragment "-1" "@"
  local raw_tag_str=$fragment
  # Tags are delimited with ; according to spec
  local IFS=";"
  for raw_tag in $raw_tag_str; do
    if [ "$raw_tag" != "" ]; then
      local raw_key=${raw_tag%%=*}
      local raw_value=${raw_tag:$((${#raw_key}+1))}
      
      tags[$raw_key]=$(parse_tag_value $raw_value)
    fi
  done
}

parse_prefix() {
  extract_fragment "-1" ":"
  prefix=$fragment
}

parse_command() {
  extract_fragment "-1"
  command=$fragment
}

parse_parameter() {
  if [ $start -lt ${#source} ] && [ ${source:$start:1} == ':' ]; then
    start=$(($start + 1))
    extract_fragment ${#source}
  else
    extract_fragment
  fi
  params+=( "$fragment" )
}

parse_message() {
  clear_message
  source=${1}

  parse_tags
  skip_empty_parts
  
  parse_prefix
  skip_empty_parts
  
  parse_command
  skip_empty_parts
  
  unset params
  while [ $start -lt ${#source} ]; do
    parse_parameter
    skip_empty_parts
  done
}

print_message() {
  echo "tags: "
  for i in "${!tags[@]}"
  do
    echo "  ${i}=${tags[$i]}"
  done
  echo "prefix: $prefix"
  echo "command: $command"
  echo "params: "
  for i in "${params[@]}"
  do
    echo "  ${i}"
  done
}

parse_message "@a=b;c=32;k;rt=ql7 :source PRIVMSG #channel :test a thing"
print_message
echo "---"
parse_message ":coolguy!ag@net\x035w\x03ork.admin PRIVMSG foo :bar baz"
print_message
echo "---"
parse_message "@tag1=value\\\\ntest COMMAND"
print_message
echo "---"
parse_message "@tag1=value1;tag2;vendor1/tag3=value2;vendor2/tag4 COMMAND param1 param2 :param3 param3"
print_message
echo "---"
parse_message ":gravel.mozilla.org 432  #momo :Erroneous Nickname: Illegal characters"
print_message