bash/irc: a bare-bones IRC line parser

bash/irc

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+host=irc.libera.chat port=6667
+nick=bashbot ident=bashbot realname=bashbot
+channels=##bashbot
+
+exec {sock}<>/dev/tcp/"$host"/"$port"
+
+while IFS= read -ru "$sock" line; do
+  line=${line%$'\r'}
+  declare -A msg=( [words]=no [original]="$line" )
+
+  if [[ ${line:0:1} = : ]]; then
+    prefix=${line%% *} line=${line#"$prefix"} line=${line# } prefix=${prefix#:}
+    msg[host]=${prefix#*@} prefix=${prefix%"${msg[host]}"} prefix=${prefix%@}
+    msg[from]=${msg[host]}
+
+    if [[ $prefix ]]; then
+      msg[ident]=${prefix#*!}
+      msg[from]=${msg[ident]}
+
+      if [[ ${msg[ident]} != "$prefix" ]]; then
+        msg[nick]=${prefix%!*}
+        msg[from]=${msg[nick]}
+      fi
+    fi
+  fi
+
+  msg[cmd]=${line%% *} msg[cmd]=${msg[cmd]^^}
+  line=${line#"${msg[cmd]}"} line=${line# }
+  msg_args=( )
+
+  while [[ $line ]]; do
+    if [[ ${line:0:1} = : ]]; then
+      msg_args+=( "${line:1}" ) msg[words]=yes line=
+      read -ra msg_words <<< "${msg_args[-1]}"
+    else
+      arg=${line%% *} msg_args+=( "$arg" )
+      line=${line#"$arg"} line=${line# }
+    fi
+  done
+
+  if [[ ${msg[cmd]} = @(PRIVMSG|NOTICE) ]]; then
+    if [[ ${msg_args[0]:0:1} = \# ]]; then
+      msg[to]=${msg_args[0]}
+    else
+      msg[to]=${msg[from]}
+    fi
+  fi
+
+  printf '%s\n' "${msg[original]}"
+done