Change the behaviour of service code detection

- Parse service codes if they are sent as `!code` or `nick: !code` in channels
  and private messages (where `!code` is an example code prefix and service
  code, and `nick` is the bot's nick). If the service code is not provided at
  the start of the message body, it will be treated as a message without a
  service code and passed to the target handler.

- If a target handler is defined, both messages in the form `nick: message`
  in a channel and `message` in a private message will be sent to the handler.
  The `nick:` at the start of `nick: message` will no longer be filtered out.

  The default name of the target handler is `target`, as in
  `itte_handlers.target(cxt, msg)`. This can be changed in the config by
  setting a new `itte_config.target_handler` value.

itte.lua

@@ -251,16 +251,31 @@ function itte.get_commands(svr)
       resp = "QUIT :",
     },
     target_private = {
+      -- Like privmsg but targets bot nick in a direct message without a
+      -- service code.
+      -- Escape magic character "-"
+      check = "PRIVMSG(.*)" .. string.gsub(svr.nick, "-", "%%-") .. "(.*):",
+      resp = nil,
+    },
+    target_private_code = {
       -- Like privmsg but targets bot nick in a direct message
       -- Escape magic character "-"
-      check = "PRIVMSG(.*)" .. string.gsub(svr.nick, "-", "%%-") .. ":",
-      resp = "PRIVMSG ",
+      check = "PRIVMSG(.*)" .. string.gsub(svr.nick, "-", "%%-") .. "(.*):" ..
+        string.gsub(svr.nick, "-", "%%-") .. "(.*)" .. svr.code_prefix,
+      resp = nil,
     },
     target_public = {
-      -- Like privmsg but targets bot nick in a channel
+      -- Like privmsg but targets bot nick in a channel without a service code.
       -- Escape magic character "-"
       check = "PRIVMSG(.*)#(.*):" .. string.gsub(svr.nick, "-", "%%-"),
-      resp = "PRIVMSG ",
+      resp = nil,
+    },
+    target_public_code = {
+      -- Like privmsg but targets bot nick in a channel
+      -- Escape magic character "-"
+      check = "PRIVMSG(.*)#(.*):" .. string.gsub(svr.nick, "-", "%%-") ..
+        "(.*)" .. svr.code_prefix,
+      resp = nil,
     },
     user = {
       check = "NOTICE",
@@ -610,18 +625,16 @@ function itte.parse_privmsg(cxt, str, mode)
   -- Separator marks the start of the message body
   body_sep, _ = string.find(str, ":", 2)
 
-  -- Message in the format `[nick]: [body]`
+  -- Message in the format `[body]` (private message) or `[nick]: [body]`
   if mode == "target" then
     msg = {
       sender = string.sub(str, string.find(str, "!") + 2,
         string.find(str, "@") - 1),
-      -- Escape magic character "-" in the nick
       recipient = string.sub(str, string.find(str, "PRIVMSG") + 8,
-        string.find(str, ":" .. string.gsub(cxt.nick, "-", "%%-")) - 2),
+        string.find(str, " :") - 1),
       reply_to = string.sub(str, string.find(str, "!") + 2,
         string.find(str, "@") - 1),
-      body = string.gsub(string.sub(str, body_sep + 2 +
-        string.len(cxt.nick)), "^%s", ""),
+      body = string.sub(str, body_sep + 1),
     }
     -- Reply to sender by default (private message), or reply in a channel if
     -- original message recipient is a channel.
@@ -635,19 +648,31 @@ function itte.parse_privmsg(cxt, str, mode)
       ", " .. itte.config.debugs.privmsg[7] .. ": " .. msg.body ..
       " }", itte.config.debug)
 
-  -- Message in the format `[code] [params]`
+  -- Message in the format `[code] [params]` or `[nick] [code] [params]`
   else
+    -- Set the code prefix position variable to a number out of range of the
+    -- service code parsing buffer, then get the position. Check for the colon
+    -- separator at exactly the start of the message body, i.e. `[code]`, or
+    -- the space char for `[nick] [code]`.
     local code_full = ""
-    -- Service code found with specified prefix
-    if util.is_substr(str, ":" .. cxt.code_prefix) then
-      code_full = string.sub(str, string.find(str, ":" ..
-        cxt.code_prefix) + 1 + string.len(cxt.code_prefix))
+    local cp_pos = body_sep + string.len(cxt.nick) + 4
+    local co_sep, _ = string.find(str, ":" .. cxt.code_prefix)
+    if co_sep == body_sep then
+      cp_pos = string.find(str, ":" .. cxt.code_prefix)
+    elseif string.find(str, " " .. cxt.code_prefix) ~= nil then
+      cp_pos = string.find(str, " " .. cxt.code_prefix)
+    end
+    -- Only parse service code if it is near the start of the message body,
+    -- within a small buffer in position to allow some variation in style, e.g.
+    -- `[nick]: [code]`, `[nick] [code]`, etc.
+    if cp_pos <= body_sep + string.len(cxt.nick) + 3 then
+      code_full = string.sub(str, cp_pos + 1 + string.len(cxt.code_prefix))
     end
     msg = {
       sender = string.sub(str, string.find(str, "!") + 2,
         string.find(str, "@") - 1),
       recipient = string.sub(str, string.find(str, "PRIVMSG") + 8,
-        string.find(str, ":" .. cxt.code_prefix) - 2),
+        string.find(str, " :") - 1),
       reply_to = string.sub(str, string.find(str, "!") + 2,
         string.find(str, "@") - 1),
       body = string.sub(str, body_sep + 1),
@@ -656,7 +681,6 @@ function itte.parse_privmsg(cxt, str, mode)
       msg.code = string.sub(code_full, 0, string.find(code_full, " ") - 1)
       msg.code_params = util.split_str(string.sub(code_full,
         string.find(code_full, " ") + 1))
-
     else
       msg.code = code_full
       msg.code_params = {}
@@ -666,7 +690,6 @@ function itte.parse_privmsg(cxt, str, mode)
     if util.is_substr(msg.recipient, "#") then
       msg.reply_to = msg.recipient
     end
-
     -- Redact debug output for admin-only handlers to avoid logging passwords.
     local body = msg.body
     local code_params = table.concat(msg.code_params, " ")
@@ -937,8 +960,12 @@ function itte.listen(name, str)
     local channel, names = itte.parse_names(cxt, str)
     cxt.chan_meta[channel:sub(2)] = { users = names }
 
-  -- Respond to service code
-  elseif util.is_substr(str, cxt.cmds.privmsg.check) then
+  -- Respond to service code, checking for `[code]` and `[nick]: [code]`.
+  -- Code prefix cannot be the last character in the data string.
+  elseif (util.is_substr(str, cxt.cmds.privmsg.check) or
+    (util.is_substr(str, cxt.cmds.target_public_code.check)) or
+    (util.is_substr(str, cxt.cmds.target_private_code.check))) and
+    (str:sub(string.len(str)) ~= cxt.code_prefix) then
     local msg = itte.parse_privmsg(cxt, str)
     -- Check for the service in the admin handlers table and redact the debug
     -- output for admin handlers.
@@ -960,6 +987,12 @@ function itte.listen(name, str)
     -- Check the handlers table
     elseif util.has_key(itte.handlers, msg.code) then
       itte.handlers[msg.code](cxt, msg)
+    -- If there is no service code found near the start of the message body,
+    -- respond as a direct address and pass the message to the target handler
+    -- if it exists.
+    elseif (util.has_key(itte.handlers, itte.config.target_handler)) and
+      (msg.code == "") then
+      itte.handlers[itte.config.target_handler](cxt, msg)
     else
       -- Only hint with unknown code error in private messages as there may be
       -- prefix collision in channels.