generic topic validation and parsing

.editorconfig

@@ -0,0 +1,14 @@
+root                     = true
+
+[*]
+end_of_line              = lf
+insert_final_newline     = true
+trim_trailing_whitespace = true
+charset                  = utf-8
+
+[*.lua]
+indent_style             = tab
+indent_size              = 4
+
+[Makefile]
+indent_style             = tab

mqtt/init.lua

@@ -81,6 +81,183 @@ function mqtt.run_sync(cl)
 	end
 end
 
+
+--- Validates a topic with wildcards.
+-- @param t (string) wildcard topic to validate
+-- @return topic, or false+error
+function mqtt.validate_subscribe_topic(t)
+	if type(t) ~= "string" then
+		return false, "not a string"
+	end
+	if #t < 1 then
+		return false, "minimum topic length is 1"
+	end
+	do
+		local _, count = t:gsub("#", "")
+		if count > 1 then
+			return false, "wildcard '#' may only appear once"
+		end
+		if count == 1 then
+			if t ~= "#" and not t:find("/#$") then
+				return false, "wildcard '#' must be the last character, and be prefixed with '/' (unless the topic is '#')"
+			end
+		end
+	end
+	do
+		local t1 = "/"..t.."/"
+		local i = 1
+		while i do
+			i = t1:find("+", i)
+			if i then
+				if t1:sub(i-1, i+1) ~= "/+/" then
+					return false, "wildcard '+' must be enclosed between '/' (except at start/end)"
+				end
+				i = i + 1
+			end
+		end
+	end
+	return t
+end
+
+--- Validates a topic without wildcards.
+-- @param t (string) topic to validate
+-- @return topic, or false+error
+function mqtt.validate_publish_topic(t)
+	if type(t) ~= "string" then
+		return false, "not a string"
+	end
+	if #t < 1 then
+		return false, "minimum topic length is 1"
+	end
+	if t:find("+", nil, true) or t:find("#", nil, true) then
+		return false, "wildcards '#', and '+' are not allowed when publishing"
+	end
+	return t
+end
+
+--- Returns a Lua pattern from topic.
+-- Takes a wildcarded-topic and returns a Lua pattern that can be used
+-- to validate if a received topic matches the wildcard-topic
+-- @param t (string) the wildcard topic
+-- @return Lua-pattern (string) or false+err
+-- @usage
+-- local patt = compile_topic_pattern("homes/+/+/#")
+--
+-- local topic = "homes/myhome/living/mainlights/brightness"
+-- local homeid, roomid, varargs = topic:match(patt)
+function mqtt.compile_topic_pattern(t)
+	local ok, err = mqtt.validate_subscribe_topic(t)
+	if not ok then
+		return ok, err
+	end
+	if t == "#" then
+		t = "(.+)" -- matches anything at least 1 character long
+	else
+		t = t:gsub("#","(.-)")  -- match anything, can be empty
+		t = t:gsub("%+","([^/]-)") -- match anything between '/', can be empty
+	end
+	return "^"..t.."$"
+end
+
+--- Parses wildcards in a topic into a table.
+-- Options include:
+--
+-- - `opts.topic`: the wild-carded topic to match against (optional if `opts.pattern` is given)
+--
+-- - `opts.pattern`: the compiled pattern for the wild-carded topic (optional if `opts.topic`
+--   is given). If not given then topic will be compiled and the result will be
+--   stored in this field for future use (cache).
+--
+-- - `opts.keys`: (optional) array of field names. The order must be the same as the
+--   order of the wildcards in `topic`
+--
+-- Returned tables:
+--
+-- - `fields` table: the array part will have the values of the wildcards, in
+--   the order they appeared. The hash part, will have the field names provided
+--   in `opts.keys`, with the values of the corresponding wildcard. If a `#`
+--   wildcard was used, that one will be the last in the table.
+--
+-- - `varargs` table: will only be returned if the wildcard topic contained the
+--   `#` wildcard. The returned table is an array, with all segments that were
+--   matched by the `#` wildcard.
+-- @param topic (string) incoming topic string (required)
+-- @param opts (table) with options (required)
+-- @return fields (table) + varargs (table or nil), or false+err on error.
+-- @usage
+-- local opts = {
+--   topic = "homes/+/+/#",
+--   keys = { "homeid", "roomid", "varargs"},
+-- }
+-- local fields, varargs = topic_match("homes/myhome/living/mainlights/brightness", opts)
+--
+-- print(fields[1], fields.homeid)  -- "myhome myhome"
+-- print(fields[2], fields.roomid)  -- "living living"
+-- print(fields[3], fields.varargs) -- "mainlights/brightness mainlights/brightness"
+--
+-- print(varargs[1]) -- "mainlights"
+-- print(varargs[2]) -- "brightness"
+function mqtt.topic_match(topic, opts)
+	if type(topic) ~= "string" then
+		return false, "expected topic to be a string"
+	end
+	if type(opts) ~= "table" then
+		return false, "expected optionss to be a table"
+	end
+	local pattern = opts.pattern
+	if not pattern then
+		local ptopic = opts.topic
+		if not ptopic then
+			return false, "either 'opts.topic' or 'opts.pattern' must set"
+		end
+		local err
+		pattern, err = mqtt.compile_topic_pattern(ptopic)
+		if not pattern then
+			return false, "failed to compile 'opts.topic' into pattern: "..tostring(err)
+		end
+		-- store/cache compiled pattern for next time
+		opts.pattern = pattern
+	end
+	local values = { topic:match(pattern) }
+	if values[1] == nil then
+		return false, "topic does not match wildcard pattern"
+	end
+	local keys = opts.keys
+	if keys ~= nil then
+		if type(keys) ~= "table" then
+			return false, "expected 'opts.keys' to be a table (array)"
+		end
+		-- we have a table with keys, copy values to fields
+		for i, value in ipairs(values) do
+			local key = keys[i]
+			if key ~= nil then
+				values[key] = value
+			end
+		end
+	end
+	if not pattern:find("%(%.[%-%+]%)%$$") then -- pattern for "#" as last char
+		-- we're done
+		return values
+	end
+	-- we have a '#' wildcard
+	local vararg = values[#values]
+	local varargs = {}
+	local i = 0
+	local ni = 0
+	while ni do
+		ni = vararg:find("/", i, true)
+		if ni then
+			varargs[#varargs + 1] = vararg:sub(i, ni-1)
+			i = ni + 1
+		else
+			varargs[#varargs + 1] = vararg:sub(i, -1)
+		end
+	end
+
+	return values, varargs
+end
+
+
 -- export module table
 return mqtt