docs update

wrs/topics/scripting.md

@@ -56,14 +56,55 @@ The variable `p` is read-only, and any modifications are ignored.
 
 ## Rule matching
 
-todo
+Let's write a simple rule that matches any URL that starts with  `https://meet.google.com/` **and** is opened from [Slack](https://slack.com/) desktop application.
 
-## Combining URL processing and rule matching
+We already know how to check the first part, but for the second the solutions also simple - if the process name is `slack.exe`. Process name can be retreived from the `p.pn` variable. Here is the Lua code for this functionality:
 
-todo
+```
+function rule_gmeet_from_slack()
+	if string.find(p.url, "https://meet.google.com/") == 1 and string.lower(p.pn) == "slack.exe" then
+		return true
+    end
+	return false
+end
+```
+
+This is how the function works:
+
+1. It checks if the URL starts with `https://meet.google.com/` by using `string.find` function against `p.url` variable.
+2. It checks if the process name is `slack.exe` by using `string.lower` function against `p.pn` variable.
+3. If both conditions are met, it returns `true`.
+4. If any of the conditions are not met, it returns `false`.
+
+To use this script in %product%:
+
+1. Paste the script into the "Lua script" editor.
+2. Press "Save" to save the script.
+3. Select the function name to run from the dropdown list. At this point you should have two functions, `ppl_gmeet` and `rule_gmeet_from_slack`.
+4. Type a URL to test, for instance `https://meet.google.com/mtg/`.
+5. Type process name to test, for instance `slack.exe`. You will notice that switching to a function prefixed with `rule_` will add extra fields for test input.
+6. Press "Run".
+7. The result will be displayed in the "Terminal" section.
+
+
+![](script-fn2.png)
+
+You might notice an interesting behavior in the terminal - message "pipeline changed URL to 'https://meet.google.com/?authuser=1'" - this is because the pipeline step `ppl_gmeet` was executed before the rule was checked. This is the expected behavior, as the pipeline steps are executed before the rule matching.
+
+To use this rule in %product%, you need to add it to the rules list. This is done by pressing the "Add" button in the "Rules" section of an appropriate browser or prifile, selecting "Lua script" and then selecting function name in the dropdown list:
+
+<img height="100" src="script-fn2-inrule.png"/>
+
+To test, use [Pipeline debugger](debugger.md) and type a URL that starts with `https://meet.google.com/` and process name `slack.exe`. You will see that the URL goes through the pipeline step `ppl_gmeet`
+
+![](script-fn2-dbg1.png)
+
+and then the rule `rule_gmeet_from_slack` is matched.
+
+![](script-fn2-dbg2.png)
 
 ## Printing to the terminal
 
-todo
+%product% allows you to print messages to the terminal from the script. This is useful for debugging purposes. To print a message, use the built-in Lua `print` function, and the message will be displayed in the "Terminal" section.