Logstash filter to copy some text from the log message

I'm currently loggin some text message like this:

"Some text: some variable text"
"Some other text: some other variable text"

And I need to copy the variable part of the message to a new field, in order to have two new fields like this

"field1" : " some variable text"
"field2" : "some other variable text"

So far only been able to copy the entire text message to a new field with the filebeat processors, and the same with logstash. I've done some research and I saw I mightbe able to use conditionals, and with the mutate filter:

filter {
  if "Some text" in [message] {
    mutate { add_field =>{ "field1" => }}}

But I'vent found how to copy the "some variable text" into the new field. Does someone knows how to do it?

One solution is to use directly grok filter like this :

  filter{
    grok {
        match => { 
          "message" => "^Some text: %{GREEDYDATA:field1}" 
          }
    }
   grok {
        match => { 
          "message" => "^Some other text: %{GREEDYDATA:field2}" 
          }
    }
}

The advantage is this is more readable and more easy to maintain than if condition.

You can change the grok to handle all case in one line :

      filter{
        grok {
            match => { 
              "message" => "^(Some text: %{GREEDYDATA:field1}|Some other text: %{GREEDYDATA:field2})" 
              }
        }
}