DAML Triggers: How can I pass arguments in DAML Trigger?

Questions
1

Sample code:

module Main.User where

data Currency = INR | USD | EUR

template User with
    username: Party
    following: [Party]    
  where
    signatory username
    observer following

    key username: Party
    maintainer key
    nonconsuming choice Follow: ContractId User with
        userToFollow: Party
      controller username
      do
        archive self
        create this with following = userToFollow :: following

    nonconsuming choice SendMessage: ContractId Message with
        sender: Party
        content: Text
        messagingFees: Optional Decimal
        feeType: Optional Currency

      controller sender
      do
        assertMsg "Designated user must follow you back to send a message" (elem sender following)
        now <- getTime
        create Message with sender, receiver = username, content, messagingFees, feeType, receivedAt = now

template Message with
    sender: Party
    receiver: Party
    content: Text
    receivedAt: Time
    messagingFees: Optional Decimal
    feeType: Currency

  where
    signatory sender, receiver

DAML Trigger:

import Main.User as User
import qualified Daml.Trigger as T
-- import qualified User
import qualified DA.List.Total as List
import DA.Action (when)
import DA.Optional (whenSome)

autoReply : T.Trigger ()
autoReply = T.Trigger
  { initialize = pure ()
  , updateState = \_ -> pure ()
  , rule = \p -> do
      message_contracts <- T.query @User.Message
      let messages = map snd message_contracts
      debug $ "Messages so far: " <> show (length messages)
      let lastMessage = List.maximumOn (.receivedAt) messages
      debug $ "Last message: " <> show lastMessage
      whenSome lastMessage $ \m ->
        when (m.receiver == p) $ do
          users <- T.query @User.User
          debug users
          let isSender = (\user -> user.username == m.sender)
          let replyTo = List.head $ filter (\(_, user) -> isSender user) users
          whenSome replyTo $ \(sender, _) ->
            T.dedupExercise sender (User.SendMessage p "Please, tell me more about that." 1000.0 USD)
  , registeredTemplates = T.AllInDar
  , heartbeat = None
  }

How can I pass values in this T.dedupExercise sender (User.SendMessage p "Please, tell me more about that." 1000.0 USD) from different templates?
E.g. If I’m listing to Message template from some other then how can I use value of that message template and pass value to our choice?

2

You’ll have to grab the message contracts, similar to the beginning lines of this trigger,
message_contracts <- T.query @User.Message
let messages = map snd message_contracts
this gives us a list of message contracts, (not CIDs)
and you can map through them, and access the message field, message.content, that is what you’ll want to pass in as an argument to the choice.