/// Routes a customer support ticket to the appropriate handler based on sentiment and priority.
///
/// Customer details and ticket history are fetched in parallel; sentiment is then
/// analysed across both inputs and a priority is classified.  A branch directs VIP
/// customers to a dedicated agent, normal-priority tickets to the standard queue, and
/// low-priority tickets to automatic resolution.
///
/// Key DSL concepts demonstrated:
///   depends_on = [a, b]   — fan-in: analyzeSentiment waits for both fetch nodes to
///                           complete before starting
///   branch on <expr>      — exactly one handler executes; the other two are skipped
///   timeout               — per-node cancellation deadline
///   retry / fallback      — automatic retry with a neutral-sentiment fallback on failure
///
/// Context variables:
///   ctx.customerId — ID of the customer who submitted the ticket
///   ctx.message    — raw message content of the ticket
graph ticketRouting {

  /// Fetches the customer's profile; retries twice on transient failure
  node fetchCustomer : FetchCustomerOperator {
    input {
      customerId = ctx.customerId
    }
    timeout = 3s
    retry = { attempts: 2, backoff: 200ms, strategy: exponential }
  }

  /// Fetches the customer's previous ticket history
  node fetchTicketHistory : FetchTicketHistoryOperator {
    input {
      customerId = ctx.customerId
    }
    timeout = 3s
  }

  /// Analyses message sentiment using customer context and history;
  /// depends_on fan-in waits for both fetch nodes to complete;
  /// falls back to a neutral-sentiment result if the operator throws
  node analyzeSentiment : AnalyzeSentimentOperator {
    depends_on = [fetchCustomer, fetchTicketHistory]
    input {
      customer = fetchCustomer.output
      history  = fetchTicketHistory.output
      message  = ctx.message
    }
    timeout = 5s
    retry = { attempts: 1, backoff: 500ms, strategy: exponential }
    fallback = { sentiment: "neutral", score: 0.0, keywords: [] }
  }

  /// Classifies the ticket priority (vip / normal / otherwise) from customer profile and sentiment
  node classifyPriority : ClassifyPriorityOperator {
    depends_on = [analyzeSentiment]
    input {
      customer  = fetchCustomer.output
      sentiment = analyzeSentiment.output
    }
  }

  /// branch on classifyPriority.output.priority — exactly one handler executes; the other two are skipped
  branch on classifyPriority.output.priority {
    "vip"    -> assignVipAgent
    "normal" -> assignNormalAgent
    otherwise -> autoResolve
  }

  /// Assigns a VIP-tier agent to handle the ticket with elevated priority
  node assignVipAgent : AssignVipAgentOperator {
    depends_on = [classifyPriority]
    input {
      customerId = fetchCustomer.output.id
      priority   = "vip"
    }
  }

  /// Assigns a standard-tier agent to handle the ticket
  node assignNormalAgent : AssignNormalAgentOperator {
    depends_on = [classifyPriority]
    input {
      customerId = fetchCustomer.output.id
      priority   = "normal"
    }
  }

  /// Automatically resolves low-priority tickets using detected sentiment keywords
  node autoResolve : AutoResolveOperator {
    depends_on = [classifyPriority]
    input {
      customerId = fetchCustomer.output.id
      keywords   = analyzeSentiment.output.keywords
    }
  }
}