sim-lib: Allows amount and interval ranges in manual activity definition

Amounts and intervals in activities can now be fixed values (e.g. 1000) or ranges (e.g.
[500, 1000]). If a range is provided, the value will be sampled uniformly at
random from it.

sim-lib/src/defined_activity.rs

@@ -1,4 +1,6 @@
-use crate::{DestinationGenerator, NodeInfo, PaymentGenerationError, PaymentGenerator};
+use crate::{
+    DestinationGenerator, NodeInfo, PaymentGenerationError, PaymentGenerator, ValueOrRange,
+};
 use std::fmt;
 use tokio::time::Duration;
 
@@ -7,17 +9,17 @@ pub struct DefinedPaymentActivity {
     destination: NodeInfo,
     start: Duration,
     count: Option<u64>,
-    wait: Duration,
-    amount: u64,
+    wait: ValueOrRange<u16>,
+    amount: ValueOrRange<u64>,
 }
 
 impl DefinedPaymentActivity {
     pub fn new(
         destination: NodeInfo,
         start: Duration,
         count: Option<u64>,
-        wait: Duration,
-        amount: u64,
+        wait: ValueOrRange<u16>,
+        amount: ValueOrRange<u64>,
     ) -> Self {
         DefinedPaymentActivity {
             destination,
@@ -33,7 +35,7 @@ impl fmt::Display for DefinedPaymentActivity {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
             f,
-            "static payment of {} to {} every {:?}",
+            "static payment of {} to {} every {}s",
             self.amount, self.destination, self.wait
         )
     }
@@ -55,7 +57,7 @@ impl PaymentGenerator for DefinedPaymentActivity {
     }
 
     fn next_payment_wait(&self) -> Duration {
-        self.wait
+        Duration::from_secs(self.wait.value() as u64)
     }
 
     fn payment_amount(
@@ -67,17 +69,17 @@ impl PaymentGenerator for DefinedPaymentActivity {
                 "destination amount must not be set for defined activity generator".to_string(),
             ))
         } else {
-            Ok(self.amount)
+            Ok(self.amount.value())
         }
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::DefinedPaymentActivity;
+    use super::*;
     use crate::test_utils::{create_nodes, get_random_keypair};
     use crate::{DestinationGenerator, PaymentGenerationError, PaymentGenerator};
-    use std::time::Duration;
 
     #[test]
     fn test_defined_activity_generator() {
@@ -91,8 +93,8 @@ mod tests {
             node.clone(),
             Duration::from_secs(0),
             None,
-            Duration::from_secs(60),
-            payment_amt,
+            crate::ValueOrRange::Value(60),
+            crate::ValueOrRange::Value(payment_amt),
         );
 
         let (dest, dest_capacity) = generator.choose_destination(source.1);

sim-lib/src/lib.rs

@@ -4,6 +4,7 @@ use bitcoin::Network;
 use csv::WriterBuilder;
 use lightning::ln::features::NodeFeatures;
 use lightning::ln::PaymentHash;
+use rand::Rng;
 use random_activity::RandomActivityError;
 use serde::{Deserialize, Serialize};
 use std::collections::HashSet;
@@ -129,6 +130,47 @@ pub struct SimParams {
     pub activity: Vec<ActivityParser>,
 }
 
+/// Either a value or a range parsed from the simulation file.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum ValueOrRange<T> {
+    Value(T),
+    Range(T, T),
+}
+
+impl<T> ValueOrRange<T>
+where
+    T: std::cmp::PartialOrd + rand_distr::uniform::SampleUniform + Copy,
+{
+    /// Get the enclosed value. If value is defined as a range, sample from it uniformly at random.
+    pub fn value(&self) -> T {
+        match self {
+            ValueOrRange::Value(x) => *x,
+            ValueOrRange::Range(x, y) => {
+                let mut rng = rand::thread_rng();
+                rng.gen_range(*x..*y)
+            },
+        }
+    }
+}
+
+impl<T> Display for ValueOrRange<T>
+where
+    T: Display,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ValueOrRange::Value(x) => write!(f, "{x}"),
+            ValueOrRange::Range(x, y) => write!(f, "({x}-{y})"),
+        }
+    }
+}
+
+/// The payment amount in msat. Either a value or a range.
+type Amount = ValueOrRange<u64>;
+/// The interval of seconds between payments. Either a value or a range.
+type Interval = ValueOrRange<u16>;
+
 /// Data structure used to parse information from the simulation file. It allows source and destination to be
 /// [NodeId], which enables the use of public keys and aliases in the simulation description.
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -146,9 +188,11 @@ pub struct ActivityParser {
     #[serde(default)]
     pub count: Option<u64>,
     /// The interval of the event, as in every how many seconds the payment is performed.
-    pub interval_secs: u16,
+    #[serde(with = "serializers::serde_value_or_range")]
+    pub interval_secs: Interval,
     /// The amount of m_sat to used in this payment.
-    pub amount_msat: u64,
+    #[serde(with = "serializers::serde_value_or_range")]
+    pub amount_msat: Amount,
 }
 
 /// Data structure used internally by the simulator. Both source and destination are represented as [PublicKey] here.
@@ -164,9 +208,9 @@ pub struct ActivityDefinition {
     /// The number of payments to send over the course of the simulation.
     pub count: Option<u64>,
     /// The interval of the event, as in every how many seconds the payment is performed.
-    pub interval_secs: u16,
+    pub interval_secs: Interval,
     /// The amount of m_sat to used in this payment.
-    pub amount_msat: u64,
+    pub amount_msat: Amount,
 }
 
 #[derive(Debug, Error)]
@@ -701,7 +745,7 @@ impl Simulation {
                     description.destination.clone(),
                     Duration::from_secs(description.start_secs.into()),
                     description.count,
-                    Duration::from_secs(description.interval_secs.into()),
+                    description.interval_secs,
                     description.amount_msat,
                 );
 

sim-lib/src/serializers.rs

@@ -45,6 +45,42 @@ pub mod serde_node_id {
     }
 }
 
+pub mod serde_value_or_range {
+    use super::*;
+    use serde::de::Error;
+
+    use crate::ValueOrRange;
+
+    pub fn serialize<S, T>(x: &ValueOrRange<T>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+        T: std::fmt::Display,
+    {
+        serializer.serialize_str(&match x {
+            ValueOrRange::Value(p) => p.to_string(),
+            ValueOrRange::Range(x, y) => format!("[{}, {}]", x, y),
+        })
+    }
+
+    pub fn deserialize<'de, D, T>(deserializer: D) -> Result<ValueOrRange<T>, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+        T: serde::Deserialize<'de> + std::cmp::PartialOrd + std::fmt::Display + Copy,
+    {
+        let a = ValueOrRange::deserialize(deserializer)?;
+        if let ValueOrRange::Range(x, y) = a {
+            if x >= y {
+                return Err(D::Error::custom(format!(
+                    "Cannot parse range. Ranges must be strictly increasing (i.e. [x, y] with x > y). Received [{}, {}]",
+                    x, y
+                )));
+            }
+        }
+
+        Ok(a)
+    }
+}
+
 pub fn deserialize_path<'de, D>(deserializer: D) -> Result<String, D::Error>
 where
     D: serde::Deserializer<'de>,