Simulation: Give user chance to use bridges each day

src/simulation/user.rs

@@ -26,6 +26,9 @@ pub struct User {
 
     // Does the user submit reports to Troll Patrol?
     submits_reports: bool,
+
+    // How likely is this user to use bridges on a given day?
+    prob_use_bridges: f64,
 }
 
 impl User {
@@ -63,12 +66,17 @@ impl User {
             cc
         };
 
+        // Randomly determine how likely this user is to use bridges on
+        // a given day
+        let prob_use_bridges = rng.gen_range(0.0..=1.0);
+
         Self {
             censor: censor,
             country: cc,
             primary_cred: cred,
             secondary_cred: None,
             submits_reports: submits_reports,
+            prob_use_bridges: prob_use_bridges,
         }
     }
 
@@ -127,12 +135,17 @@ impl User {
             cc
         };
 
+        // Randomly determine how likely this user is to use bridges on
+        // a given day
+        let prob_use_bridges = rng.gen_range(0.0..=1.0);
+
         Ok(Self {
             censor: censor,
             country: cc,
             primary_cred: friend_cred,
             secondary_cred: None,
             submits_reports: submits_reports,
+            prob_use_bridges: prob_use_bridges,
         })
     }
 
@@ -179,6 +192,10 @@ impl User {
     // newly invited friends and a vector of fingerprints of successfully
     // contacted bridges.
     pub async fn daily_tasks(&mut self, state: &State) -> (Vec<User>, Vec<[u8; 20]>) {
+        // Probabilistically decide if the user should use bridges today
+        let mut rng = rand::thread_rng();
+        let num: f64 = rng.gen_range(0.0..1.0);
+        if num < self.prob_use_bridges {
             // Download bucket to see if bridge is still reachable
             // (We assume that this step can be done even if the user can't actually
             // talk to the LA.)
@@ -187,7 +204,8 @@ impl User {
 
             // Can we level up the main credential?
             let can_level_up = reachcred.is_some()
-            && (level == 0 && eligible_for_trust_promotion(&state.net, &self.primary_cred).await
+                && (level == 0
+                    && eligible_for_trust_promotion(&state.net, &self.primary_cred).await
                     || level > 0 && eligible_for_level_up(&state.net, &self.primary_cred).await);
 
             // Can we migrate the main credential?
@@ -288,7 +306,8 @@ impl User {
                 let cred = trust_migration(
                     &state.net,
                     &second_cred,
-                &trust_promotion(&state.net, &second_cred, get_lox_pub(&state.la_pubkeys)).await,
+                    &trust_promotion(&state.net, &second_cred, get_lox_pub(&state.la_pubkeys))
+                        .await,
                     get_lox_pub(&state.la_pubkeys),
                     get_migration_pub(&state.la_pubkeys),
                 )
@@ -354,5 +373,8 @@ impl User {
             }
 
             (new_friends, connections)
+        } else {
+            (Vec::<User>::new(), Vec::<[u8; 20]>::new())
+        }
     }
 }