deterministic RNGs for tests

Cargo.lock

@@ -6442,6 +6442,7 @@ name = "tokens"
 version = "0.0.1"
 dependencies = [
  "my-workspace-hack",
+ "once_cell",
  "rand 0.8.5",
  "serde",
  "serde_derive",

crates/_types/tokens/Cargo.toml

@@ -25,7 +25,9 @@ serde = "1.0.125"
 serde_derive = "1.0.125"
 
 # Random
-rand = "0.8.5"
+rand = {  version = "0.8.5", features = ["std_rng"] }
+
+once_cell = { version = "1.18.0", features = [] }
 
 sqlx = { version = "0.7.2", features = [ "mysql", "runtime-tokio", "tls-rustls", "chrono" ] }
 sqlx-core = { version = "0.7.2" }

crates/_types/tokens/src/deterministic_rng.rs

@@ -0,0 +1,43 @@
+use std::sync::{Arc, LockResult, RwLock, RwLockWriteGuard};
+
+use once_cell::sync::Lazy;
+use rand::rngs::StdRng;
+use rand::SeedableRng;
+
+// FIXME(bt,2023-12-14): Is this threadsafe? Looks like it should be fine.
+/// Only use this in tests (and dev seed tools), never in production!
+#[derive(Clone)]
+pub struct DeterministicRng {
+  rng : Arc<RwLock<StdRng>>
+}
+
+impl DeterministicRng {
+  pub fn get_instance() -> LockResult<RwLockWriteGuard<'static, DeterministicRng>> {
+    static DETERMINISTIC_RNG : Lazy<Arc<RwLock<DeterministicRng>>> = Lazy::new(|| {
+      Arc::new(RwLock::new(DeterministicRng::new()))
+    });
+
+    DETERMINISTIC_RNG.write()
+  }
+
+  fn new() -> Self {
+    Self {
+      rng: Arc::new(RwLock::new(StdRng::seed_from_u64(0)))
+    }
+  }
+
+  /// Reset the deterministic RNG's seed.
+  pub fn reset_rng(&self) {
+    match self.rng.write() {
+      Err(err) => panic!(format!("test panic due to rng failure {err}")),
+      Ok(mut lock) => {
+        *lock = StdRng::seed_from_u64(0);
+      }
+    }
+  }
+
+  /// Grab the deterministic RNG
+  pub fn get_rng(&self) -> LockResult<RwLockWriteGuard<StdRng>>{
+    self.rng.write()
+  }
+}

crates/_types/tokens/src/lib.rs

@@ -49,6 +49,7 @@ pub(crate) static MINIMUM_CHARACTER_ENTROPY : usize = 8;
 #[macro_use]
 mod macros;
 
+pub (crate) mod deterministic_rng;
 pub (crate) mod prefixes;
 
 pub mod tokens;

crates/_types/tokens/src/macros.rs

@@ -60,6 +60,41 @@ macro_rules! impl_crockford_generator {
         $t(token)
       }
 
+      /// Constructor for a new token to be used **DETERMINISTICALLY** in tests and seeding.
+      /// This will not use a real RNG, so do not use in production code!
+      /// Once called, it will output the same random numbers in sequence.
+      pub fn reset_rng_for_testing_and_dev_seeding_never_use_in_production_seriously() {
+        let deterministic = crate::deterministic_rng::DeterministicRng::get_instance().expect("tests should not fail due to mutex");
+        deterministic.reset_rng();
+      }
+
+      /// Constructor for a new token to be used **DETERMINISTICALLY** in tests and seeding.
+      /// This will not use a real RNG, so do not use in production code!
+      /// Once called, it will output the same random numbers in sequence.
+      pub fn generate_for_testing_and_dev_seeding_never_use_in_production_seriously() -> Self {
+        use rand::Rng;
+
+        // FIXME(bt,2023-12-14): This is bad error handling. (Maybe panic if lock is poisoned?)
+        let deterministic = crate::deterministic_rng::DeterministicRng::get_instance().expect("tests should not fail due to mutex");
+        let mut rng = deterministic.get_rng().expect("tests should not fail due to mutex");
+
+        let charset = Self::token_character_set();
+        let entropy_length = Self::entropic_character_len();
+
+        let entropy_part: String = (0..entropy_length)
+          .map(|_| {
+            let idx = rng.gen_range(0..charset.len());
+            charset[idx] as char
+          })
+          .collect();
+
+        let token_prefix = Self::token_prefix();
+
+        let token = format!("{}{}", token_prefix, entropy_part);
+
+        $t(token)
+      }
+
       #[inline]
       pub fn entropy_suffix(&self) -> &str {
         use crate::prefixes::PrefixGenerator;

crates/_types/tokens/tests/media_file_token_tests.rs

@@ -21,6 +21,30 @@ mod interface {
     assert!(token.to_string().starts_with("m_"));
   }
 
+  #[test]
+  fn generate_for_testing_and_dev_seeding_never_use_in_production_seriously_1() {
+    MediaFileToken::reset_rng_for_testing_and_dev_seeding_never_use_in_production_seriously();
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_q8sz47gmfw2zx02snrbz88ns9m16ab");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_ma1xetxrwbh39vg639a9zrq8b9wk6h");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_4tswec8z27wnm01njypx4vmfhgj41e");
+  }
+
+  #[test]
+  fn generate_for_testing_and_dev_seeding_never_use_in_production_seriously_2() {
+    MediaFileToken::reset_rng_for_testing_and_dev_seeding_never_use_in_production_seriously();
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_q8sz47gmfw2zx02snrbz88ns9m16ab");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_ma1xetxrwbh39vg639a9zrq8b9wk6h");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_4tswec8z27wnm01njypx4vmfhgj41e");
+  }
+
+  #[test]
+  fn generate_for_testing_and_dev_seeding_never_use_in_production_seriously_3() {
+    MediaFileToken::reset_rng_for_testing_and_dev_seeding_never_use_in_production_seriously();
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_q8sz47gmfw2zx02snrbz88ns9m16ab");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_ma1xetxrwbh39vg639a9zrq8b9wk6h");
+    assert_eq!(MediaFileToken::generate_for_testing_and_dev_seeding_never_use_in_production_seriously().as_str(), "m_4tswec8z27wnm01njypx4vmfhgj41e");
+  }
+
   #[test]
   fn new() {
     let token = MediaFileToken::new("m_foo".to_string());

crates/service/web/storyteller_web/src/http_server/endpoints/weights/list_featured_weights.rs

@@ -122,7 +122,6 @@ pub async fn list_featured_weights_handler(
     };
   }
 
-  // generate parse a response
   let response = ListFeaturedWeightsSuccessResponse {
     success: true,
     weights: weights.into_iter()