nats adapter

crates/adapters/nats/src/config.rs

@@ -0,0 +1,101 @@
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum NatsMode {
+    Core,
+    JetStream,
+}
+
+#[derive(Debug, Clone)]
+pub struct NatsConfig {
+    pub url: String,
+    pub mode: NatsMode,
+    pub subject_prefix: String,
+    pub stream_name: String,
+    pub consumer_name: String,
+}
+
+impl NatsConfig {
+    pub fn from_env() -> anyhow::Result<Self> {
+        let url = std::env::var("NATS_URL")
+            .map_err(|_| anyhow::anyhow!("NATS_URL is not set"))?;
+
+        let mode = match std::env::var("NATS_MODE")
+            .unwrap_or_else(|_| "jetstream".to_string())
+            .as_str()
+        {
+            "core"      => NatsMode::Core,
+            "jetstream" => NatsMode::JetStream,
+            other       => anyhow::bail!("unknown NATS_MODE: {other}"),
+        };
+
+        let subject_prefix = std::env::var("NATS_SUBJECT_PREFIX")
+            .unwrap_or_else(|_| "movies-diary.events".to_string());
+        let stream_name = std::env::var("NATS_STREAM_NAME")
+            .unwrap_or_else(|_| "MOVIES_DIARY_EVENTS".to_string());
+        let consumer_name = std::env::var("NATS_CONSUMER_NAME")
+            .unwrap_or_else(|_| "worker".to_string());
+
+        Ok(Self { url, mode, subject_prefix, stream_name, consumer_name })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn errors_without_nats_url() {
+        unsafe { std::env::remove_var("NATS_URL"); }
+        assert!(NatsConfig::from_env().is_err());
+    }
+
+    #[test]
+    fn defaults_with_only_url() {
+        unsafe {
+            std::env::set_var("NATS_URL", "nats://localhost:4222");
+            std::env::remove_var("NATS_MODE");
+            std::env::remove_var("NATS_SUBJECT_PREFIX");
+            std::env::remove_var("NATS_STREAM_NAME");
+            std::env::remove_var("NATS_CONSUMER_NAME");
+        }
+
+        let cfg = NatsConfig::from_env().unwrap();
+        assert_eq!(cfg.url, "nats://localhost:4222");
+        assert_eq!(cfg.mode, NatsMode::JetStream);
+        assert_eq!(cfg.subject_prefix, "movies-diary.events");
+        assert_eq!(cfg.stream_name, "MOVIES_DIARY_EVENTS");
+        assert_eq!(cfg.consumer_name, "worker");
+
+        unsafe { std::env::remove_var("NATS_URL"); }
+    }
+
+    #[test]
+    fn core_mode_parsed() {
+        unsafe {
+            std::env::set_var("NATS_URL", "nats://test:4222");
+            std::env::set_var("NATS_MODE", "core");
+        }
+
+        let cfg = NatsConfig::from_env().unwrap();
+        assert_eq!(cfg.mode, NatsMode::Core);
+
+        unsafe {
+            std::env::remove_var("NATS_URL");
+            std::env::remove_var("NATS_MODE");
+        }
+    }
+
+    #[test]
+    fn invalid_mode_errors() {
+        unsafe {
+            std::env::set_var("NATS_URL", "nats://test:4222");
+            std::env::set_var("NATS_MODE", "kafka");
+        }
+
+        assert!(NatsConfig::from_env().is_err());
+
+        unsafe {
+            std::env::remove_var("NATS_URL");
+            std::env::remove_var("NATS_MODE");
+        }
+    }
+}