Improved Typesafety and Error Handling

Author: Empty2k12

Cargo.lock

@@ -11,3 +11,4 @@ reqwest = "0.9.17"
 futures = "0.1.27"
 tokio = "0.1.20"
 itertools = "0.8"
+failure = "0.1.5"

Cargo.toml

@@ -1,17 +1,47 @@
 #![allow(dead_code)]
 
+#[macro_use]
+extern crate failure;
+
 use futures::Future;
 use itertools::Itertools;
 use reqwest::r#async::Client;
 
+#[derive(Debug, Fail)]
+enum InfluxDbError {
+    #[fail(display = "query must contain at least one field")]
+    InvalidQueryError,
+}
+
+#[derive(Debug)]
+struct ValidQuery(String);
+impl From<String> for ValidQuery {
+    fn from(s: String) -> ValidQuery {
+        ValidQuery(s)
+    }
+}
+impl PartialEq<String> for ValidQuery {
+    fn eq(&self, other: &String) -> bool {
+        &self.0 == other
+    }
+}
+impl PartialEq<&str> for ValidQuery {
+    fn eq(&self, other: &&str) -> bool {
+        &self.0 == other
+    }
+}
+
 trait InfluxDbQuery {
-    fn build<'a>(self) -> String;
+    fn build<'a>(self) -> Result<ValidQuery, InfluxDbError>;
 }
 
 impl InfluxDbQuery {
-    pub fn write() -> InfluxDbWrite {
+    pub fn write<S>(measurement: S) -> InfluxDbWrite
+    where
+        S: Into<String>,
+    {
         InfluxDbWrite {
-            measurement: String::from("marina_3"),
+            measurement: measurement.into(),
             fields: Vec::new(),
             tags: Vec::new(),
         }
@@ -45,32 +75,40 @@ impl InfluxDbWrite {
     }
 }
 
+// todo: fuse_with(other: ValidQuery), so multiple queries can be run at the same time
 impl InfluxDbQuery for InfluxDbWrite {
     // fixme: time (with precision) and measurement
-    fn build<'a>(self) -> String {
+    fn build<'a>(self) -> Result<ValidQuery, InfluxDbError> {
+        if self.fields.is_empty() {
+            return Err(InfluxDbError::InvalidQueryError);
+        }
+
         let tags = self
             .tags
             .into_iter()
             .map(|(tag, value)| format!("{tag}={value}", tag = tag, value = value))
-            .join(",");
+            .join(",")
+            + " ";
         let fields = self
             .fields
             .into_iter()
             .map(|(field, value)| format!("{field}={value}", field = field, value = value))
-            .join(",");
+            .join(",")
+            + " ";
 
-        format!(
-            "measurement,{tags} {fields} time",
+        Ok(ValidQuery::from(format!(
+            "{measurement},{tags}{fields}time",
+            measurement = self.measurement,
             tags = tags,
             fields = fields
-        )
+        )))
     }
 }
 
 pub struct InfluxDbClient {
     url: String,
     database: String,
-    // _auth: InfluxDbAuthentication | NoAuthentication
+    // auth: Option<InfluxDbAuthentication>
 }
 
 pub fn main() {}
@@ -129,67 +167,62 @@ mod tests {
         println!("build: {} version: {}", build, version);
     }
 
+    #[test]
+    fn test_write_builder_empty_query() {
+        let query = InfluxDbQuery::write("marina_3").build();
+
+        assert!(query.is_err(), "Query was not empty");
+    }
+
     #[test]
     fn test_write_builder_single_field() {
-        let query = InfluxDbQuery::write().add_field("water_level", "2");
+        let query = InfluxDbQuery::write("marina_3")
+            .add_field("water_level", "2")
+            .build();
 
-        assert_eq!(query.build(), "measurement, water_level=2 time");
+        assert!(query.is_ok(), "Query was empty");
+        assert_eq!(query.unwrap(), "marina_3, water_level=2 time");
     }
 
     #[test]
     fn test_write_builder_multiple_fields() {
-        let query = InfluxDbQuery::write()
+        let query = InfluxDbQuery::write("marina_3")
             .add_field("water_level", "2")
             .add_field("boat_count", "31")
-            .add_field("algae_content", "0.85");
+            .add_field("algae_content", "0.85")
+            .build();
 
+        assert!(query.is_ok(), "Query was empty");
         assert_eq!(
-            query.build(),
-            "measurement, water_level=2,boat_count=31,algae_content=0.85 time"
+            query.unwrap(),
+            "marina_3, water_level=2,boat_count=31,algae_content=0.85 time"
         );
     }
 
-    // fixme: double space
     // fixme: quoting / escaping of long strings
     #[test]
-    fn test_write_builder_single_tag() {
-        let query = InfluxDbQuery::write().add_tag("marina_manager", "Smith");
-
-        assert_eq!(query.build(), "measurement,marina_manager=Smith  time");
-    }
-
-    #[test]
-    fn test_write_builder_multiple_tags() {
-        let query = InfluxDbQuery::write()
+    fn test_write_builder_only_tags() {
+        let query = InfluxDbQuery::write("marina_3")
             .add_tag("marina_manager", "Smith")
-            .add_tag("manager_to_the_marina_manager", "Jonson");
+            .build();
 
-        assert_eq!(
-            query.build(),
-            "measurement,marina_manager=Smith,manager_to_the_marina_manager=Jonson  time"
-        );
+        assert!(query.is_err(), "Query missing one or more fields");
     }
 
     #[test]
     fn test_write_builder_full_query() {
-        let query = InfluxDbQuery::write()
+        let query = InfluxDbQuery::write("marina_3")
             .add_field("water_level", "2")
             .add_field("boat_count", "31")
             .add_field("algae_content", "0.85")
             .add_tag("marina_manager", "Smith")
-            .add_tag("manager_to_the_marina_manager", "Jonson");
+            .add_tag("manager_to_the_marina_manager", "Jonson")
+            .build();
 
+        assert!(query.is_ok(), "Query was empty");
         assert_eq!(
-            query.build(),
-            "measurement,marina_manager=Smith,manager_to_the_marina_manager=Jonson water_level=2,boat_count=31,algae_content=0.85 time"
+            query.unwrap(),
+            "marina_3,marina_manager=Smith,manager_to_the_marina_manager=Jonson water_level=2,boat_count=31,algae_content=0.85 time"
         );
     }
-
-    #[test]
-    fn test_test() {
-        InfluxDbQuery::write()
-            .add_field("test", "1")
-            .add_tag("my_tag", "0.85")
-            .build();
-    }
 }