Shorten librato implementation

This commit removes some explicit derivation code in favor of the
automatic version. That we have dropped optional sources removes
the need for the more explicit approach.

Signed-off-by: Brian L. Troutwine <blt@postmates.com>

src/backends/librato.rs

@@ -1,9 +1,8 @@
 use super::super::backend::Backend;
 use super::super::buckets::Buckets;
 use std::str::FromStr;
-use std::collections::BTreeMap;
 use time;
-use rustc_serialize::json::{Json, ToJson};
+use rustc_serialize::json;
 use hyper::client::Client;
 use hyper::header::{ContentType, Authorization, Basic, Connection};
 use url;
@@ -17,55 +16,26 @@ pub struct Librato {
     host: String,
 }
 
-#[derive(Debug)]
+#[derive(Debug, RustcEncodable)]
 pub struct LCounter {
     name: String,
     value: f64,
 }
 
-impl ToJson for LCounter {
-    fn to_json(&self) -> Json {
-        let mut d = BTreeMap::new();
-        d.insert("name".to_string(), self.name.to_json());
-        d.insert("value".to_string(), self.value.to_json());
-        Json::Object(d)
-    }
-}
-
-#[derive(Debug)]
+#[derive(Debug, RustcEncodable)]
 pub struct LGauge {
     name: String,
     value: f64,
 }
 
-impl ToJson for LGauge {
-    fn to_json(&self) -> Json {
-        let mut d = BTreeMap::new();
-        d.insert("name".to_string(), self.name.to_json());
-        d.insert("value".to_string(), self.value.to_json());
-        Json::Object(d)
-    }
-}
-
-#[derive(Debug)]
+#[derive(Debug, RustcEncodable)]
 pub struct LPayload {
     gauges: Vec<LGauge>,
     counters: Vec<LCounter>,
     source: String,
     measure_time: i64,
 }
 
-impl ToJson for LPayload {
-    fn to_json(&self) -> Json {
-        let mut d = BTreeMap::new();
-        d.insert("gauges".to_string(), self.gauges.to_json());
-        d.insert("counters".to_string(), self.counters.to_json());
-        d.insert("source".to_string(), self.source.to_json());
-        d.insert("measure_time".to_string(), self.measure_time.to_json());
-        Json::Object(d)
-    }
-}
-
 impl Librato {
     /// Create a Librato formatter
     ///
@@ -127,7 +97,7 @@ impl Librato {
                 let stat: &str = tup.0;
                 let quant: f64 = tup.1;
                 gauges.push(LGauge {
-                    name: format!("{}.{}", *key, stat),
+                    name: format!("{}.{}", key, stat),
                     value: value.query(quant).unwrap().1,
                 });
             }
@@ -144,7 +114,7 @@ impl Librato {
                 let stat: &str = tup.0;
                 let quant: f64 = tup.1;
                 gauges.push(LGauge {
-                    name: format!("{}.{}", *key, stat),
+                    name: format!("{}.{}", key, stat),
                     value: value.query(quant).unwrap().1,
                 });
             }
@@ -156,7 +126,7 @@ impl Librato {
             source: self.source.clone(),
             measure_time: start,
         };
-        obj.to_json().to_string()
+        json::encode(&obj).unwrap()
     }
 }
 
@@ -211,14 +181,14 @@ mod test {
         let result = librato.format_stats(&buckets, Some(10101));
 
         println!("{:?}", result);
-        assert_eq!("{\"counters\":[{\"name\":\"cernan.bad_messages\",\"value\":0.0},{\"name\":\
-                    \"cernan.total_messages\",\"value\":6.0},{\"name\":\"test.counter\",\
-                    \"value\":1.0}],\"gauges\":[{\"name\":\"test.gauge\",\"value\":3.211},\
-                    {\"name\":\"src-test.gauge.2\",\"value\":3.211},{\"name\":\"test.timer.min\",\
-                    \"value\":1.101},{\"name\":\"test.timer.max\",\"value\":12.101},{\"name\":\
-                    \"test.timer.50\",\"value\":3.101},{\"name\":\"test.timer.90\",\"value\":12.\
-                    101},{\"name\":\"test.timer.99\",\"value\":12.101},{\"name\":\"test.timer.\
-                    999\",\"value\":12.101}],\"measure_time\":10101,\"source\":\"test-src\"}",
+        assert_eq!("{\"gauges\":[{\"name\":\"test.gauge\",\"value\":3.211},{\"name\":\"src-test.\
+                    gauge.2\",\"value\":3.211},{\"name\":\"test.timer.min\",\"value\":1.101},\
+                    {\"name\":\"test.timer.max\",\"value\":12.101},{\"name\":\"test.timer.50\",\
+                    \"value\":3.101},{\"name\":\"test.timer.90\",\"value\":12.101},{\"name\":\
+                    \"test.timer.99\",\"value\":12.101},{\"name\":\"test.timer.999\",\"value\":\
+                    12.101}],\"counters\":[{\"name\":\"cernan.bad_messages\",\"value\":0.0},\
+                    {\"name\":\"cernan.total_messages\",\"value\":6.0},{\"name\":\"test.\
+                    counter\",\"value\":1.0}],\"source\":\"test-src\",\"measure_time\":10101}",
                    result);
     }
 }