--- a/rust/src/types.rs	Wed Sep 04 23:24:13 2019 +0800
+++ b/rust/src/types.rs	Sun Sep 22 20:35:40 2019 +0800
@@ -8,12 +8,10 @@
 
 use std;
 
-use serde::{Deserialize,Serialize};
-use toml;
 use hyper;
 use serde_json;
 
-#[derive(Debug)]
+#[derive(Debug,Clone)]
 pub struct Readings {
     pub temps: HashMap<String, f32>,
 }
@@ -39,7 +37,6 @@
     None,
     Io(io::Error),
     ParseFloat(std::num::ParseFloatError),
-    TomlDe(toml::de::Error),
     SerdeJson(serde_json::Error),
     Hyper(hyper::Error),
 }
@@ -61,7 +58,6 @@
             TemplogErrorKind::None => None,
             TemplogErrorKind::Io(ref e) => Some(e),
             TemplogErrorKind::ParseFloat(ref e) => Some(e),
-            TemplogErrorKind::TomlDe(ref e) => Some(e),
             TemplogErrorKind::SerdeJson(ref e) => Some(e),
             TemplogErrorKind::Hyper(ref e) => Some(e),
         }
@@ -71,18 +67,17 @@
 
 impl fmt::Display for TemplogError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.kind_str());
+        write!(f, "{}", self.kind_str())?;
         if !self.msg.is_empty() {
-            write!(f, ": {}", self.msg);
+            write!(f, ": {}", self.msg)?;
         }
         match self.kind {
             TemplogErrorKind::None => Ok(()),
             TemplogErrorKind::Io(ref e) => write!(f, ": {}", e),
-            TemplogErrorKind::TomlDe(ref e) => write!(f, ": {}", e),
             TemplogErrorKind::SerdeJson(ref e) => write!(f, ": {}", e),
             TemplogErrorKind::ParseFloat(ref e) => write!(f, ": {}", e),
             TemplogErrorKind::Hyper(ref e) => write!(f, ": {}", e),
-        };
+        }?;
         Ok(())
     }
 }
@@ -96,10 +91,6 @@
         TemplogError::new_kind(msg, TemplogErrorKind::Io(e))
     }
 
-    pub fn new_toml_de(msg: &str, e: toml::de::Error) -> Self {
-        TemplogError::new_kind(msg, TemplogErrorKind::TomlDe(e))
-    }
-
     pub fn new_parse_float(msg: &str, e: std::num::ParseFloatError) -> Self {
         TemplogError::new_kind(msg, TemplogErrorKind::ParseFloat(e))
     }
@@ -134,7 +125,6 @@
         match self.kind {
             TemplogErrorKind::None => "Templog Error",
             TemplogErrorKind::Io(_) => "Templog IO error",
-            TemplogErrorKind::TomlDe(_) => "Templog toml error",
             TemplogErrorKind::SerdeJson(_) => "Templog Json decode error",
             TemplogErrorKind::ParseFloat(_) => "Templog parse error",
             TemplogErrorKind::Hyper(_) => "Templog http error",
@@ -148,12 +138,6 @@
     }
 }
 
-impl From<toml::de::Error> for TemplogError {
-    fn from(e: toml::de::Error) -> Self {
-        TemplogError::new_toml_de("", e)
-    }
-}
-
 impl From<std::num::ParseFloatError> for TemplogError {
     fn from(e: std::num::ParseFloatError) -> Self {
         TemplogError::new_parse_float("", e)
@@ -183,16 +167,19 @@
     pub fn new(limit_secs: u64) -> Self {
         NotTooOften {
             limit: Duration::new(limit_secs, 0),
+            // XXX why +1?
             last: Cell::new(Instant::now() - Duration::new(limit_secs+1, 0)),
         }
     }
 
-    pub fn and_then<F>(&self, op: F)
-        where F: Fn() {
+    pub fn and_then<F, U>(&self, op: F) -> Option<U>
+        where F: Fn() -> U {
         let now = Instant::now();
         if now - self.last.get() > self.limit {
             self.last.set(now);
-            op();
+            Some(op())
+        } else {
+            None
         }
     }
 }