Fix arithmetic side effects

.cargo/config.toml

@@ -17,7 +17,6 @@ rustflags = [
     "-Wtrivial_numeric_casts",
     "-Wunsafe_code",
     "-Wunused_import_braces",
-    "-Wunused_qualifications",
 
     # https://rust-lang.github.io/rust-clippy/master/index.html
     "-Aclippy::doc_markdown",

ocpi-tariffs/src/pricer.rs

@@ -128,7 +128,10 @@ impl Pricer {
 
         let total_time = if let Some(first) = periods.first() {
             let last = periods.last().unwrap();
-            (last.end_date_time - first.start_date_time).into()
+            (last
+                .end_date_time
+                .signed_duration_since(first.start_date_time))
+            .into()
         } else {
             HoursDecimal::zero()
         };

ocpi-tariffs/src/session.rs

@@ -118,11 +118,20 @@ impl InstantData {
     fn next(&self, state: &PeriodData, date_time: DateTime) -> Self {
         let mut next = self.clone();
 
-        next.total_duration = next.total_duration + (date_time - next.date_time);
+        let duration = date_time.signed_duration_since(next.date_time);
+
+        next.total_duration = next
+            .total_duration
+            .checked_add(&duration)
+            .unwrap_or_else(Duration::max_value);
+
         next.date_time = date_time;
 
         if let Some(duration) = state.charging_duration {
-            next.total_charging_duration = next.total_charging_duration + duration;
+            next.total_charging_duration = next
+                .total_charging_duration
+                .checked_add(&duration)
+                .unwrap_or_else(Duration::max_value);
         }
 
         if let Some(energy) = state.energy {

ocpi-tariffs/src/types/number.rs

@@ -90,7 +90,7 @@ impl Div for Number {
     type Output = Self;
 
     fn div(self, rhs: Self) -> Self::Output {
-        Self(self.0 / rhs.0)
+        Self(self.0.checked_div(rhs.0).expect("divide by zero"))
     }
 }
 

ocpi-tariffs/src/types/time.rs

@@ -65,13 +65,16 @@ impl From<Duration> for HoursDecimal {
 
 impl AddAssign for HoursDecimal {
     fn add_assign(&mut self, rhs: Self) {
-        self.0 = self.0 + rhs.0;
+        self.0 = self
+            .0
+            .checked_add(&rhs.0)
+            .unwrap_or_else(Duration::max_value);
     }
 }
 
 impl SubAssign for HoursDecimal {
     fn sub_assign(&mut self, rhs: Self) {
-        self.0 = self.0 - rhs.0;
+        self.0 = self.0.checked_sub(&rhs.0).unwrap_or_else(Duration::zero);
     }
 }