finalized score (for now lol)

koucha/src/score.rs

@@ -1,10 +1,15 @@
 use chrono::{DateTime, Utc, TimeDelta};
+use crate::{Result};
 
 mod default {
+  use crate::score::SECONDS_IN_A_DAY;
+
   pub const INITIAL_SCORE: i64 = 70;
   pub const GRAVITY: i64 = -10;
   pub const BOOST: i64 = 12;
+  pub const BOOST_FREEZE_IN_SECONDS: i64 = SECONDS_IN_A_DAY;
 }
+const SECONDS_IN_A_DAY: i64 = 60 * 60 * 24;
 
 macro_rules! rich_i64 {
     ($name:ident, $default:expr) => {
@@ -21,69 +26,144 @@ macro_rules! rich_i64 {
 
 rich_i64!(Gravity, default::GRAVITY);
 rich_i64!(Boost, default::BOOST);
-impl Boost {
-  fn should_apply(
-    old_boost_time: Option<DateTime<Utc>>, new_boost_time: DateTime<Utc>
-  ) -> bool {
-    old_boost_time.map_or(true, |obs| {
-      let time_delta = obs - &new_boost_time;
-      time_delta.num_days() >= 1
-    })
+pub struct UnparsedScore {
+  pub value: i64,
+  pub last_updated: DateTime<Utc>,
+  pub last_boosted: Option<DateTime<Utc>>,
+}
+
+impl UnparsedScore {
+  pub fn parse(self) -> Score {
+    match self.last_boosted {
+      None => Score::Decaying(DecayingScore {
+        value: self.value,
+        last_updated: self.last_updated,
+      }),
+      Some(last_boosted) => Score::Boosted(BoostedScore {
+        value: self.value,
+        boosted_at: last_boosted,
+      }),
     }
   }
-pub struct Score {
-  value: i64,
-  last_updated: DateTime<Utc>,
-  last_boosted: Option<DateTime<Utc>>,
+}
+
+pub enum Score {
+  Decaying(DecayingScore),
+  Boosted(BoostedScore),
 }
 
 impl Score {
-  pub fn new() -> Self {
-    Self::new_at_time(Utc::now())
-  }
-
-  pub fn new_at_time(creation_time: DateTime<Utc>) -> Self {
-    Score {
+  pub fn new() -> DecayingScore {
+    DecayingScore {
       value: default::INITIAL_SCORE,
-      last_updated: creation_time,
-      last_boosted: Some(creation_time),
+      last_updated: Utc::now(),
     }
   }
 
-  pub fn update(self) -> Self {
-    self.update_at_time(Utc::now())
+  pub fn get_score(&self) -> i64 {
+    match self {
+      Self::Decaying(s) => s.get_score(),
+      Self::Boosted(b) => b.get_score(),
+    }
   }
 
-  pub fn update_at_time(self, update_time: DateTime<Utc>) -> Self {
-    let to_elapse_from = self.last_boosted.map_or(self.last_updated, |lb| {
-      std::cmp::max(self.last_updated, lb + TimeDelta::days(1))
-    });
-    let elapsed_time = update_time.signed_duration_since(to_elapse_from);
-
-    self
+  pub fn update_score(self, gravity: Gravity) -> Self {
+    match self {
+      Self::Decaying(d) => Score::Decaying(d.update_score(gravity)),
+      Self::Boosted(b) => {
+        let try_unfrozen = b.try_unfreeze();
+        match try_unfrozen {
+          Self::Decaying(s) => Score::Decaying(s.update_score(gravity)),
+          Self::Boosted(b) => Score::Boosted(b),
+        }
+      }
+    }
   }
 
-  pub fn boost(self, boost: Boost) -> Self {
+  pub fn get_decaying(self) -> Result<DecayingScore> {
+    match self {
+      Self::Decaying(s) => Ok(s),
+      Self::Boosted(_) => Err("Attempted to get_decaying() of a boosted score".into()),
+    }
+  }
+
+  pub fn get_boosted(self) -> Result<BoostedScore> {
+    match self {
+      Self::Decaying(_) => Err("Attempted to get_boosted() of a decaying score".into()),
+      Self::Boosted(b) => Ok(b),
+    }
+  }
+}
+
+pub struct BoostedScore {
+  value: i64,
+  boosted_at: DateTime<Utc>,
+}
+
+pub struct DecayingScore {
+  value: i64,
+  last_updated: DateTime<Utc>,
+}
+
+impl DecayingScore {
+  fn get_score(&self) -> i64 {
+    self.value
+  }
+
+  fn update_score(self, gravity: Gravity) -> Self {
+    self.update_score_at_time(gravity, Utc::now())
+  }
+
+  fn update_score_at_time(
+    self, gravity: Gravity, update_time: DateTime<Utc>
+  ) -> Self {
+    let elapsed_time: TimeDelta = update_time.signed_duration_since(self.last_updated);
+    let new_value = if elapsed_time <= TimeDelta::zero() { self.value } else {
+      i64::from(gravity) * (elapsed_time.num_seconds() / SECONDS_IN_A_DAY)
+    };
+    Self {
+      last_updated: update_time,
+      value: new_value,
+    }
+  }
+
+  pub fn boost(self, boost: Boost) -> BoostedScore {
     self.boost_at_time(boost, Utc::now())
   }
 
-  // This function does not "fast-forward" the score's value to the time of
-  // boost, but still updates `last_updated`. Meaning that hours of gravity may
-  // not be applied.
-  // The expectation is that a boost is a user interaction, and that the user
-  // should be seeing a "fresh" score. We wouldn't want a boost to end up
-  // applying lots of gravity. But care should be taken to ensure that only
-  // "fresh" scores are boosted. Or that boost_time reflects the state of the
-  // user experience.
-  pub fn boost_at_time(self, boost: Boost, boost_time: DateTime<Utc>) -> Self {
-    if Boost::should_apply(self.last_boosted, boost_time) {
-      Self {
+  fn boost_at_time(self, boost: Boost, boost_time: DateTime<Utc>) -> BoostedScore {
+    BoostedScore {
       value: self.value + i64::from(boost),
-        last_updated: boost_time,
-        last_boosted: Some(boost_time),
+      boosted_at: boost_time,
     }
+  }
+}
+
+impl BoostedScore {
+  fn get_score(&self) -> i64 {
+    self.value
+  }
+
+  pub fn unboost(self, boost: Boost) -> DecayingScore {
+    DecayingScore {
+      value: self.value - i64::from(boost),
+      last_updated: self.boosted_at,
+    }
+  }
+
+  fn try_unfreeze(self) -> Score {
+    self.try_unfreeze_at_time(Utc::now())
+  }
+
+  fn try_unfreeze_at_time(self, update_time: DateTime<Utc>) -> Score {
+    let boost_end = self.boosted_at + TimeDelta::seconds(default::BOOST_FREEZE_IN_SECONDS);
+    if boost_end > update_time {
+      Score::Decaying(DecayingScore {
+        value: self.value,
+        last_updated: boost_end,
+      })
     } else {
-      self
+      Score::Boosted(self)
     }
   }
 }