add basic boon queue support

This is already pretty good to calculate the overall boon uptime/average
stacks.

2 files changed, 177 insertions, 0 deletions

diff --git a/src/statistics/boon.rs b/src/statistics/boon.rs
new file mode 100644
index 0000000..65e5c89
--- /dev/null
+++ b/src/statistics/boon.rs
@@ -0,0 +1,175 @@
+use std::cmp;
+
+/// The type of a boon.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum BoonType {
+    /// Boon stacks duration, e.g. Regeneration.
+    Duration,
+    /// Boon stacks intensity, e.g. Might.
+    Intensity,
+}
+
+/// A struct that helps with simulating boon changes over time.
+///
+/// This basically simulates a single boon-queue (for a single boon).
+///
+/// # A quick word about how boon queues work
+///
+/// For each boon, you have an internal *boon queue*, limited to a specific
+/// capacity.
+#[derive(Clone, Debug)]
+pub struct BoonQueue {
+    capacity: u32,
+    queue: Vec<u64>,
+    boon_type: BoonType,
+}
+
+impl BoonQueue {
+    /// Create a new boon queue.
+    ///
+    /// * `capacity` - The capacity of the queue.
+    /// * `boon_type` - How the boons stack.
+    pub fn new(capacity: u32, boon_type: BoonType) -> BoonQueue {
+        BoonQueue {
+            capacity,
+            queue: Vec::new(),
+            boon_type,
+        }
+    }
+
+    fn fix_queue(&mut self) {
+        // Sort reversed, so that the longest stack is at the front.
+        self.queue.sort_unstable_by(|a, b| b.cmp(a));
+        // Truncate queue by cutting of the shortest stacks
+        if self.queue.len() > self.capacity as usize {
+            self.queue.drain(self.capacity as usize..);
+        }
+    }
+
+    /// Get the type of this boon.
+    pub fn boon_type(&self) -> BoonType {
+        self.boon_type
+    }
+
+    /// Add a boon stack to this queue.
+    ///
+    /// * `duration` - Duration (in milliseconds) of the added stack.
+    pub fn add_stack(&mut self, duration: u64) {
+        self.queue.push(duration);
+        self.fix_queue();
+    }
+
+    /// Return the amount of current stacks.
+    ///
+    /// If the boon type is a duration boon, this will always return 0 or 1.
+    ///
+    /// If the boon type is an intensity boon, it will return the number of
+    /// stacks.
+    pub fn current_stacks(&self) -> u32 {
+        let result = match self.boon_type {
+            BoonType::Intensity => self.queue.len(),
+            BoonType::Duration => cmp::min(1, self.queue.len()),
+        };
+        result as u32
+    }
+
+    /// Simulate time passing.
+    ///
+    /// This will decrease the remaining duration of the stacks accordingly.
+    ///
+    /// * `duration` - The amount of time (in milliseconds) to simulate.
+    pub fn simulate(&mut self, duration: u64) {
+        let mut remaining = duration;
+        match self.boon_type {
+            BoonType::Duration => {
+                while remaining > 0 && !self.queue.is_empty() {
+                    let next = self.queue.remove(0);
+                    if next > remaining {
+                        self.queue.push(next - remaining);
+                        break;
+                    } else {
+                        remaining -= next;
+                    }
+                }
+                self.fix_queue();
+            }
+
+            BoonType::Intensity => {
+                self.queue = self.queue
+                    .iter()
+                    .cloned()
+                    .filter(|v| *v > duration)
+                    .map(|v| v - duration)
+                    .collect();
+            }
+        }
+    }
+
+    /// Remove all stacks.
+    pub fn clear(&mut self) {
+        self.queue.clear();
+    }
+
+    /// Calculate when the stacks will have the next visible change.
+    ///
+    /// This assumes that the stacks will not be modified during this time.
+    ///
+    /// The return value is the duration in milliseconds. If the boon queue is
+    /// currently empty, 0 is returned.
+    pub fn next_change(&self) -> u64 {
+        match self.boon_type {
+            BoonType::Duration => self.queue.iter().sum(),
+            BoonType::Intensity => self.queue.last().cloned().unwrap_or(0),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_queue_capacity() {
+        let mut queue = BoonQueue::new(5, BoonType::Intensity);
+        assert_eq!(queue.current_stacks(), 0);
+        for _ in 0..10 {
+            queue.add_stack(10);
+        }
+        assert_eq!(queue.current_stacks(), 5);
+    }
+
+    #[test]
+    fn test_simulate_duration() {
+        let mut queue = BoonQueue::new(10, BoonType::Duration);
+        queue.add_stack(10);
+        queue.add_stack(20);
+        assert_eq!(queue.current_stacks(), 1);
+        queue.simulate(30);
+        assert_eq!(queue.current_stacks(), 0);
+
+        queue.add_stack(50);
+        queue.simulate(30);
+        assert_eq!(queue.current_stacks(), 1);
+        queue.simulate(10);
+        assert_eq!(queue.current_stacks(), 1);
+        queue.simulate(15);
+        assert_eq!(queue.current_stacks(), 0);
+    }
+
+    #[test]
+    fn test_simulate_intensity() {
+        let mut queue = BoonQueue::new(5, BoonType::Intensity);
+
+        queue.add_stack(10);
+        queue.add_stack(20);
+        assert_eq!(queue.current_stacks(), 2);
+
+        queue.simulate(5);
+        assert_eq!(queue.current_stacks(), 2);
+
+        queue.simulate(5);
+        assert_eq!(queue.current_stacks(), 1);
+        queue.simulate(15);
+        assert_eq!(queue.current_stacks(), 0);
+    }
+}
diff --git a/src/statistics.rs b/src/statistics/mod.rs
index af208ce..a9dd178 100644
--- a/src/statistics.rs
+++ b/src/statistics/mod.rs
@@ -2,6 +2,8 @@
 use super::*;
 use std::collections::HashMap;
 
+pub mod boon;
+
 pub type StatResult<T> = Result<T, StatError>;
 
 quick_error! {