71 lines
1.9 KiB
Rust
71 lines
1.9 KiB
Rust
pub trait Messenger {
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fn send(&self, msg: &str);
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}
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pub struct LimitTracker<'a, T: 'a + Messenger> {
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messenger: &'a T,
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value: usize,
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max: usize,
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}
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impl<'a, T> LimitTracker<'a, T>
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where T: Messenger {
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pub fn new(messenger: &T, max: usize) -> LimitTracker<T> {
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LimitTracker {
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messenger,
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value: 0,
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max,
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}
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}
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pub fn set_value(&mut self, value: usize) {
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self.value = value;
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let percentage_of_max = self.value as f64 / self.max as f64;
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if percentage_of_max >=1.0 {
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self.messenger.send("Error: You are over your quota!");
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} else if percentage_of_max >= 0.9 {
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self.messenger.send("Urgent warning: You've used up over 90% of your quota!");
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} else if percentage_of_max >= 0.75 {
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self.messenger.send("Warning: You've used up over 75% of your quota!");
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use std::cell::RefCell;
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struct MockMessenger {
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// RefCell wraps the vector in a way that it can be mutably
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// referenced at runtime
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sent_messages: RefCell<Vec<String>>,
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}
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impl MockMessenger {
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fn new() -> MockMessenger {
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MockMessenger { sent_messages: RefCell::new(vec![]) }
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}
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}
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impl Messenger for MockMessenger {
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fn send(&self, message: &str) {
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// If we tried to create another mutable borrow in this scope,
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// it would cause a panic. Same rules as at compile time.
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self.sent_messages.borrow_mut().push(String::from(message));
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}
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}
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#[test]
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fn it_sends_an_over_75_percent_warning_message() {
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let mock_messenger = MockMessenger::new();
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let mut limit_tracker = LimitTracker::new(&mock_messenger, 100);
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limit_tracker.set_value(80);
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assert_eq!(mock_messenger.sent_messages.borrow().len(), 1);
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}
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}
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