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Added 'History' support, along with default SimpleHistory implementat…
…ion and tests
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| //! Trait and structs used by prompts to provide prompt-entry history navigation features. | ||
| //! | ||
| //! History is triggered upon up or down keystroke, which iterates through a historical | ||
| //! list of prompt entries. Each keystroke rewrites the contents of the prompt with the next | ||
| //! item from that history. | ||
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| use dyn_clone::DynClone; | ||
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| use crate::CustomUserError; | ||
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| /// Used when iterating through the user's prompt history | ||
| /// | ||
| /// `None` means that no completion will be made. | ||
| /// `Some(String)` will replace the current text input with the `String` in `Some`. | ||
| pub type Replacement = Option<String>; | ||
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| /// Mechanism to implement history navigation | ||
| /// | ||
| /// - `earlier_element` is called whenever the user presses the `up` key, and navigates towards less recent prompt entries | ||
| /// - `later_element` is called whenever the user presses the `down` key, and navigates towards more recent prompt entries | ||
| /// - `prepend_element` is called whenever the user hits `enter` commits a new entry into the prompt; this adds the entry to the prompt history | ||
| pub trait History: DynClone { | ||
| /// Update internal state and return the next less-recent history entry | ||
| fn earlier_element(&mut self) -> Result<Replacement, CustomUserError>; | ||
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| /// Update internal state and return the nezt more-recent history entry | ||
| fn later_element(&mut self) -> Result<Replacement, CustomUserError>; | ||
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| /// Add the given string to the history, at the beginning of the history, which is the most recent | ||
| fn prepend_element(&mut self, _: String); | ||
| } | ||
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| impl Clone for Box<dyn History> { | ||
| fn clone(&self) -> Self { | ||
| dyn_clone::clone_box(&**self) | ||
| } | ||
| } | ||
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| /// Empty struct and implementation of History trait. Used for the default | ||
| /// history of `Text` prompts. | ||
| #[derive(Clone, Default)] | ||
| pub struct NoHistory; | ||
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| impl History for NoHistory { | ||
| fn earlier_element(&mut self) -> Result<Replacement, CustomUserError> { | ||
| Ok(Replacement::None) | ||
| } | ||
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| fn later_element(&mut self) -> Result<Replacement, CustomUserError> { | ||
| Ok(Replacement::None) | ||
| } | ||
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| fn prepend_element(&mut self, _: String) { | ||
| () | ||
| } | ||
| } | ||
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| /// Simple `History` implementation. Stores a vector of strings representing prompt entries, and navigates through the | ||
| /// vector. Prepends new entries into the vector and resets internal index state. | ||
| #[derive(Clone, Debug)] | ||
| pub struct SimpleHistory { | ||
| history: Vec<String>, | ||
| index: isize | ||
| } | ||
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| impl SimpleHistory { | ||
| /// Reeturn a new SimpleHistory, bootstrappd with the given entries | ||
| pub fn new(initial_history: Vec<String>) -> Self { | ||
| SimpleHistory { | ||
| history: initial_history, | ||
| index: -1, | ||
| } | ||
| } | ||
| } | ||
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| impl History for SimpleHistory { | ||
| fn earlier_element(&mut self) -> Result<Replacement, CustomUserError> { | ||
| if self.index < self.history.len() as isize - 1 { | ||
| self.index += 1; | ||
| Ok(Replacement::Some(self.history[self.index as usize].clone())) | ||
| } else if !self.history.is_empty() && self.index == self.history.len() as isize - 1 { | ||
| // return last item in the history | ||
| Ok(Replacement::Some(self.history[self.index as usize].clone())) | ||
| } else { | ||
| Ok(Replacement::None) | ||
| } | ||
| } | ||
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| fn later_element(&mut self) -> Result<Replacement, CustomUserError> { | ||
| if self.index >= 1 { | ||
| self.index -= 1; | ||
| let e = self.history[self.index as usize].clone(); | ||
| Ok(Replacement::Some(e)) | ||
| } else { | ||
| if self.index == 0 { | ||
| self.index -= 1; | ||
| } | ||
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| Ok(Replacement::None) | ||
| } | ||
| } | ||
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| fn prepend_element(&mut self, e: String) { | ||
| if e.len() > 0 { | ||
| self.history.insert(0, e); | ||
| self.index = -1; | ||
| } | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
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| #[test] | ||
| fn test_new_history() { | ||
| let history = SimpleHistory::new(vec!["first".into(), "second".into()]); | ||
| assert_eq!(history.history.len(), 2); | ||
| assert_eq!(history.index, -1); | ||
| } | ||
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| #[test] | ||
| fn test_prepend_element() { | ||
| let mut history = SimpleHistory::new(vec![]); | ||
| history.prepend_element("new".into()); | ||
| assert_eq!(history.history.len(), 1); | ||
| assert_eq!(history.history[0], "new"); | ||
| } | ||
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| #[test] | ||
| fn test_earlier_then_later_element() { | ||
| let mut history = SimpleHistory::new(vec!["first".into(), "second".into()]); | ||
| assert_eq!(history.earlier_element().unwrap(), Replacement::Some("first".into())); | ||
| assert_eq!(history.later_element().unwrap(), Replacement::None); | ||
| assert_eq!(history.earlier_element().unwrap(), Replacement::Some("first".into())); | ||
| } | ||
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| #[test] | ||
| fn test_sequence_of_operations() { | ||
| let mut history = SimpleHistory::new(vec!["first".into(), "second".into()]); | ||
| // Prepend a new element | ||
| history.prepend_element("zero".into()); | ||
| // Move to the earlier element, which should now be "zero" | ||
| assert_eq!(history.earlier_element().unwrap(), Replacement::Some("zero".into())); | ||
| // Move to an even earlier element, which should now be "second" | ||
| assert_eq!(history.earlier_element().unwrap(), Replacement::Some("first".into())); | ||
| // Try to move later, back to "first" | ||
| assert_eq!(history.later_element().unwrap(), Replacement::Some("zero".into())); | ||
| // And now, since we're at the start, it should return None | ||
| assert_eq!(history.later_element().unwrap(), Replacement::None); | ||
| } | ||
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| #[test] | ||
| fn test_no_prepend_of_empty_string() { | ||
| let mut history = SimpleHistory::new(vec!["initial".into()]); | ||
| history.prepend_element("".into()); | ||
| assert_eq!(history.history.len(), 1); | ||
| assert_eq!(history.history[0], "initial"); | ||
| } | ||
| } |
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