add cwd aware hinter (#647)

* add cwd aware hinter

towards nushell/nushell#8883

* handle the case where get_current_dir returns Err

* WIP cwd aware hinter

 - guard CwdAwareHinter with feature flag
 - remove references to fish from DefaultHinter as fish is cwd aware
 - add example

* document that CwdAwareHinter is only compatible with sqlite history

* handle non-sqlite history

* handle no sqlite feature in example

* fix warnings

examples/cwd_aware_hinter.rs

@@ -0,0 +1,86 @@
+// Create a reedline object with in-line hint support.
+// cargo run --example cwd_aware_hinter
+//
+// Fish-style cwd history based hinting
+// assuming history ["abc", "ade"]
+// pressing "a" hints to abc.
+// Up/Down or Ctrl p/n, to select next/previous match
+
+use std::io;
+
+fn create_item(cwd: &str, cmd: &str, exit_status: i64) -> reedline::HistoryItem {
+    use std::time::Duration;
+
+    use reedline::HistoryItem;
+    HistoryItem {
+        id: None,
+        start_timestamp: None,
+        command_line: cmd.to_string(),
+        session_id: None,
+        hostname: Some("foohost".to_string()),
+        cwd: Some(cwd.to_string()),
+        duration: Some(Duration::from_millis(1000)),
+        exit_status: Some(exit_status),
+        more_info: None,
+    }
+}
+
+fn create_filled_example_history(home_dir: &str, orig_dir: &str) -> Box<dyn reedline::History> {
+    use reedline::History;
+    #[cfg(not(any(feature = "sqlite", feature = "sqlite-dynlib")))]
+    let mut history = Box::new(reedline::FileBackedHistory::new(100));
+    #[cfg(any(feature = "sqlite", feature = "sqlite-dynlib"))]
+    let mut history = Box::new(reedline::SqliteBackedHistory::in_memory().unwrap());
+
+    history.save(create_item(orig_dir, "dummy", 0)).unwrap(); // add dummy item so ids start with 1
+    history.save(create_item(orig_dir, "ls /usr", 0)).unwrap();
+    history.save(create_item(orig_dir, "pwd", 0)).unwrap();
+
+    history.save(create_item(home_dir, "cat foo", 0)).unwrap();
+    history.save(create_item(home_dir, "ls bar", 0)).unwrap();
+    history.save(create_item(home_dir, "rm baz", 0)).unwrap();
+
+    history
+}
+
+fn main() -> io::Result<()> {
+    use nu_ansi_term::{Color, Style};
+    use reedline::{CwdAwareHinter, DefaultPrompt, Reedline, Signal};
+
+    let orig_dir = std::env::current_dir().unwrap();
+    #[allow(deprecated)]
+    let home_dir = std::env::home_dir().unwrap();
+
+    let history = create_filled_example_history(
+        &home_dir.to_string_lossy().to_string(),
+        &orig_dir.to_string_lossy().to_string(),
+    );
+
+    let mut line_editor = Reedline::create()
+        .with_hinter(Box::new(
+            CwdAwareHinter::default().with_style(Style::new().italic().fg(Color::Yellow)),
+        ))
+        .with_history(history);
+
+    let prompt = DefaultPrompt::default();
+
+    let mut iterations = 0;
+    loop {
+        if iterations % 2 == 0 {
+            std::env::set_current_dir(&orig_dir).unwrap();
+        } else {
+            std::env::set_current_dir(&home_dir).unwrap();
+        }
+        let sig = line_editor.read_line(&prompt)?;
+        match sig {
+            Signal::Success(buffer) => {
+                println!("We processed: {buffer}");
+            }
+            Signal::CtrlD | Signal::CtrlC => {
+                println!("\nAborted!");
+                break Ok(());
+            }
+        }
+        iterations += 1;
+    }
+}

src/hinter/cwd_aware.rs

@@ -0,0 +1,108 @@
+use crate::{
+    history::SearchQuery,
+    result::{ReedlineError, ReedlineErrorVariants::HistoryFeatureUnsupported},
+    Hinter, History,
+};
+use nu_ansi_term::{Color, Style};
+
+/// A hinter that uses the completions or the history to show a hint to the user
+///
+/// Similar to `fish` autosuggestions
+pub struct CwdAwareHinter {
+    style: Style,
+    current_hint: String,
+    min_chars: usize,
+}
+
+impl Hinter for CwdAwareHinter {
+    fn handle(
+        &mut self,
+        line: &str,
+        #[allow(unused_variables)] pos: usize,
+        history: &dyn History,
+        use_ansi_coloring: bool,
+    ) -> String {
+        self.current_hint = if line.chars().count() >= self.min_chars {
+            history
+                .search(SearchQuery::last_with_prefix_and_cwd(
+                    line.to_string(),
+                    history.session(),
+                ))
+                .or_else(|err| {
+                    if let ReedlineError(HistoryFeatureUnsupported { .. }) = err {
+                        history.search(SearchQuery::last_with_prefix(
+                            line.to_string(),
+                            history.session(),
+                        ))
+                    } else {
+                        Err(err)
+                    }
+                })
+                .expect("todo: error handling")
+                .get(0)
+                .map_or_else(String::new, |entry| {
+                    entry
+                        .command_line
+                        .get(line.len()..)
+                        .unwrap_or_default()
+                        .to_string()
+                })
+        } else {
+            String::new()
+        };
+
+        if use_ansi_coloring && !self.current_hint.is_empty() {
+            self.style.paint(&self.current_hint).to_string()
+        } else {
+            self.current_hint.clone()
+        }
+    }
+
+    fn complete_hint(&self) -> String {
+        self.current_hint.clone()
+    }
+
+    fn next_hint_token(&self) -> String {
+        let mut reached_content = false;
+        let result: String = self
+            .current_hint
+            .chars()
+            .take_while(|c| match (c.is_whitespace(), reached_content) {
+                (true, true) => false,
+                (true, false) => true,
+                (false, true) => true,
+                (false, false) => {
+                    reached_content = true;
+                    true
+                }
+            })
+            .collect();
+        result
+    }
+}
+
+impl Default for CwdAwareHinter {
+    fn default() -> Self {
+        CwdAwareHinter {
+            style: Style::new().fg(Color::LightGray),
+            current_hint: String::new(),
+            min_chars: 1,
+        }
+    }
+}
+
+impl CwdAwareHinter {
+    /// A builder that sets the style applied to the hint as part of the buffer
+    #[must_use]
+    pub fn with_style(mut self, style: Style) -> Self {
+        self.style = style;
+        self
+    }
+
+    /// A builder that sets the number of characters that have to be present to enable history hints
+    #[must_use]
+    pub fn with_min_chars(mut self, min_chars: usize) -> Self {
+        self.min_chars = min_chars;
+        self
+    }
+}

src/hinter/default.rs

@@ -1,9 +1,7 @@
 use crate::{history::SearchQuery, Hinter, History};
 use nu_ansi_term::{Color, Style};
 
-/// A hinter that use the completions or the history to show a hint to the user
-///
-/// Similar to `fish` autosuggestins
+/// A hinter that uses the completions or the history to show a hint to the user
 pub struct DefaultHinter {
     style: Style,
     current_hint: String,

src/hinter/mod.rs

@@ -1,4 +1,6 @@
+mod cwd_aware;
 mod default;
+pub use cwd_aware::CwdAwareHinter;
 pub use default::DefaultHinter;
 
 use crate::History;

src/history/base.rs

@@ -66,6 +66,18 @@ impl SearchFilter {
         s
     }
 
+    /// Create a search filter with a [`CommandLineSearch`] and `cwd`
+    pub fn from_text_search_cwd(
+        cwd: String,
+        cmd: CommandLineSearch,
+        session: Option<HistorySessionId>,
+    ) -> SearchFilter {
+        let mut s = SearchFilter::anything(session);
+        s.command_line = Some(cmd);
+        s.cwd_exact = Some(cwd);
+        s
+    }
+
     /// anything within this session
     pub fn anything(session: Option<HistorySessionId>) -> SearchFilter {
         SearchFilter {
@@ -134,6 +146,26 @@ impl SearchQuery {
         ))
     }
 
+    /// Get the most recent entry starting with the `prefix` and `cwd` same as the current cwd
+    pub fn last_with_prefix_and_cwd(
+        prefix: String,
+        session: Option<HistorySessionId>,
+    ) -> SearchQuery {
+        let cwd = std::env::current_dir();
+        if let Ok(cwd) = cwd {
+            SearchQuery::last_with_search(SearchFilter::from_text_search_cwd(
+                cwd.to_string_lossy().to_string(),
+                CommandLineSearch::Prefix(prefix),
+                session,
+            ))
+        } else {
+            SearchQuery::last_with_search(SearchFilter::from_text_search(
+                CommandLineSearch::Prefix(prefix),
+                session,
+            ))
+        }
+    }
+
     /// Query to get all entries in the given [`SearchDirection`]
     pub fn everything(
         direction: SearchDirection,

src/lib.rs

@@ -269,6 +269,7 @@ mod completion;
 pub use completion::{Completer, DefaultCompleter, Span, Suggestion};
 
 mod hinter;
+pub use hinter::CwdAwareHinter;
 pub use hinter::{DefaultHinter, Hinter};
 
 mod validator;