Refactor the repl loop

src/shell/completer.rs

@@ -0,0 +1,41 @@
+use rustyline::completion::{Candidate, Completer};
+use rustyline::line_buffer::LineBuffer;
+
+#[derive(Debug)]
+crate struct NuCompleter;
+
+impl Completer for NuCompleter {
+    type Candidate = NuPair;
+
+    fn complete(
+        &self,
+        _line: &str,
+        _pos: usize,
+        _context: &rustyline::Context,
+    ) -> rustyline::Result<(usize, Vec<NuPair>)> {
+        Ok((
+            0,
+            vec![
+                NuPair("exit", "exit"),
+                NuPair("ls", "ls"),
+                NuPair("ps", "ps"),
+            ],
+        ))
+    }
+
+    fn update(&self, line: &mut LineBuffer, start: usize, elected: &str) {
+        let end = line.pos();
+        line.replace(start..end, elected)
+    }
+}
+
+crate struct NuPair(&'static str, &'static str);
+
+impl Candidate for NuPair {
+    fn display(&self) -> &str {
+        self.0
+    }
+    fn replacement(&self) -> &str {
+        self.1
+    }
+}

src/shell/helper.rs

@@ -0,0 +1,62 @@
+use crate::shell::completer::{NuCompleter, NuPair};
+
+use rustyline::completion::Completer;
+use rustyline::error::ReadlineError;
+use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
+use rustyline::hint::{Hinter, HistoryHinter};
+use std::borrow::Cow::{self, Owned};
+
+crate struct Helper {
+    completer: NuCompleter,
+    highlighter: MatchingBracketHighlighter,
+    hinter: HistoryHinter,
+}
+
+impl Helper {
+    crate fn new() -> Helper {
+        Helper {
+            completer: NuCompleter,
+            highlighter: MatchingBracketHighlighter::new(),
+            hinter: HistoryHinter {},
+        }
+    }
+}
+
+impl Completer for Helper {
+    type Candidate = NuPair;
+
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        ctx: &rustyline::Context<'_>,
+    ) -> Result<(usize, Vec<NuPair>), ReadlineError> {
+        self.completer.complete(line, pos, ctx)
+    }
+}
+
+impl Hinter for Helper {
+    fn hint(&self, line: &str, pos: usize, ctx: &rustyline::Context<'_>) -> Option<String> {
+        self.hinter.hint(line, pos, ctx)
+    }
+}
+
+impl Highlighter for Helper {
+    fn highlight_prompt<'p>(&self, prompt: &'p str) -> Cow<'p, str> {
+        Owned("\x1b[32m".to_owned() + &prompt[0..prompt.len() - 2] + "\x1b[m> ")
+    }
+
+    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
+        Owned("\x1b[1m".to_owned() + hint + "\x1b[m")
+    }
+
+    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {
+        self.highlighter.highlight(line, pos)
+    }
+
+    fn highlight_char(&self, line: &str, pos: usize) -> bool {
+        self.highlighter.highlight_char(line, pos)
+    }
+}
+
+impl rustyline::Helper for Helper {}