1 files changed, 93 insertions, 0 deletions

diff --git a/src/readline/mod.rs b/src/readline/mod.rs
new file mode 100644
index 0000000..1f9fe98
--- /dev/null
+++ b/src/readline/mod.rs
@@ -0,0 +1,93 @@
+use std::borrow::Cow::{self,Owned};
+
+use rustyline::error::ReadlineError;
+use rustyline::{ Editor, Context, Helper };
+use rustyline::config::{ Builder, ColorMode, EditMode, CompletionType };
+use rustyline::hint::Hinter;
+use rustyline::completion::{ FilenameCompleter, Completer, Pair };
+use rustyline::highlight::Highlighter;
+
+use crate::eval_math_expression;
+
+pub struct RLHelper {
+    completer: FilenameCompleter,
+    highlighter: LineHighlighter,
+    hinter: AnswerHinter,
+}
+
+struct AnswerHinter { }
+impl Hinter for AnswerHinter {
+    fn hint(&self, line: &str, _: usize, _: &Context) -> Option<String> {
+        let input = line.trim();
+        let input = input.replace(" ", "");
+        if input.len() == 0 {
+            return Some("".into())
+        }
+        let dry_run = eval_math_expression(&input);
+        match dry_run {
+            Ok(ans) =>  return Some(format!(" = {}", ans)),
+            Err(_) => return Some(format!(""))
+        };
+    }
+}
+
+struct LineHighlighter { }
+impl Highlighter for LineHighlighter {
+    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
+        Owned(format!("\x1b[90m{}\x1b[0m", hint))
+    }
+    fn highlight<'l>(&self, line: &'l str, _: usize) -> Cow<'l, str> {
+        let op = eval_math_expression(line);
+        match op {
+            Ok(_) => Owned(line.into()),
+            Err(_) => Owned(format!("\x1b[31m{}\x1b[0m", line))
+        }
+    }
+}
+
+impl Highlighter for RLHelper { 
+    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
+        self.highlighter.highlight_hint(hint)
+    }
+    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {
+        self.highlighter.highlight(line, pos)
+    }
+}
+
+impl Completer for RLHelper {
+    type Candidate = Pair;
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        ctx: &Context<'_>,
+        ) -> Result<(usize, Vec<Pair>), ReadlineError> {
+        self.completer.complete(line, pos, ctx)
+    }
+}
+ 
+impl Hinter for RLHelper {
+    fn hint(&self, line: &str, a: usize, b: &Context) -> Option<String> {
+        self.hinter.hint(line, a, b)
+    }
+}
+
+impl Helper for RLHelper {}
+
+pub fn create_readline() -> Editor<RLHelper> {
+        let config_builder = Builder::new();
+        let config = config_builder.color_mode(ColorMode::Enabled)
+            .edit_mode(EditMode::Emacs)
+            .history_ignore_space(true)
+            .completion_type(CompletionType::Circular)
+            .max_history_size(1000)
+            .build();
+        let mut rl = Editor::with_config(config);
+        let h = RLHelper {
+            completer: FilenameCompleter::new(),
+            highlighter: LineHighlighter {},
+            hinter: AnswerHinter {}
+        };
+        rl.set_helper(Some(h));
+        return rl;
+}