From 9f37a6558adfd637236ad6d27080e1bd30c82b79 Mon Sep 17 00:00:00 2001
From: "NGnius (Graham)" <ngniusness@gmail.com>
Date: Thu, 10 Mar 2022 20:52:48 -0500
Subject: [PATCH] Fix backspacing in middle of line for REPL

---
 mps-interpreter/src/tokens/tokenizer.rs |  1 -
 src/repl.rs                             | 55 +++++++++++++++++++------
 2 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/mps-interpreter/src/tokens/tokenizer.rs b/mps-interpreter/src/tokens/tokenizer.rs
index f79a3e6..5b6a73e 100644
--- a/mps-interpreter/src/tokens/tokenizer.rs
+++ b/mps-interpreter/src/tokens/tokenizer.rs
@@ -182,7 +182,6 @@ where
     }
 
     fn current_column(&self) -> usize {
-        println!("Current column: {}", self.column);
         self.column
     }
 
diff --git a/src/repl.rs b/src/repl.rs
index 6ec3da2..596ba72 100644
--- a/src/repl.rs
+++ b/src/repl.rs
@@ -168,21 +168,52 @@ fn read_loop<F: FnMut()>(args: &CliArgs, state: &mut ReplState, mut execute: F)
                 }
             },
             Key::Backspace => {
-                if let Some(c) = state.statement_buf.pop() {
-                    match c {
-                        '\n' | '\r' => {
-                            // another line, cannot backspace that far
-                            state.statement_buf.push(c);
-                        }
-                        _ => {
-                            state.current_line.pop();
-                            state.terminal.move_cursor_left(1).expect("Failed to write to terminal output");
-                            write!(state.terminal, " ").expect("Failed to write to terminal output");
-                            state.terminal.flush().expect("Failed to flush terminal output");
-                            state.terminal.move_cursor_left(1).expect("Failed to write to terminal output");
+                if state.cursor_rightward_position == 0 {
+                    if let Some(c) = state.statement_buf.pop() {
+                        match c {
+                            '\n' | '\r' => {
+                                // another line, cannot backspace that far
+                                state.statement_buf.push(c);
+                            }
+                            _ => {
+                                state.current_line.pop();
+                                state.terminal.move_cursor_left(1).expect("Failed to write to terminal output");
+                                write!(state.terminal, " ").expect("Failed to write to terminal output");
+                                state.terminal.flush().expect("Failed to flush terminal output");
+                                state.terminal.move_cursor_left(1).expect("Failed to write to terminal output");
+                            }
                         }
                     }
+                } else {
+                    if state.current_line.len() != state.cursor_rightward_position {
+                        // if not at start of line
+                        let removed_char = state.current_line.remove(state.current_line.len()-state.cursor_rightward_position-1);
+                        state.statement_buf.remove(state.statement_buf.len()-state.cursor_rightward_position-1);
+                        // re-sync unclosed syntax tracking
+                        match removed_char {
+                            '"' | '`' => {
+                                if let Some(c) = state.in_literal {
+                                    if c == removed_char {
+                                        state.in_literal = None;
+                                    }
+                                }
+                            },
+                            '(' => if state.bracket_depth != 0 { state.bracket_depth -= 1 },
+                            ')' => state.bracket_depth += 1,
+                            '{' => if state.curly_depth != 0 { state.curly_depth -= 1 },
+                            '}' => state.curly_depth += 1,
+                            _ => {},
+                        }
+                        // re-print end of line to remove character in middle
+                        state.terminal.move_cursor_left(1).expect("Failed to write to terminal output");
+                        for i in state.current_line.len() - state.cursor_rightward_position .. state.current_line.len() {
+                            write!(state.terminal, "{}", state.current_line[i]).expect("Failed to write to terminal output");
+                        }
+                        write!(state.terminal, " ").expect("Failed to write to terminal output");
+                        state.terminal.move_cursor_left(state.cursor_rightward_position + 1).expect("Failed to write to terminal output");
+                    }
                 }
+
             },
             Key::Enter => {
                 state.terminal.write_line("").expect("Failed to write to terminal output");