From 5b303aa3a8a1185ccd8ea6059436a8273731275a Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Fri, 12 Nov 2021 16:34:49 -0500
Subject: implement moving the readline cursor

---
 src/readline.rs | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 67 insertions(+), 7 deletions(-)

(limited to 'src/readline.rs')

diff --git a/src/readline.rs b/src/readline.rs
index 37fc054..8d7a87f 100644
--- a/src/readline.rs
+++ b/src/readline.rs
@@ -1,10 +1,11 @@
 use textmode::Textmode as _;
-use unicode_width::UnicodeWidthChar as _;
+use unicode_width::{UnicodeWidthChar as _, UnicodeWidthStr as _};
 
 pub struct Readline {
     size: (u16, u16),
     prompt: String,
     input_line: String,
+    pos: usize,
     action: async_std::channel::Sender<crate::action::Action>,
 }
 
@@ -16,6 +17,7 @@ impl Readline {
             size: (24, 80),
             prompt: "$ ".into(),
             input_line: "".into(),
+            pos: 0,
             action,
         }
     }
@@ -39,6 +41,8 @@ impl Readline {
             }
             textmode::Key::Ctrl(b'u') => self.clear_backwards(),
             textmode::Key::Backspace => self.backspace(),
+            textmode::Key::Left => self.cursor_left(),
+            textmode::Key::Right => self.cursor_right(),
             _ => {}
         }
         self.action
@@ -59,6 +63,7 @@ impl Readline {
         out.move_to(self.size.0 - 1, 0);
         out.write_str(&self.prompt);
         out.write_str(&self.input_line);
+        out.move_to(self.size.0 - 1, self.prompt_width() + self.pos_width());
         Ok(())
     }
 
@@ -71,22 +76,77 @@ impl Readline {
     }
 
     fn add_input(&mut self, s: &str) {
-        self.input_line.push_str(s);
+        self.input_line.insert_str(self.byte_pos(), s);
+        self.pos += s.chars().count();
     }
 
     fn backspace(&mut self) {
-        let mut width = 0;
-        while width == 0 {
-            width =
-                self.input_line.pop().map_or(1, |c| c.width().unwrap_or(0));
+        while self.pos > 0 {
+            self.pos -= 1;
+            let width =
+                self.input_line.remove(self.byte_pos()).width().unwrap_or(0);
+            if width > 0 {
+                break;
+            }
         }
     }
 
     fn clear_input(&mut self) {
         self.input_line.clear();
+        self.pos = 0;
     }
 
     fn clear_backwards(&mut self) {
-        self.input_line.clear();
+        self.input_line = self.input_line.chars().skip(self.pos).collect();
+        self.pos = 0;
+    }
+
+    fn cursor_left(&mut self) {
+        if self.pos == 0 {
+            return;
+        }
+        self.pos -= 1;
+        while let Some(c) = self.input_line.chars().nth(self.pos) {
+            if c.width().unwrap_or(0) == 0 {
+                self.pos -= 1;
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn cursor_right(&mut self) {
+        if self.pos == self.input_line.chars().count() {
+            return;
+        }
+        self.pos += 1;
+        while let Some(c) = self.input_line.chars().nth(self.pos) {
+            if c.width().unwrap_or(0) == 0 {
+                self.pos += 1;
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn prompt_width(&self) -> u16 {
+        self.prompt.width().try_into().unwrap()
+    }
+
+    fn pos_width(&self) -> u16 {
+        self.input_line
+            .chars()
+            .take(self.pos)
+            .collect::<String>()
+            .width()
+            .try_into()
+            .unwrap()
+    }
+
+    fn byte_pos(&self) -> usize {
+        self.input_line
+            .char_indices()
+            .nth(self.pos)
+            .map_or(self.input_line.len(), |(i, _)| i)
     }
 }
-- 
cgit v1.2.3-54-g00ecf