Keep track of cursor position.

1 files changed, 65 insertions, 10 deletions

diff --git a/src/main.rs b/src/main.rs
index 592f89c..de25e9c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,10 +3,15 @@ mod term;
 
 use rope::Rope;
 use std::ffi::{OsStr, OsString};
-use std::io::Write;
+use std::io::{Stdout, Write};
 use std::path::Path;
 use term::Key;
 
+fn move_cursor(stdout: &mut Stdout, row: usize, col: usize) {
+    let _ = write!(stdout, "\x1b[{};{}H", row + 1, col + 1);
+    let _ = stdout.flush();
+}
+
 fn edit(file: &OsStr) -> Result<(), String> {
     let _raw_handle = match term::raw() {
         Some(h) => h,
@@ -28,14 +33,25 @@ fn edit(file: &OsStr) -> Result<(), String> {
         }
     };
     let mut stdout = std::io::stdout();
+    let _ = stdout.write(b"\x1b[J");
     for i in 0..usize::from(size.ws_row) {
         if i > 0 {
             let _ = stdout.write(b"\r\n");
         }
-        let _ = r.print_line(&mut stdout, i);
+        let line = match r.line(i) {
+            Some(line) => line,
+            None => {
+                break;
+            }
+        };
+        let _ = line.print(&mut stdout);
     }
+    let _ = stdout.write(b"\x1b[H");
     let _ = stdout.flush();
 
+    let mut cursor_row = 0;
+    let mut cursor_col = 0;
+
     let mut stdin = std::io::stdin();
     loop {
         let c = match term::read_key(&mut stdin) {
@@ -49,20 +65,59 @@ fn edit(file: &OsStr) -> Result<(), String> {
                 break;
             }
             Key::Up => {
-                let _ = stdout.write(b"\x1b[A");
-                let _ = stdout.flush();
+                if cursor_row == 0 {
+                    continue;
+                }
+                cursor_row -= 1;
+
+                let len = r
+                    .line(cursor_row)
+                    .expect("cursor_row should always be valid")
+                    .len();
+                if cursor_col > len {
+                    move_cursor(&mut stdout, cursor_row, len);
+                } else {
+                    move_cursor(&mut stdout, cursor_row, cursor_col);
+                }
             }
             Key::Down => {
-                let _ = stdout.write(b"\x1b[B");
-                let _ = stdout.flush();
+                if cursor_row == usize::from(size.ws_row - 1) || cursor_row == r.lines() {
+                    continue;
+                }
+                cursor_row += 1;
+
+                let len = r
+                    .line(cursor_row)
+                    .expect("cursor_row should always be valid")
+                    .len();
+                if cursor_col > len {
+                    move_cursor(&mut stdout, cursor_row, len);
+                } else {
+                    move_cursor(&mut stdout, cursor_row, cursor_col);
+                }
             }
             Key::Left => {
-                let _ = stdout.write(b"\x1b[D");
-                let _ = stdout.flush();
+                let len = r
+                    .line(cursor_row)
+                    .expect("cursor_row should always be valid")
+                    .len();
+                cursor_col = std::cmp::min(cursor_col, len);
+                if cursor_col == 0 {
+                    continue;
+                }
+                cursor_col -= 1;
+                move_cursor(&mut stdout, cursor_row, cursor_col);
             }
             Key::Right => {
-                let _ = stdout.write(b"\x1b[C");
-                let _ = stdout.flush();
+                let len = r
+                    .line(cursor_row)
+                    .expect("cursor_row should always be valid")
+                    .len();
+                if cursor_col == usize::from(size.ws_col - 1) || cursor_col >= len {
+                    continue;
+                }
+                cursor_col += 1;
+                move_cursor(&mut stdout, cursor_row, cursor_col);
             }
             Key::Char(c) => {
                 print!("{} ", c);