From ad507849196dbdb864044444eee3b732f14a5c87 Mon Sep 17 00:00:00 2001
From: Tom You <email.tomyou@gmail.com>
Date: Tue, 7 Jul 2026 00:03:40 -0500
Subject: [PATCH] feat(core): add terminal grid model

---
 rabby-core/src/lib.rs                |   1 +
 rabby-core/src/terminal_model/mod.rs | 109 +++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)
 create mode 100644 rabby-core/src/terminal_model/mod.rs

diff --git a/rabby-core/src/lib.rs b/rabby-core/src/lib.rs
index 830e48a..177f096 100644
--- a/rabby-core/src/lib.rs
+++ b/rabby-core/src/lib.rs
@@ -5,6 +5,7 @@
 
 pub mod config;
 pub mod feature;
+pub mod terminal_model;
 pub mod workspace;
 
 pub use config::{AppConfig, ShortcutBinding};
diff --git a/rabby-core/src/terminal_model/mod.rs b/rabby-core/src/terminal_model/mod.rs
new file mode 100644
index 0000000..ed81456
--- /dev/null
+++ b/rabby-core/src/terminal_model/mod.rs
@@ -0,0 +1,109 @@
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Cell {
+    pub ch: char,
+}
+
+impl Default for Cell {
+    fn default() -> Self {
+        Self { ch: ' ' }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TerminalGrid {
+    cols: u16,
+    rows: u16,
+    cursor_col: u16,
+    cursor_row: u16,
+    cells: Vec<Cell>,
+}
+
+impl TerminalGrid {
+    pub fn new(cols: u16, rows: u16) -> Self {
+        let size = usize::from(cols) * usize::from(rows);
+        Self {
+            cols,
+            rows,
+            cursor_col: 0,
+            cursor_row: 0,
+            cells: vec![Cell::default(); size],
+        }
+    }
+
+    pub fn write_utf8(&mut self, bytes: &[u8]) {
+        let text = String::from_utf8_lossy(bytes);
+        for ch in text.chars() {
+            match ch {
+                '\r' => self.cursor_col = 0,
+                '\n' => self.newline(),
+                _ => self.put_char(ch),
+            }
+        }
+    }
+
+    pub fn visible_text(&self) -> String {
+        self.line_text(0)
+    }
+
+    pub fn line_text(&self, row: u16) -> String {
+        if row >= self.rows {
+            return String::new();
+        }
+        let start = usize::from(row) * usize::from(self.cols);
+        let end = start + usize::from(self.cols);
+        self.cells[start..end].iter().map(|cell| cell.ch).collect()
+    }
+
+    fn put_char(&mut self, ch: char) {
+        if self.cursor_row >= self.rows || self.cursor_col >= self.cols {
+            return;
+        }
+        let index =
+            usize::from(self.cursor_row) * usize::from(self.cols) + usize::from(self.cursor_col);
+        self.cells[index].ch = ch;
+        self.cursor_col += 1;
+        if self.cursor_col >= self.cols {
+            self.newline();
+        }
+    }
+
+    fn newline(&mut self) {
+        self.cursor_col = 0;
+        if self.cursor_row + 1 < self.rows {
+            self.cursor_row += 1;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn writes_ascii_text_to_grid() {
+        let mut grid = TerminalGrid::new(8, 2);
+
+        grid.write_utf8(b"hello");
+
+        assert_eq!(grid.visible_text(), "hello   ");
+    }
+
+    #[test]
+    fn handles_newline_and_carriage_return() {
+        let mut grid = TerminalGrid::new(6, 2);
+
+        grid.write_utf8(b"abc\rZ\ndef");
+
+        assert_eq!(grid.line_text(0), "Zbc   ");
+        assert_eq!(grid.line_text(1), "def   ");
+    }
+
+    #[test]
+    fn tolerates_utf8_double_width_input() {
+        let mut grid = TerminalGrid::new(6, 1);
+
+        grid.write_utf8("한A".as_bytes());
+
+        assert!(grid.line_text(0).starts_with("한A"));
+    }
+}