From f79ff6ae02962bdd8edbcb128ed8262b147cabdd Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Mon, 8 Mar 2021 09:50:15 -0500
Subject: [PATCH] Complete chapter 3

---
 src/editor.rs   | 57 +++++++++++++++++++++++++++++++++++++++++++------
 src/main.rs     |  1 +
 src/terminal.rs | 12 ++++++++---
 3 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/src/editor.rs b/src/editor.rs
index 5068903..0aecd3e 100644
--- a/src/editor.rs
+++ b/src/editor.rs
@@ -3,9 +3,15 @@ use termion::event::Key;
 
 const VERSION: &str = env!("CARGO_PKG_VERSION");
 
+pub struct Position {
+    pub x: usize,
+    pub y: usize,
+}
+
 pub struct Editor {
     should_quit: bool,
     terminal: Terminal,
+    cursor_position: Position,
 }
 
 impl Editor {
@@ -27,18 +33,19 @@ impl Editor {
         Self {
             should_quit: false,
             terminal: Terminal::default().expect("Failed to initialize terminal"),
+            cursor_position: Position { x: 0, y: 0 }
         }
     }
 
     fn refresh_screen(&self) -> Result<(), std::io::Error> {
         Terminal::cursor_hide();
-        Terminal::cursor_position(0, 0);
+        Terminal::cursor_position(&Position { x: 0, y: 0});
         if self.should_quit {
             Terminal::clear_screen();
             println!("Goodbye.\r");
         } else {
             self.draw_rows();
-            Terminal::cursor_position(0, 0);
+            Terminal::cursor_position(&self.cursor_position);
         }
         Terminal::cursor_show();
         Terminal::flush()
@@ -48,11 +55,52 @@ impl Editor {
         let pressed_key = Terminal::read_key()?;
         match pressed_key {
             Key::Ctrl('q') => self.should_quit = true,
+            Key::Up | Key::Down | Key::Left | Key::Right | Key::PageUp | Key::PageDown | Key::End | Key::Home => self.move_cursor(pressed_key),
             _ => (),
         }
         Ok(())
     }
 
+    fn move_cursor(&mut self, key: Key) {
+        let Position { mut y, mut x } = self.cursor_position;
+        let size = self.terminal.size();
+        let height = size.height.saturating_sub(1) as usize;
+        let width = size.width.saturating_sub(1) as usize;
+
+        match key {
+            Key::Up => y = y.saturating_sub(1),
+            Key::Down => {
+                if y < height {
+                    y = y.saturating_add(1);
+                }
+            },
+            Key::Left => x = x.saturating_sub(1),
+            Key::Right => {
+                if x < width {
+                    x = x.saturating_add(1);
+                }
+            },
+            Key::PageUp => y = 0,
+            Key::PageDown => y = height,
+            Key::Home => x = 0,
+            Key::End => x = width,
+            _ => (),
+        }
+
+        self.cursor_position = Position { x, y }
+    }
+
+    fn draw_welcome_message(&self) {
+        let mut welcome_message = format!("Hecto editor -- version {}", VERSION);
+        let width = self.terminal.size().width as usize;
+        let len = welcome_message.len();
+        let padding = width.saturating_sub(len) / 2;
+        let spaces = " ".repeat(padding.saturating_sub(1));
+        welcome_message = format!("~{}{}", spaces, welcome_message);
+        welcome_message.truncate(width);
+        println!("{}\r", welcome_message);
+    }
+
     fn draw_rows(&self) {
         let height = self.terminal.size().height;
 
@@ -60,10 +108,7 @@ impl Editor {
             Terminal::clear_current_line();
 
             if row == height / 3 {
-                let welcome_message = format!("Hecto editor -- version {}", VERSION);
-
-                let width = std::cmp::min(self.terminal.size().width as usize, welcome_message.len());
-                println!("{}\r", &welcome_message[..width]);
+                self.draw_welcome_message();
             } else {
                 println!("~\r");
             }
diff --git a/src/main.rs b/src/main.rs
index 2d0d27b..b78daea 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,6 +4,7 @@ mod terminal;
 
 use editor::Editor;
 pub use terminal::Terminal;
+pub use editor::Position;
 
 fn main() {
     Editor::default().run();
diff --git a/src/terminal.rs b/src/terminal.rs
index fb8435d..9f1b598 100644
--- a/src/terminal.rs
+++ b/src/terminal.rs
@@ -1,3 +1,4 @@
+use crate::Position;
 use std::io::{self, stdout, Write};
 use termion::event::Key;
 use termion::input::TermRead;
@@ -33,9 +34,14 @@ impl Terminal {
         print!("{}", termion::clear::All);
     }
 
-    pub fn cursor_position(x: u16, y: u16) {
-        let x = x.saturating_add(1);
-        let y = y.saturating_add(1);
+    #[allow(clippy::cast_possible_truncation)]
+    pub fn cursor_position(position: &Position) {
+        let Position{mut x, mut y} = position;
+        x = x.saturating_add(1);
+        y = y.saturating_add(1);
+
+        let x = x as u16;
+        let y = y as u16;
 
         print!("{}", termion::cursor::Goto(x, y));
     }