diff --git a/assets/test.rs b/assets/test.rs
new file mode 100644
index 0000000..5065550
--- /dev/null
+++ b/assets/test.rs
@@ -0,0 +1,154 @@
+use std::ops::Deref;
+
+pub mod plain;
+pub mod rust_lang;
+
+#[derive(Debug, Clone)]
+pub enum Language {
+    PlainText,
+}
+
+#[derive(Debug, Clone)]
+pub enum TokenType {
+    Whitespace { token: Token },
+    Keyword { token: Token },
+    String { token: Token },
+    Number { token: Token },
+    Identifier { token: Token },
+    Literal { token: Token },
+    Comment { token: Token },
+    Operator { token: Token },
+    Separator { token: Token },
+}
+
+impl TokenType {
+    pub fn move_to(&self, line: usize, character: usize, start: usize, end: usize) -> Self {
+        match self {
+            TokenType::Whitespace { token } => TokenType::Whitespace {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Keyword { token } => TokenType::Keyword {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::String { token } => TokenType::String {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Number { token } => TokenType::Number {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Identifier { token } => TokenType::Identifier {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Literal { token } => TokenType::Literal {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Comment { token } => TokenType::Comment {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Operator { token } => TokenType::Operator {
+                token: token.move_to(line, character, start, end),
+            },
+            TokenType::Separator { token } => TokenType::Separator {
+                token: token.move_to(line, character, start, end),
+            },
+        }
+    }
+
+    pub fn is_new_line(&self) -> bool {
+        match self {
+            TokenType::Whitespace { token } => token.text().as_str() == "\n",
+            _ => false,
+        }
+    }
+
+    pub fn is_space(&self) -> bool {
+        match self {
+            TokenType::Whitespace { token } => token.text().as_str() == " ",
+            _ => false,
+        }
+    }
+}
+
+impl Deref for TokenType {
+    type Target = Token;
+
+    fn deref(&self) -> &<Self as Deref>::Target {
+        match self {
+            TokenType::Whitespace { token } => token,
+            TokenType::Keyword { token } => token,
+            TokenType::String { token } => token,
+            TokenType::Number { token } => token,
+            TokenType::Identifier { token } => token,
+            TokenType::Literal { token } => token,
+            TokenType::Comment { token } => token,
+            TokenType::Operator { token } => token,
+            TokenType::Separator { token } => token,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Token {
+    line: usize,
+    character: usize,
+    start: usize,
+    end: usize,
+    text: String,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Span {
+    pub lo: usize,
+    pub hi: usize,
+}
+
+impl Token {
+    pub fn new(text: String, line: usize, character: usize, start: usize, end: usize) -> Self {
+        Self {
+            text,
+            line,
+            character,
+            start,
+            end,
+        }
+    }
+
+    pub fn text(&self) -> &String {
+        &self.text
+    }
+
+    pub fn line(&self) -> usize {
+        self.line.clone()
+    }
+
+    pub fn character(&self) -> usize {
+        self.character.clone()
+    }
+
+    pub fn start(&self) -> usize {
+        self.start.clone()
+    }
+
+    pub fn end(&self) -> usize {
+        self.end.clone()
+    }
+
+    pub fn move_to(&self, line: usize, character: usize, start: usize, end: usize) -> Self {
+        Self {
+            text: self.text.clone(),
+            line,
+            character,
+            start,
+            end,
+        }
+    }
+}
+
+pub fn parse(text: String, language: Language) -> Vec<TokenType> {
+    match language {
+        Language::PlainText => plain::lexer::Lexer::new(text.as_str())
+//            .inspect(|tok| println!("tok: {:?}", tok))
+            .map(|t| t.0)
+            .collect(),
+    }
+}
diff --git a/src/app/app_state.rs b/src/app/app_state.rs
index 4043fc8..9c94622 100644
--- a/src/app/app_state.rs
+++ b/src/app/app_state.rs
@@ -1,15 +1,16 @@
 use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
-use crate::ui::file::*;
-use crate::ui::file::editor_file::EditorFile;
 use crate::renderer::Renderer;
-use crate::ui::*;
 use crate::ui::caret::Caret;
+use crate::ui::file::editor_file::EditorFile;
+use crate::ui::file::*;
 use crate::ui::menu_bar::MenuBar;
+use crate::ui::*;
+use sdl2::rect::{Point, Rect};
+use sdl2::VideoSubsystem;
 use std::boxed::Box;
 use std::rc::Rc;
 use std::sync::Arc;
-use sdl2::rect::{Rect, Point};
 
 pub struct AppState {
     menu_bar: MenuBar,
@@ -55,23 +56,17 @@ impl AppState {
         if position == 0 {
             return;
         }
-        buffer.remove(position);
+        buffer.remove(position - 1);
         match file.get_character_at(position - 1) {
             Some(character) => {
                 let dest: &Rect = character.dest();
-                caret.move_caret(position - 1, Point::new(
-                    dest.x(), dest.y(),
-                ));
+                caret.move_caret(position - 1, Point::new(dest.x(), dest.y()));
             }
             _ => {
                 caret.reset_caret();
             }
         }
-        let new_file = EditorFile::new(
-            file.path(),
-            buffer,
-            self.config.clone(),
-        );
+        let new_file = EditorFile::new(file.path(), buffer, self.config.clone());
         self.files[self.current_file] = new_file;
     }
 
@@ -88,15 +83,11 @@ impl AppState {
             return;
         }
         buffer.remove(position);
-        let new_file = EditorFile::new(
-            file.path(),
-            buffer,
-            self.config.clone(),
-        );
+        let new_file = EditorFile::new(file.path(), buffer, self.config.clone());
         self.files[self.current_file] = new_file;
     }
 
-    pub fn insert_character(&mut self, character: char, renderer: &mut Renderer) {
+    pub fn insert_text(&mut self, text: String, renderer: &mut Renderer) {
         let file: &mut EditorFile = if let Some(file) = self.files.get_mut(self.current_file) {
             file
         } else {
@@ -104,30 +95,40 @@ impl AppState {
         };
         let mut buffer: String = file.buffer();
         let caret: &mut Caret = &mut self.caret;
-        let position: usize = caret.text_position();
-        buffer.insert(position, character.clone());
-        let new_file = EditorFile::new(
-            file.path(),
-            buffer,
-            self.config.clone(),
-        );
-        if let Some(rect) = get_text_character_rect(character, renderer) {
-            if let Some(current) = file.get_character_at(position) {
-                caret.move_caret(position + 1, Point::new(
-                    current.dest().x() + rect.width() as i32,
-                    current.dest().y(),
-                ));
+
+        let current = match file.get_character_at(caret.text_position()) {
+            Some(c) => c,
+            _ => return,
+        };
+        let mut pos = Point::new(current.dest().x(), current.dest().y());
+        let mut position: usize = caret.text_position();
+        for character in text.chars() {
+            buffer.insert(position, character);
+            if let Some(rect) = get_text_character_rect(character, renderer) {
+                pos = pos + Point::new(rect.width() as i32, 0);
+                position += 1;
+                caret.move_caret(position, pos.clone());
             }
         }
+
+        let new_file = EditorFile::new(file.path(), buffer, self.config.clone());
         self.files[self.current_file] = new_file;
     }
 
-    fn current_file(&mut self) -> Option<&mut EditorFile> {
+//    fn current_file(&self) -> Option<&EditorFile> {
+//        self.files.get(self.current_file)
+//    }
+
+    fn current_file_mut(&mut self) -> Option<&mut EditorFile> {
         self.files.get_mut(self.current_file)
     }
 
-    fn on_editor_clicked(&mut self, point: &Point) -> UpdateResult {
-        let current_file: &mut EditorFile = if let Some(current_file) = self.current_file() {
+    fn on_editor_clicked(
+        &mut self,
+        point: &Point,
+        video_subsystem: &mut VideoSubsystem,
+    ) -> UpdateResult {
+        let current_file: &mut EditorFile = if let Some(current_file) = self.current_file_mut() {
             current_file
         } else {
             return UpdateResult::NoOp;
@@ -135,9 +136,11 @@ impl AppState {
         if !current_file.is_left_click_target(point) {
             return UpdateResult::NoOp;
         }
+        video_subsystem.text_input().start();
         match current_file.on_left_click(point) {
             UpdateResult::MoveCaret(rect, position) => {
-                self.caret.move_caret(position, Point::new(rect.x(), rect.y()));
+                self.caret
+                    .move_caret(position, Point::new(rect.x(), rect.y()));
             }
             _ => (),
         };
@@ -149,7 +152,7 @@ impl AppState {
 impl Render for AppState {
     fn render(&mut self, canvas: &mut WindowCanvas, renderer: &mut Renderer) -> UpdateResult {
         self.menu_bar.render(canvas, renderer);
-        if let Some(file) = self.files.get_mut(self.current_file) {
+        if let Some(file) = self.current_file_mut() {
             file.render(canvas, renderer);
         }
         self.caret.render(canvas, renderer);
@@ -168,16 +171,21 @@ impl Update for AppState {
     }
 }
 
-impl ClickHandler for AppState {
-    fn on_left_click(&mut self, point: &Point) -> UpdateResult {
+impl AppState {
+    pub fn on_left_click(
+        &mut self,
+        point: &Point,
+        video_subsystem: &mut VideoSubsystem,
+    ) -> UpdateResult {
         if self.menu_bar.is_left_click_target(point) {
+            video_subsystem.text_input().stop();
             return self.menu_bar.on_left_click(point);
         }
-        self.on_editor_clicked(point);
+        self.on_editor_clicked(point, video_subsystem);
         UpdateResult::NoOp
     }
 
-    fn is_left_click_target(&self, _point: &Point) -> bool {
+    pub fn is_left_click_target(&self, _point: &Point) -> bool {
         true
     }
 }
diff --git a/src/app/keyboard_handler.rs b/src/app/keyboard_handler.rs
deleted file mode 100644
index 0c50272..0000000
--- a/src/app/keyboard_handler.rs
+++ /dev/null
@@ -1,281 +0,0 @@
-use sdl2::keyboard::{Keycode, Scancode};
-use sdl2::event::EventPollIterator;
-use sdl2::EventPump;
-
-use crate::app::UpdateResult;
-
-pub fn resolve_action(key_code: Keycode, event_pump: &mut EventPump) -> UpdateResult {
-    match key_code {
-        Keycode::Backspace => return UpdateResult::DeleteFront,
-        Keycode::Delete => return UpdateResult::DeleteBack,
-
-        Keycode::Escape => return UpdateResult::NoOp,
-
-        Keycode::Space => {
-            let character: char = ' ';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Exclaim => {
-            let character: char = '!';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Quotedbl => {
-            let character: char = '"';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Hash => {
-            let character: char = '#';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Dollar => {
-            let character: char = '$';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Percent => {
-            let character: char = '%';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Ampersand => {
-            let character: char = '&';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Quote => {
-            let character: char = '\'';
-            return UpdateResult::Input(character);
-        }
-        Keycode::LeftParen => {
-            let character: char = '{';
-            return UpdateResult::Input(character);
-        }
-        Keycode::RightParen => {
-            let character: char = '}';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Asterisk => {
-            let character: char = '*';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Plus => {
-            let character: char = '+';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Comma => {
-            let character: char = ',';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Minus => {
-            let character: char = '-';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Period => {
-            let character: char = '.';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Slash => {
-            let character: char = '/';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num0 => {
-            let character: char = '0';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num1 => {
-            let character: char = '1';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num2 => {
-            let character: char = '2';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num3 => {
-            let character: char = '3';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num4 => {
-            let character: char = '4';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num5 => {
-            let character: char = '5';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num6 => {
-            let character: char = '6';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num7 => {
-            let character: char = '7';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num8 => {
-            let character: char = '8';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Num9 => {
-            let character: char = '9';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Colon => {
-            let character: char = ':';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Semicolon => {
-            let character: char = ';';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Less => {
-            let character: char = '<';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Equals => {
-            let character: char = '=';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Greater => {
-            let character: char = '>';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Question => {
-            let character: char = '?';
-            return UpdateResult::Input(character);
-        }
-        Keycode::At => {
-            let character: char = '@';
-            return UpdateResult::Input(character);
-        }
-        Keycode::LeftBracket => {
-            let character: char = '[';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Backslash => {
-            let character: char = '\\';
-            return UpdateResult::Input(character);
-        }
-        Keycode::RightBracket => {
-            let character: char = ']';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Caret => {
-            let character: char = '^';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Underscore => {
-            let character: char = '_';
-            return UpdateResult::Input(character);
-        }
-        Keycode::Backquote => {
-            let character: char = '`';
-            return UpdateResult::Input(character);
-        }
-        Keycode::A => {
-            let character: char = if with_shift(event_pump) { 'A' } else { 'a' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::B => {
-            let character: char = if with_shift(event_pump) { 'B' } else { 'b' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::C => {
-            let character: char = if with_shift(event_pump) { 'C' } else { 'c' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::D => {
-            let character: char = if with_shift(event_pump) { 'D' } else { 'd' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::E => {
-            let character: char = if with_shift(event_pump) { 'E' } else { 'e' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::F => {
-            let character: char = if with_shift(event_pump) { 'F' } else { 'f' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::G => {
-            let character: char = if with_shift(event_pump) { 'G' } else { 'g' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::H => {
-            let character: char = if with_shift(event_pump) { 'H' } else { 'h' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::I => {
-            let character: char = if with_shift(event_pump) { 'I' } else { 'i' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::J => {
-            let character: char = if with_shift(event_pump) { 'J' } else { 'j' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::K => {
-            let character: char = if with_shift(event_pump) { 'K' } else { 'k' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::L => {
-            let character: char = if with_shift(event_pump) { 'L' } else { 'l' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::M => {
-            let character: char = if with_shift(event_pump) { 'M' } else { 'm' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::N => {
-            let character: char = if with_shift(event_pump) { 'N' } else { 'n' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::O => {
-            let character: char = if with_shift(event_pump) { 'O' } else { 'o' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::P => {
-            let character: char = if with_shift(event_pump) { 'P' } else { 'p' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::Q => {
-            let character: char = if with_shift(event_pump) { 'Q' } else { 'q' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::R => {
-            let character: char = if with_shift(event_pump) { 'R' } else { 'r' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::S => {
-            let character: char = if with_shift(event_pump) { 'S' } else { 's' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::T => {
-            let character: char = if with_shift(event_pump) { 'T' } else { 't' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::U => {
-            let character: char = if with_shift(event_pump) { 'U' } else { 'u' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::V => {
-            let character: char = if with_shift(event_pump) { 'V' } else { 'v' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::W => {
-            let character: char = if with_shift(event_pump) { 'W' } else { 'w' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::X => {
-            let character: char = if with_shift(event_pump) { 'X' } else { 'x' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::Y => {
-            let character: char = if with_shift(event_pump) { 'Y' } else { 'y' };
-            return UpdateResult::Input(character);
-        }
-        Keycode::Z => {
-            let character: char = if with_shift(event_pump) { 'Z' } else { 'z' };
-            return UpdateResult::Input(character);
-        }
-        _ => UpdateResult::NoOp
-    }
-}
-
-fn with_shift(event_pump: &mut EventPump) -> bool {
-    event_pump.keyboard_state().is_scancode_pressed(Scancode::LShift) ||
-    event_pump.keyboard_state().is_scancode_pressed(Scancode::RShift)
-}
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 57fdfb8..cc9b1ef 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -4,24 +4,23 @@ use crate::renderer::Renderer;
 use crate::themes::*;
 use crate::ui::*;
 
+use std::rc::Rc;
 use std::thread::sleep;
 use std::time::Duration;
-use std::rc::Rc;
 
-use sdl2::{Sdl, VideoSubsystem, TimerSubsystem};
 use sdl2::event::Event;
-use sdl2::EventPump;
-use sdl2::keyboard::{Keycode, Mod};
 use sdl2::hint;
+use sdl2::keyboard::{Keycode, Mod};
 use sdl2::mouse::MouseButton;
 use sdl2::pixels::Color;
 use sdl2::rect::{Point, Rect};
 use sdl2::render::Canvas;
-use sdl2::video::Window;
 use sdl2::ttf::Sdl2TtfContext;
+use sdl2::video::Window;
+use sdl2::EventPump;
+use sdl2::{Sdl, TimerSubsystem, VideoSubsystem};
 
 pub mod app_state;
-pub mod keyboard_handler;
 
 pub type WindowCanvas = Canvas<Window>;
 
@@ -34,7 +33,7 @@ pub enum UpdateResult {
     MoveCaret(Rect, usize),
     DeleteFront,
     DeleteBack,
-    Input(char)
+    Input(String),
 }
 
 pub enum Task {
@@ -70,7 +69,6 @@ impl Application {
             .unwrap();
 
         let canvas = window.into_canvas().accelerated().build().unwrap();
-//        let font_context = Rc::new(sdl2::ttf::init().unwrap());
 
         Self {
             sdl_context,
@@ -102,17 +100,18 @@ impl Application {
                 UpdateResult::NoOp => (),
                 UpdateResult::MoveCaret(_, _pos) => (),
                 UpdateResult::MouseLeftClicked(point) => {
-                    app_state.on_left_click(&point);
+                    app_state.on_left_click(&point, &mut self.video_subsystem);
                 }
                 UpdateResult::DeleteFront => {
                     app_state.delete_front();
-                },
+                }
                 UpdateResult::DeleteBack => {
                     app_state.delete_back();
-                },
-                UpdateResult::Input(text_character) => {
-                    app_state.insert_character(text_character, &mut renderer);
-                },
+                }
+                UpdateResult::Input(text) => {
+                    println!("text input: {}", text);
+                    app_state.insert_text(text, &mut renderer);
+                }
             }
             for task in self.tasks.iter() {
                 match task {
@@ -163,10 +162,15 @@ impl Application {
                     } else {
                         return UpdateResult::NoOp;
                     };
-                    return keyboard_handler::resolve_action(
-                        keycode,
-                    event_pump
-                    );
+                    match keycode {
+                        Keycode::Backspace => return UpdateResult::DeleteFront,
+                        Keycode::Delete => return UpdateResult::DeleteBack,
+                        _ => UpdateResult::NoOp,
+                    };
+                }
+                Event::TextInput { text, .. } => {
+                    println!("text input: {}", text);
+                    return UpdateResult::Input(text);
                 }
                 _ => (),
             }
diff --git a/src/lexer/mod.rs b/src/lexer/mod.rs
index e4774fa..2841fe7 100644
--- a/src/lexer/mod.rs
+++ b/src/lexer/mod.rs
@@ -1,6 +1,7 @@
 use std::ops::Deref;
 
 pub mod plain;
+pub mod rust_lang;
 
 #[derive(Debug, Clone)]
 pub enum Language {
@@ -146,7 +147,7 @@ impl Token {
 pub fn parse(text: String, language: Language) -> Vec<TokenType> {
     match language {
         Language::PlainText => plain::lexer::Lexer::new(text.as_str())
-            .inspect(|tok| println!("tok: {:?}", tok))
+            //            .inspect(|tok| println!("tok: {:?}", tok))
             .map(|t| t.0)
             .collect(),
     }
diff --git a/src/lexer/rust_lang.rs b/src/lexer/rust_lang.rs
new file mode 100644
index 0000000..46c7639
--- /dev/null
+++ b/src/lexer/rust_lang.rs
@@ -0,0 +1,84 @@
+use crate::lexer::{Token, TokenType};
+
+pub mod lexer {
+    use crate::lexer::{Span, Token, TokenType};
+    use plex::lexer;
+
+    lexer! {
+        fn next_token(text: 'a) -> (TokenType, &'a str);
+
+        r"[ \t\r\n]" => (TokenType::Whitespace {
+            token: Token::new(text.to_string(), 0, 0, 0, 0)
+        }, text),
+
+        r"(let|fn|type|struct|pub|impl|for|self|Self)" => (TokenType::Keyword {
+            token: Token::new(text.to_string(), 0, 0, 0, 0)
+        }, text),
+
+        r"[^ \t\r\n]+" => (TokenType::Identifier {
+            token: Token::new(text.to_string(), 0, 0, 0, 0)
+        }, text),
+    }
+
+    pub struct Lexer<'a> {
+        original: &'a str,
+        remaining: &'a str,
+        line: usize,
+        character: usize,
+    }
+
+    impl<'a> Lexer<'a> {
+        pub fn new(s: &'a str) -> Self {
+            Self {
+                original: s,
+                remaining: s,
+                line: 0,
+                character: 0,
+            }
+        }
+    }
+
+    impl<'a> Iterator for Lexer<'a> {
+        type Item = (TokenType, Span);
+
+        fn next(&mut self) -> Option<(TokenType, Span)> {
+            loop {
+                let tok: (TokenType, &str) =
+                    if let Some(((token_type, text), new_remaining)) = next_token(self.remaining) {
+                        self.remaining = new_remaining;
+                        if token_type.is_new_line() {
+                            self.line += 1;
+                            self.character = text.len();
+                        } else {
+                            self.character += text.len();
+                        }
+                        (token_type, text)
+                    } else {
+                        return None;
+                    };
+                match tok {
+                    (tok, text) => {
+                        let span = self.span_in(text);
+                        let token = tok.move_to(
+                            self.line.clone(),
+                            self.character - text.len(),
+                            span.lo.clone(),
+                            span.hi.clone(),
+                        );
+                        return Some((token, span));
+                    }
+                }
+            }
+        }
+    }
+
+    impl<'a> Lexer<'a> {
+        fn span_in(&self, s: &str) -> Span {
+            let lo = s.as_ptr() as usize - self.original.as_ptr() as usize;
+            Span {
+                lo,
+                hi: lo + s.len(),
+            }
+        }
+    }
+}
diff --git a/src/renderer/managers.rs b/src/renderer/managers.rs
index caeb1a3..e20bfa8 100644
--- a/src/renderer/managers.rs
+++ b/src/renderer/managers.rs
@@ -34,7 +34,7 @@ impl TextDetails {
             "text({}) size({}) {:?}",
             self.text, self.font.size, self.color
         )
-            .to_string()
+        .to_string()
     }
 }
 
@@ -72,18 +72,18 @@ pub type FontManager<'l> = ResourceManager<'l, FontDetails, Font<'l, 'static>, S
 
 #[derive(Clone)]
 pub struct ResourceManager<'l, K, R, L>
-    where
-        K: Hash + Eq,
-        L: 'l + ResourceLoader<'l, R>,
+where
+    K: Hash + Eq,
+    L: 'l + ResourceLoader<'l, R>,
 {
     loader: &'l L,
     cache: HashMap<K, Rc<R>>,
 }
 
 impl<'l, K, R, L> ResourceManager<'l, K, R, L>
-    where
-        K: Hash + Eq,
-        L: ResourceLoader<'l, R>,
+where
+    K: Hash + Eq,
+    L: ResourceLoader<'l, R>,
 {
     pub fn new(loader: &'l L) -> Self {
         Self {
@@ -93,10 +93,10 @@ impl<'l, K, R, L> ResourceManager<'l, K, R, L>
     }
 
     pub fn load<D>(&mut self, details: &D) -> Result<Rc<R>, String>
-        where
-            L: ResourceLoader<'l, R, Args=D>,
-            D: Eq + Hash + ?Sized,
-            K: Borrow<D> + for<'a> From<&'a D>,
+    where
+        L: ResourceLoader<'l, R, Args = D>,
+        D: Eq + Hash + ?Sized,
+        K: Borrow<D> + for<'a> From<&'a D>,
     {
         self.cache.get(details).cloned().map_or_else(
             || {
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index debdda6..d16dbcf 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -1,12 +1,12 @@
 use crate::app::WindowCanvas;
 use crate::config::Config;
-use crate::renderer::managers::{FontManager, TextureManager};
 use crate::renderer::managers::TextDetails;
-use std::rc::Rc;
+use crate::renderer::managers::{FontManager, TextureManager};
 use sdl2::rect::{Point, Rect};
 use sdl2::render::{Texture, TextureCreator};
 use sdl2::ttf::Sdl2TtfContext;
 use sdl2::video::WindowContext;
+use std::rc::Rc;
 
 pub mod managers;
 
diff --git a/src/themes/mod.rs b/src/themes/mod.rs
index 7681635..6819cd2 100644
--- a/src/themes/mod.rs
+++ b/src/themes/mod.rs
@@ -1,6 +1,6 @@
 use crate::config::directories::*;
 use sdl2::pixels::Color;
-use serde::ser::{Serialize, SerializeMap, Serializer, SerializeSeq};
+use serde::ser::{Serialize, SerializeMap, SerializeSeq, Serializer};
 use serde_json;
 use std::env;
 use std::fs;
diff --git a/src/ui/caret.rs b/src/ui/caret.rs
index 780d8db..e278624 100644
--- a/src/ui/caret.rs
+++ b/src/ui/caret.rs
@@ -1,12 +1,12 @@
 use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
 use crate::renderer::Renderer;
-use crate::ui::*;
 use crate::ui::text_character::TextCharacter;
-use std::rc::Rc;
+use crate::ui::*;
 use sdl2::pixels::Color;
 use sdl2::rect::{Point, Rect};
 use sdl2::render::Texture;
+use std::rc::Rc;
 
 #[derive(Clone, Debug, PartialEq)]
 enum CaretState {
@@ -14,11 +14,12 @@ enum CaretState {
     Blur,
 }
 
+#[derive(Clone, Debug, PartialEq)]
 pub struct Caret {
     pending: bool,
     text_position: usize,
     blink_delay: u8,
-    config: Rc<Config>,
+//    config: Rc<Config>,
     state: CaretState,
     dest: Rect,
     reset_position: Rect,
@@ -49,7 +50,7 @@ impl Caret {
             blur_character_color,
             pending: true,
             text_position: 0,
-            config,
+//            config,
         }
     }
 
@@ -96,10 +97,7 @@ impl Render for Caret {
             self.pending = false;
         }
         let start = Point::new(self.dest.x(), self.dest.y());
-        let end = Point::new(
-            self.dest.x(),
-            self.dest.y() + self.dest.height() as i32,
-        );
+        let end = Point::new(self.dest.x(), self.dest.y() + self.dest.height() as i32);
         let color = match self.state {
             CaretState::Bright => &self.bright_character_color,
             CaretState::Blur => &self.blur_character_color,
diff --git a/src/ui/file/editor_file.rs b/src/ui/file/editor_file.rs
index b1e87d0..c9c789e 100644
--- a/src/ui/file/editor_file.rs
+++ b/src/ui/file/editor_file.rs
@@ -1,12 +1,12 @@
-use std::rc::Rc;
 use sdl2::rect::{Point, Rect};
+use std::rc::Rc;
 
 use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
-use crate::ui::file::editor_file_section::EditorFileSection;
 use crate::renderer::Renderer;
-use crate::ui::*;
+use crate::ui::file::editor_file_section::EditorFileSection;
 use crate::ui::text_character::TextCharacter;
+use crate::ui::*;
 
 #[derive(Clone)]
 pub struct EditorFile {
@@ -14,14 +14,12 @@ pub struct EditorFile {
     sections: Vec<EditorFileSection>,
     render_position: Rect,
     buffer: String,
-    config: Rc<Config>
+    config: Rc<Config>,
 }
 
 impl EditorFile {
     pub fn new(path: String, buffer: String, config: Rc<Config>) -> Self {
-        let sections = vec![
-            EditorFileSection::new(buffer.clone(), config.clone())
-        ];
+        let sections = vec![EditorFileSection::new(buffer.clone(), config.clone())];
         let x = config.editor_left_margin();
         let y = config.editor_top_margin();
         Self {
@@ -29,7 +27,7 @@ impl EditorFile {
             sections,
             render_position: Rect::new(x, y, 0, 0),
             buffer,
-            config
+            config,
         }
     }
 
@@ -44,7 +42,7 @@ impl EditorFile {
     pub fn get_character_at(&self, index: usize) -> Option<&TextCharacter> {
         for section in self.sections.iter() {
             if let Some(text_character) = section.get_character_at(index) {
-                return Some(text_character)
+                return Some(text_character);
             }
         }
         None
diff --git a/src/ui/file/editor_file_section.rs b/src/ui/file/editor_file_section.rs
index 1e9226a..f770da3 100644
--- a/src/ui/file/editor_file_section.rs
+++ b/src/ui/file/editor_file_section.rs
@@ -1,13 +1,13 @@
-use std::rc::Rc;
 use sdl2::rect::{Point, Rect};
+use std::rc::Rc;
 
 use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
-use crate::ui::file::editor_file_token::EditorFileToken;
 use crate::lexer::Language;
 use crate::renderer::Renderer;
-use crate::ui::*;
+use crate::ui::file::editor_file_token::EditorFileToken;
 use crate::ui::text_character::TextCharacter;
+use crate::ui::*;
 
 #[derive(Clone)]
 pub struct EditorFileSection {
@@ -27,7 +27,11 @@ impl EditorFileSection {
             tokens.push(token.clone());
         }
         let language = Language::PlainText;
-        Self { tokens, language, config }
+        Self {
+            tokens,
+            language,
+            config,
+        }
     }
 
     pub fn update_positions(&mut self, current: &mut Rect) {
@@ -39,7 +43,7 @@ impl EditorFileSection {
     pub fn get_character_at(&self, index: usize) -> Option<&TextCharacter> {
         for token in self.tokens.iter() {
             if let Some(text_character) = token.get_character_at(index) {
-                return Some(text_character)
+                return Some(text_character);
             }
         }
         None
diff --git a/src/ui/file/editor_file_token.rs b/src/ui/file/editor_file_token.rs
index 74e613e..dd10b0e 100644
--- a/src/ui/file/editor_file_token.rs
+++ b/src/ui/file/editor_file_token.rs
@@ -3,19 +3,19 @@ use crate::config::Config;
 use crate::lexer::TokenType;
 use crate::renderer::managers::{FontDetails, TextDetails};
 use crate::renderer::Renderer;
-use crate::ui::*;
 use crate::ui::text_character::*;
-use std::rc::Rc;
+use crate::ui::*;
 use sdl2::pixels::Color;
 use sdl2::rect::{Point, Rect};
 use sdl2::render::Texture;
 use sdl2::ttf::Font;
+use std::rc::Rc;
 
 #[derive(Clone)]
 pub struct EditorFileToken {
     characters: Vec<TextCharacter>,
     token_type: TokenType,
-    config: Rc<Config>
+    config: Rc<Config>,
 }
 
 impl EditorFileToken {
@@ -23,7 +23,7 @@ impl EditorFileToken {
         Self {
             characters: vec![],
             token_type,
-            config
+            config,
         }
     }
 
@@ -36,7 +36,7 @@ impl EditorFileToken {
     pub fn get_character_at(&self, index: usize) -> Option<&TextCharacter> {
         for character in self.characters.iter() {
             if character.position() == index {
-                return Some(&character)
+                return Some(&character);
             }
         }
         None
@@ -61,7 +61,7 @@ impl EditorFileToken {
                 self.token_type.start() + index,
                 self.token_type.line(),
                 color.clone(),
-                    self.config.clone()
+                self.config.clone(),
             );
             text_character.update_view(renderer);
             self.characters.push(text_character);
diff --git a/src/ui/menu_bar.rs b/src/ui/menu_bar.rs
index d7aa05c..cfe6589 100644
--- a/src/ui/menu_bar.rs
+++ b/src/ui/menu_bar.rs
@@ -2,9 +2,9 @@ use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
 use crate::renderer::Renderer;
 use crate::ui::*;
-use std::rc::Rc;
 use sdl2::pixels::Color;
-use sdl2::rect::{Rect, Point};
+use sdl2::rect::{Point, Rect};
+use std::rc::Rc;
 
 pub struct MenuBar {
     background_color: Color,
diff --git a/src/ui/mod.rs b/src/ui/mod.rs
index d3a2103..512eb5a 100644
--- a/src/ui/mod.rs
+++ b/src/ui/mod.rs
@@ -2,13 +2,13 @@ use sdl2::rect::{Point, Rect};
 
 use crate::app::{UpdateResult, WindowCanvas};
 use crate::config::Config;
-use crate::renderer::Renderer;
 use crate::renderer::managers::FontDetails;
+use crate::renderer::Renderer;
 
 pub mod caret;
+pub mod file;
 pub mod menu_bar;
 pub mod text_character;
-pub mod file;
 
 pub fn is_in_rect(point: &Point, rect: &Rect) -> bool {
     let start = Point::new(rect.x(), rect.y());
diff --git a/src/ui/text_character.rs b/src/ui/text_character.rs
index 6644792..fb8b582 100644
--- a/src/ui/text_character.rs
+++ b/src/ui/text_character.rs
@@ -6,11 +6,11 @@ use crate::renderer::managers::TextDetails;
 use crate::renderer::Renderer;
 use crate::ui::*;
 
-use std::rc::Rc;
 use sdl2::pixels::Color;
-use sdl2::rect::{Rect, Point};
+use sdl2::rect::{Point, Rect};
 use sdl2::render::Texture;
 use sdl2::ttf::Font;
+use std::rc::Rc;
 
 #[derive(Clone)]
 pub struct TextCharacter {
@@ -21,11 +21,17 @@ pub struct TextCharacter {
     source: Rect,
     dest: Rect,
     color: Color,
-    config: Rc<Config>
+    config: Rc<Config>,
 }
 
 impl TextCharacter {
-    pub fn new(text_character: char, position: usize, line: usize, color: Color, config: Rc<Config>) -> Self {
+    pub fn new(
+        text_character: char,
+        position: usize,
+        line: usize,
+        color: Color,
+        config: Rc<Config>,
+    ) -> Self {
         Self {
             pending: true,
             text_character,
@@ -34,7 +40,7 @@ impl TextCharacter {
             source: Rect::new(0, 0, 0, 0),
             dest: Rect::new(0, 0, 0, 0),
             color,
-            config
+            config,
         }
     }
 
@@ -148,10 +154,7 @@ impl Update for TextCharacter {
 
 impl ClickHandler for TextCharacter {
     fn on_left_click(&mut self, _point: &Point) -> UpdateResult {
-        UpdateResult::MoveCaret(
-            self.dest().clone(),
-            self.position()
-        )
+        UpdateResult::MoveCaret(self.dest().clone(), self.position())
     }
 
     fn is_left_click_target(&self, point: &Point) -> bool {