3 files changed, 81 insertions, 32 deletions

diff --git a/src/app.rs b/src/app.rs
index ffa73dd..fb6e9df 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -2,14 +2,15 @@ use crate::{
     bitmap::{positive_angle_with_x, MapPoint, Pixmap},
     brush::{Brush, CircleBrush, LineBrush},
     command::CommandBox,
-    consts::{colors::*, FONT_PATH},
+    consts::{colors::*, FONT_PATH, STDLIB_PATH},
     dither,
+    error::AppError,
     lisp::{eval, lex::Lexer, parse::Parser, prelude, EnvList},
     message::Message,
     rect,
     symmetry::Symmetry,
     undo::{ModifyRecord, OpKind, PaintRecord, UndoStack},
-    utils::{draw_text, handle_error, is_copy_event, is_paste_event},
+    utils::{draw_text, handle_error, is_copy_event, is_paste_event, load_script},
 };
 
 use std::{convert::From, fs::File, io::prelude::*, path::Path};
@@ -284,7 +285,7 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
                 Ok(val) => self.message.set_info(format!("{}", val)),
                 Err(eval_err) => self.message.set_error(format!("{}", eval_err)),
             },
-            Err(err) => self.message = handle_error(err, &lisp_expr),
+            Err(err) => self.message = handle_error(err, &lisp_expr, "repl"),
         }
         self.command_box.hist_append();
 
@@ -510,8 +511,8 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
         ttf_context: &'ctx Sdl2TtfContext,
         start_data: Option<Vec<bool>>,
         file_name: Option<&'file Path>,
-    ) -> Self {
-        let video_subsystem = context.video().unwrap();
+    ) -> Result<Self, AppError> {
+        let video_subsystem = context.video().map_err(AppError::Sdl)?;
 
         let window = video_subsystem
             .window("Pixel editor", 500, 500)
@@ -519,18 +520,16 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
             .resizable()
             .opengl()
             .build()
-            .map_err(|e| e.to_string())
-            .unwrap();
+            .map_err(|e| AppError::Sdl(e.to_string()))?;
 
         let canvas = window
             .into_canvas()
             .build()
-            .map_err(|e| e.to_string())
-            .unwrap();
+            .map_err(|e| AppError::Sdl(e.to_string()))?;
 
         let data = start_data.unwrap_or(vec![false; (width * height) as usize]);
         let pixmap = Pixmap::new_with(width, height, data);
-        Self {
+        let mut app = Self {
             active_color: true,
             brush: Brush::new(0),
             canvas,
@@ -540,7 +539,7 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
             dither_level: 16,
             file_name,
             grid: Grid::new(),
-            lisp_env: vec![prelude::new_env()],
+            lisp_env: vec![prelude::new_env().map_err(AppError::Lisp)?],
             message: Message::new().text(" "),
             mode: Mode::Draw,
             mouse: (0, 0),
@@ -550,7 +549,9 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
             ttf_context,
             undo_stack: UndoStack::new(),
             zoom: 5,
-        }
+        };
+        load_script(STDLIB_PATH, &mut app).map_err(AppError::Lisp)?;
+        Ok(app)
     }
 
     pub fn export(&self) -> Image {
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..ff25db7
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,42 @@
+use crate::lisp::error::LispError;
+
+use std::{error, fmt, io};
+
+use sdl2::ttf;
+
+#[derive(Debug)]
+pub enum AppError {
+    Lisp(LispError),
+    File(io::Error),
+    Sdl(String),
+    SdlTTF(SdlTTFError),
+}
+
+impl fmt::Display for AppError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Lisp(e) => write!(f, "lisp error: {}", e),
+            Self::File(e) => write!(f, "file error: {}", e),
+            Self::Sdl(e) => write!(f, "sdl2 error: {}", e),
+            Self::SdlTTF(e) => write!(f, "ttf error: {}", e),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum SdlTTFError {
+    Font(ttf::FontError),
+    Init(ttf::InitError),
+}
+
+impl fmt::Display for SdlTTFError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Font(e) => write!(f, "font error: {}", e),
+            Self::Init(e) => write!(f, "init error: {}", e),
+        }
+    }
+}
+
+impl error::Error for AppError {}
+impl error::Error for SdlTTFError {}
diff --git a/src/lisp/parse.rs b/src/lisp/parse.rs
index 6a8de9f..737e7ad 100644
--- a/src/lisp/parse.rs
+++ b/src/lisp/parse.rs
@@ -25,22 +25,28 @@ impl<'lex> Parser<'lex> {
         }
     }
 
-    pub fn parse_expr(&mut self) -> Result<LispExpr, LispError> {
+    pub fn parse_expr(&mut self) -> Result<LispExpr, ParseError> {
         let mut stack = Vec::new();
         let mut total_backticks = 0;
         loop {
             let (span, token) = self.next()?;
-            let r: Result<LispExpr, LispError> = match token {
+            let r: Result<LispExpr, ParseError> = match token {
                 Token::LeftParen => {
                     stack.push(Group::Parens(Vec::new()));
                     continue;
                 }
                 Token::RightParen => {
-                    let group = stack.pop().ok_or_else(
-                        || (ParseError::new(span, ParseErrorKind::UnmatchedParen)), // unmatched paren here
-                    )?;
+                    let group = stack
+                        .pop()
+                        .ok_or_else(|| (ParseError::new(span, ParseErrorKind::UnmatchedParen)))?;
                     match group {
-                        Group::Parens(v) => Ok(LispExpr::List(v)),
+                        Group::Parens(v) => {
+                            if v.len() == 0 {
+                                Ok(LispExpr::Unit)
+                            } else {
+                                Ok(LispExpr::List(v))
+                            }
+                        }
                         _ => Err(From::from(ParseError::new(
                             span,
                             ParseErrorKind::UnexpectedToken {
@@ -59,11 +65,11 @@ impl<'lex> Parser<'lex> {
                     .map(|n| LispExpr::Number(LispNumber::Integer(n)))
                     .map_err(|_| ParseError::new(span, ParseErrorKind::LiteralParseError).into()),
                 Token::String(s) => Ok(LispExpr::StringLit(s[1..s.len() - 1].into())),
-                Token::Char(s) => Ok(LispExpr::Char(s.chars().nth(2).ok_or_else(
-                    || -> LispError {
-                        ParseError::new(span, ParseErrorKind::LiteralParseError).into()
-                    },
-                )?)),
+                Token::Char(s) => {
+                    Ok(LispExpr::Char(s.chars().nth(2).ok_or_else(|| {
+                        ParseError::new(span, ParseErrorKind::LiteralParseError)
+                    })?))
+                }
                 Token::Name(n) => Ok(name_expr(n)),
                 Token::BackQuote => {
                     total_backticks += 1;
@@ -76,7 +82,7 @@ impl<'lex> Parser<'lex> {
                 }
                 Token::Comma => {
                     if total_backticks <= 0 {
-                        return Err(ParseError::new(span, ParseErrorKind::UnbalancedComma).into());
+                        return Err(ParseError::new(span, ParseErrorKind::UnbalancedComma));
                     }
                     total_backticks -= 1;
                     if let Some(&mut Group::Backticks(ref mut n)) = stack.last_mut() {
@@ -88,7 +94,7 @@ impl<'lex> Parser<'lex> {
                 }
                 Token::CommaAt => {
                     if total_backticks <= 0 {
-                        return Err(ParseError::new(span, ParseErrorKind::UnbalancedComma).into());
+                        return Err(ParseError::new(span, ParseErrorKind::UnbalancedComma));
                     }
                     total_backticks -= 1;
                     stack.push(Group::CommaAt);
@@ -109,9 +115,9 @@ impl<'lex> Parser<'lex> {
                     });
 
                     if any_paren {
-                        Err(ParseError::new(span, ParseErrorKind::MissingCloseParen).into())
+                        Err(ParseError::new(span, ParseErrorKind::MissingCloseParen))
                     } else {
-                        Err(ParseError::new(span, ParseErrorKind::UnexpectedEof).into())
+                        Err(ParseError::new(span, ParseErrorKind::UnexpectedEof))
                     }
                 }
             };
@@ -148,13 +154,13 @@ impl<'lex> Parser<'lex> {
         }
     }
 
-    fn next(&mut self) -> Result<(Span, Token<'lex>), LispError> {
+    fn next(&mut self) -> Result<(Span, Token<'lex>), ParseError> {
         let r = self.peek()?;
         self.cur_token = None;
         Ok(r)
     }
 
-    fn peek(&mut self) -> Result<(Span, Token<'lex>), LispError> {
+    fn peek(&mut self) -> Result<(Span, Token<'lex>), ParseError> {
         if let Some(tok) = self.cur_token {
             Ok(tok)
         } else {
@@ -164,7 +170,7 @@ impl<'lex> Parser<'lex> {
         }
     }
 
-    pub fn parse_single_expr(&mut self) -> Result<LispExpr, LispError> {
+    pub fn parse_single_expr(&mut self) -> Result<LispExpr, ParseError> {
         let expr = self.parse_expr()?;
 
         match self.next()? {
@@ -180,7 +186,7 @@ impl<'lex> Parser<'lex> {
         }
     }
 
-    pub fn parse_exprs(&mut self) -> Result<Vec<LispExpr>, LispError> {
+    pub fn parse_exprs(&mut self) -> Result<Vec<LispExpr>, ParseError> {
         let mut res = Vec::new();
         loop {
             match self.peek()? {
@@ -203,7 +209,7 @@ fn name_expr(input: &str) -> LispExpr {
 #[cfg(test)]
 mod tests {
     use super::*;
-    fn parse(input: &str) -> Result<LispExpr, LispError> {
+    fn parse(input: &str) -> Result<LispExpr, ParseError> {
         let mut parser = Parser::new(Lexer::new(input, 0));
 
         parser.parse_single_expr()