From cdb2011efa6580865a1a658a00b5448cea93f069 Mon Sep 17 00:00:00 2001
From: Austen Adler <agadler@austenadler.com>
Date: Tue, 27 Apr 2021 00:08:10 -0400
Subject: [PATCH] Bubble more errors up for cleaner code

---
 src/calc/errors.rs     | 25 ++++++++++++++-----------
 src/calc/operations.rs |  6 ++++--
 src/main.rs            | 30 +++++++++++++++---------------
 3 files changed, 33 insertions(+), 28 deletions(-)

diff --git a/src/calc/errors.rs b/src/calc/errors.rs
index 64aefe1..37052ad 100644
--- a/src/calc/errors.rs
+++ b/src/calc/errors.rs
@@ -1,3 +1,5 @@
+use std::fmt;
+
 pub enum CalculatorError {
     ArithmeticError,
     NotEnoughStackEntries,
@@ -7,22 +9,23 @@ pub enum CalculatorError {
     NoSuchRegister,
     NoSuchMacro,
     ParseError,
+    NoSuchOperator,
 }
 
-impl CalculatorError {
-    //TODO: Use &str instead of Strings
-    pub fn message(&self) -> String {
+impl fmt::Display for CalculatorError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
-            CalculatorError::ArithmeticError => String::from("Arithmetic Error"),
-            CalculatorError::NotEnoughStackEntries => String::from("Not enough items in the stack"),
+            CalculatorError::ArithmeticError => write!(f, "Arithmetic Error"),
+            CalculatorError::NotEnoughStackEntries => write!(f, "Not enough items in the stack"),
             CalculatorError::CorruptStateChange(msg) => {
-                String::from("Corrupt state change: ") + msg
+                write!(f, "Corrupt state change: {}", msg)
             }
-            CalculatorError::EmptyHistory(msg) => String::from("No history to ") + msg,
-            CalculatorError::NoSuchConstant => String::from("No such constant"),
-            CalculatorError::NoSuchRegister => String::from("No such register"),
-            CalculatorError::NoSuchMacro => String::from("No such macro"),
-            CalculatorError::ParseError => String::from("Parse error"),
+            CalculatorError::EmptyHistory(msg) => write!(f, "No history to {}", msg),
+            CalculatorError::NoSuchOperator => write!(f, "No such operator"),
+            CalculatorError::NoSuchConstant => write!(f, "No such constant"),
+            CalculatorError::NoSuchRegister => write!(f, "No such register"),
+            CalculatorError::NoSuchMacro => write!(f, "No such macro"),
+            CalculatorError::ParseError => write!(f, "Parse error"),
         }
     }
 }
diff --git a/src/calc/operations.rs b/src/calc/operations.rs
index 4bfcca7..c64c328 100644
--- a/src/calc/operations.rs
+++ b/src/calc/operations.rs
@@ -1,3 +1,5 @@
+use super::errors::CalculatorError;
+
 pub enum CalculatorOperation {
     Add,
     Subtract,
@@ -29,7 +31,7 @@ pub enum CalculatorOperation {
 }
 
 impl CalculatorOperation {
-    pub fn from_char(key: char) -> Result<CalculatorOperation, ()> {
+    pub fn from_char(key: char) -> Result<CalculatorOperation, CalculatorError> {
         match key {
             '+' => Ok(CalculatorOperation::Add),
             '-' => Ok(CalculatorOperation::Subtract),
@@ -59,7 +61,7 @@ impl CalculatorOperation {
             'l' => Ok(CalculatorOperation::Log),
             'L' => Ok(CalculatorOperation::Ln),
             'e' => Ok(CalculatorOperation::E),
-            _ => Err(()),
+            _ => Err(CalculatorError::NoSuchOperator),
         }
     }
 
diff --git a/src/main.rs b/src/main.rs
index 4e46d9e..74cfe94 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -228,7 +228,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                 // Exit the program
                 Ok(true) => break 'outer Ok(()),
                 Ok(false) => None,
-                Err(e) => Some(e.message()),
+                Err(e) => Some(format!("{}", e)),
             };
         }
 
@@ -239,7 +239,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                         // Exit the program
                         Ok(true) => break 'outer Ok(()),
                         Ok(false) => None,
-                        Err(e) => Some(e.message()),
+                        Err(e) => Some(format!("{}", e)),
                     };
                 }
                 Event::MacroEnd => app.current_macro = None,
@@ -290,7 +290,7 @@ fn handle_key(app: &mut App, events: &Events, key: Key) -> Result<bool, Calculat
             }
             Key::Char('\n') | Key::Char(' ') => {
                 if app.input.is_empty() {
-                    calc_operation(app, '\n');
+                    calc_operation(app, '\n')?;
                 } else {
                     let mut tmp_input = app.input.clone();
                     if tmp_input.ends_with('e') {
@@ -305,7 +305,7 @@ fn handle_key(app: &mut App, events: &Events, key: Key) -> Result<bool, Calculat
                 }
             }
             Key::Right => {
-                calc_operation(app, '>');
+                calc_operation(app, '>')?;
             }
             Key::Down => {
                 if let Ok(x) = app.calculator.pop() {
@@ -319,7 +319,7 @@ fn handle_key(app: &mut App, events: &Events, key: Key) -> Result<bool, Calculat
                 app.input.clear();
             }
             Key::Char(c) => {
-                calc_operation(app, c);
+                calc_operation(app, c)?;
             }
             _ => {}
         },
@@ -365,6 +365,7 @@ fn handle_key(app: &mut App, events: &Events, key: Key) -> Result<bool, Calculat
             Key::Char(c) => {
                 if !app.input.is_empty() {
                     //TODO: A better way to do this
+                    //Can use calc_operation in the future. Already performs this check
                     if let Ok(f) = app.input.parse::<f64>() {
                         match app.calculator.push(f) {
                             Ok(()) => app.input.clear(),
@@ -386,19 +387,18 @@ fn handle_key(app: &mut App, events: &Events, key: Key) -> Result<bool, Calculat
     return Ok(false);
 }
 
-fn calc_operation(app: &mut App, c: char) {
-    if let Ok(op) = CalculatorOperation::from_char(c) {
+fn calc_operation(app: &mut App, c: char) -> Result<(), CalculatorError> {
+    let op = CalculatorOperation::from_char(c)?;
+    if !app.input.is_empty() {
         if let Ok(f) = app.input.parse::<f64>() {
-            if app.calculator.push(f).is_ok() {
-                app.input.clear();
-            }
-        }
-
-        app.error_msg = match app.calculator.op(op) {
-            Err(e) => Some(e.message()),
-            Ok(()) => None,
+            app.calculator.push(f)?;
+            app.input.clear();
+        } else {
+            return Err(CalculatorError::ParseError);
         }
     }
+
+    app.calculator.op(op)
 }
 
 struct ClippyRectangle<'a> {