7 files changed, 81 insertions, 36 deletions

diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..e05d4e3
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,71 @@
+/* Copyright (C) 2019  Akshay Oppiliappan <[email protected]>
+ * Refer to LICENCE for more information.
+ * */
+
+use std::iter::ExactSizeIterator;
+
+use crate::lex;
+
+#[derive(Debug)]
+pub enum CalcError {
+    Math(Math),
+    Syntax(String),
+    Parser(String),
+    Help,
+}
+
+#[derive(Debug)]
+pub enum Math {
+    DivideByZero,
+    OutOfBounds,
+    UnknownBase,
+}
+
+pub fn handler(e: CalcError) -> String {
+    match e {
+        CalcError::Math(math_err) => match math_err {
+            Math::DivideByZero => "Math Error: Divide by zero error!".to_string(),
+            Math::OutOfBounds => "Domain Error: Out of bounds!".to_string(),
+            Math::UnknownBase => "Base too large! Accepted ranges: 0 - 36".to_string(),
+        },
+        CalcError::Syntax(details) => format!("Syntax Error: {}", details),
+        CalcError::Parser(details) => format!("Parser Error: {}", details),
+        CalcError::Help => {
+            // calculate max width but ideally this should be calculated once
+            let mut max_width = 79; // capped at 79
+            if let Some((w, _)) = term_size::dimensions() {
+                if w < max_width {
+                    max_width = w;
+                }
+            }
+            let operators: Vec<_> = lex::OPERATORS.keys().map(|c| c.to_string()).collect();
+            format!(
+                "Constants\n{}\nFunctions\n{}\nOperators\n{}\n",
+                blocks(max_width, lex::CONSTANTS.keys().cloned()),
+                blocks(max_width, lex::FUNCTIONS.keys().cloned()),
+                operators.join(" ")
+            )
+        }
+    }
+}
+
+/// Convert iterator into strings of chunks of 8 right padded with space.
+fn blocks(
+    max_width: usize,
+    mut iter: impl Iterator<Item = &'static str> + ExactSizeIterator,
+) -> String {
+    // multiply by eight since we are formatting it into chunks of 8
+    let items_per_line = max_width / 8;
+    let full_bytes = (iter.len() - iter.len() % items_per_line) * 8;
+    let part_bytes = iter.len() % items_per_line * 8; // leftovers
+    let n_newlines = iter.len() / items_per_line + if part_bytes > 0 { 1 } else { 0 };
+    let mut s = String::with_capacity(full_bytes + part_bytes + n_newlines);
+    for _ in 0..n_newlines {
+        for item in iter.by_ref().take(items_per_line) {
+            s.extend(format!("{:>8}", item).chars());
+        }
+        s.push('\n');
+    }
+    debug_assert_eq!(s.capacity(), s.len()); // check capacity calculation
+    s
+}
diff --git a/src/error/mod.rs b/src/error/mod.rs
deleted file mode 100644
index ec2b555..0000000
--- a/src/error/mod.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (C) 2019  Akshay Oppiliappan <[email protected]>
- * Refer to LICENCE for more information.
- * */
-
-#[derive(Debug)]
-pub enum CalcError {
-    Math(Math),
-    Syntax(String),
-    Parser(String),
-}
-
-#[derive(Debug)]
-pub enum Math {
-    DivideByZero,
-    OutOfBounds,
-    UnknownBase,
-}
-
-pub fn handler(e: CalcError) -> String {
-    match e {
-        CalcError::Math(math_err) => match math_err {
-            Math::DivideByZero => "Math Error: Divide by zero error!".to_string(),
-            Math::OutOfBounds => "Domain Error: Out of bounds!".to_string(),
-            Math::UnknownBase => "Base too large! Accepted ranges: 0 - 36".to_string(),
-        },
-        CalcError::Syntax(details) => format!("Syntax Error: {}", details),
-        CalcError::Parser(details) => format!("Parser Error: {}", details),
-    }
-}
diff --git a/src/format/mod.rs b/src/format.rs
index 45673d7..45673d7 100644
--- a/src/format/mod.rs
+++ b/src/format.rs
diff --git a/src/lex/mod.rs b/src/lex.rs
index 3222c12..76f61a0 100644
--- a/src/lex/mod.rs
+++ b/src/lex.rs
@@ -5,9 +5,8 @@
 use lazy_static::lazy_static;
 use std::collections::HashMap;
 
-use crate::CONFIGURATION;
-
 use crate::error::{CalcError, Math};
+use crate::CONFIGURATION;
 
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct Operator {
@@ -70,14 +69,14 @@ pub enum Token {
 }
 
 lazy_static! {
-    static ref CONSTANTS: HashMap<&'static str, Token> = {
+    pub static ref CONSTANTS: HashMap<&'static str, Token> = {
         let mut m = HashMap::new();
         m.insert("e",  Token::Num(std::f64::consts::E));
         m.insert("pi", Token::Num(std::f64::consts::PI));
         m
     };
 
-    static ref FUNCTIONS: HashMap<&'static str, Token> = {
+    pub static ref FUNCTIONS: HashMap<&'static str, Token> = {
         let mut m = HashMap::new();
         m.insert("sin",   Function::token_from_fn("sin".into(),   |x| is_radian_mode(x, CONFIGURATION.radian_mode).sin()));
         m.insert("cos",   Function::token_from_fn("cos".into(),   |x| is_radian_mode(x, CONFIGURATION.radian_mode).cos()));
@@ -106,7 +105,7 @@ lazy_static! {
         m
     };
 
-    static ref OPERATORS: HashMap<char, Token> = {
+    pub static ref OPERATORS: HashMap<char, Token> = {
         let mut m = HashMap::new();
         m.insert('+', Operator::token_from_op('+', |x, y| x + y, 2, true));
         m.insert('-', Operator::token_from_op('-', |x, y| x - y, 2, true));
diff --git a/src/main.rs b/src/main.rs
index 5b7fdb4..75c33bb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -193,8 +193,10 @@ fn parse_arguments() -> Configuration {
 }
 
 pub fn eval_math_expression(input: &str, prev_ans: Option<f64>) -> Result<f64, CalcError> {
-    let input = input.trim();
-    let input = input.replace(" ", "");
+    let input = input.trim().replace(" ", "");
+    if input == "help" {
+        return Err(CalcError::Help);
+    }
     if input.is_empty() {
         return Ok(0.);
     }
diff --git a/src/parse/mod.rs b/src/parse.rs
index aa8bd4b..aa8bd4b 100644
--- a/src/parse/mod.rs
+++ b/src/parse.rs
diff --git a/src/readline/mod.rs b/src/readline.rs
index ea195ee..d689f95 100644
--- a/src/readline/mod.rs
+++ b/src/readline.rs
@@ -12,6 +12,7 @@ use directories::ProjectDirs;
 
 use regex::Regex;
 
+use crate::error::CalcError;
 use crate::eval_math_expression;
 
 pub struct RLHelper {
@@ -67,6 +68,7 @@ impl Highlighter for LineHighlighter {
                 }
                 Owned(coloured)
             }
+            Err(CalcError::Help) => Owned(line.replace("help", "\x1b[36mhelp\x1b[0m")),
             Err(_) => Owned(format!("\x1b[31m{}\x1b[0m", line)),
         }
     }