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/* 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 => format!(
"Constants\n{}\nFunctions\n{}\nOperators\n{}\n",
blocks(lex::CONSTANTS.keys().cloned()),
blocks(lex::FUNCTIONS.keys().cloned()),
{
let l: Vec<_> = lex::OPERATORS.keys().map(|c| c.to_string()).collect();
l.join(" ")
}
),
}
}
/// Convert iterator into strings of chunks of 8 right padded with space.
fn blocks(mut iter: impl Iterator<Item = &'static str> + ExactSizeIterator) -> String {
// calculate max width but ideally this should be calculated once
let mut max_width = 79; // capped at 79
if let Ok(s) = std::env::var("COLUMNS") {
if let Ok(n) = s.parse() {
if n < max_width {
max_width = n;
}
}
}
// 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
}
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