// Author: NithinU2802

// Octal to Hexadecimal Converter: Converts Octal to Hexadecimal

// Wikipedia References:

// 1. https://en.wikipedia.org/wiki/Octal

// 2. https://en.wikipedia.org/wiki/Hexadecimal

pub fn octal_to_hexadecimal(octal_str: &str) -> Result<String, &'static str> {

let octal_str = octal_str.trim();

if octal_str.is_empty() {

return Err("Empty string");

}

// Validate octal string

if !octal_str.chars().all(|c| ('0'..='7').contains(&c)) {

return Err("Invalid octal string");

}

// Convert octal to decimal first

let decimal = u64::from_str_radix(octal_str, 8).map_err(|_| "Conversion error")?;

// Special case for zero

if decimal == 0 {

return Ok("0".to_string());

}

// Convert decimal to hexadecimal

Ok(format!("{decimal:X}"))

}

#[cfg(test)]

mod tests {

use super::*;

#[test]

fn test_octal_to_hexadecimal() {

assert_eq!(octal_to_hexadecimal("12"), Ok("A".to_string()));

assert_eq!(octal_to_hexadecimal("377"), Ok("FF".to_string()));

assert_eq!(octal_to_hexadecimal("144"), Ok("64".to_string()));

assert_eq!(octal_to_hexadecimal("0"), Ok("0".to_string()));

}

#[test]

fn test_invalid_input() {

assert_eq!(octal_to_hexadecimal(""), Err("Empty string"));

assert_eq!(octal_to_hexadecimal("8"), Err("Invalid octal string"));

assert_eq!(octal_to_hexadecimal("9"), Err("Invalid octal string"));

assert_eq!(octal_to_hexadecimal("ABC"), Err("Invalid octal string"));

}

}