Basic Pig Latin Translator - Rust

main.rs

use std::{
    fs::File,
    io::{prelude::*, BufReader},
};

mod pig_latin;

fn main() {
    let file = File::open("text.txt").expect("Can't open file.");
    let file_size = file.metadata().unwrap().len();
    let file_buffer = BufReader::with_capacity(file_size as usize, file);
    let mut translated = File::create("translated.txt").expect("Cannot create translation file.");

    for line in file_buffer.lines() {
        for word in line.unwrap().split_whitespace() {
            translated
                // keep formatting with `format!` so it doesn't look like garbarge
                .write_all(&format!("{} ", pig_latin::translate(word)).as_bytes())
                .ok();
        }
    }
}

pig_latin.rs

struct WordParts {
    first_lower: char,
    is_vowel: bool,
    rest_of_word: String,
    punctuation: char,
}

pub fn translate(word: &str) -> String {
    let mut word_parts = build_word_parts(word);
    word_parts.rest_of_word = word_parts.rest_of_word.replace(word_parts.punctuation, "");

    print(&word_parts)
}

fn build_word_parts(word: &str) -> WordParts {
    let ftl = first_to_lower(word);
    let rest = word[1..].to_string();
    let index = punctuation_index(&rest);

    WordParts {
        first_lower: ftl,
        is_vowel: is_vowel(&ftl),
        punctuation: punctuation_char(index, &rest),
        rest_of_word: rest,
    }
}

fn is_vowel(subject: &char) -> bool {
    ['a', 'e', 'i', 'o', 'u'].contains(subject)
}

fn punctuation_index(subject: &str) -> usize {
    match subject.find(|x: char| x.is_ascii_punctuation()) {
        Some(index) => index,
        None => usize::max_value(), // Really high number that can't be possible index
    }
}

fn punctuation_char(index: usize, subject: &str) -> char {
    if index != usize::max_value() {
        match subject.chars().nth(index) {
            Some(character) => character,
            None => ' ', // Return space to be trimmed
        }
    } else {
        ' ' // Return space to be trimmed
    }
}

fn first_to_lower(word: &str) -> char {
    String::from(&word[..1])
        .to_lowercase()
        .chars()
        .next()
        .unwrap()
}

fn print(parts: &WordParts) -> String {
    if parts.is_vowel {
        String::from(
            format!(
                "{}{}-hay{}",
                parts.first_lower, parts.rest_of_word, parts.punctuation
            )
            .trim(),
        )
    } else {
        String::from(
            format!(
                "{}-{}ay{}",
                parts.rest_of_word, parts.first_lower, parts.punctuation
            )
            .trim(),
        )
    }
}

text.txt

Both versions convey a topic; it’s pretty easy to predict that the paragraph will be about epidemiological evidence, but only the second version establishes an argumentative point and puts it in context. The paragraph doesn’t just describe the epidemiological evidence; it shows how epidemiology is telling the same story as etiology. Similarly, while Version A doesn’t relate to anything in particular, Version B immediately suggests that the prior paragraph addresses the biological pathway (i.e. etiology) of a disease and that the new paragraph will bolster the emerging hypothesis with a different kind of evidence. As a reader, it’s easy to keep track of how the paragraph about cells and chemicals and such relates to the paragraph about populations in different places.