1 files changed, 79 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..bacaef9
--- /dev/null
+++ b/src/main.rs
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+use std::io::stdin;
+use std::io::BufRead;
+use std::io::BufReader;
+
+/// Words that will not be capitalized unless they are at the start or end of a title.
+static EXCEPTIONS: [&str; 36] = [
+    "above", "across", "against", "at", "between", "by", "along", "among", "down", "in", "around",
+    "of", "off", "on", "to", "with", "before", "behind", "below", "beneath", "down", "from",
+    "near", "toward", "upon", "within", "a", "an", "the", "and", "but", "for", "or", "nor", "yet",
+    "so",
+];
+
+/// Here are the rules:
+///
+/// - Every line is its own title. No multi-line titles.
+/// - All words are capitalized, except...
+/// - Words are not capitalized if they are EXCEPTIONS, unless...
+/// - Words are either the first or the last word.
+fn main() {
+    for line in BufReader::new(stdin()).lines() {
+        println!("{}", capitalize_line(&line.expect("IO error")));
+    }
+}
+
+/// Capitalizes a single line (title) based on placement and exceptions.
+fn capitalize_line(line: &str) -> String {
+    let mut line = line.split_whitespace().map(str::to_lowercase).peekable();
+    let mut result: Vec<String> = Vec::new();
+
+    // handle first word
+    let first = line.next().expect("No words on line");
+    result.push(capitalize_word(&first));
+
+    while let Some(word) = line.next() {
+        let word = if line.peek().is_none() || !EXCEPTIONS.contains(&word.as_str()) {
+            // capitalize words that are last or aren't in exceptions
+            capitalize_word(&word)
+        } else {
+            // ignore the rest
+            word
+        };
+
+        result.push(word);
+    }
+
+    // join words into title
+    result.join(" ")
+}
+
+/// Capitalizes a single word.
+fn capitalize_word(word: &str) -> String {
+    let mut chars = word.chars();
+    let first = chars.next().unwrap();
+    format!("{}{}", first.to_uppercase(), chars.collect::<String>())
+}
+
+#[cfg(test)]
+mod tests {
+    // Note this useful idiom: importing names from outer (for mod tests) scope.
+    use super::*;
+
+    #[test]
+    fn test_capitalize_word() {
+        assert_eq!(capitalize_word("word"), String::from("Word"));
+        assert_eq!(capitalize_word("as"), String::from("As"));
+    }
+
+    #[test]
+    fn test_capitalize_line() {
+        assert_eq!(
+            capitalize_line("this is a test"),
+            String::from("This Is a Test")
+        );
+        assert_eq!(
+            capitalize_line("similEs: lIke Or As"),
+            String::from("Similes: Like or As")
+        );
+    }
+}