// iterators2.rs
// In this module, you'll learn some of unique advantages that iterators can offer.
// Step 1. Complete the `capitalize_first` function to pass the first two cases.
// Step 2. Apply the `capitalize_first` function to a vector of strings.
//         Ensure that it returns a vector of strings as well.
// Step 3. Apply the `capitalize_first` function again to a list.
//         Try to ensure it returns a single string.
// As always, there are hints if you execute `rustlings hint iterators2`!


pub fn capitalize_first(input: Vec<&str>) -> String{
    input.iter().map(|s| {
        let mut c = s.chars();
        match c.next() {
            None => String::new(),
            Some(first) => first.to_string().to_uppercase() + c.as_str(),
        }
    }).collect::<Vec<_>>().join("")
}

#[cfg(test)]
mod tests {
    use super::*;

    // Step 1.
    // Tests that verify your `capitalize_first` function implementation
    // #[test]
    // fn test_success() {
    //     assert_eq!(capitalize_first("hello"), "Hello");
    // }

    // #[test]
    // fn test_empty() {
    //     assert_eq!(capitalize_first(""), "");
    // }

    // Step 2.
    // #[test]
    // fn test_iterate_string_vec() {
    //     let words = vec!["hello", "world"];
    //     let capitalized_words: Vec<String> = capitalize_first(words);// TODO
    //     assert_eq!(capitalized_words, ["Hello", "World"]);
    // }

    #[test]
    fn test_iterate_into_string() {
        let words = vec!["hello", " ", "world"];
        let capitalized_words = capitalize_first(words);// TODO
        assert_eq!(capitalized_words, "Hello World");
    }
}
