#[derive(Copy, Clone, Debug, PartialEq)]
pub enum StartingCase {
    Lowercase,
    Uppercase,
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum IsSarcasm {
    Yes(StartingCase),
    No,
    TooShort,
}

fn is_sarcasm(input: &str) -> IsSarcasm {
    fn iter_is_sarcasm(mut chars: impl Iterator<Item=char>) -> IsSarcasm {
        let mut chars_chunk = (&mut chars)
            .skip_while(|c| !c.is_alphabetic())
            .take_while(|c| c.is_alphabetic());

        match chars_chunk.next() {
            Some(first_char) => {
                let first_char_uppercase = first_char.is_uppercase();

                let mod_bit = match first_char_uppercase {
                    true => 1,
                    false => 0,
                };

                dbg!(first_char_uppercase);
                dbg!(mod_bit);

                let is_sarcasm = chars_chunk
                    .enumerate()
                    .all(|(i, c)| {
                        dbg!((i, c));
                        dbg!((i % 2 == 1));
                        dbg!(((i % 2 == 1) ^ first_char_uppercase));
                        dbg!((((i % 2 == 1) ^ first_char_uppercase) == c.is_lowercase()));

                        ((i % 2 == 1) ^ first_char_uppercase) == c.is_lowercase()
                    });

                let is_sarcasm = is_sarcasm && match iter_is_sarcasm(chars) {
                    IsSarcasm::Yes(_) => true,
                    IsSarcasm::TooShort => true,
                    _ => false,
                };

                match is_sarcasm {
                    true => IsSarcasm::Yes(match first_char_uppercase {
                        true => StartingCase::Uppercase,
                        false => StartingCase::Lowercase,
                    }),
                    false => IsSarcasm::No,
                }
            },
            None => IsSarcasm::TooShort,
        }
    }
    iter_is_sarcasm(input.chars())
}

fn main() {
    assert_eq!(
        crate::is_sarcasm("HeLlO! hElLo!"),
        IsSarcasm::Yes(StartingCase::Uppercase)
    );
    assert_eq!(
        crate::is_sarcasm("hElLo! HeLlO!"),
        IsSarcasm::Yes(StartingCase::Lowercase)
    );
    assert_eq!(
        crate::is_sarcasm("HeLlO! HeLlO!"),
        IsSarcasm::Yes(StartingCase::Uppercase)
    );
    assert_eq!(
        crate::is_sarcasm("hElLo! hElLo!"),
        IsSarcasm::Yes(StartingCase::Lowercase)
    );
    assert_eq!(crate::is_sarcasm(""), IsSarcasm::TooShort);
    assert_eq!(crate::is_sarcasm("Not Sarcasm"), IsSarcasm::No);
    assert_eq!(crate::is_sarcasm("NoT SaRcASM"), IsSarcasm::No);
}