use base64::{Engine as _, engine::general_purpose};
use std::error::Error;

fn xor_bytes(buffer: &mut Vec<u8>, xor: u8) {
    for b in buffer {
        *b = *b ^ xor
    }
}

// See:  https://stackoverflow.com/questions/41034635/how-do-i-convert-between-string-str-vecu8-and-u8
// for conversion examples (to/from str/String/Vec<u8>).

pub fn encode(text: &str, xor: u8) -> String {
    let mut temp = text.as_bytes().to_owned();
    xor_bytes(temp.as_mut(), xor);
    general_purpose::STANDARD.encode(temp)
}

pub fn decode(text: &str, xor: u8) -> Result<String, Box<dyn Error>> {
    let mut chars = general_purpose::STANDARD.decode(text)?;
    xor_bytes(chars.as_mut(), xor);
    Ok(String::from_utf8(chars)?)
}

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

    #[test]
    fn encode_test() {
        let t1 = "hello world";
        let t2 = encode(t1, 'U' as u8);
        assert_eq!(t2, "PTA5OTp1IjonOTE=");
    }

    #[test]
    fn encode_utf8_test() {
        let t1 = "🍺";
        let t2 = encode(&t1, 'U' as u8);
        assert_eq!(t2, "pcrY7w==");
    }

    #[test]
    fn decode_test() {
        let t1= "ICYiPCE2PW9vMTA2OjEw";
        let t2 = decode(&t1, 'U' as u8);
        match t2 {
            Ok(s) => assert_eq!(s, "uswitch::decode"),
            Err(err) => panic!("{}", err),
        }
    }

    #[test]
    fn decode_utf8_test() {
        let t1 = "t9f5";
        let t2 = decode(&t1, 'U' as u8);
        match t2 {
            Ok(s) => assert_eq!(s, "€"),
            Err(err) => panic!("{}", err),
        }
    }

    #[test]
    fn decode_fail_test() {
        let t1 = "yAyL3WlysPBdTEnPDs+JnWlytjv"; // Invalid base64
        let t2 = decode(&t1, 'U' as u8);
        match t2 {
            Ok(s) => panic!("Expected failure! Got '{}'", s),
            Err(_) => ()
        }
    }

    #[test]
    fn decode_fail_utf8_test() {
        let t1 = "woXChQ=="; // Invalid UTF-8
        let t2 = decode(&t1, 'U' as u8);
        match t2 {
            Ok(s) => panic!("Expected failure! Got '{}'", s),
            Err(_) => ()
        }
    }
}