use std::{borrow::Borrow, fmt::Display, str::FromStr};

use chacha20::cipher::{generic_array::GenericArray, ArrayLength};
use rand::{distributions, Rng};
use sha3::{Digest, Sha3_256};

use crate::{error::Error, PHRASE_LENGTH, SALT_LENGTH};

#[derive(Debug, PartialEq)]
pub(crate) struct Phrase(String);
#[derive(Debug, PartialEq, Eq, Clone)]
pub(crate) struct Id(String);
#[derive(Debug, Clone, PartialEq)]
pub(crate) struct IdSalt(Vec<u8>);
#[derive(Debug, PartialEq)]
pub(crate) struct Key(Vec<u8>);
#[derive(Debug, Clone, PartialEq)]
pub(crate) struct KeySalt(Vec<u8>);
#[derive(Debug, PartialEq)]
pub(crate) struct Nonce(Vec<u8>);

impl Phrase {
    pub(crate) fn random() -> Self {
        let phrase = rand::thread_rng()
            .sample_iter(distributions::Alphanumeric)
            .take(PHRASE_LENGTH)
            .map(char::from)
            .collect::<String>();
        Self(phrase)
    }
}
impl FromStr for Phrase {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.chars().any(|x| !x.is_ascii_alphanumeric()) {
            Err(Error::PhraseInvalid)
        } else {
            Ok(Self(s.to_string()))
        }
    }
}
impl Display for Phrase {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.0.fmt(f)
    }
}

impl Id {
    pub(crate) fn from_phrase(phrase: &Phrase, salt: &IdSalt) -> Self {
        let mut hasher = Sha3_256::new();
        hasher.update(&phrase.0);
        hasher.update(&salt.0);

        let id = hex::encode(hasher.finalize());
        Self(id)
    }
    pub(crate) fn from_str(s: &str) -> Self {
        Self(s.to_string())
    }
    pub(crate) fn raw(&self) -> &str {
        &self.0
    }
}
impl Display for Id {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.0.fmt(f)
    }
}

impl IdSalt {
    pub(crate) fn random() -> Self {
        let salt = rand::thread_rng()
            .sample_iter(distributions::Standard)
            .take(SALT_LENGTH)
            .collect();
        Self(salt)
    }
    pub(crate) fn raw(&self) -> &[u8] {
        &self.0
    }
}
impl FromStr for IdSalt {
    type Err = hex::FromHexError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self(hex::decode(s)?))
    }
}

impl Key {
    pub(crate) fn from_phrase(phrase: &Phrase, salt: &KeySalt) -> Self {
        let mut hasher = Sha3_256::new();
        hasher.update(&phrase.0);
        hasher.update(&salt.0);
        Self(hasher.finalize().to_vec())
    }
}

impl<L: ArrayLength<u8>> Borrow<GenericArray<u8, L>> for Key {
    fn borrow(&self) -> &GenericArray<u8, L> {
        GenericArray::<u8, L>::from_slice(&self.0)
    }
}

impl KeySalt {
    pub(crate) fn random() -> Self {
        let salt = rand::thread_rng()
            .sample_iter(distributions::Standard)
            .take(SALT_LENGTH)
            .collect();
        Self(salt)
    }
    pub(crate) fn raw(&self) -> &[u8] {
        &self.0
    }
}
impl FromStr for KeySalt {
    type Err = hex::FromHexError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self(hex::decode(s)?))
    }
}

impl Nonce {
    pub(crate) fn random() -> Self {
        // generate a 12 byte / 96 bit nonce for chacha20 as defined in rfc7539
        let nonce = rand::thread_rng()
            .sample_iter(distributions::Standard)
            .take(12)
            .collect();
        Self(nonce)
    }
    pub(crate) fn from_hex(hex_value: &str) -> Result<Self, Error> {
        Ok(Self(hex::decode(hex_value)?))
    }
    pub(crate) fn to_hex(&self) -> String {
        hex::encode(&self.0)
    }
}

impl<L: ArrayLength<u8>> Borrow<GenericArray<u8, L>> for Nonce {
    fn borrow(&self) -> &GenericArray<u8, L> {
        GenericArray::from_slice(&self.0)
    }
}

#[cfg(test)]
mod test {
    use crate::{
        util::{Id, IdSalt, Key, KeySalt, Nonce, Phrase},
        PHRASE_LENGTH, SALT_LENGTH,
    };

    #[test]
    fn phrase() {
        assert_eq!(PHRASE_LENGTH, Phrase::random().0.len());
        assert_ne!(Phrase::random(), Phrase::random());
    }

    #[test]
    fn id() {
        let phrase = Phrase::random();
        let salt = IdSalt::random();
        let phrase2 = Phrase::random();
        let salt2 = IdSalt::random();

        assert_eq!(
            Id::from_phrase(&phrase, &salt),
            Id::from_phrase(&phrase, &salt)
        );

        assert_ne!(
            Id::from_phrase(&phrase, &salt),
            Id::from_phrase(&phrase, &salt2)
        );

        assert_ne!(
            Id::from_phrase(&phrase, &salt),
            Id::from_phrase(&phrase2, &salt)
        );
    }

    #[test]
    fn key() {
        let phrase = Phrase::random();
        let salt = KeySalt::random();
        let phrase2 = Phrase::random();
        let salt2 = KeySalt::random();

        assert_eq!(
            Key::from_phrase(&phrase, &salt),
            Key::from_phrase(&phrase, &salt)
        );

        assert_ne!(
            Key::from_phrase(&phrase, &salt),
            Key::from_phrase(&phrase, &salt2)
        );

        assert_ne!(
            Key::from_phrase(&phrase, &salt),
            Key::from_phrase(&phrase2, &salt)
        );
    }

    #[test]
    #[allow(clippy::unwrap_used)]
    fn key_id_collision() {
        let phrase = Phrase::random();
        let id_salt = IdSalt::random();
        let key_salt = KeySalt::random();

        assert_ne!(
            hex::decode(Id::from_phrase(&phrase, &id_salt).0).unwrap(),
            Key::from_phrase(&phrase, &key_salt).0
        );
    }

    #[test]
    fn id_salt() {
        assert_eq!(SALT_LENGTH, IdSalt::random().0.len());
        assert_ne!(IdSalt::random(), IdSalt::random());
    }

    #[test]
    fn key_salt() {
        assert_eq!(SALT_LENGTH, KeySalt::random().0.len());
        assert_ne!(KeySalt::random(), KeySalt::random());
    }

    #[test]
    fn nonce() {
        assert_eq!(12, Nonce::random().0.len());
        assert_ne!(Nonce::random(), Nonce::random());
    }
}