use actix_web::http::header;
use actix_web::middleware::{Middleware, Response};
use actix_web::{HttpRequest, HttpResponse, Result};
use sha2::{Digest, Sha256, Sha512};

pub struct Auth;

/// HTTP Basic authentication errors
pub enum BasicAuthError {
    Base64DecodeError,
}

#[derive(Clone, Debug)]
/// HTTP Basic authentication parameters
pub struct BasicAuthParams {
    pub username: String,
    pub password: String,
}

#[derive(Clone, Debug, PartialEq)]
pub enum RequiredAuthPassword {
    Plain(String),
    Sha256(Vec<u8>),
    Sha512(Vec<u8>),
}

#[derive(Clone, Debug, PartialEq)]
/// Authentication structure to match BasicAuthParams against
pub struct RequiredAuth {
    pub username: String,
    pub password: RequiredAuthPassword,
}

/// Decode a HTTP basic auth string into a tuple of username and password.
pub fn parse_basic_auth(
    authorization_header: &header::HeaderValue,
) -> Result<BasicAuthParams, BasicAuthError> {
    let basic_removed = authorization_header.to_str().unwrap().replace("Basic ", "");
    let decoded = base64::decode(&basic_removed).map_err(|_| BasicAuthError::Base64DecodeError)?;
    let decoded_str = String::from_utf8_lossy(&decoded);
    let credentials: Vec<&str> = decoded_str.splitn(2, ':').collect();

    // If argument parsing went fine, it means the HTTP credentials string is well formatted
    // So we can safely unpack the username and the password

    Ok(BasicAuthParams {
        username: credentials[0].to_owned(),
        password: credentials[1].to_owned(),
    })
}

pub fn match_auth(basic_auth: BasicAuthParams, required_auth: &RequiredAuth) -> bool {
    if basic_auth.username != required_auth.username {
        return false;
    }

    match &required_auth.password {
        RequiredAuthPassword::Plain(ref required_password) => {
            basic_auth.password == *required_password
        }
        RequiredAuthPassword::Sha256(password_hash) => {
            compare_hash::<Sha256>(basic_auth.password, password_hash)
        }
        RequiredAuthPassword::Sha512(password_hash) => {
            compare_hash::<Sha512>(basic_auth.password, password_hash)
        }
    }
}

pub fn compare_hash<T: Digest>(password: String, hash: &Vec<u8>) -> bool {
    get_hash::<T>(password) == *hash
}

pub fn get_hash<T: Digest>(text: String) -> Vec<u8> {
    let mut hasher = T::new();
    hasher.input(text);
    hasher.result().to_vec()
}

impl Middleware<crate::MiniserveConfig> for Auth {
    fn response(
        &self,
        req: &HttpRequest<crate::MiniserveConfig>,
        resp: HttpResponse,
    ) -> Result<Response> {
        if let Some(ref required_auth) = req.state().auth {
            if let Some(auth_headers) = req.headers().get(header::AUTHORIZATION) {
                let auth_req = match parse_basic_auth(auth_headers) {
                    Ok(auth_req) => auth_req,
                    Err(BasicAuthError::Base64DecodeError) => {
                        return Ok(Response::Done(HttpResponse::BadRequest().body(format!(
                            "Error decoding basic auth base64: '{}'",
                            auth_headers.to_str().unwrap()
                        ))));
                    }
                };
                if !match_auth(auth_req, required_auth) {
                    let new_resp = HttpResponse::Unauthorized().finish();
                    return Ok(Response::Done(new_resp));
                }
            } else {
                let new_resp = HttpResponse::Unauthorized()
                    .header(
                        header::WWW_AUTHENTICATE,
                        header::HeaderValue::from_static("Basic realm=\"miniserve\""),
                    )
                    .finish();
                return Ok(Response::Done(new_resp));
            }
        }
        Ok(Response::Done(resp))
    }
}

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

    fn get_hash_func(name: &str) -> impl FnOnce(String) -> Vec<u8> {
        match name {
            "sha256" => get_hash::<Sha256>,
            "sha512" => get_hash::<Sha512>,
            _ => panic!("Invalid hash method"),
        }
    }

    #[rstest_parametrize(
        password, hash_method, hash,
        case("abc", "sha256", "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"),
        case("abc", "sha512", "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f"),
    )]
    fn test_get_hash(password: &str, hash_method: &str, hash: &str) {
        let hash_func = get_hash_func(hash_method);
        let expected = hex::decode(hash).expect("Provided hash is not a valid hex code");
        let received = hash_func(password.to_owned());
        assert_eq!(received, expected);
    }

    fn create_required_auth(username: &str, password: &str, encrypt: &str) -> RequiredAuth {
        use RequiredAuthPassword::*;

        RequiredAuth {
            username: username.to_owned(),
            password: match encrypt {
                "plain" => Plain(password.to_owned()),
                "sha256" => Sha256(get_hash::<sha2::Sha256>(password.to_owned())),
                "sha512" => Sha512(get_hash::<sha2::Sha512>(password.to_owned())),
                _ => panic!("Unknown encryption type"),
            },
        }
    }

    #[rstest_parametrize(
        should_pass, param_username, param_password, required_username, required_password, encrypt,
        case(true, "obi", "hello there", "obi", "hello there", "plain"),
        case(false, "obi", "hello there", "obi", "hi!", "plain"),
        case(true, "obi", "hello there", "obi", "hello there", "sha256"),
        case(false, "obi", "hello there", "obi", "hi!", "sha256"),
        case(true, "obi", "hello there", "obi", "hello there", "sha512"),
        case(false, "obi", "hello there", "obi", "hi!", "sha512"),
    )]
    fn test_auth(
        should_pass: bool,
        param_username: &str,
        param_password: &str,
        required_username: &str,
        required_password: &str,
        encrypt: &str,
    ) {
        assert_eq!(
            match_auth(
                BasicAuthParams {
                    username: param_username.to_owned(),
                    password: param_password.to_owned(),
                },
                &create_required_auth(required_username, required_password, encrypt),
            ),
            should_pass,
        )
    }
}