// Copyright 2021 Flavio Oliveira
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use crate::u2f_crate::authorization::*;
use crate::u2f_crate::messages::*;
use crate::u2f_crate::register::*;
use crate::u2f_crate::u2ferror::U2fError;
use crate::u2f_crate::util::*;

use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
use chrono::prelude::*;
use chrono::Duration;
use serde::{Deserialize, Serialize};

type Result<T> = ::std::result::Result<T, U2fError>;

#[derive(Clone)]
pub struct U2f {
    app_id: String,
}

#[derive(Deserialize, Serialize, Clone)]
#[serde(rename_all = "camelCase")]
pub struct Challenge {
    pub app_id: String,
    pub challenge: String,
    pub timestamp: String,
}

impl Challenge {
    // Not used in this plugin.
    #[allow(dead_code)]
    pub fn new() -> Self {
        Challenge {
            app_id: String::new(),
            challenge: String::new(),
            timestamp: String::new(),
        }
    }
}

impl U2f {
    // The app ID is a string used to uniquely identify an U2F app
    pub fn new(app_id: String) -> Self {
        U2f { app_id }
    }

    // Not used in this plugin.
    #[allow(dead_code)]
    pub fn generate_challenge(&self) -> Result<Challenge> {
        let utc: DateTime<Utc> = Utc::now();

        let challenge_bytes = generate_challenge(32)?;
        let challenge = Challenge {
            challenge: URL_SAFE_NO_PAD.encode(challenge_bytes),
            timestamp: format!("{:?}", utc),
            app_id: self.app_id.clone(),
        };

        Ok(challenge.clone())
    }

    // Not used in this plugin.
    #[allow(dead_code)]
    pub fn request(
        &self,
        challenge: Challenge,
        registrations: Vec<Registration>,
    ) -> Result<U2fRegisterRequest> {
        let u2f_request = U2fRegisterRequest {
            app_id: self.app_id.clone(),
            register_requests: self.register_request(challenge),
            registered_keys: self.registered_keys(registrations),
        };

        Ok(u2f_request)
    }

    fn register_request(&self, challenge: Challenge) -> Vec<RegisterRequest> {
        let mut requests: Vec<RegisterRequest> = vec![];

        let request = RegisterRequest {
            version: U2F_V2.into(),
            challenge: challenge.challenge,
        };
        requests.push(request);

        requests
    }

    pub fn register_response(
        &self,
        challenge: Challenge,
        response: RegisterResponse,
    ) -> Result<Registration> {
        if expiration(challenge.timestamp) > Duration::seconds(300) {
            return Err(U2fError::ChallengeExpired);
        }

        let registration_data: Vec<u8> = URL_SAFE_NO_PAD
            .decode(&response.registration_data[..])
            .unwrap();
        let client_data: Vec<u8> = URL_SAFE_NO_PAD.decode(&response.client_data[..]).unwrap();

        parse_registration(challenge.app_id, client_data, registration_data)
    }

    fn registered_keys(&self, registrations: Vec<Registration>) -> Vec<RegisteredKey> {
        let mut keys: Vec<RegisteredKey> = vec![];

        for registration in registrations {
            keys.push(get_registered_key(
                self.app_id.clone(),
                registration.key_handle,
            ));
        }

        keys
    }

    // Not used in this plugin.
    #[allow(dead_code)]
    pub fn sign_request(
        &self,
        challenge: Challenge,
        registrations: Vec<Registration>,
    ) -> U2fSignRequest {
        let mut keys: Vec<RegisteredKey> = vec![];

        for registration in registrations {
            keys.push(get_registered_key(
                self.app_id.clone(),
                registration.key_handle,
            ));
        }

        let signed_request = U2fSignRequest {
            app_id: self.app_id.clone(),
            challenge: URL_SAFE_NO_PAD.encode(challenge.challenge.as_bytes()),
            registered_keys: keys,
        };

        signed_request
    }

    pub fn sign_response(
        &self,
        challenge: Challenge,
        reg: Registration,
        sign_resp: SignResponse,
        counter: u32,
    ) -> Result<u32> {
        if expiration(challenge.timestamp) > Duration::seconds(300) {
            return Err(U2fError::ChallengeExpired);
        }

        if sign_resp.key_handle != get_encoded(&reg.key_handle[..]) {
            return Err(U2fError::WrongKeyHandler);
        }

        let client_data: Vec<u8> = URL_SAFE_NO_PAD
            .decode(&sign_resp.client_data[..])
            .map_err(|_e| U2fError::InvalidClientData)?;
        let sign_data: Vec<u8> = URL_SAFE_NO_PAD
            .decode(&sign_resp.signature_data[..])
            .map_err(|_e| U2fError::InvalidSignatureData)?;

        let public_key = reg.pub_key;

        let auth = parse_sign_response(
            self.app_id.clone(),
            client_data.clone(),
            public_key,
            sign_data.clone(),
        );

        match auth {
            Ok(ref res) => {
                // CounterTooLow is raised when the counter value received from the device is
                // lower than last stored counter value.
                if res.counter < counter {
                    Err(U2fError::CounterTooLow)
                } else {
                    Ok(res.counter)
                }
            }
            Err(e) => Err(e),
        }
    }
}