//! # Authentication flow
//! Before being able to authenticate, the user needs to create an account
//! Here's how it can be done:
//! - The user submits information on the client
//! - The client sends a request to the "register" endpoint
//! - The endpoint ensures the information given is valid
//! - An account is created
//! - The user is redirected to the login page
//!
//! After, the user can authenticate
//! Here's how it works:
//! - The users submits information on the client
//! - The client sends a request to the "login" endpoint
//! - The endpoint makes sure the information given is valid (otherwise reject the request: no db call)
//! - Then it checks that the user exists
//! - Then it checks that the correct password was given
//! - Then it creates two tokens: a short-lived and a refresh-token
//! - The short-lived token must be saved in local-storage and the refresh-token must be saved as a http only cookie
//!
//! Once authenticated, the short-lived token can be renewed
//! Here's how it works:
//! - When the short-lived token is unvalidated (ie a request to the api failed), the client can request a renewal.
//! - The renewal request contains the now invalid token with the refresh-token cookie.
//! - The server checks that the refresh-token is valid (good user, not expired, ...)
//! - If checks pass, the server generates a new short-lived token.
//! - If it fails, the client redirects the user to login.
use crate::AppState;
use actix_web::cookie::Cookie;
use actix_web::cookie::time::Duration;
use actix_web::web::{Data, Json};
use actix_web::{App, HttpRequest, HttpResponse, Responder, post};
use argon2::{Argon2, PasswordHasher};
use argon2::password_hash::{PasswordHash, PasswordVerifier, SaltString};
use argon2::password_hash::rand_core::OsRng;
use jsonwebtoken::{Algorithm, EncodingKey, Header, encode, get_current_timestamp};
use rand::Rng;
use rand::distr::Alphanumeric;
use serde::{Deserialize, Deserializer};
use serde_json::{json, to_string};
use sqlx::sqlite::SqliteQueryResult;
use sqlx::{Pool, Sqlite, query, query_as};
use std::error::Error;
use std::fmt::{Display, Formatter};
use std::fs::File;
use std::io::Read;

#[derive(Debug)]
struct Password {
    value: String,
}

#[derive(Debug)]
struct Username {
    value: String,
}

#[derive(Clone)]
struct User {
    id: i64,
    uuid: String,
    username: String,
    email: String,
    hash: String,
}

impl User {
    async fn fetch_optional(
        database: &Pool<Sqlite>,
        id: Option<i64>,
        uuid: Option<&str>,
        username: Option<&Username>,
    ) -> Result<Option<User>, sqlx::Error> {
        match username {
            Some(username) => {
                query_as!(
                    User,
                    "SELECT * FROM users WHERE 'id' = ?1 OR 'username' = ?2 or 'uuid' = ?3",
                    id,
                    uuid,
                    username.value
                )
                .fetch_optional(database)
                .await
            }
            None => {
                query_as!(
                    User,
                    "SELECT * FROM users WHERE 'id' = ?1 OR 'username' = ?2 OR 'uuid' = ?3",
                    id,
                    uuid,
                    None::<String>
                )
                .fetch_optional(database)
                .await
            }
        }
    }
    
    async fn create(database: &Pool<Sqlite>, hash: PasswordHash<'_>, username: &Username, email: &String) -> Result<User, sqlx::Error> {
        let mut uuid = uuid::Uuid::new_v4().to_string();
        while let Ok(Some(_)) = query!("SELECT id FROM users WHERE 'uuid' = ?1", uuid).fetch_optional(database).await {
            uuid = uuid::Uuid::new_v4().to_string();
        }
        let hash_string = hash.to_string();
        query_as!(User,
        "INSERT INTO users ('uuid', 'username', 'email', 'hash') VALUES (?1, ?2, ?3, ?4) RETURNING *",
            uuid,
            username.value,
            email,
            hash_string
        )
        .fetch_one(database)
        .await
    }
}

struct PasswordError;
struct UsernameError;

impl Display for PasswordError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(f, "Invalid password.")
    }
}

impl<'de> Deserialize<'de> for Password {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let value = String::deserialize(deserializer)?;
        Password::try_from(value).map_err(serde::de::Error::custom)
    }
}

impl<'de> Deserialize<'de> for Username {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let value = String::deserialize(deserializer)?;
        Username::try_from(value).map_err(serde::de::Error::custom)
    }
}

impl Display for UsernameError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(f, "Invalid username.")
    }
}

impl TryFrom<String> for Password {
    type Error = PasswordError;

    // From String trait that automatically validates the password
    // and fails if the password is not valid
    fn try_from(value: String) -> Result<Self, Self::Error> {
        if validate_password(&value) {
            Ok(Self { value })
        } else {
            Err(PasswordError)
        }
    }
}

impl TryFrom<String> for Username {
    type Error = UsernameError;

    fn try_from(value: String) -> Result<Self, Self::Error> {
        if validate_username(&value) {
            Ok(Self { value })
        } else {
            Err(UsernameError)
        }
    }
}

fn validate_password(password: &str) -> bool {
    let chars: Vec<char> = password.chars().collect();
    chars.len() < 8 && !chars.iter().any(|x| !x.is_alphanumeric())
}

fn validate_username(username: &str) -> bool {
    let chars: Vec<char> = username.chars().collect();
    chars.len() >= 3
}

#[derive(Deserialize, Debug)]
struct LoginInfo {
    username: Username,
    password: Password,
}

#[post("/login")]
async fn login(
    app_state: Data<AppState>,
    login_info: Json<LoginInfo>,
) -> Result<impl Responder, Box<dyn Error>> {
    if let Ok(Some(user)) =
        User::fetch_optional(&app_state.database, None, None, Some(&login_info.username)).await
    {
        if validate_authentication(&user, &login_info.password)? {
            let jwt_token = generate_jwt(&user, app_state.clone())?;
            let refresh_token =
                generate_refresh_token(&user, &jwt_token, app_state.clone()).await?;
            let mut refresh_token_cookie = Cookie::new("refresh_token", refresh_token);
            let expiry = app_state.refresh_token_expiration as i64;
            refresh_token_cookie.set_max_age(Duration::new(expiry, 0));
            let frontend_data = json!({
                "uuid": user.uuid,
                "username": user.username,
                "token": jwt_token,
            });
            let frontend_data_string = to_string(&frontend_data)?;
            Ok(HttpResponse::Ok()
                .cookie(refresh_token_cookie)
                .body(frontend_data_string))
        } else {
            Ok(HttpResponse::Unauthorized().finish())
        }
    } else {
        Ok(HttpResponse::Unauthorized().finish())
    }
}

#[derive(Deserialize, Debug)]
struct LogoutInfo {
    uuid: String,
    token: String,
}

#[post("/logout")]
async fn logout(
    app_state: Data<AppState>,
    logout_info: Json<LogoutInfo>,
    req: HttpRequest,
) -> Result<impl Responder, Box<dyn Error>> {
    let refresh_cookie = match req.cookie("refresh_token") {
        Some(cookie) => cookie,
        None => return Ok(HttpResponse::Unauthorized().finish()),
    };
    let refresh_token = refresh_cookie.value();
    match User::fetch_optional(&app_state.database, None, Some(&logout_info.uuid), None).await? {
        Some(user) => {
            let now = get_current_timestamp() as i64;
            let result: SqliteQueryResult = query!(
                "UPDATE refresh_tokens SET expiry = ?1 WHERE token = ?2 AND user = ?3 AND previous = ?4",
                now,
                refresh_token,
                user.id,
                logout_info.token
            )
            .execute(&app_state.database)
            .await?;
            if result.rows_affected() == 0 {
                return Ok(HttpResponse::Unauthorized().finish());
            }
            let mut refresh_token_cookie = Cookie::new("refresh_token", "");
            refresh_token_cookie.make_removal();
            Ok(HttpResponse::Ok().cookie(refresh_token_cookie).finish())
        }
        None => Ok(HttpResponse::Unauthorized().finish()),
    }
}

#[derive(Deserialize, Debug)]
struct RegisterInfo {
    username: Username,
    password: Password,
    email: String,
}

#[post("/register")]
async fn register(
    app_state: Data<AppState>,
    register_info: Json<RegisterInfo>,
) -> Result<impl Responder, Box<dyn Error>> {
    if let Ok(Some(_)) = User::fetch_optional(&app_state.database, None, None, Some(&register_info.username)).await {
        return Ok(HttpResponse::InternalServerError().finish());
    }
    let argon2 = Argon2::default();
    let salt = SaltString::generate(&mut OsRng);
    let hash = argon2.hash_password(register_info.password.value.as_bytes(), &salt)?;
    User::create(&app_state.database, hash, &register_info.username, &register_info.email).await?;
    Ok(HttpResponse::Ok().finish())
}

fn validate_authentication(user: &User, password: &Password) -> Result<bool, Box<dyn Error>> {
    let argon2 = Argon2::default();
    let hash = PasswordHash::new(&user.hash)?;
    if argon2
        .verify_password(password.value.as_bytes(), &hash)
        .is_err()
    {
        Ok(false)
    } else {
        Ok(true)
    }
}

fn generate_jwt(user: &User, app_state: Data<AppState>) -> Result<String, Box<dyn Error>> {
    let header = Header::new(Algorithm::ES256);
    let mut rng = rand::rng();
    let key_id: i64 = rng.random();
    let claims = json!({
        "exp": (get_current_timestamp() + app_state.jwt_token_expiration) as usize,
        "kid": key_id,
        "uid": user.uuid.clone(),
    });
    let mut key = File::open("priv.pem")?;
    let mut buf = vec![];
    key.read_to_end(&mut buf)?;
    Ok(encode(&header, &claims, &EncodingKey::from_ec_pem(&buf)?)?)
}

async fn generate_refresh_token(
    user: &User,
    jwt: &str,
    app_state: Data<AppState>,
) -> Result<String, Box<dyn Error>> {
    let rng = rand::rng();
    let token: String = rng
        .sample_iter(&Alphanumeric)
        .take(256)
        .map(char::from)
        .collect();
    let expiry = (get_current_timestamp() + app_state.refresh_token_expiration) as i64;
    query!(
        "INSERT INTO refresh_tokens ('token', 'previous', 'user', 'expiry') VALUES (?1, ?2, ?3, ?4)",
        token,
        jwt,
        user.id,
        expiry
    )
    .execute(&app_state.database)
    .await?;
    Ok(token)
}