// Copyright 2020 - developers of the `grammers` project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use super::net::connect_sender;
use super::Client;
use crate::types::{LoginToken, PasswordToken, TermsOfService, User};
use crate::utils;
use grammers_crypto::two_factor_auth::{calculate_2fa, check_p_and_g};
pub use grammers_mtsender::{AuthorizationError, InvocationError};
use grammers_tl_types as tl;
use std::fmt;

/// The error type which is returned when signing in fails.
#[derive(Debug)]
#[allow(clippy::large_enum_variant)]
pub enum SignInError {
    SignUpRequired {
        terms_of_service: Option<TermsOfService>,
    },
    PasswordRequired(PasswordToken),
    InvalidCode,
    InvalidPassword,
    Other(InvocationError),
}

impl fmt::Display for SignInError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use SignInError::*;
        match self {
            SignUpRequired {
                terms_of_service: tos,
            } => write!(
                f,
                "sign in error: sign up with official client required: {:?}",
                tos
            ),
            PasswordRequired(_password) => write!(f, "2fa password required"),
            InvalidCode => write!(f, "sign in error: invalid code"),
            InvalidPassword => write!(f, "invalid password"),
            Other(e) => write!(f, "sign in error: {}", e),
        }
    }
}

impl std::error::Error for SignInError {}

/// Method implementations related with the authentication of the user into the API.
///
/// Most requests to the API require the user to have authorized their key, stored in the session,
/// before being able to use them.
impl Client {
    /// Returns `true` if the current account is authorized. Otherwise,
    /// logging in will be required before being able to invoke requests.
    ///
    /// This will likely be the first method you want to call on a connected [`Client`]. After you
    /// determine if the account is authorized or not, you will likely want to use either
    /// [`Client::bot_sign_in`] or [`Client::request_login_code`].
    ///
    /// # Examples
    ///
    /// ```
    /// # async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// if client.is_authorized().await? {
    ///     println!("Client is not authorized, you will need to sign_in!");
    /// } else {
    ///     println!("Client already authorized and ready to use!")
    /// }
    /// # Ok(())
    /// # }
    /// ```
    pub async fn is_authorized(&self) -> Result<bool, InvocationError> {
        match self.invoke(&tl::functions::updates::GetState {}).await {
            Ok(_) => Ok(true),
            Err(InvocationError::Rpc(e)) if e.code == 401 => Ok(false),
            Err(err) => Err(err),
        }
    }

    async fn complete_login(
        &self,
        auth: tl::types::auth::Authorization,
    ) -> Result<User, InvocationError> {
        // In the extremely rare case where `Err` happens, there's not much we can do.
        // `message_box` will try to correct its state as updates arrive.
        let update_state = self.invoke(&tl::functions::updates::GetState {}).await.ok();

        let user = User::from_raw(auth.user);

        let sync_state = {
            let mut state = self.0.state.write().unwrap();
            self.0
                .config
                .session
                .set_user(user.id(), state.dc_id, user.is_bot());

            state.chat_hashes.set_self_user(user.pack());
            if let Some(us) = update_state {
                state.message_box.set_state(us);
                true
            } else {
                false
            }
        };

        if sync_state {
            self.sync_update_state();
        }

        Ok(user)
    }

    /// Signs in to the bot account associated with this token.
    ///
    /// This is the method you need to call to use the client under a bot account.
    ///
    /// It is recommended to save the [`Client::session()`] on successful login, and if saving
    /// fails, it is recommended to [`Client::sign_out`]. If the session cannot be saved, then the
    /// authorization will be "lost" in the list of logged-in clients, since it is unaccessible.
    ///
    /// # Examples
    ///
    /// ```
    /// # async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// // Note: this token is obviously fake.
    /// //       Obtain your own by talking to @BotFather via a Telegram app.
    /// const TOKEN: &str = "776609994:AAFXAy5-PawQlnYywUlZ_b_GOXgarR3ah_yq";
    ///
    /// let user = match client.bot_sign_in(TOKEN).await {
    ///     Ok(user) => user,
    ///     Err(err) => {
    ///         println!("Failed to sign in as a bot :(\n{}", err);
    ///         return Err(err.into());
    ///     }
    /// };
    ///
    /// println!("Signed in as {}!", user.first_name());
    /// # Ok(())
    /// # }
    /// ```
    pub async fn bot_sign_in(&self, token: &str) -> Result<User, AuthorizationError> {
        let request = tl::functions::auth::ImportBotAuthorization {
            flags: 0,
            api_id: self.0.config.api_id,
            api_hash: self.0.config.api_hash.clone(),
            bot_auth_token: token.to_string(),
        };

        let result = match self.invoke(&request).await {
            Ok(x) => x,
            Err(InvocationError::Rpc(err)) if err.code == 303 => {
                let dc_id = err.value.unwrap() as i32;
                let (sender, request_tx) = connect_sender(dc_id, &self.0.config).await?;
                {
                    *self.0.conn.sender.lock().await = sender;
                    *self.0.conn.request_tx.write().unwrap() = request_tx;
                    let mut state = self.0.state.write().unwrap();
                    state.dc_id = dc_id;
                }
                self.invoke(&request).await?
            }
            Err(e) => return Err(e.into()),
        };

        match result {
            tl::enums::auth::Authorization::Authorization(x) => {
                self.complete_login(x).await.map_err(Into::into)
            }
            tl::enums::auth::Authorization::SignUpRequired(_) => {
                panic!("API returned SignUpRequired even though we're logging in as a bot");
            }
        }
    }

    /// Requests the login code for the account associated to the given phone
    /// number via another Telegram application or SMS.
    ///
    /// This is the method you need to call before being able to sign in to a user account.
    /// After you obtain the code and it's inside your program (e.g. ask the user to enter it
    /// via the console's standard input), you will need to [`Client::sign_in`] to complete the
    /// process.
    ///
    /// # Examples
    ///
    /// ```
    /// # async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// // Note: this phone number is obviously fake.
    /// //       The phone used here does NOT need to be the same as the one used by the developer
    /// //       to obtain the API ID and hash.
    /// const PHONE: &str = "+1 415 555 0132";
    ///
    /// if !client.is_authorized().await? {
    ///     // We're not logged in, so request the login code.
    ///     client.request_login_code(PHONE).await?;
    /// }
    /// # Ok(())
    /// # }
    /// ```
    pub async fn request_login_code(&self, phone: &str) -> Result<LoginToken, AuthorizationError> {
        let request = tl::functions::auth::SendCode {
            phone_number: phone.to_string(),
            api_id: self.0.config.api_id,
            api_hash: self.0.config.api_hash.clone(),
            settings: tl::types::CodeSettings {
                allow_flashcall: false,
                current_number: false,
                allow_app_hash: false,
                allow_missed_call: false,
                allow_firebase: false,
                logout_tokens: None,
                token: None,
                app_sandbox: None,
                unknown_number: false,
            }
            .into(),
        };

        use tl::enums::auth::SentCode as SC;

        let sent_code: tl::types::auth::SentCode = match self.invoke(&request).await {
            Ok(x) => match x {
                SC::Code(code) => code,
                SC::Success(_) => panic!("should not have logged in yet"),
            },
            Err(InvocationError::Rpc(err)) if err.code == 303 => {
                // Since we are not logged in (we're literally requesting for
                // the code to login now), there's no need to export the current
                // authorization and re-import it at a different datacenter.
                //
                // Just connect and generate a new authorization key with it
                // before trying again.
                let dc_id = err.value.unwrap() as i32;
                let (sender, request_tx) = connect_sender(dc_id, &self.0.config).await?;
                {
                    *self.0.conn.sender.lock().await = sender;
                    *self.0.conn.request_tx.write().unwrap() = request_tx;
                    let mut state = self.0.state.write().unwrap();
                    state.dc_id = dc_id;
                }
                match self.invoke(&request).await? {
                    SC::Code(code) => code,
                    SC::Success(_) => panic!("should not have logged in yet"),
                }
            }
            Err(e) => return Err(e.into()),
        };

        Ok(LoginToken {
            phone: phone.to_string(),
            phone_code_hash: sent_code.phone_code_hash,
        })
    }

    /// Signs in to the user account.
    ///
    /// You must call [`Client::request_login_code`] before using this method in order to obtain
    /// necessary login token, and also have asked the user for the login code.
    ///
    /// It is recommended to save the [`Client::session()`] on successful login, and if saving
    /// fails, it is recommended to [`Client::sign_out`]. If the session cannot be saved, then the
    /// authorization will be "lost" in the list of logged-in clients, since it is unaccessible.
    ///
    /// # Examples
    ///
    /// ```
    /// # use grammers_client::SignInError;
    ///
    ///  async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// # const PHONE: &str = "";
    /// fn ask_code_to_user() -> String {
    ///     unimplemented!()
    /// }
    ///
    /// let token = client.request_login_code(PHONE).await?;
    /// let code = ask_code_to_user();
    ///
    /// let user = match client.sign_in(&token, &code).await {
    ///     Ok(user) => user,
    ///     Err(SignInError::PasswordRequired(_token)) => panic!("Please provide a password"),
    ///     Err(SignInError::SignUpRequired { terms_of_service: tos }) => panic!("Sign up required"),
    ///     Err(err) => {
    ///         println!("Failed to sign in as a user :(\n{}", err);
    ///         return Err(err.into());
    ///     }
    /// };
    ///
    /// println!("Signed in as {}!", user.first_name());
    /// # Ok(())
    /// # }
    /// ```
    pub async fn sign_in(&self, token: &LoginToken, code: &str) -> Result<User, SignInError> {
        match self
            .invoke(&tl::functions::auth::SignIn {
                phone_number: token.phone.clone(),
                phone_code_hash: token.phone_code_hash.clone(),
                phone_code: Some(code.to_string()),
                email_verification: None,
            })
            .await
        {
            Ok(tl::enums::auth::Authorization::Authorization(x)) => {
                self.complete_login(x).await.map_err(SignInError::Other)
            }
            Ok(tl::enums::auth::Authorization::SignUpRequired(x)) => {
                Err(SignInError::SignUpRequired {
                    terms_of_service: x.terms_of_service.map(TermsOfService::from_raw),
                })
            }
            Err(err) if err.is("SESSION_PASSWORD_NEEDED") => {
                let password_token = self.get_password_information().await;
                match password_token {
                    Ok(token) => Err(SignInError::PasswordRequired(token)),
                    Err(e) => Err(SignInError::Other(e)),
                }
            }
            Err(err) if err.is("PHONE_CODE_*") => Err(SignInError::InvalidCode),
            Err(error) => Err(SignInError::Other(error)),
        }
    }

    /// Extract information needed for the two-factor authentication
    /// It's called automatically when we get SESSION_PASSWORD_NEEDED error during sign in.
    async fn get_password_information(&self) -> Result<PasswordToken, InvocationError> {
        let request = tl::functions::account::GetPassword {};

        let password: tl::types::account::Password = self.invoke(&request).await?.into();

        Ok(PasswordToken::new(password))
    }

    /// Sign in using two-factor authentication (user password).
    ///
    /// [`PasswordToken`] can be obtained from [`SignInError::PasswordRequired`] error after the
    /// [`Client::sign_in`] method fails.
    ///
    /// # Examples
    ///
    /// ```
    /// use grammers_client::SignInError;
    ///
    /// # async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// # const PHONE: &str = "";
    /// fn get_user_password(hint: &str) -> Vec<u8> {
    ///     unimplemented!()
    /// }
    ///
    /// # let token = client.request_login_code(PHONE).await?;
    /// # let code = "";
    ///
    /// // ... enter phone number, request login code ...
    ///
    /// let user = match client.sign_in(&token, &code).await {
    ///     Err(SignInError::PasswordRequired(password_token) ) => {
    ///         let mut password = get_user_password(password_token.hint().unwrap());
    ///
    ///         client
    ///             .check_password(password_token, password)
    ///             .await.unwrap()
    ///     }
    ///     Ok(user) => user,
    ///     Ok(_) => panic!("Sign in required"),
    ///     Err(err) => {
    ///         panic!("Failed to sign in as a user :(\n{err}");
    ///     }
    /// };
    /// # Ok(())
    /// # }
    /// ```
    pub async fn check_password(
        &self,
        password_token: PasswordToken,
        password: impl AsRef<[u8]>,
    ) -> Result<User, SignInError> {
        let mut password_info = password_token.password;
        let current_algo = password_info.current_algo.unwrap();
        let mut params = utils::extract_password_parameters(&current_algo);

        // Telegram sent us incorrect parameters, trying to get them again
        if !check_p_and_g(params.2, params.3) {
            password_info = self
                .get_password_information()
                .await
                .map_err(SignInError::Other)?
                .password;
            params =
                utils::extract_password_parameters(password_info.current_algo.as_ref().unwrap());
            if !check_p_and_g(params.2, params.3) {
                panic!("Failed to get correct password information from Telegram")
            }
        }

        let (salt1, salt2, p, g) = params;

        let g_b = password_info.srp_b.unwrap();
        let a: Vec<u8> = password_info.secure_random;

        let (m1, g_a) = calculate_2fa(salt1, salt2, p, g, g_b, a, password);

        let check_password = tl::functions::auth::CheckPassword {
            password: tl::enums::InputCheckPasswordSrp::Srp(tl::types::InputCheckPasswordSrp {
                srp_id: password_info.srp_id.unwrap(),
                a: g_a.to_vec(),
                m1: m1.to_vec(),
            }),
        };

        match self.invoke(&check_password).await {
            Ok(tl::enums::auth::Authorization::Authorization(x)) => {
                self.complete_login(x).await.map_err(SignInError::Other)
            }
            Ok(tl::enums::auth::Authorization::SignUpRequired(_x)) => panic!("Unexpected result"),
            Err(err) if err.is("PASSWORD_HASH_INVALID") => Err(SignInError::InvalidPassword),
            Err(error) => Err(SignInError::Other(error)),
        }
    }

    /// Signs out of the account authorized by this client's session.
    ///
    /// If the client was not logged in, this method returns false.
    ///
    /// The client is not disconnected after signing out.
    ///
    /// Note that after using this method you will have to sign in again. If all you want to do
    /// is disconnect, simply [`drop`] the [`Client`] instance.
    ///
    /// # Examples
    ///
    /// ```
    /// # async fn f(client: grammers_client::Client) -> Result<(), Box<dyn std::error::Error>> {
    /// if client.sign_out().await.is_ok() {
    ///     println!("Signed out successfully!");
    /// } else {
    ///     println!("No user was signed in, so nothing has changed...");
    /// }
    /// # Ok(())
    /// # }
    /// ```
    pub async fn sign_out(&self) -> Result<tl::enums::auth::LoggedOut, InvocationError> {
        self.invoke(&tl::functions::auth::LogOut {}).await
    }

    /// Synchronize all state to the session file and provide mutable access to it.
    ///
    /// You can use this to temporarily access the session and save it wherever you want to.
    ///
    /// Panics if the type parameter does not match the actual session type.
    pub fn session(&self) -> &grammers_session::Session {
        self.sync_update_state();
        &self.0.config.session
    }

    /// Calls [`Client::sign_out`] and disconnects.
    ///
    /// The client will be disconnected even if signing out fails.
    pub async fn sign_out_disconnect(&self) -> Result<(), InvocationError> {
        let _res = self.invoke(&tl::functions::auth::LogOut {}).await;
        panic!("disconnect now only works via dropping");
    }
}