//! Sign in, sign out and registration (hub spec §5.1).

use super::{Error, Page, Shell};

use crate::auth::{self, totp, Viewer};

use crate::db::{self, accounts};

use crate::throttle::{self, Key};

use crate::Shared;

use askama::Template;

use axum::extract::{Form, Query, State};

use axum::http::header;

use axum::response::{IntoResponse, Redirect, Response};

use serde::Deserialize;

#[derive(Template)]

#[template(path = "login.html")]

pub struct LoginPage {

    shell: Shell,

    error: Option<String>,

    next: String,

    /// Second step: the password was right, a one-time code is needed.

    totp_for: Option<String>,

    /// That step's proof of the password (`auth::pending_login`), so it

    /// asks only for the code.

    pending: String,

    /// Arrived from a password reset.

    reset: bool,

    /// Providers to sign in with (#106): (id, name).

    providers: Vec<(&'static str, &'static str)>,

}

#[derive(Deserialize)]

pub struct NextQuery {

    next: Option<String>,

    reset: Option<String>,

    #[serde(default)]

    error: Option<String>,

}

fn safe_next(next: Option<String>) -> String {

    match next {

        Some(n) if n.starts_with('/') && !n.starts_with("//") => n,

        _ => "/".into(),

    }

}

pub async fn login_form(State(app): State<Shared>, viewer: Viewer, Query(q): Query<NextQuery>) -> Response {

    if viewer.signed_in() {

        return Redirect::to(&safe_next(q.next)).into_response();

    }

    let reset = q.reset.is_some();

    let providers = super::signin::buttons(&app).await;

    Page(LoginPage {

        shell: Shell::new(&app, "/login", &viewer),

        error: q.error,

        next: safe_next(q.next),

        totp_for: None,

        pending: String::new(),

        reset,

        providers,

    })

    .into_response()

}

#[derive(Deserialize)]

pub struct LoginForm {

    username: String,

    #[serde(default)]

    password: String,

    /// The code step's proof of the password (`auth::pending_login`).

    #[serde(default)]

    pending: String,

    #[serde(default)]

    code: String,

    #[serde(default)]

    next: String,

}

pub async fn login(

    State(app): State<Shared>,

    viewer: Viewer,

    headers: axum::http::HeaderMap,

    extensions: axum::http::Extensions,

    Form(f): Form<LoginForm>,

) -> Result<Response, Error> {

    let shell = Shell::new(&app, "/login", &viewer);

    let next = safe_next(Some(f.next.clone()));

    let username = f.username.trim().to_string();

    let account = accounts::account_by_name(&app.db, &username).await.map_err(|e| Error::from_db(shell.clone(), e))?;

    // The code step carries proof of the password, good for a few minutes;

    // a fresh one goes with each retry of the code.

    let now_ms = db::now_ms();

    let proven = !f.pending.is_empty()

        && account.as_ref().is_some_and(|a| auth::pending_login_ok(&app.cookie_key, &a.username, &a.session_salt, &f.pending, now_ms));

    let pending = account

        .as_ref()

        .map(|a| auth::pending_login(&app.cookie_key, &a.username, &a.session_salt, now_ms + PENDING_LOGIN_MS))

        .unwrap_or_default();

    let fail = |msg: &str, totp_for: Option<String>| {

        Page(LoginPage {

            shell: shell.clone(),

            error: Some(msg.into()),

            next: next.clone(),

            totp_for,

            pending: pending.clone(),

            reset: false,

            providers: vec![],

        })

        .into_response()

    };

    // Guessing is slowed per account and per address (oxygenhub#221),

    // before the password is even looked at.

    let addr = crate::api::client_addr(&app, &headers, &extensions);

    let keys = [Key::account("login", &username), Key::address("login", &addr)];

    if let Some(wait) = app.throttle.lock().unwrap().wait(&keys, now_ms) {

        return Ok(fail(&throttle::message(wait), proven.then(|| username.clone())));

    }

    let failed = |app: &Shared| {

        let wait = app.throttle.lock().unwrap().failed(&keys, now_ms);

        let (app, username, addr) = (app.clone(), username.clone(), addr.clone());

        async move {

            if let Some(wait) = wait {

                let detail = format!("from {} for {}s", if addr.is_empty() { "an unknown address" } else { &addr }, wait / 1000);

                accounts::audit(&app.db, None, "login.throttled", &username, &detail).await.ok();

            }

        }

    };

    if !f.pending.is_empty() && !proven {

        return Ok(fail("That took too long: sign in again.", None));

    }

    let Some(account) = account.filter(|a| proven || auth::verify_password(&a.password_hash, &f.password)) else {

        accounts::audit(&app.db, None, "login.failed", &username, "").await.ok();

        failed(&app).await;

        return Ok(fail("Wrong username or password.", None));

    };

    if account.banned {

        return Ok(fail("This account is banned.", None));

    }

    if account.disabled {

        accounts::audit(&app.db, None, "login.disabled", &username, "").await.ok();

        return Ok(fail("Your account has been disabled. Contact the hub's administrator.", None));

    }

    if let Some(secret) = &account.totp_secret {

        if f.code.trim().is_empty() {

            return Ok(fail("Enter the code from your authenticator app.", Some(username)));

        }

        let now = (db::now_ms() / 1000) as u64;

        if !totp::verify(secret, &f.code, now) {

            match totp::use_recovery_code(&account.recovery_codes, &f.code) {

                Some(rest) => {

                    accounts::set_totp(&app.db, account.id, Some(secret), &rest).await.map_err(|e| Error::from_db(shell.clone(), e))?

                }

                None => {

                    accounts::audit(&app.db, Some(&account), "login.totp_failed", &username, "").await.ok();

                    failed(&app).await;

                    return Ok(fail("That code is not right.", Some(username)));

                }

            }

        }

    }

    app.throttle.lock().unwrap().cleared(&keys[0]);

    accounts::audit(&app.db, Some(&account), "login", &username, "").await.ok();

    Ok(signed_in(&app, &account, &next).await)

}

/// How long the code step of a sign-in may take after the password.

const PENDING_LOGIN_MS: i64 = 5 * 60 * 1000;

/// A redirect that sets the session cookie: a new session each time, so

/// signing in (after the code, with two-factor) always rotates it

/// (oxygenhub#223).

pub async fn signed_in(app: &Shared, account: &accounts::Account, to: &str) -> Response {

    let value = auth::new_session_id();

    if let Err(e) = db::sessions::create(&app.db, account.id, &auth::token_hash(&value), &account.session_salt).await {

        tracing::warn!("session for {}: {e}", account.username);

        return (axum::http::StatusCode::SERVICE_UNAVAILABLE, "Signing in failed for a moment: try again.").into_response();

    }

    let secure = if app.config.base_url().starts_with("https://") { "; Secure" } else { "" };

    let cookie = format!("{}={value}; Path=/; HttpOnly; SameSite=Lax; Max-Age=2592000{secure}", auth::SESSION_COOKIE);

    ([(header::SET_COOKIE, cookie)], Redirect::to(to)).into_response()

}

#[derive(Deserialize)]

pub struct CsrfForm {

    #[serde(rename = "_csrf")]

    pub csrf: String,

}

pub async fn logout(State(app): State<Shared>, viewer: Viewer, Form(f): Form<CsrfForm>) -> Response {

    if !viewer.csrf_ok(&f.csrf) {

        return Redirect::to("/").into_response();

    }

    if let Some(v) = &viewer.0 {

        db::sessions::end_hash(&app.db, &auth::token_hash(&v.session)).await.ok();

        accounts::audit(&app.db, Some(&v.account), "logout", &v.account.username, "").await.ok();

    }

    let secure = if app.config.base_url().starts_with("https://") { "; Secure" } else { "" };

    let cookie = format!("{}=; Path=/; HttpOnly; SameSite=Lax; Max-Age=0{secure}", auth::SESSION_COOKIE);

    ([(header::SET_COOKIE, cookie)], Redirect::to("/")).into_response()

}

#[derive(Template)]

#[template(path = "register.html")]

pub struct RegisterPage {

    shell: Shell,

    error: Option<String>,

    mode: String,

    first: bool,

    invite: String,

    /// Providers to sign up with, when registration is open (#213) or

    /// the page has a usable invitation (oxygenhub#214).

    providers: Vec<(&'static str, &'static str)>,

    /// What the provider buttons carry: `?invite=CODE`, or nothing.

    provider_query: String,

}

/// The registration mode: the settings table overrides `hub.toml`.

pub async fn registration_mode(app: &Shared) -> String {

    accounts::setting(&app.db, "registration_mode").await.ok().flatten().unwrap_or_else(|| app.config.registration.mode.clone())

}

#[derive(Deserialize)]

pub struct InviteQuery {

    invite: Option<String>,

}

pub async fn register_form(State(app): State<Shared>, viewer: Viewer, Query(q): Query<InviteQuery>) -> Result<Response, Error> {

    if viewer.signed_in() {

        return Ok(Redirect::to("/").into_response());

    }

    let shell = Shell::new(&app, "/register", &viewer);

    let first = accounts::account_count(&app.db).await.map_err(|e| Error::from_db(shell.clone(), e))? == 0;

    let mode = registration_mode(&app).await;

    let invite = q.invite.unwrap_or_default().trim().to_string();

    let usable_invite = mode == "invite"

        && super::signin::invite_code_ok(&invite)

        && accounts::invitation_unused(&app.db, &invite).await.map_err(|e| Error::from_db(shell.clone(), e))?;

    let providers = if !first && (mode == "open" || usable_invite) { super::signin::buttons(&app).await } else { vec![] };

    let provider_query = if usable_invite { format!("?invite={invite}") } else { String::new() };

    Ok(Page(RegisterPage { shell, error: None, mode, first, invite, providers, provider_query }).into_response())

}

#[derive(Deserialize)]

pub struct RegisterForm {

    username: String,

    email: String,

    password: String,

    #[serde(default)]

    invite: String,

}

pub async fn register(State(app): State<Shared>, viewer: Viewer, Form(f): Form<RegisterForm>) -> Result<Response, Error> {

    let shell = Shell::new(&app, "/register", &viewer);

    let first = accounts::account_count(&app.db).await.map_err(|e| Error::from_db(shell.clone(), e))? == 0;

    let mode = registration_mode(&app).await;

    let fail = |msg: &str| {

        Page(RegisterPage {

            shell: shell.clone(),

            error: Some(msg.into()),

            mode: mode.clone(),

            first,

            invite: f.invite.clone(),

            providers: vec![],

            provider_query: String::new(),

        })

        .into_response()

    };

    let username = f.username.trim().to_string();

    if !crate::repos::names::valid_owner(&username) {

        return Ok(fail("A username is letters, digits, dots, dashes and underscores, and is not a reserved word."));

    }

    if let Err(e) = auth::password_ok(&f.password) {

        return Ok(fail(e));

    }

    if !first {

        match mode.as_str() {

            "open" => {}

            "invite" => {

                let ok = !f.invite.trim().is_empty()

                    && accounts::invitation_unused(&app.db, f.invite.trim()).await.map_err(|e| Error::from_db(shell.clone(), e))?;

                if !ok {

                    return Ok(fail("Registration needs a valid invitation code."));

                }

            }

            _ => return Ok(fail("Registration is closed.")),

        }

    }

    if accounts::account_by_name(&app.db, &username).await.map_err(|e| Error::from_db(shell.clone(), e))?.is_some()

        || accounts::org_by_name(&app.db, &username).await.map_err(|e| Error::from_db(shell.clone(), e))?.is_some()

        || accounts::username_retired(&app.db, &username).await.map_err(|e| Error::from_db(shell.clone(), e))?

    {

        return Ok(fail("That name is taken."));

    }

    let hash = auth::hash_password(&f.password).map_err(|e| Error::bad(shell.clone(), e.to_string()))?;

    let account = accounts::create_account(&app.db, &username, f.email.trim(), &hash, &auth::random_hex(16), first)

        .await

        .map_err(|e| Error::from_db(shell.clone(), e))?;

    if !first && mode == "invite" {

        accounts::use_invitation(&app.db, f.invite.trim(), account.id).await.ok();

    }

    accounts::audit(&app.db, Some(&account), "register", &username, if first { "first account: administrator" } else { "" }).await.ok();

    if let Err(e) = super::recovery::send_verification(&app, &account).await {

        tracing::info!("verification for {username}: {e}");

    }

    // The site's administrators hear of each new account (oxygenhub#183).

    if !first {

        let admins: Vec<(i64, crate::db::notify::Reason)> = accounts::accounts(&app.db)

            .await

            .unwrap_or_default()

            .into_iter()

            .filter(|a| a.is_admin)

            .map(|a| (a.id, crate::db::notify::Reason::Participating))

            .collect();

        let title = format!("New account: {username} signed up on {}", app.config.site.name);

        crate::notify::tell(&app, "account.registered", &title, &format!("/{username}"), &username, None, admins).await;

    }

    Ok(signed_in(&app, &account, "/").await)

}