//! The server driven through its router in-process: sign-in end to end, the
//! library's compare-and-swap, and device revocation.

use axum::body::Body;
use axum::http::{header, Request, Response, StatusCode};
use axum::Router;
use http_body_util::BodyExt;
use mtgc_server::auth::local::hash_password;
use mtgc_server::auth::pkce_challenge;
use mtgc_server::{db, router, AppState, Config};
use serde_json::{json, Value};
use tower::ServiceExt;

const VERIFIER: &str = "a-perfectly-good-pkce-verifier-that-is-long-enough-0123456789";
const REDIRECT: &str = "http://127.0.0.1:43210/callback";

struct Server {
    state: AppState,
}

impl Server {
    fn new(vars: &[(&str, &str)]) -> Self {
        let mut all = vec![("MTGC_PUBLIC_URL", "https://mtgc.example")];
        all.extend_from_slice(vars);
        let config = Config::from_lookup(|k| {
            all.iter().find(|(name, _)| *name == k).map(|(_, v)| v.to_string())
        })
        .unwrap();
        let state = AppState::new(config, db::open_in_memory().unwrap()).unwrap();
        Self { state }
    }

    fn local() -> Self {
        let s = Self::new(&[]);
        s.add_user("alice", "correct horse battery");
        s
    }

    fn add_user(&self, name: &str, password: &str) {
        let hash = hash_password(password).unwrap();
        db::create_local_user(&self.state.db(), name, name, &hash).unwrap();
    }

    fn app(&self) -> Router {
        router(self.state.clone())
    }

    async fn send(&self, req: Request<Body>) -> Response<Body> {
        self.app().oneshot(req).await.unwrap()
    }

    /// Open the sign-in page as the app would. Returns the pending id (from
    /// the cookie that binds it to this "browser") and the page.
    async fn start(&self) -> (String, Response<Body>) {
        let uri = format!(
            "/auth/start?redirect_uri={}&code_challenge={}&code_challenge_method=S256&state=app-state&device_name=Test%20phone",
            urlencode(REDIRECT),
            pkce_challenge(VERIFIER),
        );
        let resp = self.send(get(&uri)).await;
        let cookie = resp
            .headers()
            .get(header::SET_COOKIE)
            .expect("the sign-in should be bound to the browser")
            .to_str()
            .unwrap()
            .to_string();
        let pending = cookie
            .split(';')
            .next()
            .unwrap()
            .strip_prefix("mtgc_login=")
            .unwrap()
            .to_string();
        (pending, resp)
    }

    async fn submit_password(&self, pending: &str, cookie: Option<&str>, user: &str, pw: &str) -> String {
        let body = format!(
            "pending={}&username={}&password={}",
            urlencode(pending),
            urlencode(user),
            urlencode(pw)
        );
        let mut req = Request::post("/auth/password")
            .header(header::CONTENT_TYPE, "application/x-www-form-urlencoded");
        if let Some(c) = cookie {
            req = req.header(header::COOKIE, format!("mtgc_login={c}"));
        }
        text(self.send(req.body(Body::from(body)).unwrap()).await).await
    }

    /// Sign in with a password and return the code the app would receive.
    async fn code_for(&self, user: &str, pw: &str) -> String {
        let (pending, _) = self.start().await;
        let page = self.submit_password(&pending, Some(&pending), user, pw).await;
        code_from(&page).unwrap_or_else(|| panic!("no code in:\n{page}"))
    }

    async fn redeem(&self, code: &str, verifier: &str) -> Response<Body> {
        self.send(post_json("/auth/token", json!({ "code": code, "code_verifier": verifier }), None))
            .await
    }

    async fn sign_in(&self, user: &str, pw: &str) -> String {
        let code = self.code_for(user, pw).await;
        let resp = self.redeem(&code, VERIFIER).await;
        assert_eq!(resp.status(), StatusCode::OK);
        body_json(resp).await["token"].as_str().unwrap().to_string()
    }

    async fn get_library(&self, token: &str) -> Response<Body> {
        self.send(
            Request::get("/api/library")
                .header(header::AUTHORIZATION, format!("Bearer {token}"))
                .body(Body::empty())
                .unwrap(),
        )
        .await
    }

    async fn put_library(&self, token: &str, if_match: Option<&str>, doc: Value) -> Response<Body> {
        let mut req = Request::put("/api/library")
            .header(header::AUTHORIZATION, format!("Bearer {token}"))
            .header(header::CONTENT_TYPE, "application/json");
        if let Some(v) = if_match {
            req = req.header(header::IF_MATCH, v);
        }
        self.send(req.body(Body::from(doc.to_string())).unwrap()).await
    }
}

fn get(uri: &str) -> Request<Body> {
    Request::get(uri).body(Body::empty()).unwrap()
}

fn post_json(uri: &str, body: Value, token: Option<&str>) -> Request<Body> {
    let mut req = Request::post(uri).header(header::CONTENT_TYPE, "application/json");
    if let Some(t) = token {
        req = req.header(header::AUTHORIZATION, format!("Bearer {t}"));
    }
    req.body(Body::from(body.to_string())).unwrap()
}

async fn text(resp: Response<Body>) -> String {
    String::from_utf8(resp.into_body().collect().await.unwrap().to_bytes().to_vec()).unwrap()
}

async fn body_json(resp: Response<Body>) -> Value {
    serde_json::from_str(&text(resp).await).unwrap()
}

fn urlencode(s: &str) -> String {
    url::form_urlencoded::byte_serialize(s.as_bytes()).collect()
}

/// The code from the "returning to the app" page's link.
fn code_from(page: &str) -> Option<String> {
    let start = page.find(r#"href=""#)? + 6;
    let href = &page[start..start + page[start..].find('"')?];
    let href = href.replace("&amp;", "&");
    let u = url::Url::parse(&href).ok()?;
    assert!(href.starts_with(REDIRECT), "code must go to the app: {href}");
    assert_eq!(
        u.query_pairs().find(|(k, _)| k == "state").map(|(_, v)| v.into_owned()).as_deref(),
        Some("app-state"),
        "the app's state must come back with the code"
    );
    u.query_pairs().find(|(k, _)| k == "code").map(|(_, v)| v.into_owned())
}

fn library(cards: &[(&str, i64)]) -> Value {
    let cards: serde_json::Map<String, Value> =
        cards.iter().map(|(id, q)| (id.to_string(), json!({ "quantity": q }))).collect();
    json!({ "version": 1, "cards": cards, "decks": {} })
}

// --- sign-in ------------------------------------------------------------------

#[tokio::test]
async fn a_password_sign_in_yields_a_working_device_token() {
    let s = Server::local();
    let token = s.sign_in("alice", "correct horse battery").await;

    let resp = s.get_library(&token).await;
    assert_eq!(resp.status(), StatusCode::OK);
    let body = body_json(resp).await;
    assert_eq!(body["version"], 0, "a new account starts empty");
    assert_eq!(body["doc"]["cards"], json!({}));

    let me = s
        .send(Request::get("/api/me").header(header::AUTHORIZATION, format!("Bearer {token}")).body(Body::empty()).unwrap())
        .await;
    let me = body_json(me).await;
    assert_eq!(me["user"]["username"], "alice");
    assert_eq!(me["user"]["method"], "local");
    assert_eq!(me["devices"][0]["name"], "Test phone");
    assert_eq!(me["devices"][0]["current"], true);
}

#[tokio::test]
async fn usernames_are_not_case_sensitive() {
    let s = Server::local();
    s.sign_in("  Alice ", "correct horse battery").await;
}

#[tokio::test]
async fn a_wrong_password_and_an_unknown_user_look_the_same() {
    let s = Server::local();
    let (pending, _) = s.start().await;

    let wrong = s.submit_password(&pending, Some(&pending), "alice", "nope").await;
    let unknown = s.submit_password(&pending, Some(&pending), "mallory", "nope").await;

    for page in [&wrong, &unknown] {
        assert!(page.contains("Invalid username or password."));
        assert!(code_from(page).is_none());
    }
    assert!(wrong.contains(r#"value="alice""#), "the username is kept for the retry");
}

#[tokio::test]
async fn repeated_failures_are_slowed_down() {
    let s = Server::local();
    let (pending, _) = s.start().await;
    for _ in 0..5 {
        s.submit_password(&pending, Some(&pending), "alice", "nope").await;
    }
    // Even the right password has to wait now.
    let page = s.submit_password(&pending, Some(&pending), "alice", "correct horse battery").await;
    assert!(page.contains("Too many attempts"), "{page}");
}

#[tokio::test]
async fn a_password_post_from_another_browser_is_refused() {
    let s = Server::local();
    let (pending, _) = s.start().await;

    let no_cookie = s.submit_password(&pending, None, "alice", "correct horse battery").await;
    let other = s.submit_password(&pending, Some("someone-elses"), "alice", "correct horse battery").await;

    for page in [&no_cookie, &other] {
        assert!(page.contains("expired"), "{page}");
        assert!(code_from(page).is_none());
    }
}

#[tokio::test]
async fn codes_need_the_right_verifier_and_work_once() {
    let s = Server::local();

    let code = s.code_for("alice", "correct horse battery").await;
    assert_eq!(s.redeem(&code, "some-other-verifier-of-a-reasonable-length-0000000").await.status(), StatusCode::BAD_REQUEST);
    assert_eq!(
        s.redeem(&code, VERIFIER).await.status(),
        StatusCode::BAD_REQUEST,
        "a failed attempt burns the code"
    );

    let code = s.code_for("alice", "correct horse battery").await;
    assert_eq!(s.redeem(&code, VERIFIER).await.status(), StatusCode::OK);
    assert_eq!(s.redeem(&code, VERIFIER).await.status(), StatusCode::BAD_REQUEST, "single use");
}

#[tokio::test]
async fn an_expired_code_is_refused() {
    let s = Server::local();
    let code = s.code_for("alice", "correct horse battery").await;
    s.state.db().execute("UPDATE auth_codes SET expires_at = 0", []).unwrap();
    assert_eq!(s.redeem(&code, VERIFIER).await.status(), StatusCode::BAD_REQUEST);
}

#[tokio::test]
async fn codes_are_only_ever_sent_to_the_app() {
    let s = Server::local();
    for bad in [
        "https://evil.example/callback",
        "http://127.0.0.1.evil.example:80/callback",
        "http://localhost:1234/callback",
        "http://127.0.0.1:1234/elsewhere",
        "mtgc://elsewhere",
    ] {
        let uri = format!(
            "/auth/start?redirect_uri={}&code_challenge={}&state=x",
            urlencode(bad),
            pkce_challenge(VERIFIER)
        );
        assert_eq!(s.send(get(&uri)).await.status(), StatusCode::BAD_REQUEST, "{bad}");
    }
}

#[tokio::test]
async fn the_phone_apps_scheme_is_accepted() {
    let s = Server::local();
    let uri = format!(
        "/auth/start?redirect_uri={}&code_challenge={}&state=x",
        urlencode("mtgc://auth/callback"),
        pkce_challenge(VERIFIER)
    );
    assert_eq!(s.send(get(&uri)).await.status(), StatusCode::OK);
}

#[tokio::test]
async fn with_only_oidc_the_server_skips_straight_to_the_provider() {
    let s = Server::new(&[
        ("MTGC_LOCAL_AUTH", "false"),
        ("MTGC_OIDC_ISSUER", "https://id.example/realms/home"),
        ("MTGC_OIDC_CLIENT_ID", "mtgc"),
        ("MTGC_OIDC_CLIENT_SECRET", "secret"),
    ]);
    let (pending, resp) = s.start().await;
    assert_eq!(resp.status(), StatusCode::SEE_OTHER);
    assert_eq!(
        resp.headers()[header::LOCATION].to_str().unwrap(),
        format!("/auth/oidc?pending={pending}")
    );

    // And the password form is gone, not just hidden.
    let page = s.submit_password(&pending, Some(&pending), "alice", "whatever").await;
    assert!(page.contains("turned off"), "{page}");
}

#[tokio::test]
async fn with_both_methods_the_page_offers_both() {
    let s = Server::new(&[
        ("MTGC_OIDC_ISSUER", "https://id.example/realms/home"),
        ("MTGC_OIDC_CLIENT_ID", "mtgc"),
        ("MTGC_OIDC_CLIENT_SECRET", "secret"),
        ("MTGC_OIDC_NAME", "Authentik"),
    ]);
    let (_, resp) = s.start().await;
    let page = text(resp).await;
    assert!(page.contains("Sign in with Authentik"));
    assert!(page.contains(r#"action="/auth/password""#));
}

#[tokio::test]
async fn the_server_describes_itself() {
    let s = Server::local();
    let info = body_json(s.send(get("/api/info")).await).await;
    assert_eq!(info["server"], "mtgc");
    assert_eq!(info["local_auth"], true);
    assert_eq!(info["oidc"], Value::Null);
}

// --- devices ------------------------------------------------------------------

#[tokio::test]
async fn the_library_needs_a_valid_token() {
    let s = Server::local();
    assert_eq!(s.send(get("/api/library")).await.status(), StatusCode::UNAUTHORIZED);
    assert_eq!(s.get_library("mtgc_made-up").await.status(), StatusCode::UNAUTHORIZED);
}

#[tokio::test]
async fn signing_out_revokes_only_that_device() {
    let s = Server::local();
    let phone = s.sign_in("alice", "correct horse battery").await;
    let desktop = s.sign_in("alice", "correct horse battery").await;

    let resp = s.send(post_json("/auth/logout", json!({}), Some(&phone))).await;
    assert_eq!(resp.status(), StatusCode::NO_CONTENT);

    assert_eq!(s.get_library(&phone).await.status(), StatusCode::UNAUTHORIZED);
    assert_eq!(s.get_library(&desktop).await.status(), StatusCode::OK);
}

#[tokio::test]
async fn a_lost_device_can_be_revoked_from_another_but_not_by_someone_else() {
    let s = Server::local();
    s.add_user("bob", "another fine password");
    let lost = s.sign_in("alice", "correct horse battery").await;
    let mine = s.sign_in("alice", "correct horse battery").await;
    let bobs = s.sign_in("bob", "another fine password").await;

    let me = s
        .send(Request::get("/api/me").header(header::AUTHORIZATION, format!("Bearer {mine}")).body(Body::empty()).unwrap())
        .await;
    let devices = body_json(me).await["devices"].clone();
    let lost_id = devices
        .as_array()
        .unwrap()
        .iter()
        .find(|d| d["current"] == false)
        .unwrap()["id"]
        .as_i64()
        .unwrap();

    let revoke = |token: String| {
        Request::delete(format!("/api/devices/{lost_id}"))
            .header(header::AUTHORIZATION, format!("Bearer {token}"))
            .body(Body::empty())
            .unwrap()
    };
    assert_eq!(s.send(revoke(bobs)).await.status(), StatusCode::NOT_FOUND, "not bob's to revoke");
    assert_eq!(s.get_library(&lost).await.status(), StatusCode::OK);

    assert_eq!(s.send(revoke(mine)).await.status(), StatusCode::NO_CONTENT);
    assert_eq!(s.get_library(&lost).await.status(), StatusCode::UNAUTHORIZED);
}

// --- the library ----------------------------------------------------------------

#[tokio::test]
async fn writes_must_name_the_version_they_replace() {
    let s = Server::local();
    let t = s.sign_in("alice", "correct horse battery").await;

    let resp = s.put_library(&t, Some("\"0\""), library(&[("a", 1)])).await;
    assert_eq!(resp.status(), StatusCode::OK);
    assert_eq!(body_json(resp).await["version"], 1);

    // A second device still thinks it's at 0: refused, and told what is there.
    let resp = s.put_library(&t, Some("0"), library(&[("b", 2)])).await;
    assert_eq!(resp.status(), StatusCode::PRECONDITION_FAILED);
    let current = body_json(resp).await;
    assert_eq!(current["version"], 1);
    assert_eq!(current["doc"]["cards"]["a"]["quantity"], 1);

    let resp = s.put_library(&t, None, library(&[("b", 2)])).await;
    assert_eq!(resp.status(), StatusCode::PRECONDITION_REQUIRED, "no blind overwrites");

    let got = body_json(s.get_library(&t).await).await;
    assert_eq!(got["version"], 1);
    assert_eq!(got["doc"]["cards"]["a"]["quantity"], 1);
}

#[tokio::test]
async fn a_write_to_a_library_that_does_not_exist_yet_must_say_version_zero() {
    let s = Server::local();
    let t = s.sign_in("alice", "correct horse battery").await;
    let resp = s.put_library(&t, Some("3"), library(&[("a", 1)])).await;
    assert_eq!(resp.status(), StatusCode::PRECONDITION_FAILED);
    assert_eq!(body_json(resp).await["version"], 0);
}

#[tokio::test]
async fn only_valid_libraries_are_stored() {
    let s = Server::local();
    let t = s.sign_in("alice", "correct horse battery").await;

    let newer = json!({ "version": 99, "cards": {}, "decks": {} });
    assert_eq!(s.put_library(&t, Some("0"), newer).await.status(), StatusCode::BAD_REQUEST);
    assert_eq!(s.put_library(&t, Some("0"), json!(["nope"])).await.status(), StatusCode::BAD_REQUEST);
}

#[tokio::test]
async fn each_user_has_their_own_library() {
    let s = Server::local();
    s.add_user("bob", "another fine password");
    let alice = s.sign_in("alice", "correct horse battery").await;
    let bob = s.sign_in("bob", "another fine password").await;

    s.put_library(&alice, Some("0"), library(&[("a", 1)])).await;

    let bobs = body_json(s.get_library(&bob).await).await;
    assert_eq!(bobs["version"], 0);
    assert_eq!(bobs["doc"]["cards"], json!({}));
}

#[tokio::test]
async fn old_versions_are_kept_up_to_a_limit() {
    let s = Server::local();
    let t = s.sign_in("alice", "correct horse battery").await;
    let total = db::HISTORY_KEEP + 10;
    for v in 0..total {
        let resp = s.put_library(&t, Some(&v.to_string()), library(&[("a", v)])).await;
        assert_eq!(resp.status(), StatusCode::OK);
    }

    let user_id: i64 = s.state.db().query_row("SELECT id FROM users WHERE sub = 'alice'", [], |r| r.get(0)).unwrap();
    let kept = db::history_versions(&s.state.db(), user_id).unwrap();
    assert_eq!(kept.len() as i64, db::HISTORY_KEEP);
    assert_eq!(*kept.last().unwrap(), total - 1, "the newest superseded version is kept");
}