use core::net::IpAddr;
use futures::{future::TryFutureExt, stream::TryStreamExt};
use ldap3::{Ldap, LdapConnAsync};
use rocket::fairing::{self, AdHoc};
use rocket::form::Form;
use rocket::http::{Cookie, CookieJar, Status};
use rocket::outcome::{try_outcome, IntoOutcome};
use rocket::request::{FromRequest, Outcome, Request};
use rocket::response::status::Unauthorized;
use rocket::serde::json::{self, Json};
use rocket::serde::{Deserialize, Serialize};
use rocket::{Build, Rocket, State};
use rocket_db_pools::{sqlx, Connection, Database};
use std::borrow::Cow;
use std::cmp::Ordering;
use std::collections::BTreeMap;
use std::sync::Mutex;
use std::sync::OnceLock;
use std::time::Instant;
use time::Duration;
use utoipa::openapi::security::{ApiKey, ApiKeyValue, SecurityScheme};
use utoipa::{Modify, OpenApi, ToSchema};

use crate::api_model;
use crate::Db;

#[derive(OpenApi)]
#[openapi(
    paths(login, logout, status,),
    modifiers(&AuthApiAddon),
)]
pub struct AuthApi;

pub struct AuthApiAddon;

impl Modify for AuthApiAddon {
    fn modify(&self, openapi: &mut utoipa::openapi::OpenApi) {
        let components = openapi.components.as_mut().unwrap();
        components.add_security_scheme(
            "session",
            SecurityScheme::ApiKey(ApiKey::Cookie(ApiKeyValue::new(SESSION_COOKIE))),
        )
    }
}

#[derive(FromForm, ToSchema)]
struct Login<'r> {
    username: &'r str,
    password: &'r str,
}

#[derive(Debug, Deserialize)]
#[cfg_attr(test, allow(dead_code))]
struct AuthConfig<'a> {
    session_max_age_days: u32,
    ldap_url: Cow<'a, str>,
    ldap_users: Cow<'a, str>,
    ldap_filter: Cow<'a, str>,
}

struct SessionsData {
    active_ids: BTreeMap<u32, Instant>,
    next_id: u32,
}

struct Sessions {
    data: Mutex<SessionsData>,
}

#[cfg_attr(test, allow(dead_code))]
struct LdapState {
    ldap: OnceLock<ldap3::Ldap>,
}

#[derive(Debug, Deserialize, Serialize)]
pub struct Session {
    pub user_id: u64,
    session_id: u32,
    remote: String,
}

#[derive(Debug)]
pub enum SessionError {
    Invalid,
}

const SESSION_COOKIE: &str = "s";
const STATUS_OK: api_model::StatusResponse = api_model::StatusResponse {
    ok: true,
    error: None,
};
const STATUS_UNAUTHORIZED: api_model::StatusResponse = api_model::StatusResponse {
    ok: false,
    error: Some("Unauthorized"),
};

fn validate(sessions: &State<Sessions>, session: &Session, request: &Request<'_>) -> bool {
    match request.client_ip() {
        Some(addr) => {
            if session.remote == addr.to_string() {
                {
                    let sessions_data = sessions.data.lock().unwrap();
                    match sessions_data.active_ids.get(&session.session_id) {
                        // We could remove the expired session here, but it will be cleaned
                        // next time anyone logs in anyway.
                        Some(&expire) => expire > Instant::now(),
                        None => false,
                    }
                }
            } else {
                false
            }
        }
        None => false,
    }
}

#[rocket::async_trait]
impl<'r> FromRequest<'r> for Session {
    type Error = SessionError;

    async fn from_request(request: &'r Request<'_>) -> Outcome<Session, SessionError> {
        let sessions = try_outcome!(request
            .guard::<&State<Sessions>>()
            .await
            .map_error(|_| (Status::Unauthorized, SessionError::Invalid)));

        request
            .cookies()
            .get_private(SESSION_COOKIE)
            .and_then(|cookie| -> Option<Session> { json::from_str(cookie.value()).ok() })
            .and_then(|session| {
                if validate(sessions, &session, request) {
                    Some(session)
                } else {
                    None
                }
            })
            .or_error((Status::Unauthorized, SessionError::Invalid))
    }
}

fn new_session(
    sessions: &State<Sessions>,
    user_id: u64,
    remote: String,
    max_age: Duration,
) -> Session {
    let session_id;
    {
        let mut sessions_data = sessions.data.lock().unwrap();
        session_id = sessions_data.next_id;
        sessions_data.next_id += 1;

        let now = Instant::now();
        // Remove expired sessions first
        sessions_data
            .active_ids
            .retain(|_, &mut expire| expire > now);

        sessions_data.active_ids.insert(session_id, now + max_age);
    }
    Session {
        user_id,
        session_id,
        remote,
    }
}

#[cfg(not(test))]
async fn authenticate(ldap_state: &State<LdapState>, dn: &str, password: &str) -> bool {
    let mut ldap = ldap_state.ldap.get().unwrap().clone();
    let maybe_result = ldap.compare(dn, "userPassword", password.as_bytes()).await;
    if let Ok(result) = maybe_result {
        if let Ok(is_equal) = result.equal() {
            return is_equal;
        }
    }
    false
}

#[cfg(test)]
async fn authenticate(_ldap_state: &State<LdapState>, dn: &str, password: &str) -> bool {
    match dn {
        "user" => password == "password",
        "other" => password == "secret",
        _ => false,
    }
}

#[utoipa::path(
    responses(
        (status = 200, description = "Login successful", body = api_model::StatusResponse,
         example = json!(STATUS_OK)),
        (status = 401, description = "Login failed", body = api_model::StatusResponse,
         example = json!(STATUS_UNAUTHORIZED)),
    ),
    security(
        (),
    ),
)]
#[post("/login", data = "<login>")]
async fn login(
    auth_config: &State<AuthConfig<'_>>,
    ldap_state: &State<LdapState>,
    sessions: &State<Sessions>,
    ipaddr: IpAddr,
    cookies: &CookieJar<'_>,
    mut db: Connection<Db>,
    login: Form<Login<'_>>,
) -> Result<Json<api_model::StatusResponse>, Unauthorized<&'static str>> {
    let (user_id, maybe_dn) =
        sqlx::query!("SELECT id,dn FROM users WHERE username=?", login.username)
            .fetch_one(&mut **db)
            .map_ok(|r| (r.id, r.dn))
            .map_err(|_| Unauthorized("Unknown username or password"))
            .await?;

    if let Some(dn) = maybe_dn {
        if authenticate(ldap_state, dn.as_str(), login.password).await {
            let max_age = Duration::days(i64::from(auth_config.session_max_age_days));
            let session = new_session(sessions, user_id, ipaddr.to_string(), max_age);

            let cookie = Cookie::build((SESSION_COOKIE, json::to_string(&session).unwrap()))
                .path("/api")
                .max_age(max_age)
                .http_only(true)
                .build();

            cookies.add_private(cookie);
            return Ok(Json(STATUS_OK));
        }
    }

    Err(Unauthorized("Unknown username or password"))
}

#[utoipa::path(
    responses(
        (status = 200, description = "Logout successful", body = api_model::StatusResponse, example = json!(STATUS_OK)),
    ),
    security(
        ("session" = []),
    ),
)]
#[get("/logout")]
fn logout(
    session: Session,
    sessions: &State<Sessions>,
    cookies: &CookieJar<'_>,
) -> Json<api_model::StatusResponse> {
    {
        let mut sessions_data = sessions.data.lock().unwrap();
        sessions_data.active_ids.remove(&session.session_id);
    }

    let cookie = Cookie::build((SESSION_COOKIE, ""))
        .path("/api")
        .http_only(true)
        .build();

    cookies.remove_private(cookie);

    Json(STATUS_OK)
}

#[utoipa::path(
    responses(
        (status = 200, description = "Current status", body = api_model::StatusResponse, example = json!(STATUS_OK)),
        (status = 401, description = "Not authorized", body = api_model::StatusResponse, example = json!(STATUS_UNAUTHORIZED)),
    ),
    security(
        (),
        ("session" = []),
    ),
)]
#[get("/status")]
fn status(_session: Session) -> Json<api_model::StatusResponse> {
    Json(STATUS_OK)
}

#[catch(401)]
fn unauthorized() -> Json<api_model::StatusResponse> {
    Json(STATUS_UNAUTHORIZED)
}

#[cfg_attr(test, allow(dead_code))]
async fn setup_ldap(
    ldap_state: &LdapState,
    config: &AuthConfig<'_>,
) -> Result<Ldap, ldap3::LdapError> {
    let (conn, ldap) = LdapConnAsync::new(&config.ldap_url).await?;
    ldap3::drive!(conn);
    let ret = ldap.clone();
    ldap_state
        .ldap
        .set(ldap)
        .expect("setup_ldap must only be called once");
    Ok(ret)
}

#[derive(Debug)]
#[allow(dead_code)]
enum LdapOrSqlError {
    LdapError(ldap3::LdapError),
    SqlError(sqlx::Error),
}

#[cfg_attr(test, allow(dead_code))]
async fn sync_ldap(
    ldap_state: &LdapState,
    config: &AuthConfig<'_>,
    db: &Db,
) -> Result<(), LdapOrSqlError> {
    let mut ldap = setup_ldap(ldap_state, config)
        .map_err(LdapOrSqlError::LdapError)
        .await?;
    let (entries, _) = ldap
        .search(
            &config.ldap_users,
            ldap3::Scope::OneLevel,
            &config.ldap_filter,
            vec!["uid"],
        )
        .map_err(LdapOrSqlError::LdapError)
        .await?
        .success()
        .map_err(LdapOrSqlError::LdapError)?;

    let mut tx = db.begin().await.unwrap();

    // TODO: Insert/Update name as well as dn.

    let db_users = sqlx::query!("SELECT id,username,dn FROM users ORDER BY username")
        .fetch(&mut *tx)
        .map_ok(|r| (r.id, r.username, r.dn))
        .try_collect::<Vec<_>>()
        .await
        .unwrap();

    let mut new_users: Vec<(String, String)> = Vec::new();
    let mut updated_users: Vec<(u64, String)> = Vec::new();
    let mut old_users: Vec<u64> = Vec::new();

    let mut db_user = db_users.iter().peekable();

    for entry in entries {
        let se = ldap3::SearchEntry::construct(entry);
        let uid = se.attrs.get("uid").unwrap().first().unwrap();
        loop {
            if let Some(du) = db_user.peek() {
                match du.1.cmp(uid) {
                    Ordering::Equal => {
                        if du.2.as_ref().is_none_or(|x| *x != se.dn) {
                            updated_users.push((du.0, se.dn));
                        }
                        db_user.next();
                        break;
                    }
                    Ordering::Less => {
                        old_users.push(du.0);
                        db_user.next();
                        continue;
                    }
                    Ordering::Greater => (),
                }
            }
            new_users.push((uid.to_string(), se.dn));
            break;
        }
    }

    if !new_users.is_empty() {
        let mut query_builder: sqlx::QueryBuilder<sqlx::MySql> =
            sqlx::QueryBuilder::new("INSERT INTO users (username,dn) VALUES");

        let mut first = true;
        for pair in new_users {
            if first {
                first = false;
            } else {
                query_builder.push(",");
            }
            query_builder.push("(");
            query_builder.push_bind(pair.0);
            query_builder.push(",");
            query_builder.push_bind(pair.1);
            query_builder.push(")");
        }

        query_builder
            .build()
            .execute(&mut *tx)
            .map_err(LdapOrSqlError::SqlError)
            .await?;
    }

    for pair in updated_users {
        sqlx::query!("UPDATE users SET dn=? WHERE id=?", pair.1, pair.0)
            .execute(&mut *tx)
            .map_err(LdapOrSqlError::SqlError)
            .await?;
    }

    if !old_users.is_empty() {
        let params = format!("?{}", ", ?".repeat(old_users.len() - 1));
        let query_str = format!("UPDATE users SET dn=NULL WHERE id IN ({})", params);
        let mut query = sqlx::query(&query_str);

        for id in old_users {
            query = query.bind(id);
        }

        query
            .execute(&mut *tx)
            .map_err(LdapOrSqlError::SqlError)
            .await?;
    }

    tx.commit().map_err(LdapOrSqlError::SqlError).await?;

    Ok(())
}

#[cfg(not(test))]
async fn run_import(rocket: Rocket<Build>) -> fairing::Result {
    match rocket.state::<AuthConfig>() {
        Some(config) => match rocket.state::<LdapState>() {
            Some(ldap) => match Db::fetch(&rocket) {
                Some(db) => match sync_ldap(ldap, config, db).await {
                    Ok(_) => Ok(rocket),
                    Err(_) => Err(rocket),
                },
                None => Err(rocket),
            },
            None => Err(rocket),
        },
        None => Err(rocket),
    }
}

#[cfg(test)]
async fn run_import(rocket: Rocket<Build>) -> fairing::Result {
    match Db::fetch(&rocket) {
        Some(db) => match sqlx::query!(
            "INSERT IGNORE INTO users (username,dn) VALUES (?,?), (?,?)",
            "user",
            "user",
            "other",
            "other",
        )
        .execute(&**db)
        .await
        {
            Ok(_) => Ok(rocket),
            Err(_) => Err(rocket),
        },
        None => Err(rocket),
    }
}

pub fn stage(basepath: &str) -> AdHoc {
    let l_basepath = basepath.to_string();
    AdHoc::on_ignite("Auth Stage", |rocket| async {
        rocket
            .manage(Sessions {
                data: Mutex::new(SessionsData {
                    active_ids: BTreeMap::new(),
                    next_id: 1,
                }),
            })
            .attach(AdHoc::config::<AuthConfig>())
            .manage(LdapState {
                ldap: OnceLock::new(),
            })
            .attach(AdHoc::try_on_ignite("Auth Import", run_import))
            .mount(l_basepath.clone(), routes![login, logout, status])
            .register(l_basepath, catchers![unauthorized])
    })
}