use actix_web::{get, middleware::Logger, post, web, App, HttpResponse, HttpServer, Responder};
use chrono::{DateTime, Utc};
use clap::Parser;
use handlebars::{DirectorySourceOptions, Handlebars};
use log::info;
use proptest::test_runner::{Config, RngAlgorithm, TestRng, TestRunner};
use rand::Rng;
use serde::{Deserialize, Serialize};
use std::sync::Mutex;
use std::time::Duration;
use std::{collections::HashMap, sync::Arc};
use tokio::task::{self, JoinHandle};
use uuid::Uuid;

use lambda::lambda::{eval_all, eval_whnf, generate_expr, generate_exprs, gensym, Environment};
use lambda::parser::{parse, parse_total};

#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
struct Registration {
    url: String,
    name: String,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct ClientData {
    name: String,
    grade: u8,
    last_query: DateTime<Utc>,
    success: bool,
}

impl ClientData {
    fn from(client: &Client) -> Self {
        ClientData {
            name: client.name.clone(),
            grade: client.grade,
            last_query: client
                .results
                .last()
                .map_or(chrono::offset::Utc::now(), |q| q.timestamp),
            success: client
                .results
                .last()
                .map_or(false, |q| matches!(q.result, TestResult::TestSucceeded)),
        }
    }
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct Leaderboard {
    clients: Vec<ClientData>,
}

trait AppState: Send + Sync {
    fn register(&mut self, registration: &Registration) -> RegistrationResult;
    fn unregister(&mut self, url: &String);
}

#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
enum RegistrationResult {
    RegistrationSuccess { id: String, url: String },
    UrlAlreadyRegistered { url: String },
}

#[derive(Debug, Clone)]
struct Client {
    id: Uuid,
    name: String,
    url: String,
    grade: u8,
    runner: TestRunner,
    results: Vec<Test>,
    delay: std::time::Duration,
}

#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
struct Test {
    timestamp: DateTime<Utc>,
    result: TestResult,
}

#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
enum TestResult {
    TestFailed(String),
    ErrorSendingTest(String),
    TestSucceeded,
}

impl Client {
    fn new(url: String, name: String, delay: Duration) -> Self {
        let id = Uuid::new_v4();
        let runner = TestRunner::new_with_rng(
            Config::default(),
            TestRng::from_seed(RngAlgorithm::XorShift, &id.to_bytes_le()),
        );
        Self {
            id,
            url,
            name,
            grade: 1,
            runner,
            results: Vec::new(),
            delay,
        }
    }

    fn time_to_next_test(&self) -> Duration {
        self.delay
    }

    fn generate_expr(&mut self) -> (String, String) {
        if self.grade >= 10 {
            self.generate_exprs()
        } else {
            let input = generate_expr(self.grade.into(), &mut self.runner);
            let expected = eval_whnf(&input, &mut Environment::new());
            (input.to_string(), expected.to_string())
        }
    }

    fn generate_exprs(&mut self) -> (String, String) {
        let exprs = generate_exprs(self.grade.into(), &mut self.runner);
        let input = exprs
            .iter()
            .map(|v| format!("{}", v))
            .collect::<Vec<_>>()
            .join("\n");
        let expected = eval_all(&exprs);
        (
            input,
            expected
                .iter()
                .map(|v| format!("{}", v))
                .collect::<Vec<_>>()
                .join("\n"),
        )
    }

    /// Applies a `Test` to update client's state
    fn apply(&mut self, test: &Test) {
        match test.result {
            TestResult::TestSucceeded => {
                self.grade = self.grade.saturating_add(1);
                self.delay = Duration::from_secs_f64(self.delay.as_secs_f64() * 0.8);
                if self.delay.as_millis() < 500 {
                    self.delay = Duration::from_millis(500);
                }
            }
            TestResult::TestFailed(_) => {
                self.delay = Duration::from_secs_f64(self.delay.as_secs_f64() * 1.2);
                if self.delay.as_secs() > 30 {
                    self.delay = Duration::from_secs(30);
                }
            }
            _ => (),
        }
        self.results.push(test.clone());
    }

    fn check_result(&self, expected: &String, response: &Result<String, TestResult>) -> Test {
        let result = match response {
            Ok(expr) => {
                if let Ok(vals) = parse_total(expr) {
                    let actual = eval_all(&vals)
                        .iter()
                        .map(|v| format!("{}", v))
                        .collect::<Vec<_>>()
                        .join("\n");
                    if actual == *expected {
                        TestResult::TestSucceeded
                    } else {
                        TestResult::TestFailed(actual)
                    }
                } else {
                    TestResult::TestFailed("Could not parse response".to_string())
                }
            }
            Err(res) => res.clone(),
        };
        Test {
            result,
            timestamp: chrono::offset::Utc::now(),
        }
    }
}

#[derive(Debug)]
struct State {
    base_duration: Duration,
    clients: HashMap<String, (Arc<Mutex<Client>>, JoinHandle<()>)>,
}

impl State {
    fn new() -> Self {
        State::with_duration(Duration::from_secs(10))
    }

    fn with_duration(base_duration: Duration) -> Self {
        Self {
            base_duration,
            clients: HashMap::new(),
        }
    }

    fn client_events(&self, url: &String) -> usize {
        let client = self.clients.get(url).unwrap().0.lock().unwrap();
        client.results.len()
    }
}

impl AppState for State {
    fn register(&mut self, registration: &Registration) -> RegistrationResult {
        if self.clients.contains_key(&registration.url) {
            RegistrationResult::UrlAlreadyRegistered {
                url: registration.url.clone(),
            }
        } else {
            let client = Client::new(
                registration.url.clone(),
                registration.name.clone(),
                self.base_duration,
            );
            let id = client.id.to_string();
            let client_ref = Arc::new(Mutex::new(client));
            // let it run in the background
            // FIXME: should find a way to handle graceful termination
            let client_handle = task::spawn(send_tests(client_ref.clone()));

            self.clients.insert(
                registration.url.clone(),
                (client_ref.clone(), client_handle),
            );

            RegistrationResult::RegistrationSuccess {
                id,
                url: registration.url.clone(),
            }
        }
    }

    fn unregister(&mut self, url: &String) {
        let (_, handle) = self.clients.get(url).unwrap();
        handle.abort()
    }
}

#[post("/register")]
async fn register(
    app_state: web::Data<Arc<Mutex<State>>>,
    registration: web::Json<Registration>,
) -> impl Responder {
    let result = app_state.lock().unwrap().register(&registration);
    match result {
        RegistrationResult::RegistrationSuccess { .. } => HttpResponse::Ok().json(result),
        RegistrationResult::UrlAlreadyRegistered { .. } => HttpResponse::BadRequest().json(result),
    }
}

#[post("/eval")]
async fn eval(input: String) -> impl Responder {
    let exprs = parse_total(&input);
    match exprs {
        Ok(exprs) => {
            let mut rng = rand::thread_rng();
            if rng.gen_range(0..10) <= 2 {
                return HttpResponse::Ok().body(gensym());
            }
            let output = eval_all(&exprs)
                .iter()
                .map(|v| format!("{}", v))
                .collect::<Vec<_>>()
                .join("\n");
            HttpResponse::Ok().body(output.to_string())
        }
        Err(e) => HttpResponse::BadRequest().body(e.to_string()),
    }
}

#[get("/leaderboard")]
async fn leaderboard(
    app_state: web::Data<Arc<Mutex<State>>>,
    hb: web::Data<Handlebars<'_>>,
) -> impl Responder {
    let clients = &app_state.lock().unwrap().clients;
    let mut client_data = vec![];
    for client in clients.values() {
        let client = client.0.lock().unwrap();
        client_data.push(ClientData::from(&client));
    }
    client_data.sort_by(|a, b| b.grade.cmp(&a.grade));

    let body = hb
        .render(
            "leaderboard",
            &Leaderboard {
                clients: client_data,
            },
        )
        .unwrap();

    web::Html::new(body)
}

#[derive(Parser, Debug)]
struct Options {
    /// The port to listen on
    /// Defaults to 8080
    #[arg(short, long, default_value_t = 8080)]
    port: u16,
    /// The host to bind the server to
    /// Defaults to 127.0.0.1
    #[arg(long, default_value = "127.0.0.1")]
    host: String,
}

#[tokio::main]
async fn main() -> std::io::Result<()> {
    let options = Options::parse();
    let app_state = Arc::new(Mutex::new(State::new()));

    env_logger::init();
    // Handlebars uses a repository for the compiled templates. This object must be
    // shared between the application threads, and is therefore passed to the
    // Application Builder as an atomic reference-counted pointer.
    let mut handlebars = Handlebars::new();
    handlebars
        .register_templates_directory(
            "./templates",
            DirectorySourceOptions {
                tpl_extension: ".html".to_owned(),
                hidden: false,
                temporary: false,
            },
        )
        .unwrap();

    HttpServer::new(move || {
        App::new()
            .wrap(Logger::default())
            .app_data(web::Data::new(app_state.clone()))
            .app_data(web::Data::new(handlebars.clone()))
            .service(register)
            .service(eval)
            .service(leaderboard)
            .service(actix_files::Files::new("/", "./static").show_files_listing() )
    })
    .bind((options.host, options.port))?
    .run()
    .await
}

fn get_test(client_m: &Mutex<Client>) -> (String, String, String) {
    let mut client = client_m.lock().unwrap();
    let (input, expected) = client.generate_expr();
    (input, client.url.clone(), expected)
}

async fn send_tests(client_m: Arc<Mutex<Client>>) {
    loop {
        let sleep = sleep_time(&client_m);
        tokio::time::sleep(sleep).await;
        {
            let (input, url, expected) = get_test(&client_m);

            let response = send_test(&input, &url, sleep).await;

            apply_result(&client_m, expected, response);
        }
    }
}

fn apply_result(client_m: &Mutex<Client>, expected: String, response: Result<String, TestResult>) {
    let mut client = client_m.lock().unwrap();
    let test = client.check_result(&expected, &response);
    client.apply(&test);
}

fn sleep_time(client_m: &Arc<Mutex<Client>>) -> Duration {
    client_m.lock().unwrap().time_to_next_test()
}

async fn send_test(input: &String, url: &String, timeout: Duration) -> Result<String, TestResult> {
    info!("Sending {} to {}", input, url);
    let body = input.clone();
    let response = reqwest::Client::new()
        .post(url)
        .timeout(timeout)
        .header("content-type", "text/plain")
        .body(body)
        .send()
        .await;
    match response {
        Ok(response) => {
            let body = response.text().await.unwrap();
            info!("Response from {}: {}", url, body);
            Ok(body)
        }
        Err(e) => {
            info!("Error sending test: {}", e);
            Err(TestResult::ErrorSendingTest(e.to_string()))
        }
    }
}

#[cfg(test)]
mod app_tests {
    use std::str::from_utf8;
    use std::sync::Arc;

    use actix_web::http::header::TryIntoHeaderValue;
    use actix_web::{body, http::header::ContentType, middleware::Logger, test, App};
    use lambda::ast::Value;

    use super::*;

    #[actix_web::test]
    async fn post_registration_returns_success_with_unique_id() {
        let state = Arc::new(Mutex::new(State::new()));
        // FIXME should only be called once, move to setup
        env_logger::init();

        let app = test::init_service(
            App::new()
                .wrap(Logger::default())
                .app_data(web::Data::new(state))
                .service(register),
        )
        .await;
        let url = "http://192.168.1.1".to_string();
        let req = test::TestRequest::post()
            .uri("/register")
            .set_json(Registration {
                url: url.clone(),
                name: "foo".to_string(),
            })
            .insert_header(ContentType::json())
            .to_request();

        let resp = test::call_service(&app, req).await;

        assert!(resp.status().is_success());

        let body = resp.into_body();
        let bytes = body::to_bytes(body).await;
        match serde_json::from_slice::<RegistrationResult>(bytes.as_ref().unwrap()).unwrap() {
            RegistrationResult::RegistrationSuccess { id: _, url: url1 } => assert_eq!(url1, url),
            _ => panic!("Expected RegistrationSuccess, got {:?}", bytes.unwrap()),
        };
    }

    #[actix_web::test]
    async fn post_registration_returns_400_when_register_fails() {
        let state = Arc::new(Mutex::new(State::new()));

        let app = test::init_service(
            App::new()
                .wrap(Logger::default())
                .app_data(web::Data::new(state.clone()))
                .service(register),
        )
        .await;
        let url = "http://192.168.1.1".to_string();
        let registration = Registration {
            url: url.clone(),
            name: "foo".to_string(),
        };

        state.lock().unwrap().register(&registration);

        let req = test::TestRequest::post()
            .uri("/register")
            .set_json(registration)
            .insert_header(ContentType::json())
            .to_request();

        let resp = test::call_service(&app, req).await;

        assert!(resp.status().is_client_error());
        assert_eq!(
            ContentType::json().try_into_value().unwrap(),
            resp.headers().get("content-type").unwrap()
        );
    }

    #[actix_web::test]
    async fn post_expression_returns_evaluation() {
        let app = test::init_service(App::new().wrap(Logger::default()).service(eval)).await;

        let req = test::TestRequest::post()
            .uri("/eval")
            .set_payload("((lam (x y) x) 1 2)")
            .insert_header(ContentType::plaintext())
            .to_request();

        let resp = test::call_service(&app, req).await;

        assert!(resp.status().is_success());

        let body = resp.into_body();
        let bytes = body::to_bytes(body).await.unwrap();
        assert_eq!(bytes, "1".to_string().into_bytes());
    }

    #[actix_web::test]
    async fn post_expression_returns_multiple_evaluations() {
        let app = test::init_service(App::new().wrap(Logger::default()).service(eval)).await;

        let req = test::TestRequest::post()
            .uri("/eval")
            .set_payload("((lam (x y) x) 1 2)\n42")
            .insert_header(ContentType::plaintext())
            .to_request();

        let resp = test::call_service(&app, req).await;

        assert!(resp.status().is_success());

        let body = resp.into_body();
        let bytes = body::to_bytes(body).await.unwrap();
        assert_eq!("1\n42".to_string().into_bytes(), bytes);
    }

    #[actix_web::test]
    async fn get_leaderboard_returns_html_page_listing_clients_state() {
        let app_state = Arc::new(Mutex::new(State::new()));
        app_state.lock().unwrap().register(&Registration {
            url: "http://1.2.3.4".to_string(),
            name: "client1".to_string(),
        });

        let mut handlebars = Handlebars::new();
        handlebars
            .register_templates_directory(
                "./templates",
                DirectorySourceOptions {
                    tpl_extension: ".html".to_owned(),
                    hidden: false,
                    temporary: false,
                },
            )
            .unwrap();

        let app = test::init_service(
            App::new()
                .wrap(Logger::default())
                .app_data(web::Data::new(app_state.clone()))
                .app_data(web::Data::new(handlebars.clone()))
                .service(leaderboard),
        )
        .await;

        let req = test::TestRequest::get().uri("/leaderboard").to_request();

        let resp = test::call_service(&app, req).await;

        assert!(resp.status().is_success());

        let bytes = body::to_bytes(resp.into_body()).await.unwrap();
        assert!(from_utf8(&bytes).unwrap().contains("client1"));
    }

    #[test]
    async fn app_does_not_register_same_url_twice() {
        let mut app_state = State::new();
        let registration = Registration {
            name: "foo".to_string(),
            url: "http://1.2.3.4".to_string(),
        };

        app_state.register(&registration);
        let result = app_state.register(&registration);

        assert_eq!(
            RegistrationResult::UrlAlreadyRegistered {
                url: "http://1.2.3.4".to_string()
            },
            result
        );
    }

    #[test]
    async fn unregistering_registered_client_stops_tester_thread_from_sending_tests() {
        let mut app_state = State::with_duration(Duration::from_millis(100));
        let registration = Registration {
            name: "foo".to_string(),
            url: "http://1.2.3.4".to_string(),
        };

        let reg = app_state.register(&registration);
        assert!(matches!(
            reg,
            RegistrationResult::RegistrationSuccess { .. }
        ));

        tokio::time::sleep(Duration::from_millis(500)).await;

        app_state.unregister(&registration.url);

        let grade_before = app_state.client_events(&registration.url);
        tokio::time::sleep(Duration::from_millis(500)).await;
        let grade_after = app_state.client_events(&registration.url);

        assert_eq!(grade_before, grade_after);
    }

    fn client() -> Client {
        Client::new(
            "http://1.2.3.4".to_string(),
            "foo".to_string(),
            Duration::from_secs(10),
        )
    }

    #[test]
    async fn client_generates_constant_at_level_1() {
        let mut client = client();

        let (input, _) = client.generate_expr();

        match parse(&input)[..] {
            [Value::Num(_)] => (),
            _ => panic!("Expected constant 3"),
        }
    }

    #[test]
    async fn client_generates_different_inputs_on_each_call() {
        let mut client = client();

        let (input1, _) = client.generate_expr();
        let (input2, _) = client.generate_expr();

        assert_ne!(input1, input2);
    }

    #[test]
    async fn client_generates_ascii_variables_at_level_2() {
        let mut client = client();
        client.grade = 2;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::Sym(name)] => {
                assert!(name.chars().all(|c| c.is_ascii_alphanumeric()));
            }
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_unicode_variables_at_level_3() {
        let mut client = client();
        client.grade = 3;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::Sym(_)] => (),
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_binary_application_at_level_4() {
        let mut client = client();
        client.grade = 4;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::App(_, _)] => (),
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_nested_applications_and_constants_at_level_5() {
        let mut client = client();
        client.grade = 5;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::App(_, _)] => (),
            [Value::Sym(_)] => (),
            [Value::Num(_)] => (),
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_lambda_terms_at_level_6() {
        let mut client = client();
        client.grade = 6;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::Lam(_, _)] => (),
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_application_with_lambda_terms_at_level_7() {
        let mut client = client();
        client.grade = 7;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        match &parsed[..] {
            [Value::App(t1, _)] if matches!(**t1, Value::Lam(_, _)) => (),
            _ => panic!("Expected symbol, got {:?}", parsed),
        }
    }

    #[test]
    async fn client_generates_applications_with_more_than_2_terms_at_level_8() {
        let mut client = client();
        client.grade = 8;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);
        if let [Value::App(_, _)] = &parsed[..] {
            assert!(input.split(' ').count() >= 2)
        }
    }

    #[test]
    async fn client_generates_more_complex_terms_at_level_9() {
        let mut client = client();
        client.grade = 9;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);

        assert!(!parsed.is_empty());
    }

    #[test]
    async fn client_generates_multiple_terms_at_level_10() {
        let mut client = client();
        client.grade = 10;

        let (input, _) = client.generate_expr();

        let parsed = parse(&input);

        assert!(!parsed.is_empty());
    }

    #[test]
    async fn client_increases_grade_on_successful_test() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestSucceeded,
        };

        client.apply(&test);

        assert_eq!(2, client.grade);
    }

    #[test]
    async fn client_stores_test_results() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestSucceeded,
        };

        client.apply(&test);

        assert_eq!(test, client.results.first().unwrap().clone());
    }

    #[test]
    async fn client_returns_test_successful_if_result_match() {
        let client = client();
        let expected = "1".to_string();
        let response = Ok("1".to_string());

        let test = client.check_result(&expected, &response);

        assert_eq!(TestResult::TestSucceeded, test.result);
    }

    #[test]
    async fn client_returns_test_failed_given_result_do_not_match() {
        let client = client();
        let expected = "1".to_string();
        let response = Ok("2".to_string());

        let test = client.check_result(&expected, &response);

        assert_eq!(TestResult::TestFailed("2".to_string()), test.result);
    }

    #[test]
    async fn client_does_not_increase_grade_on_failed_test() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestFailed("2".to_string()),
        };

        client.apply(&test);

        assert_eq!(1, client.grade);
    }

    #[test]
    async fn client_starts_delay_to_next_test_at_10s() {
        let client = client();

        let delay = client.time_to_next_test();

        assert_eq!(std::time::Duration::from_secs(10), delay);
    }

    #[test]
    async fn client_increases_delay_to_next_upon_failed_test() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestFailed("2".to_string()),
        };
        let delay_before = client.time_to_next_test();

        client.apply(&test);

        assert!(delay_before < client.time_to_next_test());
    }

    #[test]
    async fn client_increases_delay_to_maximum_of_30s() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestFailed("2".to_string()),
        };

        for _ in 0..100 {
            client.apply(&test);
        }

        assert_eq!(Duration::from_secs(30), client.time_to_next_test());
    }

    #[test]
    async fn client_score_cannot_go_beyond_255() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestSucceeded,
        };

        for _ in 0..256 {
            client.apply(&test);
        }

        assert_eq!(255, client.grade);
    }

    #[test]
    async fn client_decreases_delay_to_next_upon_successful_test() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestSucceeded,
        };
        let delay_before = client.time_to_next_test();

        client.apply(&test);

        assert!(delay_before > client.time_to_next_test());
    }

    #[test]
    async fn client_decreases_delay_to_minimum_of_500ms() {
        let mut client = client();
        let test = Test {
            timestamp: chrono::offset::Utc::now(),
            result: TestResult::TestSucceeded,
        };

        for _ in 0..100 {
            client.apply(&test);
        }

        assert_eq!(Duration::from_millis(500), client.time_to_next_test());
    }
}