use std::fs;
use std::io::{Read, Write};
use std::net::{TcpListener, TcpStream};
use std::path::{Path, PathBuf};
use std::process::Command;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::thread;
use std::time::{Duration, Instant};
use thirtyfour::prelude::*;

const WEBDRIVER_ADDR: &str = "127.0.0.1:4451";
const STARTUP_TIMEOUT: Duration = Duration::from_secs(12);

#[tokio::test]
async fn client_handler_applies_effect_batch_without_network() -> WebDriverResult<()> {
    // req: client_local/005 req: client_local/009 req: client_local/010
    // test: client_local/014
    let workspace = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .parent()
        .expect("workspace root")
        .to_owned();
    build_browser_artifact(&workspace);
    let package = workspace.join("target/client-local-bindgen");
    let runtime = workspace.join("hemx-js/runtime/hemx.js");
    let server = StaticServer::start(package, runtime);

    let mut webdriver = Command::new("geckodriver");
    webdriver.arg("--port").arg("4451");
    let _webdriver = ProcessGuard::start(webdriver, WEBDRIVER_ADDR);

    let mut caps = DesiredCapabilities::firefox();
    caps.set_headless()?;
    let driver = WebDriver::new(&format!("http://{WEBDRIVER_ADDR}"), caps).await?;
    let result = async {
        driver.goto(&server.url()).await?;
        wait_until(&driver, "return window.__clientReady === true").await?;
        let network_before = resource_count(&driver).await?;

        driver
            .find(By::Css("[data-hemx-client='increment']"))
            .await?
            .click()
            .await?;
        wait_for_text(
            &driver,
            "[data-hemx-slot='counter_panel']",
            "updated by Rust/WASM",
        )
        .await?;

        assert_eq!(
            resource_count(&driver).await?,
            network_before,
            "client handler made a network request"
        );
        Ok::<(), WebDriverError>(())
    }
    .await;
    let quit = driver.quit().await;
    result.and(quit)
}

fn build_browser_artifact(workspace: &Path) {
    let status = Command::new("cargo")
        .current_dir(workspace)
        .args([
            "build",
            "-p",
            "hemx-client-local-example",
            "--target",
            "wasm32-unknown-unknown",
        ])
        .status()
        .expect("run wasm cargo build");
    assert!(status.success(), "WASM build failed");

    let output = workspace.join("target/client-local-bindgen");
    fs::create_dir_all(&output).expect("create wasm-bindgen output");
    let status = Command::new("wasm-bindgen")
        .current_dir(workspace)
        .arg("--target")
        .arg("web")
        .arg("--out-name")
        .arg("client_local")
        .arg("--out-dir")
        .arg(&output)
        .arg(workspace.join("target/wasm32-unknown-unknown/debug/hemx_client_local_example.wasm"))
        .status()
        .expect("run wasm-bindgen");
    assert!(status.success(), "wasm-bindgen failed");
}

struct StaticServer {
    address: String,
    stop: Arc<AtomicBool>,
}

impl StaticServer {
    fn start(package: PathBuf, runtime: PathBuf) -> Self {
        let listener = TcpListener::bind("127.0.0.1:0").expect("bind browser fixture");
        listener.set_nonblocking(true).expect("nonblocking fixture");
        let address = listener.local_addr().expect("fixture address").to_string();
        let stop = Arc::new(AtomicBool::new(false));
        let thread_stop = Arc::clone(&stop);
        thread::spawn(move || {
            while !thread_stop.load(Ordering::Relaxed) {
                match listener.accept() {
                    Ok((stream, _)) => serve(stream, &package, &runtime),
                    Err(error) if error.kind() == std::io::ErrorKind::WouldBlock => {
                        thread::sleep(Duration::from_millis(10))
                    }
                    Err(error) => panic!("fixture accept failed: {error}"),
                }
            }
        });
        Self { address, stop }
    }

    fn url(&self) -> String {
        format!("http://{}", self.address)
    }
}

impl Drop for StaticServer {
    fn drop(&mut self) {
        self.stop.store(true, Ordering::Relaxed);
    }
}

fn serve(mut stream: TcpStream, package: &Path, runtime: &Path) {
    let mut request = [0_u8; 2048];
    let length = stream.read(&mut request).unwrap_or(0);
    let first = String::from_utf8_lossy(&request[..length]);
    let path = first.split_whitespace().nth(1).unwrap_or("/");
    let (content_type, body) = match path {
        "/" => ("text/html; charset=utf-8", fixture_html().into_bytes()),
        "/hemx.js" => (
            "text/javascript; charset=utf-8",
            fs::read(runtime).expect("read runtime"),
        ),
        "/client_local.js" => (
            "text/javascript; charset=utf-8",
            fs::read(package.join("client_local.js")).expect("read bindings"),
        ),
        "/client_local_bg.wasm" => (
            "application/wasm",
            fs::read(package.join("client_local_bg.wasm")).expect("read wasm"),
        ),
        _ => ("text/plain", b"not found".to_vec()),
    };
    let status = if path == "/" || path == "/hemx.js" || path.starts_with("/client_local") {
        "200 OK"
    } else {
        "404 Not Found"
    };
    write!(stream, "HTTP/1.1 {status}\r\nContent-Type: {content_type}\r\nContent-Length: {}\r\nConnection: close\r\n\r\n", body.len()).expect("write fixture headers");
    stream.write_all(&body).expect("write fixture body");
}

fn fixture_html() -> String {
    r#"<!doctype html><html><body>
<main data-hemx-root="client_local">
  <section data-hemx-slot="counter_panel">idle</section>
  <button type="button" data-hid="1" data-hemx-client="increment">Increment locally</button>
</main>
<script src="/hemx.js"></script>
<script type="module">
import init, { __hemx_client_increment } from "/client_local.js";
await init();
const root = document.querySelector("[data-hemx-root]");
const slot = root.querySelector("[data-hemx-slot]");
const probe = __hemx_client_increment();
const batch = window.hemx.decodeBatch(probe);
root.dataset.hemxBuild = String(batch.fingerprint);
slot.dataset.sid = String(batch.ops[0].target.resource.id);
window.hemx.registerClientHandler("increment", __hemx_client_increment);
window.__clientReady = true;
</script></body></html>"#
        .to_owned()
}

async fn wait_until(driver: &WebDriver, script: &str) -> WebDriverResult<()> {
    let deadline = Instant::now() + STARTUP_TIMEOUT;
    loop {
        if driver
            .execute(script, Vec::new())
            .await?
            .json()
            .as_bool()
            .unwrap_or(false)
        {
            return Ok(());
        }
        if Instant::now() >= deadline {
            panic!("timed out waiting for browser fixture");
        }
        tokio::time::sleep(Duration::from_millis(50)).await;
    }
}

async fn wait_for_text(driver: &WebDriver, selector: &str, text: &str) -> WebDriverResult<()> {
    let deadline = Instant::now() + STARTUP_TIMEOUT;
    loop {
        if let Ok(element) = driver.find(By::Css(selector)).await {
            if element.text().await.unwrap_or_default().contains(text) {
                return Ok(());
            }
        }
        if Instant::now() >= deadline {
            panic!("timed out waiting for {text:?}");
        }
        tokio::time::sleep(Duration::from_millis(50)).await;
    }
}

async fn resource_count(driver: &WebDriver) -> WebDriverResult<u64> {
    Ok(driver
        .execute(
            "return performance.getEntriesByType('resource').length",
            Vec::new(),
        )
        .await?
        .json()
        .as_u64()
        .unwrap_or_default())
}

struct ProcessGuard(std::process::Child);

impl ProcessGuard {
    fn start(mut command: Command, address: &str) -> Self {
        let child = command.spawn().expect("start geckodriver");
        let deadline = Instant::now() + STARTUP_TIMEOUT;
        while std::net::TcpStream::connect(address).is_err() {
            assert!(Instant::now() < deadline, "timed out starting geckodriver");
            thread::sleep(Duration::from_millis(50));
        }
        Self(child)
    }
}

impl Drop for ProcessGuard {
    fn drop(&mut self) {
        let _ = self.0.kill();
        let _ = self.0.wait();
    }
}