use std::collections::HashMap;
use std::io;
use std::sync::Arc;
use std::sync::Mutex;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering;

use pretty_assertions::assert_eq;

use super::*;
use crate::OutboundProxyPolicy;

#[tokio::test]
async fn forwards_exact_urls_and_reuses_clients_by_resolved_route() {
    let builder_count = Arc::new(AtomicUsize::new(0));
    let observed_builder_count = Arc::clone(&builder_count);
    let pool = RouteAwareClientPool::with_builder_factory(
        HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
        ClientRouteClass::Api,
        move || {
            observed_builder_count.fetch_add(1, Ordering::SeqCst);
            reqwest::Client::builder()
        },
    );

    let direct_url = "https://example.com/first?target=direct";
    let same_route_url = "https://example.com/second?target=direct%202";
    let proxy_url = "https://example.com/third?target=proxy";
    let resolver = FakeRouteResolver::new(HashMap::from([
        (direct_url.to_string(), OutboundProxyRoute::Direct),
        (same_route_url.to_string(), OutboundProxyRoute::Direct),
        (
            proxy_url.to_string(),
            OutboundProxyRoute::Proxy {
                url: "http://proxy.example".to_string(),
            },
        ),
    ]));

    resolve_with(&pool, &resolver, direct_url)
        .await
        .expect("first client should build");
    resolve_with(&pool, &resolver, same_route_url)
        .await
        .expect("second client should reuse the route");
    resolve_with(&pool, &resolver, proxy_url)
        .await
        .expect("proxy client should build separately");

    assert_eq!(builder_count.load(Ordering::SeqCst), 2);
    assert_eq!(
        resolver.observed_urls(),
        vec![
            direct_url.to_string(),
            same_route_url.to_string(),
            proxy_url.to_string(),
        ]
    );
}

#[tokio::test]
async fn bounds_cached_routes_and_rebuilds_an_evicted_route() {
    let builder_count = Arc::new(AtomicUsize::new(0));
    let observed_builder_count = Arc::clone(&builder_count);
    let pool = RouteAwareClientPool::with_builder_factory(
        HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
        ClientRouteClass::Api,
        move || {
            observed_builder_count.fetch_add(1, Ordering::SeqCst);
            reqwest::Client::builder()
        },
    );
    let routes = (0..=MAX_CACHED_ROUTES)
        .map(|index| {
            (
                format!("https://target-{index}.example"),
                OutboundProxyRoute::Proxy {
                    url: format!("http://proxy-{index}.example"),
                },
            )
        })
        .collect::<HashMap<_, _>>();
    let resolver = FakeRouteResolver::new(routes.clone());

    for request_url in routes.keys() {
        resolve_with(&pool, &resolver, request_url)
            .await
            .expect("client should build");
    }
    let evicted_route = {
        let clients = pool.clients.lock().expect("client cache lock");
        assert_eq!(clients.len(), MAX_CACHED_ROUTES);
        routes
            .iter()
            .find(|(_, route)| !clients.contains_key(*route))
            .map(|(request_url, _)| request_url.clone())
            .expect("one route should have been evicted")
    };

    resolve_with(&pool, &resolver, &evicted_route)
        .await
        .expect("evicted client should rebuild");

    assert_eq!(builder_count.load(Ordering::SeqCst), MAX_CACHED_ROUTES + 2);
    assert_eq!(
        pool.clients.lock().expect("client cache lock").len(),
        MAX_CACHED_ROUTES
    );
}

#[derive(Clone)]
struct FakeRouteResolver {
    routes: Arc<HashMap<String, OutboundProxyRoute>>,
    observed_urls: Arc<Mutex<Vec<String>>>,
}

impl FakeRouteResolver {
    fn new(routes: HashMap<String, OutboundProxyRoute>) -> Self {
        Self {
            routes: Arc::new(routes),
            observed_urls: Arc::new(Mutex::new(Vec::new())),
        }
    }

    async fn resolve(&self, request_url: String) -> io::Result<OutboundProxyRoute> {
        self.observed_urls
            .lock()
            .expect("observed URL lock")
            .push(request_url.clone());
        self.routes
            .get(&request_url)
            .cloned()
            .ok_or_else(|| io::Error::other(format!("no route for {request_url}")))
    }

    fn observed_urls(&self) -> Vec<String> {
        self.observed_urls
            .lock()
            .expect("observed URL lock")
            .clone()
    }
}

async fn resolve_with(
    pool: &RouteAwareClientPool,
    resolver: &FakeRouteResolver,
    request_url: &str,
) -> Result<HttpClient, RouteAwareClientPoolError> {
    let resolver = resolver.clone();
    pool.client_for_url_with_resolver(request_url, move |request_url| async move {
        resolver.resolve(request_url).await
    })
    .await
}