use std::{
    collections::HashSet,
    sync::Arc,
    time::Duration,
};
use futures::{Stream, StreamExt};
use url::Url;
use cave::{
    activitypub::{
        self,
        fetch::authorized_fetch,
    },
    block_list::BlockList,
    config::LoadConfig,
    feed,
};
use metrics_util::MetricKindMask;
use metrics_exporter_prometheus::PrometheusBuilder;

mod config;

pub async fn connect_relay_in(redis_url: Url, in_topic: &str) -> Result<impl Stream<Item = activitypub::Action<serde_json::Value>>, redis::RedisError> {
    let client = redis::Client::open(redis_url)?;
    let mut pubsub_conn = client.get_async_connection()
        .await?
        .into_pubsub();

    pubsub_conn.subscribe(in_topic)
        .await?;

    Ok(pubsub_conn.into_on_message().filter_map(|msg| async move {
        let data = msg.get_payload::<String>().ok()?;
        let json = serde_json::from_str(&data)
            .ok()?;
        Some(json)
    }))
}

const KEY_ID: &str = "https://relay.fedi.buzz/instance/fedi.buzz#key";

#[tokio::main]
async fn main() {
    cave::init::exit_on_panic();
    cave::init::init_logger(5557);

    let config = config::Config::load();
    let block_list = BlockList::new(&config.blocklist).await;

    PrometheusBuilder::new()
        .with_http_listener(([0; 8], config.prometheus_port))
        .add_global_label("application", env!("CARGO_PKG_NAME"))
        .idle_timeout(MetricKindMask::ALL, Some(Duration::from_secs(600)))
        .install()
        .unwrap();

    let priv_key = Arc::new(config.priv_key());
    let relay_in = connect_relay_in(config.redis_url(), &config.in_topic)
        .await
        .unwrap();

    let client = reqwest::Client::builder()
        .timeout(Duration::from_secs(5))
        .user_agent(concat!(
            env!("CARGO_PKG_NAME"),
            "/",
            env!("CARGO_PKG_VERSION"),
        ))
        .pool_max_idle_per_host(1)
        .pool_idle_timeout(Some(Duration::from_secs(5)))
        .build()
        .unwrap();

    let store = cave::store::Store::new(1, config.redis, config.redis_password_file).await;

    let posts_cache = cave::posts_cache::PostsCache::new(65536);
    let allowed_action_types: Arc<HashSet<String>> = Arc::new([
        "Create", "Announce", "Update",
    ].into_iter().map(|s| s.to_string()).collect());

    tracing::info!("ready");
    cave::systemd::ready();

    relay_in.for_each(|action| async {
        // Filter by action type
        if ! allowed_action_types.contains(&action.action_type) {
            metrics::counter!("sieve_activity", 1, "type" => "type_ignored");
            return;
        }

        let posts_cache = posts_cache.clone();
        let block_list = block_list.clone();
        let client = client.clone();
        let mut store = store.clone();
        let priv_key = priv_key.clone();

        tokio::spawn(async move {
            // Avoid duplicate work
            let id = if let Some(id) = action.object_id() {
                let id = id.to_string();
                if posts_cache.insert(id.clone()) {
                    return;
                }
                id
            } else {
                // no object id
                tracing::warn!("No object id in action: {:?}", action);
                return;
            };

            let object = if action.object.is_object() {
                // all good, can be forwarded
                action.object
            } else if let Some(id) = action.object.as_str() {
                // fetch info for id
                tracing::debug!("GET {id}");
                match authorized_fetch(&client, id, KEY_ID, &priv_key).await {
                    Ok(res) => {
                        metrics::counter!("sieve_activity", 1, "type" => "fetch_object_ok");
                        res
                    }
                    Err(e) => {
                        tracing::error!("{id} HTTP: {e:?}");
                        metrics::counter!("sieve_activity", 1, "type" => "fetch_object_error");
                        return;
                    }
                }
            } else {
                tracing::warn!("Invalid object {id} in action: {:?}", action);
                return;
            };

            let post: activitypub::Post = match serde_json::from_value(object) {
                Ok(post) =>
                    post,
                Err(e) => {
                    tracing::error!("JSON of {id}: {e:?}");
                    metrics::counter!("sieve_activity", 1, "type" => "json_error");
                    return;
                }
            };

            let author: activitypub::Actor = if let Some(author_url) = &post.attributed_to {
                if let Ok(url) = Url::parse(author_url) {
                    let Some(host) = url.host_str() else {
                        tracing::error!("No host in author {author_url}");
                        return;
                    };
                    if block_list.is_blocked(host).await {
                        tracing::warn!("Ignore blocked author {author_url}");
                        metrics::counter!("sieve_activity", 1, "type" => "blocked_author");
                        return;
                    }
                } else {
                    tracing::error!("Invalid author: {author_url}");
                    metrics::counter!("sieve_activity", 1, "type" => "invalid_author");
                    return;

                }

                match authorized_fetch(&client, author_url, KEY_ID, &priv_key).await {
                    Ok(author) => {
                        metrics::counter!("sieve_activity", 1, "type" => "fetch_author_ok");
                        author
                    }
                    Err(e) => {
                        tracing::error!("{author_url} HTTP: {e:?}");
                        metrics::counter!("sieve_activity", 1, "type" => "fetch_author_error");
                        return;
                    }
                }
            } else {
                tracing::error!("No attributedTo in {id}");
                metrics::counter!("sieve_activity", 1, "type" => "no_author");
                return;
            };
            // Translate ActivityPub post to Mastodon client API post format
            let feed_post = post.to_feed_post(author);
            let event_type = if action.action_type == "Update" {
                // Translate more weird Mastodon client API naming
                "status.update"
            } else {
                "update"
            }.to_string();
            let Ok(encodable_post) = feed::EncodablePost::from_post(event_type, feed_post) else {
                tracing::error!("Cannot serialize post {id}");
                metrics::counter!("sieve_activity", 1, "type" => "serialize_error");
                return;
            };

            match store.save_post(encodable_post).await {
                Ok(true) => {
                    tracing::info!("Post was new: {id}");
                    metrics::counter!("sieve_activity", 1, "type" => "post_new");
                    cave::systemd::watchdog();
                }
                Ok(false) => {
                    tracing::info!("Post was already known: {id}");
                    metrics::counter!("sieve_activity", 1, "type" => "post_known");
                    cave::systemd::watchdog();
                }
                Err(e) => {
                    tracing::error!("Error forwarding post {id}: {e:?}");
                    metrics::counter!("sieve_activity", 1, "type" => "post_error");
                }
            }
        });
    }).await;
}