feat: add a simple gerrit event filter

This worker transforms a native Gerrit stream event into a OfBorg VCS
generic stream event.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

ofborg/src/bin/gerrit-generic-vcs-filter.rs

@@ -0,0 +1,86 @@
+/// This converts a Gerrit event to a OfBorg's VCS general event.
+use std::env;
+use std::error::Error;
+
+use ofborg::easyamqp::{self, ChannelExt, ConsumerExt};
+use ofborg::easylapin;
+use ofborg::tasks;
+
+use ofborg::config;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    ofborg::setup_log();
+
+    let arg = env::args()
+        .nth(1)
+        .expect("usage: gerrit-generic-vcs-filter <config>");
+    let cfg = config::load(arg.as_ref());
+
+    let conn = easylapin::from_config(&cfg.rabbitmq).await?;
+    let mut chan = conn.create_channel().await?;
+
+    // Destination exchange: `vcs-events`
+    chan.declare_exchange(easyamqp::ExchangeConfig {
+        exchange: "vcs-events".to_owned(),
+        exchange_type: easyamqp::ExchangeType::Topic,
+        passive: false,
+        durable: true,
+        auto_delete: false,
+        no_wait: false,
+        internal: false,
+    })
+    .await?;
+
+    // Source exchange: `gerrit-events`
+    chan.declare_exchange(easyamqp::ExchangeConfig {
+        exchange: "gerrit-events".to_owned(),
+        exchange_type: easyamqp::ExchangeType::Topic,
+        passive: false,
+        durable: true,
+        auto_delete: false,
+        no_wait: false,
+        internal: false,
+    })
+    .await?;
+
+    // Source queue: `gerrit-generic-filter`
+    let queue_name = String::from("gerrit-generic-filter");
+    chan.declare_queue(easyamqp::QueueConfig {
+        queue: queue_name.clone(),
+        passive: false,
+        durable: true,
+        exclusive: false,
+        auto_delete: false,
+        no_wait: false,
+    })
+    .await?;
+
+    chan.bind_queue(easyamqp::BindQueueConfig {
+        queue: queue_name.clone(),
+        exchange: "gerrit-events".to_owned(),
+        routing_key: Some("gerrit.events.*".to_owned()),
+        no_wait: false,
+    })
+    .await?;
+
+    tracing::info!("Fetching jobs from '{}'", &queue_name);
+    easylapin::WorkerChannel(chan)
+        .consume(
+            tasks::gerrit::GerritEventFilterWorker::new(),
+            easyamqp::ConsumeConfig {
+                queue: queue_name.clone(),
+                consumer_tag: format!("{}-gerrit-generic-vcs-filter", cfg.whoami()),
+                no_local: false,
+                no_ack: false,
+                no_wait: false,
+                exclusive: false,
+            },
+        )
+        .await?;
+
+    drop(conn);
+    tracing::info!("Closed the session... EOF");
+
+    Ok(())
+}

ofborg/src/tasks/gerrit/mod.rs

@@ -0,0 +1,66 @@
+use crate::vcs::gerrit::data_structures::GerritStreamEvent;
+use crate::worker;
+use async_trait::async_trait;
+use tracing::debug_span;
+
+/// This transforms a Gerrit event into a OfBorg event.
+
+pub struct GerritEventFilterWorker;
+
+impl GerritEventFilterWorker {
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+#[async_trait]
+impl worker::SimpleWorker for GerritEventFilterWorker {
+    type J = GerritStreamEvent;
+
+    async fn msg_to_job(
+        &mut self,
+        _: &str,
+        _: &Option<String>,
+        body: &[u8],
+    ) -> Result<Self::J, String> {
+        match serde_json::from_slice(body) {
+            Ok(e) => Ok(e),
+            Err(e) => Err(format!(
+                "Failed to deserialize event {:?}: {:?}",
+                e,
+                String::from_utf8(body.to_vec())
+            )),
+        }
+    }
+
+    async fn consumer(
+        &mut self,
+        _chan: &mut lapin::Channel,
+        evt: &GerritStreamEvent,
+    ) -> worker::Actions {
+        let span = debug_span!("event");
+        let _enter = span.enter();
+
+        match evt {
+            GerritStreamEvent::DroppedOutput => {
+                tracing::warn!("Gerrit reported loss of output!");
+                // TODO: Update the stat worker about this.
+            }
+            // Transform this into a "new pull request"
+            // Change restored -> rerun CI on it if not already.
+            // Exitting WIP -> run CI if not already
+            GerritStreamEvent::PatchSetCreated { .. } => {}
+            // Change abandoned or deleted or updated -> Change no longer relevant
+            // Entering into WIP -> Change no longer relevant
+            GerritStreamEvent::ChangeAbandoned { .. } => {}
+            // TODO: CommentAdded / HashtagsChanged / TopicChanged
+            // propagate them for chatops support and tagging manipulations
+            // TODO: ChangeMerged
+            // dispatch something to support periodic jobs or further workflows after a commit is
+            // merged, e.g. performance CI, etc.
+            _ => {}
+        }
+
+        vec![worker::Action::Ack]
+    }
+}

ofborg/src/tasks/mod.rs

@@ -2,6 +2,7 @@ pub mod build;
 pub mod eval;
 pub mod evaluate;
 pub mod evaluationfilter;
+pub mod gerrit;
 pub mod log_message_collector;
 pub mod pastebin_collector;
 pub mod statscollector;