webhooks (#1)

Reviewed-on: #1

k-tv-backend/api/src/webhook.rs

@@ -0,0 +1,164 @@
+//! WebhookConsumer background task.
+//!
+//! Subscribes to the domain-event broadcast channel, looks up each channel's
+//! webhook_url, and fires HTTP POST requests (fire-and-forget).
+
+use chrono::Utc;
+use serde_json::{Value, json};
+use std::sync::Arc;
+use tokio::sync::broadcast;
+use tracing::{info, warn};
+use uuid::Uuid;
+
+use domain::{ChannelRepository, DomainEvent};
+
+/// Consumes domain events and delivers them to per-channel webhook URLs.
+///
+/// Uses fire-and-forget HTTP POST — failures are logged as warnings, never retried.
+pub async fn run_webhook_consumer(
+    mut rx: broadcast::Receiver<DomainEvent>,
+    channel_repo: Arc<dyn ChannelRepository>,
+    client: reqwest::Client,
+) {
+    loop {
+        match rx.recv().await {
+            Ok(event) => {
+                let channel_id = event_channel_id(&event);
+                let payload = build_payload(&event);
+
+                match channel_repo.find_by_id(channel_id).await {
+                    Ok(Some(channel)) => {
+                        if let Some(url) = channel.webhook_url {
+                            let client = client.clone();
+                            tokio::spawn(async move {
+                                post_webhook(&client, &url, payload).await;
+                            });
+                        }
+                        // No webhook_url configured — skip silently
+                    }
+                    Ok(None) => {
+                        // Channel deleted — nothing to do
+                    }
+                    Err(e) => {
+                        warn!("webhook consumer: failed to look up channel {}: {}", channel_id, e);
+                    }
+                }
+            }
+            Err(broadcast::error::RecvError::Lagged(n)) => {
+                warn!("webhook consumer lagged, {} events dropped", n);
+                // Continue — don't break; catch up from current position
+            }
+            Err(broadcast::error::RecvError::Closed) => {
+                info!("webhook consumer: event bus closed, shutting down");
+                break;
+            }
+        }
+    }
+}
+
+/// Extract the channel_id from any event variant.
+fn event_channel_id(event: &DomainEvent) -> Uuid {
+    match event {
+        DomainEvent::BroadcastTransition { channel_id, .. } => *channel_id,
+        DomainEvent::NoSignal { channel_id } => *channel_id,
+        DomainEvent::ScheduleGenerated { channel_id, .. } => *channel_id,
+        DomainEvent::ChannelCreated { channel } => channel.id,
+        DomainEvent::ChannelUpdated { channel } => channel.id,
+        DomainEvent::ChannelDeleted { channel_id } => *channel_id,
+    }
+}
+
+/// Build the JSON payload for an event.
+fn build_payload(event: &DomainEvent) -> Value {
+    let now = Utc::now().to_rfc3339();
+    match event {
+        DomainEvent::BroadcastTransition { channel_id, slot } => {
+            let offset_secs = (Utc::now() - slot.start_at).num_seconds().max(0) as u64;
+            json!({
+                "event": "broadcast_transition",
+                "timestamp": now,
+                "channel_id": channel_id,
+                "data": {
+                    "slot_id": slot.id,
+                    "item": {
+                        "id": slot.item.id.as_ref(),
+                        "title": slot.item.title,
+                        "duration_secs": slot.item.duration_secs,
+                    },
+                    "start_at": slot.start_at.to_rfc3339(),
+                    "end_at": slot.end_at.to_rfc3339(),
+                    "offset_secs": offset_secs,
+                }
+            })
+        }
+        DomainEvent::NoSignal { channel_id } => {
+            json!({
+                "event": "no_signal",
+                "timestamp": now,
+                "channel_id": channel_id,
+                "data": {}
+            })
+        }
+        DomainEvent::ScheduleGenerated { channel_id, schedule } => {
+            json!({
+                "event": "schedule_generated",
+                "timestamp": now,
+                "channel_id": channel_id,
+                "data": {
+                    "generation": schedule.generation,
+                    "valid_from": schedule.valid_from.to_rfc3339(),
+                    "valid_until": schedule.valid_until.to_rfc3339(),
+                    "slot_count": schedule.slots.len(),
+                }
+            })
+        }
+        DomainEvent::ChannelCreated { channel } => {
+            json!({
+                "event": "channel_created",
+                "timestamp": now,
+                "channel_id": channel.id,
+                "data": {
+                    "name": channel.name,
+                    "description": channel.description,
+                }
+            })
+        }
+        DomainEvent::ChannelUpdated { channel } => {
+            json!({
+                "event": "channel_updated",
+                "timestamp": now,
+                "channel_id": channel.id,
+                "data": {
+                    "name": channel.name,
+                    "description": channel.description,
+                }
+            })
+        }
+        DomainEvent::ChannelDeleted { channel_id } => {
+            json!({
+                "event": "channel_deleted",
+                "timestamp": now,
+                "channel_id": channel_id,
+                "data": {}
+            })
+        }
+    }
+}
+
+/// Fire-and-forget HTTP POST to a webhook URL.
+async fn post_webhook(client: &reqwest::Client, url: &str, payload: Value) {
+    match client.post(url).json(&payload).send().await {
+        Ok(resp) => {
+            if !resp.status().is_success() {
+                warn!(
+                    "webhook POST to {} returned status {}",
+                    url,
+                    resp.status()
+                );
+            }
+        }
+        Err(e) => {
+            warn!("webhook POST to {} failed: {}", url, e);
+        }
+    }
+}