bring in khatru and eventstore.

khatru/docs/cookbook/custom-live-events.md

@@ -0,0 +1,64 @@
+---
+outline: deep
+---
+
+# Generating custom live events
+
+Suppose you want to generate a new event every time a goal is scored on some soccer game and send that to all clients subscribed to a given game according to a tag `t`.
+
+We'll assume you'll be polling some HTTP API that gives you the game's current score, and that in your `main` function you'll start the function that does the polling:
+
+```go
+func main () {
+	// other stuff here
+	relay := khatru.NewRelay()
+
+	go startPollingGame(relay)
+	// other stuff here
+}
+
+type GameStatus struct {
+	TeamA int `json:"team_a"`
+	TeamB int `json:"team_b"`
+}
+
+func startPollingGame(relay *khatru.Relay) {
+	current := GameStatus{0, 0}
+
+	for {
+		newStatus, err := fetchGameStatus()
+		if err != nil {
+				continue
+		}
+
+		if newStatus.TeamA > current.TeamA {
+				// team A has scored a goal, here we generate an event
+				evt := nostr.Event{
+					CreatedAt: nostr.Now(),
+					Kind: 1,
+					Content: "team A has scored!",
+					Tags: nostr.Tags{{"t", "this-game"}}
+				}
+				evt.Sign(global.RelayPrivateKey)
+				// calling BroadcastEvent will send the event to everybody who has been listening for tag "t=[this-game]"
+				// there is no need to do any code to keep track of these clients or who is listening to what, khatru
+				// does that already in the background automatically
+				relay.BroadcastEvent(evt)
+
+				// just calling BroadcastEvent won't cause this event to be be stored,
+				// if for any reason you want to store these events you must call the store functions manually
+				for _, store := range relay.StoreEvent {
+					store(context.TODO(), evt)
+				}
+		}
+		if newStatus.TeamB > current.TeamB {
+				// same here, if team B has scored a goal
+				// ...
+		}
+	}
+}
+
+func fetchGameStatus() (GameStatus, error) {
+	// implementation of calling some external API goes here
+}
+```