From 9abe817aae35f68f698c8fc4451ff8851c3da8a0 Mon Sep 17 00:00:00 2001
From: Steve Cliff <steve@devcloud.guru>
Date: Mon, 4 May 2026 19:47:09 +0100
Subject: [PATCH] alert: engine skeleton + event channels

---
 internal/alert/engine.go | 134 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 internal/alert/engine.go

diff --git a/internal/alert/engine.go b/internal/alert/engine.go
new file mode 100644
index 0000000..56c8427
--- /dev/null
+++ b/internal/alert/engine.go
@@ -0,0 +1,134 @@
+// Package alert evaluates the hardcoded rule set and persists raises
+// / acknowledges / resolves. Three event sources feed it:
+//   - JobFinishedEvent — pushed when a job lands a terminal state
+//     (the existing MarkJobFinished site)
+//   - HostOfflineEvent / HostOnlineEvent — pushed by the offline
+//     sweeper and by the ws hello handler
+//   - 60s ticker (internal) — drives stale-schedule + auto-resolve
+//
+// All output goes through store.RaiseOrTouch / Acknowledge / Resolve
+// and the notification.Hub. The engine is one goroutine started at
+// boot; non-blocking sends from hot paths.
+package alert
+
+import (
+	"context"
+	"log/slog"
+	"sync"
+	"time"
+
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/notification"
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
+)
+
+// JobFinishedEvent carries everything the engine needs to evaluate
+// the failed-X rules. Pushed via Engine.NotifyJobFinished from the
+// MarkJobFinished site.
+type JobFinishedEvent struct {
+	HostID string
+	JobID  string
+	Kind   string // backup | forget | prune | check | unlock | restore | diff
+	Status string // succeeded | failed | cancelled
+	When   time.Time
+}
+
+// Engine evaluates hardcoded alert rules and dispatches via notification.Hub.
+type Engine struct {
+	store *store.Store
+	hub   *notification.Hub
+
+	jobs     chan JobFinishedEvent
+	hostDown chan string // host_id
+	hostUp   chan string
+
+	// agentOfflineFloor is the duration a host must be offline before
+	// we raise. Configurable for tests; default 15m.
+	agentOfflineFloor time.Duration
+	tickPeriod        time.Duration
+
+	closeOnce sync.Once
+	done      chan struct{}
+}
+
+// NewEngine builds the engine. agentOfflineFloor + tickPeriod default
+// to 15min and 60s respectively when zero.
+func NewEngine(st *store.Store, hub *notification.Hub) *Engine {
+	return &Engine{
+		store:             st,
+		hub:               hub,
+		jobs:              make(chan JobFinishedEvent, 32),
+		hostDown:          make(chan string, 32),
+		hostUp:            make(chan string, 32),
+		agentOfflineFloor: 15 * time.Minute,
+		tickPeriod:        60 * time.Second,
+		done:              make(chan struct{}),
+	}
+}
+
+// Run drives the event loop. Returns when ctx is done. Blocks; call in
+// its own goroutine.
+func (e *Engine) Run(ctx context.Context) {
+	t := time.NewTicker(e.tickPeriod)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			e.closeOnce.Do(func() { close(e.done) })
+			return
+		case ev := <-e.jobs:
+			e.handleJobFinished(ctx, ev)
+		case hostID := <-e.hostDown:
+			e.handleHostOffline(ctx, hostID)
+		case hostID := <-e.hostUp:
+			e.handleHostOnline(ctx, hostID)
+		case now := <-t.C:
+			e.tick(ctx, now)
+		}
+	}
+}
+
+// NotifyJobFinished is the hot-path hook called from MarkJobFinished's
+// caller (ws.handler.dispatchAgentMessage). Non-blocking: drops on a
+// full channel with a slog warning.
+func (e *Engine) NotifyJobFinished(ev JobFinishedEvent) {
+	select {
+	case e.jobs <- ev:
+	default:
+		slog.Warn("alert: jobs channel full; dropping event", "kind", ev.Kind, "host_id", ev.HostID)
+	}
+}
+
+// NotifyHostOffline notifies the engine that a host is offline.
+func (e *Engine) NotifyHostOffline(hostID string) {
+	select {
+	case e.hostDown <- hostID:
+	default:
+		slog.Warn("alert: hostDown channel full; dropping", "host_id", hostID)
+	}
+}
+
+// NotifyHostOnline notifies the engine that a host is online.
+func (e *Engine) NotifyHostOnline(hostID string) {
+	select {
+	case e.hostUp <- hostID:
+	default:
+		slog.Warn("alert: hostUp channel full; dropping", "host_id", hostID)
+	}
+}
+
+// Placeholder method stubs for C2 implementation
+func (e *Engine) handleJobFinished(ctx context.Context, ev JobFinishedEvent) {
+	// Implemented in C2
+}
+
+func (e *Engine) handleHostOffline(ctx context.Context, hostID string) {
+	// Implemented in C2
+}
+
+func (e *Engine) handleHostOnline(ctx context.Context, hostID string) {
+	// Implemented in C2
+}
+
+func (e *Engine) tick(ctx context.Context, now time.Time) {
+	// Implemented in C2
+}