all the refactor

cmd/inventory/level.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"context"
+	"log"
+	"strconv"
+	"time"
+
+	"git.k6n.net/mats/platform/event"
+	invlevel "git.k6n.net/mats/platform/inventory"
+	"git.k6n.net/mats/platform/rabbit"
+	"github.com/redis/go-redis/v9"
+)
+
+// emitLevelIfChanged classifies qty into a Level and emits an
+// inventory.level_changed bus event only when it differs from the level last
+// emitted for this SKU+location (the levelKey marker). Exact quantity never
+// leaves the service; only the coarse crossing does. Shared by every write path
+// (catalog feed, order.created commit). A nil conn (no bus) makes it a no-op.
+func emitLevelIfChanged(ctx context.Context, rdb *redis.Client, conn *rabbit.Conn, country string, low int64, sku, loc string, qty int64) {
+	if conn == nil {
+		return
+	}
+	lvl := invlevel.LevelFor(qty, low)
+	// Atomic read-old + write-new of the level marker; redis.Nil means the
+	// marker didn't exist yet (first observation), which we treat as a crossing.
+	prev, err := rdb.SetArgs(ctx, levelKey(sku, loc), string(lvl), redis.SetArgs{Get: true}).Result()
+	if err != nil && err != redis.Nil {
+		log.Printf("inventory: level marker sku=%s: %v", sku, err)
+		return
+	}
+	if prev == string(lvl) {
+		return // no threshold crossing — stay off the bus
+	}
+	payload, err := invlevel.LevelChanged{SKU: sku, Location: loc, Level: lvl}.Encode()
+	if err != nil {
+		log.Printf("inventory: encode level payload sku=%s: %v", sku, err)
+		return
+	}
+	ev := event.Event{
+		ID:      "invlvl-" + sku + "-" + loc + "-" + strconv.FormatInt(time.Now().UnixNano(), 36),
+		Type:    event.InventoryLevelChanged,
+		Source:  "inventory",
+		Subject: sku,
+		Payload: payload,
+		Time:    time.Now(),
+		Meta:    map[string]string{"country": country},
+	}
+	if err := rabbit.PublishEvent(conn.Connection(), "inventory", ev); err != nil {
+		log.Printf("inventory: publish level event sku=%s: %v", sku, err)
+	}
+}