Load sheet into in-memory data model and serve it as the API

internal/directory/cache.go

@@ -0,0 +1,55 @@
+package directory
+
+import (
+	"log"
+	"sync"
+	"time"
+
+	"heliosian/internal/data"
+)
+
+const refreshInterval = 5 * time.Minute
+
+type Cache struct {
+	source data.Source
+	mu     sync.RWMutex
+	model  *Model
+}
+
+func NewCache(source data.Source) (*Cache, error) {
+	c := &Cache{source: source}
+	if err := c.refresh(); err != nil {
+		return nil, err
+	}
+	go c.refreshLoop()
+	return c, nil
+}
+
+func (c *Cache) Model() *Model {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.model
+}
+
+func (c *Cache) refreshLoop() {
+	for range time.Tick(refreshInterval) {
+		if err := c.refresh(); err != nil {
+			log.Printf("[ERROR] directory model refresh: %v", err)
+		}
+	}
+}
+
+func (c *Cache) refresh() error {
+	start := time.Now()
+	model, err := LoadModel(c.source)
+	if err != nil {
+		return err
+	}
+	c.mu.Lock()
+	c.model = model
+	c.mu.Unlock()
+	log.Printf("loaded directory model: %d people, %d families, %d classrooms, %d sections in %s",
+		len(model.People), len(model.Families), len(model.Classrooms), len(model.Sections),
+		time.Since(start).Round(time.Millisecond))
+	return nil
+}