CDN

utils/middleware/edge_cache.go

@@ -0,0 +1,77 @@
+package middleware
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+
+	"github.com/gofiber/fiber/v2"
+)
+
+// CacheStrategy defines caching profiles for different API data mutability tiers
+type CacheStrategy string
+
+const (
+	// Immutable: For historical completed games, past seasons, and shot charts.
+	// Edge TTL: 30 Days | Browser TTL: 1 Day
+	Immutable CacheStrategy = "immutable"
+
+	// SemiDynamic: For daily leaderboards, player season averages, and standings.
+	// Edge TTL: 1 Day | Browser TTL: 1 Minute | Stale-While-Revalidate: 10 Minutes
+	SemiDynamic CacheStrategy = "semi_dynamic"
+
+	// Realtime: For active game telemetry, live quarter stats, and fast-updating data.
+	// Edge TTL: 10 Seconds | Browser TTL: 5 Seconds | Stale-While-Revalidate: 30 Seconds
+	Realtime CacheStrategy = "realtime"
+
+	// NoCache: For transactional mutations, scrapers, and admin endpoints.
+	NoCache CacheStrategy = "no_cache"
+)
+
+// EdgeCache injects standardized Cloudflare & HTTP caching headers
+func EdgeCache(strategy CacheStrategy, tags ...string) fiber.Handler {
+	return func(c *fiber.Ctx) error {
+		// Only cache idempotent read requests (GET / HEAD)
+		if c.Method() != fiber.MethodGet && c.Method() != fiber.MethodHead {
+			c.Set("Cache-Control", "no-store, no-cache, must-revalidate, proxy-revalidate")
+			c.Set("Pragma", "no-cache")
+			c.Set("Expires", "0")
+			return c.Next()
+		}
+
+		switch strategy {
+		case Immutable:
+			// Served directly by Cloudflare US Edge for 30 days without hitting Europe origin
+			c.Set("Cache-Control", "public, max-age=86400, s-maxage=2592000, immutable")
+		case SemiDynamic:
+			// Instant edge delivery; background revalidation over transatlantic backbone
+			c.Set("Cache-Control", "public, max-age=60, s-maxage=86400, stale-while-revalidate=600")
+		case Realtime:
+			c.Set("Cache-Control", "public, max-age=5, s-maxage=10, stale-while-revalidate=30")
+		case NoCache:
+			c.Set("Cache-Control", "no-store, no-cache, must-revalidate")
+			return c.Next()
+		}
+
+		// Cloudflare Cache-Tag header for instantaneous programmatic purge by entity
+		if len(tags) > 0 {
+			var tagHeader string
+			for i, tag := range tags {
+				if i > 0 {
+					tagHeader += ","
+				}
+				tagHeader += tag
+			}
+			c.Set("Cache-Tag", tagHeader)
+		}
+
+		c.Set("Vary", "Accept-Encoding, Origin")
+		return c.Next()
+	}
+}
+
+// ComputeETag generates a weak ETag based on response body bytes for 304 Not Modified optimization
+func ComputeETag(data []byte) string {
+	hash := sha256.Sum256(data)
+	return fmt.Sprintf(`W/"%s"`, hex.EncodeToString(hash[:8]))
+}