dev day #79

internal/middleware/asset_cache.go

@@ -0,0 +1,70 @@
+package middleware
+
+import (
+    "net/http"
+    "path/filepath"
+    "strings"
+
+    "github.com/gin-gonic/gin"
+)
+
+// AssetCacheControl sets optimal Cache-Control headers for static assets served by this server.
+// It only affects GET requests for well-known static prefixes and does not override
+// cache headers explicitly set by handlers downstream (they can still modify after c.Next if needed).
+func AssetCacheControl() gin.HandlerFunc {
+    return func(c *gin.Context) {
+        // Only apply to GET requests
+        if c.Request.Method == http.MethodGet {
+            p := c.Request.URL.Path
+            lower := strings.ToLower(p)
+            switch {
+            // Specific: YouTube channel static cache can be cached longer (content changes infrequently)
+            case strings.HasPrefix(lower, "/cache/prefetch/") && strings.HasSuffix(lower, "youtube_channel.json"):
+                c.Header("Cache-Control", "public, max-age=3600") // 1 hour
+            case strings.HasPrefix(lower, "/dist/"):
+                // Fingerprinted build assets should be cached for a year and immutable
+                c.Header("Cache-Control", "public, max-age=31536000, immutable")
+            case strings.HasPrefix(lower, "/uploads/"):
+                // User uploads: cache for a week; allow clients to revalidate if replaced
+                // Heuristic: if file name appears fingerprinted (e.g., .<hash>.ext), use longer cache
+                base := filepath.Base(lower)
+                if looksFingerprinted(base) {
+                    c.Header("Cache-Control", "public, max-age=31536000, immutable")
+                } else {
+                    c.Header("Cache-Control", "public, max-age=604800") // 7 days
+                }
+            case strings.HasPrefix(lower, "/cache/"):
+                // Prefetched JSON and other generated cache files: short to medium cache
+                c.Header("Cache-Control", "public, max-age=300") // 5 minutes
+            }
+        }
+        c.Next()
+    }
+}
+
+// looksFingerprinted checks if a filename contains a long hex-like segment before the extension
+// e.g. logo.7eacd9f0bfa04928a9b6936140168f58.png
+func looksFingerprinted(name string) bool {
+    dot := strings.LastIndexByte(name, '.')
+    if dot <= 0 || dot >= len(name)-1 {
+        return false
+    }
+    core := name[:dot]
+    // Find final segment after last dot/underscore/hyphen in core
+    lastSep := strings.LastIndexAny(core, "._-")
+    if lastSep < 0 || lastSep+1 >= len(core) {
+        return false
+    }
+    seg := core[lastSep+1:]
+    if len(seg) < 16 { // require at least 16 chars to treat as a hash
+        return false
+    }
+    // hex-like check
+    for i := 0; i < len(seg); i++ {
+        ch := seg[i]
+        if !((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f')) {
+            return false
+        }
+    }
+    return true
+}