zero: merge pomerium/zero-sdk (#4848)

pkg/zero/cluster/urlcache.go

@@ -0,0 +1,55 @@
+package cluster
+
+import (
+	"net/url"
+	"sync"
+	"time"
+)
+
+// URLCache is a cache of URLs to download bundles from.
+type URLCache struct {
+	mx    sync.RWMutex
+	cache map[string]DownloadCacheEntry
+}
+
+// DownloadCacheEntry is a cache entry for a URL to download a bundle from.
+type DownloadCacheEntry struct {
+	// URL is the URL to download the bundle from.
+	URL url.URL
+	// ExpiresAt is the time at which the URL expires.
+	ExpiresAt time.Time
+	// CaptureHeaders is a list of headers to capture from the response.
+	CaptureHeaders []string
+}
+
+// NewURLCache creates a new URL cache.
+func NewURLCache() *URLCache {
+	return &URLCache{
+		cache: make(map[string]DownloadCacheEntry),
+	}
+}
+
+// Get gets the cache entry for the given key, if it exists and has not expired.
+func (c *URLCache) Get(key string, minTTL time.Duration) (*DownloadCacheEntry, bool) {
+	c.mx.RLock()
+	defer c.mx.RUnlock()
+
+	entry, ok := c.cache[key]
+	if !ok {
+		return nil, false
+	}
+
+	if time.Until(entry.ExpiresAt) < minTTL {
+		return nil, false
+	}
+
+	return &entry, true
+}
+
+// Set sets the cache entry for the given key.
+func (c *URLCache) Set(key string, entry DownloadCacheEntry) {
+	c.mx.Lock()
+	defer c.mx.Unlock()
+
+	c.cache[key] = entry
+}