most simple relay pool.

pool.ts

@@ -0,0 +1,27 @@
+import {Relay, relayInit} from './relay'
+import {normalizeURL} from './utils'
+
+export function pool(defaultRelays: string[] = []) {
+  return new SimplePool(defaultRelays)
+}
+
+class SimplePool {
+  private _conn: {[url: string]: Relay}
+  private _knownIds: Set<string> = new Set()
+
+  constructor(defaultRelays: string[]) {
+    this._conn = {}
+    defaultRelays.forEach(this.ensureRelay)
+  }
+
+  ensureRelay(url: string): Relay {
+    const nm = normalizeURL(url)
+    const existing = this._conn[nm]
+    if (existing) return existing
+
+    const hasEventId = (id: string): boolean => this._knownIds.has(id)
+    const relay = relayInit(nm, hasEventId)
+    this._conn[nm] = relay
+    return relay
+  }
+}