Add invalidate and cachedResponse functions to CachingTokenSource

Author: davidliu

livekit-android-sdk/src/main/java/io/livekit/android/token/CachingTokenSource.kt

@@ -25,7 +25,13 @@ abstract class BaseCachingTokenSource(
     private val store: TokenStore,
     private val validator: TokenValidator,
 ) {
-    suspend fun fetchImpl(options: TokenRequestOptions?): TokenSourceResponse {
+
+    /**
+     * The entrypoint for the caching store; subclasses should call this from their fetch methods.
+     *
+     * If a new token is needed, [fetchFromSource] will be called.
+     */
+    internal suspend fun fetchImpl(options: TokenRequestOptions?): TokenSourceResponse {
         val cached = store.retrieve()
 
         if (cached != null && cached.options == options && validator.invoke(cached.options, cached.response)) {
@@ -37,7 +43,24 @@ abstract class BaseCachingTokenSource(
         return response
     }
 
+    /**
+     * Implement this to fetch the [TokenSourceResponse] from the token source.
+     */
     abstract suspend fun fetchFromSource(options: TokenRequestOptions?): TokenSourceResponse
+
+    /**
+     * Invalidate the cached credentials, forcing a fresh fetch on the next request.
+     */
+    suspend fun invalidate() {
+        store.clear()
+    }
+
+    /**
+     * Get the cached credentials if one exists.
+     */
+    suspend fun cachedResponse(): TokenSourceResponse? {
+        return store.retrieve()?.response
+    }
 }
 
 class CachingFixedTokenSource(

livekit-android-sdk/src/main/java/io/livekit/android/token/TokenSource.kt

@@ -66,16 +66,25 @@ interface TokenSource {
     companion object {
         /**
          * Creates a [FixedTokenSource] that immediately returns with the supplied [serverUrl] and [participantToken].
+         *
+         * @see cached
+         * @see CachingFixedTokenSource
          */
         fun fromLiteral(serverUrl: String, participantToken: String): FixedTokenSource = LiteralTokenSource(serverUrl, participantToken)
 
         /**
          * Creates a custom [ConfigurableTokenSource] that executes [block] to fetch the credentials.
+         *
+         * @see cached
+         * @see CachingConfigurableTokenSource
          */
         fun fromCustom(block: suspend (options: TokenRequestOptions) -> TokenSourceResponse): ConfigurableTokenSource = CustomTokenSource(block)
 
         /**
          * Creates a [ConfigurableTokenSource] that fetches from a given [url] using the standard token server format.
+         *
+         * @see cached
+         * @see CachingConfigurableTokenSource
          */
         fun fromEndpoint(url: URL, method: String = "POST", headers: Map<String, String> = emptyMap()): ConfigurableTokenSource = EndpointTokenSourceImpl(
             url = url,
@@ -88,6 +97,9 @@ interface TokenSource {
          * which supports quick prototyping/getting started types of use cases.
          *
          * Note: This token provider is **insecure** and should **not** be used in production.
+         *
+         * @see cached
+         * @see CachingConfigurableTokenSource
          */
         fun fromSandboxTokenServer(sandboxId: String, options: SandboxTokenServerOptions = SandboxTokenServerOptions()): ConfigurableTokenSource = SandboxTokenSource(
             sandboxId = sandboxId,