RetrostashPlugin

Ktor HttpClient plugin that adds annotation-style query caching and mutation invalidation.

Installs request/response hooks that:

• On request: look up RetrostashKtorMetadata.queryTemplate in the store. If present, mark the call as a cache hit (sets Cache-Control: only-if-cached + custom headers) and stash the cached payload under RetrostashCachedPayloadKey for the caller to read.

• On response: skip on non-2xx. Otherwise invalidate any RetrostashKtorMetadata.invalidateTemplates (resolved against bindings) and persist the response body when the metadata declares a query template + maxAgeMs > 0.

Wire metadata onto a request with retrostashQuery / retrostashMutate.

val client = HttpClient {
    install(RetrostashPlugin) {
        store = InMemoryRetrostashStore()
        timeoutMs = 250
    }
}

client.get("https://api.example.com/feed/7") {
    retrostashQuery(
        scopeName = "FeedApi",
        template = "feed/{id}",
        bindings = mapOf("id" to "7"),
        maxAgeMs = 60_000L,
    )
}