// Copyright (c) 2017-2022 Cloudflare, Inc.
// Licensed under the Apache 2.0 license found in the LICENSE file or at:
//     https://opensource.org/licenses/Apache-2.0

#pragma once

#include <workerd/io/io-util.h>
#include <workerd/jsg/jsg.h>

namespace workerd::api {

// Analytics Engine is a tool for customers to get telemetry about anything
// using Workers. The data points gathered from the edge are stored into
// ClickHouse and can be queried through the Analytics Engine's SQL API.
//
// The generated data points are encoded through the
// analytics_engine_event.capnp format and sent to logfwdr for them to enter
// the Data Pipeline. Each data point consists of an array of index values, 20
// numeric fields (doubles) and 20 text fields (blobs), alongside some
// metadata. Aside from ordinality and maximum length, the semantics of the
// `blobs` and `doubles` fields are left up to applications submitting
// messages.
//
// https://blog.cloudflare.com/workers-analytics-engine/
class AnalyticsEngine: public jsg::Object {
 public:
  explicit AnalyticsEngine(
      uint logfwdrChannel, kj::String dataset, int64_t version, uint32_t ownerId)
      : logfwdrChannel(logfwdrChannel),
        dataset(kj::mv(dataset)),
        version(version),
        ownerId(ownerId) {}
  struct AnalyticsEngineEvent {
    // An array of values for the user-defined indexes, that provide a way for
    // users to improve the efficiency of common queries. In addition, by
    // default, the sampling key includes all the indexes in the list. This
    // gives users some control over the way data is sampled.
    jsg::Optional<kj::Array<kj::Maybe<kj::OneOf<kj::Array<byte>, kj::String>>>> indexes;
    jsg::Optional<kj::Array<double>> doubles;
    jsg::Optional<kj::Array<kj::Maybe<kj::OneOf<kj::Array<byte>, kj::String>>>> blobs;

    // The ordering of the elements within the `doubles` and `blobs` fields matters, insofar as the
    // elements within each array will be unrolled, and based on the element's ordinality, the
    // `.set{Blob,Data}{1..20}(element)` method is invoked. Because of this, these arrays can each
    // have a maximum of 20 elements.

    JSG_STRUCT(indexes, doubles, blobs);
    JSG_STRUCT_TS_OVERRIDE(AnalyticsEngineDataPoint);
  };

  // Send an Analytics Engine-compatible event to the configured logfwdr socket.
  // Like logfwdr itself, `writeDataPoint` makes no delivery guarantees.
  void writeDataPoint(
      jsg::Lock& js, jsg::Optional<api::AnalyticsEngine::AnalyticsEngineEvent> event);

  JSG_RESOURCE_TYPE(AnalyticsEngine) {
    JSG_METHOD(writeDataPoint);
    JSG_TS_ROOT();
    JSG_TS_OVERRIDE(AnalyticsEngineDataset);
  }

  void visitForMemoryInfo(jsg::MemoryTracker& tracker) const {
    tracker.trackField("dataset", dataset);
  }

 private:
  double millisToNanos(double m) {
    return m * 1000000;
  }

  // Called within writeDataPoint after waiting for output locks
  void writeDataPointNoOutputLock(
      jsg::Lock& js, jsg::Optional<api::AnalyticsEngine::AnalyticsEngineEvent>&& event);

  uint logfwdrChannel;
  kj::String dataset;
  int64_t version;
  uint32_t ownerId;

  uint64_t now() {
    return millisToNanos(dateNow());
  }
};
#define EW_ANALYTICS_ENGINE_ISOLATE_TYPES                                                          \
  ::workerd::api::AnalyticsEngine, ::workerd::api::AnalyticsEngine::AnalyticsEngineEvent

}  // namespace workerd::api