//
// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import Foundation

@_implementationOnly import GoogleDataTransport

///
/// SessionStartEvent is responsible for:
///   1) Writing fields to the Session proto
///   2) Synthesizing itself for persisting to disk and logging to GoogleDataTransport
///
class SessionStartEvent: NSObject, GDTCOREventDataObject {
  var proto: firebase_appquality_sessions_SessionEvent

  init(identifiers: IdentifierProvider, time: TimeProvider = Time()) {
    proto = firebase_appquality_sessions_SessionEvent()

    super.init()

    proto.event_type = firebase_appquality_sessions_EventType_EVENT_SESSION_START
    proto.session_data.session_id = makeProtoString(identifiers.sessionID)
    proto.session_data.previous_session_id = makeProtoString(identifiers.previousSessionID)
    proto.session_data.event_timestamp_us = time.timestampUS
  }

  func setInstallationID(identifiers: IdentifierProvider) {
    proto.session_data.firebase_installation_id = makeProtoString(identifiers.installationID)
  }

  private func makeProtoString(_ string: String) -> UnsafeMutablePointer<pb_bytes_array_t>? {
    return FIRSESEncodeString(string)
  }

  // MARK: - GDTCOREventDataObject

  func transportBytes() -> Data {
    var fields = firebase_appquality_sessions_SessionEvent_fields
    var error: NSError?
    let data = FIRSESEncodeProto(&fields.0, &proto, &error)
    if error != nil {
      Logger.logError(error.debugDescription)
    }
    guard let data = data else {
      Logger.logError("Session event generated nil transportBytes. Returning empty data.")
      return Data()
    }
    return data
  }
}