// Copyright 2025-present 650 Industries. All rights reserved.

import ExpoModulesCore
import Foundation

/// Event names emitted by `NetworkRequestObserver`, matching the keys in the JS
/// `NetworkRequestObserverEvents` type.
// swift-format-ignore: AlwaysUseLowerCamelCase
let REQUEST_STARTED_EVENT = "requestStarted"
// swift-format-ignore: AlwaysUseLowerCamelCase
let REQUEST_COMPLETED_EVENT = "requestCompleted"

/// JS-facing `SharedObject` that bridges per-instance subscriptions to the singleton
/// `NetworkRequestMonitor`. Each JS `new NetworkRequestObserver()` allocates one of these and
/// registers it as a delegate; the native instance is released when JS drops the reference, at
/// which point `sharedObjectWillRelease` removes the delegate registration.
///
/// The class only forwards events — it doesn't store request history. Use `NetworkRequestMonitor`'s
/// in-process API for that.
public final class NetworkRequestObserver: SharedObject, NetworkRequestObserverDelegate, @unchecked Sendable {
  /// The active filter, or `nil` to observe every request. Held in a `Mutex` so the read from the
  /// monitor's fan-out (`shouldObserveRequest`) and the swap from `setFilter` are atomic: a
  /// `setFilter` call never leaves a request evaluated under a half-applied filter.
  private let filter = Mutex<NetworkRequestFilter?>(nil)

  public init(filter: NetworkRequestFilter? = nil) {
    super.init()
    self.filter.withLock { $0 = filter }
    AppMetricsActor.isolated { [weak self] in
      guard let self else {
        return
      }
      NetworkRequestMonitor.shared.addDelegate(self)
    }
  }

  /// Replaces the active filter. Pass `nil` to observe every request. The swap is atomic: a request
  /// mid-fan-out is evaluated against either the old or the new filter, never a mix.
  public func setFilter(_ filter: NetworkRequestFilter?) {
    self.filter.withLock { $0 = filter }
  }

  public override func sharedObjectWillRelease() {
    // The monitor holds delegates weakly, but deregister explicitly so the slot doesn't linger
    // until the next fan-out prunes it — matches the Android `sharedObjectDidRelease` cleanup.
    AppMetricsActor.isolated { [weak self] in
      guard let self else {
        return
      }
      NetworkRequestMonitor.shared.removeDelegate(self)
    }
    super.sharedObjectWillRelease()
  }

  // MARK: - NetworkRequestObserverDelegate

  public func onNetworkRequestStarted(_ request: NetworkRequestStarted) {
    emit(event: REQUEST_STARTED_EVENT, payload: NetworkRequestObserver.startedPayload(for: request))
  }

  public func onNetworkRequestCompleted(_ request: NetworkRequest) {
    emit(event: REQUEST_COMPLETED_EVENT, payload: NetworkRequestObserver.completedPayload(for: request))
  }

  public func shouldObserveRequest(url: URL, method: String) -> Bool {
    guard let filter = filter.withLock({ $0 }) else {
      return true
    }
    return filter.matches(url: url, method: method)
  }

  /// Internal so tests can assert the payload shape without going through `emit`, which needs a
  /// live JS runtime. The keys here are part of the public JS contract — additions are safe but
  /// renames are breaking.
  static func startedPayload(for request: NetworkRequestStarted) -> [String: Any?] {
    return [
      "id": request.id.uuidString,
      "url": request.url.absoluteString,
      "method": request.method,
      "startedAt": request.startedAt.ISO8601Format(),
    ]
  }

  static func completedPayload(for request: NetworkRequest) -> [String: Any?] {
    return [
      "id": request.id.uuidString,
      "url": request.url.absoluteString,
      "method": request.method,
      "statusCode": request.statusCode,
      "networkProtocol": request.networkProtocol,
      "requestBytesSent": request.requestBytesSent,
      "responseBytesReceived": request.responseBytesReceived,
      "errorDescription": request.errorDescription,
      "startedAt": request.timings.fetchStart?.ISO8601Format(),
      "completedAt": request.timings.responseEnd?.ISO8601Format(),
      "totalDuration": request.timings.totalDuration,
      "redirects": request.redirects.map {
        return [
          "fromUrl": $0.fromUrl.absoluteString,
          "toUrl": $0.toUrl.absoluteString,
          "statusCode": $0.statusCode,
        ]
      },
    ]
  }
}