//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

@_exported import Csourcekitd

import SKSupport
import LSPLogging
import TSCBasic
import Dispatch
import Foundation

/// Access to sourcekitd API, taking care of initialization, shutdown, and notification handler
/// multiplexing.
///
/// *Users* of this protocol should not call the api functions `initialize`, `shutdown`, or
/// `set_notification_handler`, which are global state managed internally by this class.
///
/// *Implementors* are expected to handle initialization and shutdown, e.g. during `init` and
/// `deinit` or by wrapping an existing sourcekitd session that outlives this object.
public protocol SourceKitD: AnyObject {
  /// The sourcekitd API functions.
  var api: sourcekitd_functions_t { get }

  /// Convenience for accessing known keys.
  var keys: sourcekitd_keys { get }

  /// Convenience for accessing known keys.
  var requests: sourcekitd_requests { get }

  /// Convenience for accessing known keys.
  var values: sourcekitd_values { get }

  /// Adds a new notification handler, which will be weakly referenced.
  func addNotificationHandler(_ handler: SKDNotificationHandler)

  /// Removes a previously registered notification handler.
  func removeNotificationHandler(_ handler: SKDNotificationHandler)
}

public enum SKDError:Error {
  /// The service has crashed.
  case connectionInterrupted

  /// The request was unknown or had an invalid or missing parameter.
  case requestInvalid(String)

  /// The request failed.
  case requestFailed(String)

  /// The request was cancelled.
  case requestCancelled

  /// Loading a required symbol from the sourcekitd library failed.
  case missingRequiredSymbol(String)
}

extension SourceKitD {

  // MARK: - Convenience API for requests.

  /// Send the given request and synchronously receive a reply dictionary (or error).
  public func sendSync(_ req: SKDRequestDictionary) throws -> SKDResponseDictionary {
    logRequest(req)

    let resp = SKDResponse(api.send_request_sync(req.dict), sourcekitd: self)

    logResponse(resp)

    guard let dict = resp.value else {
      throw resp.error!
    }

    return dict
  }

  /// Send the given request and asynchronously receive a reply dictionary (or error) on the given queue.
  public func send(
    _ req: SKDRequestDictionary,
    _ queue: DispatchQueue,
    reply: @escaping (Result<SKDResponseDictionary, SKDError>) -> Void
  ) -> sourcekitd_request_handle_t? {
    logRequest(req)

    var handle: sourcekitd_request_handle_t? = nil

    api.send_request(req.dict, &handle) { [weak self] _resp in
      guard let self = self else { return }

      let resp = SKDResponse(_resp, sourcekitd: self)

      logResponse(resp)

      guard let dict = resp.value else {
        queue.async {
         reply(.failure(resp.error!))
        }
        return
      }

      queue.async {
        reply(.success(dict))
      }
    }

    return handle
  }
}

private func logRequest(_ request: SKDRequestDictionary) {
  // FIXME: Ideally we could log the request key here at the info level but the dictionary is
  // readonly.
  logAsync(level: .debug) { _ in request.description }
}

private func logResponse(_ response: SKDResponse) {
  if let value = response.value {
    logAsync(level: .debug) { _ in value.description }
  } else if case .requestCancelled = response.error! {
    log(response.description, level: .debug)
  } else {
    log(response.description, level: .error)
  }
}

/// A sourcekitd notification handler in a class to allow it to be uniquely referenced.
public protocol SKDNotificationHandler: AnyObject {
  func notification(_: SKDResponse) -> Void
}