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import Foundation
public typealias CommunicationTokenCompletionHandler = (CommunicationAccessToken?, Error?) -> Void
public typealias TokenRefreshHandler = (String?, Error?) -> Void

/**
 The Azure Communication Services User token credential. This class is used to cache/refresh the access token required by Azure Communication Services.
 */
@objcMembers public class CommunicationTokenCredential: NSObject, Cancellable {
    private let userTokenCredential: CommunicationTokenCredentialProviding
    private var isCancelled = false
    /**
     Creates a static `CommunicationTokenCredential` object from the provided token.

     - Parameter token: The static token to use for authenticating all requests.

     - Throws: `NSError` if the provided token is not a valid user token. `userInfo` contains `message` key for reason.
     */
    public init(token: String) throws {
        self.userTokenCredential = try StaticTokenCredential(token: token)
    }

    /**
     Creates a CommunicationTokenCredential that automatically refreshes the token.
     - Parameters:
        - options: Options for how the token will be refreshed
     - Throws: `NSError` if the provided token is not a valid user token. `userInfo` contains `message` key for reason.
     */
    public init(withOptions options: CommunicationTokenRefreshOptions) throws {
        self.userTokenCredential = try AutoRefreshTokenCredential(
            tokenRefresher: options.tokenRefresher,
            refreshProactively: options.refreshProactively,
            initialToken: options.initialToken
        )
    }

    /**
     Retrieve an access token from the credential.
     - Parameter completionHandler: Closure that accepts an optional `AccessToken` or optional `Error` as parameters.
     `AccessToken` returns a token and an expiry date if applicable. `Error` returns `nil` if the current token can be returned.
     */
    public func token(completionHandler: @escaping CommunicationTokenCompletionHandler) {
        guard !isCancelled else {
            let exception = NSError(
                domain: "AzureCommunicationCommon.CommunicationTokenCredential.token",
                code: 0,
                userInfo: [
                    "message": "An instance of CommunicationTokenCredential cannot be reused once it has been canceled."
                ]
            )
            completionHandler(nil, exception)
            return
        }
        userTokenCredential.token(completionHandler: completionHandler)
    }

    /**
     Disposes the CommunicationTokenCredential and cancels any internal auto-refresh operation.
     */
    public func cancel() {
        isCancelled = true
        userTokenCredential.cancel()
    }
}
