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import Foundation
/**
 The Azure Communication Services User token credential. This class is used to cache/refresh the access token required by Azure Communication Services.
 */
internal class AutoRefreshTokenCredential: CommunicationTokenCredentialProviding {
    private let accessTokenCache: ThreadSafeRefreshableAccessTokenCache

    /**
     Creates a `CommunicationTokenCredential` that automatically refreshes the token using the provided `tokenRefresher`.
     - SeeAlso: `CommunicationTokenCredential.init(...)`
     */
    public init(
        tokenRefresher: @escaping (@escaping TokenRefreshHandler) -> Void,
        refreshProactively: Bool,
        initialToken: String?
    ) throws {
        if let initialToken = initialToken {
            let initialAccessToken = try JwtTokenParser.createAccessToken(initialToken)

            self.accessTokenCache = ThreadSafeRefreshableAccessTokenCache(
                refreshProactively: refreshProactively,
                initialValue: initialAccessToken,
                tokenRefresher: tokenRefresher
            )
        } else {
            self.accessTokenCache = ThreadSafeRefreshableAccessTokenCache(
                refreshProactively: refreshProactively,
                tokenRefresher: tokenRefresher
            )
        }
    }

    /**
     Retrieve an access token from the cache, or from the `tokenRefresher` if the token is not in the cache or is expired.

     - 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) {
        accessTokenCache.getValue { newAccessToken, error in
            completionHandler(newAccessToken, error)
        }
    }

    /**
     Cancels any internal auto-refresh operation.
     */
    public func cancel() {
        accessTokenCache.cancel()
    }
}
