/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import Alamofire
import Shared
import Foundation
import Deferred
import SwiftyJSON

let TokenServerClientErrorDomain = "org.mozilla.token.error"
let TokenServerClientUnknownError = TokenServerError.local(
    NSError(domain: TokenServerClientErrorDomain, code: 999,
    userInfo: [NSLocalizedDescriptionKey: "Invalid server response"]))

public struct TokenServerToken {
    public let id: String
    public let key: String
    public let api_endpoint: String
    public let uid: UInt64
    public let hashedFxAUID: String
    public let durationInSeconds: UInt64
    // A healthy token server reports its timestamp.
    public let remoteTimestamp: Timestamp

    /**
     * Return true if this token points to the same place as the other token.
     */
    public func sameDestination(_ other: TokenServerToken) -> Bool {
        return self.uid == other.uid &&
               self.api_endpoint == other.api_endpoint
    }

    public static func fromJSON(_ json: JSON) -> TokenServerToken? {
        if let
            id = json["id"].string,
            let key = json["key"].string,
            let api_endpoint = json["api_endpoint"].string,
            let uid = json["uid"].int64,
            let hashedFxAUID = json["hashed_fxa_uid"].string,
            let durationInSeconds = json["duration"].int64,
            let remoteTimestamp = json["remoteTimestamp"].int64 {
                return TokenServerToken(id: id, key: key, api_endpoint: api_endpoint, uid: UInt64(uid),
                                        hashedFxAUID: hashedFxAUID, durationInSeconds: UInt64(durationInSeconds),
                                        remoteTimestamp: Timestamp(remoteTimestamp))
        }
        return nil
    }

    public func asJSON() -> JSON {
        let D: [String: AnyObject] = [
            "id": id as AnyObject,
            "key": key as AnyObject,
            "api_endpoint": api_endpoint as AnyObject,
            "uid": NSNumber(value: uid as UInt64),
            "hashed_fxa_uid": hashedFxAUID as AnyObject,
            "duration": NSNumber(value: durationInSeconds as UInt64),
            "remoteTimestamp": NSNumber(value: remoteTimestamp),
        ]
        return JSON(D as NSDictionary)
    }
}

enum TokenServerError {
    // A Remote error definitely has a status code, but we may not have a well-formed JSON response
    // with a status; and we could have an unhealthy server that is not reporting its timestamp.
    case remote(code: Int32, status: String?, remoteTimestamp: Timestamp?)
    case local(NSError)
}

extension TokenServerError: MaybeErrorType {
    var description: String {
        switch self {
        case let .remote(code: code, status: status, remoteTimestamp: _):
            if let status = status {
                return "<TokenServerError.Remote \(code): \(status)>"
            } else {
                return "<TokenServerError.Remote \(code)>"
            }
        case let .local(error):
            return "<TokenServerError.Local Error Domain=\(error.domain) Code=\(error.code) \"\(error.localizedDescription)\">"
        }
    }
}

open class TokenServerClient {
    let URL: URL

    public init(URL: URL? = nil) {
        self.URL = URL ?? ProductionSync15Configuration().tokenServerEndpointURL
    }

    open class func getAudience(forURL URL: URL) -> String {
        if let port = URL.port {
            return "\(URL.scheme!)://\(URL.host!):\(port)"
        } else {
            return "\(URL.scheme!)://\(URL.host!)"
        }
    }

    fileprivate class func parseTimestampHeader(_ header: String?) -> Timestamp? {
        if let timestampString = header {
            return decimalSecondsStringToTimestamp(timestampString)
        } else {
            return nil
        }
    }

    fileprivate class func remoteError(fromJSON json: JSON, statusCode: Int, remoteTimestampHeader: String?) -> TokenServerError? {
        if json.error != nil {
            return nil
        }
        if 200 <= statusCode && statusCode <= 299 {
            return nil
        }
        return TokenServerError.remote(code: Int32(statusCode), status: json["status"].string,
            remoteTimestamp: parseTimestampHeader(remoteTimestampHeader))
    }

    fileprivate class func token(fromJSON json: JSON, remoteTimestampHeader: String?) -> TokenServerToken? {
        if json.error != nil {
            return nil
        }
        if let
            remoteTimestamp = parseTimestampHeader(remoteTimestampHeader), // A token server that is not providing its timestamp is not healthy.
            let id = json["id"].string,
            let key = json["key"].string,
            let api_endpoint = json["api_endpoint"].string,
            let uid = json["uid"].int,
            let hashedFxAUID = json["hashed_fxa_uid"].string,
            let durationInSeconds = json["duration"].int64, durationInSeconds > 0 {
            return TokenServerToken(id: id, key: key, api_endpoint: api_endpoint, uid: UInt64(uid),
                                    hashedFxAUID: hashedFxAUID, durationInSeconds: UInt64(durationInSeconds),
                                    remoteTimestamp: remoteTimestamp)
        }
        return nil
    }

    lazy fileprivate var alamofire: SessionManager = {
        let ua = UserAgent.tokenServerClientUserAgent
        let configuration = URLSessionConfiguration.ephemeral
        var defaultHeaders = SessionManager.default.session.configuration.httpAdditionalHeaders ?? [:]
        defaultHeaders["User-Agent"] = ua
        configuration.httpAdditionalHeaders = defaultHeaders
        return SessionManager(configuration: configuration)
    }()

    open func token(_ assertion: String, clientState: String? = nil) -> Deferred<Maybe<TokenServerToken>> {
        let deferred = Deferred<Maybe<TokenServerToken>>()

        var mutableURLRequest = URLRequest(url: URL)
        mutableURLRequest.setValue("BrowserID " + assertion, forHTTPHeaderField: "Authorization")
        if let clientState = clientState {
            mutableURLRequest.setValue(clientState, forHTTPHeaderField: "X-Client-State")
        }

        alamofire.request(mutableURLRequest)
                 .validate(contentType: ["application/json"])
                 .responseJSON { response in

                    // Don't cancel requests just because our Manager is deallocated.
                    withExtendedLifetime(self.alamofire) {
                        if let error = response.result.error {
                            deferred.fill(Maybe(failure: TokenServerError.local(error as NSError)))
                            return
                        }

                        if let data = response.result.value as AnyObject? { // Declaring the type quiets a Swift warning about inferring AnyObject.
                            let json = JSON(data)
                            let remoteTimestampHeader = response.response?.allHeaderFields["X-Timestamp"] as? String

                            if let remoteError = TokenServerClient.remoteError(fromJSON: json, statusCode: response.response!.statusCode,
                                remoteTimestampHeader: remoteTimestampHeader) {
                                    deferred.fill(Maybe(failure: remoteError))
                                    return
                            }

                            if let token = TokenServerClient.token(fromJSON: json, remoteTimestampHeader: remoteTimestampHeader) {
                                deferred.fill(Maybe(success: token))
                                return
                            }
                        }

                        deferred.fill(Maybe(failure: TokenServerClientUnknownError))
                    }
        }
        return deferred
    }
}