// 
// Copyright 2022 New Vector Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

import Foundation

/// The parameters used for registration requests.
struct RegistrationParameters: Codable {
    /// Authentication parameters
    var auth: AuthenticationParameters?
    
    /// The account username
    var username: String?
    
    /// The account password
    var password: String?
    
    /// Device name
    var initialDeviceDisplayName: String?
    
    /// Temporary flag to notify the server that we support MSISDN flow. Used to prevent old app
    /// versions to end up in fallback because the HS returns the MSISDN flow which they don't support
    var xShowMSISDN: Bool?
    
    enum CodingKeys: String, CodingKey {
        case auth
        case username
        case password
        case initialDeviceDisplayName = "initial_device_display_name"
        case xShowMSISDN = "x_show_msisdn"
    }
    
    /// The parameters as a JSON dictionary for use in MXRestClient.
    func dictionary() throws -> [String: Any] {
        let jsonData = try JSONEncoder().encode(self)
        let object = try JSONSerialization.jsonObject(with: jsonData)
        guard let dictionary = object as? [String: Any] else {
            MXLog.error("[RegistrationParameters] dictionary: Unexpected type decoded \(type(of: object)). Expected a Dictionary.")
            throw AuthenticationError.dictionaryError
        }
        
        return dictionary
    }
}

/// The data passed to the `auth` parameter in authentication requests.
struct AuthenticationParameters: Codable {
    /// The type of authentication taking place. The identifier from `MXLoginFlowType`.
    let type: String
    
    /// Note: session can be null for reset password request
    var session: String?
    
    /// parameter for "m.login.recaptcha" type
    var captchaResponse: String?
    
    /// parameter for "m.login.email.identity" type
    var threePIDCredentials: ThreePIDCredentials?
    
    enum CodingKeys: String, CodingKey {
        case type
        case session
        case captchaResponse = "response"
        case threePIDCredentials = "threepid_creds"
    }
    
    /// Creates the authentication parameters for a captcha step.
    static func captchaParameters(session: String, captchaResponse: String) -> AuthenticationParameters {
        AuthenticationParameters(type: kMXLoginFlowTypeRecaptcha, session: session, captchaResponse: captchaResponse)
    }
    
    /// Creates the authentication parameters for a third party ID step using an email address.
    static func emailIdentityParameters(session: String, threePIDCredentials: ThreePIDCredentials) -> AuthenticationParameters {
        AuthenticationParameters(type: kMXLoginFlowTypeEmailIdentity, session: session, threePIDCredentials: threePIDCredentials)
    }
    
    // Note that there is a bug in Synapse (needs investigation), but if we pass .msisdn,
    // the homeserver answer with the login flow with MatrixError fields and not with a simple MatrixError 401.
    /// Creates the authentication parameters for a third party ID step using a phone number.
    static func msisdnIdentityParameters(session: String, threePIDCredentials: ThreePIDCredentials) -> AuthenticationParameters {
        AuthenticationParameters(type: kMXLoginFlowTypeMSISDN, session: session, threePIDCredentials: threePIDCredentials)
    }
    
    /// Creates the authentication parameters for a password reset step.
    static func resetPasswordParameters(clientSecret: String, sessionID: String) -> AuthenticationParameters {
        AuthenticationParameters(type: kMXLoginFlowTypeEmailIdentity,
                                 session: nil,
                                 threePIDCredentials: ThreePIDCredentials(clientSecret: clientSecret, sessionID: sessionID))
    }
}

/// The result from a registration screen's coordinator
enum AuthenticationRegistrationStageResult {
    /// The screen completed with the associated registration result.
    case completed(RegistrationResult)
    /// The user would like to cancel the registration.
    case cancel
}

/// The result from a response of a registration flow step.
enum RegistrationResult {
    /// Registration has completed, creating an `MXSession` for the account.
    case success(MXSession)
    /// The request was successful but there are pending steps to complete.
    case flowResponse(FlowResult)
}

/// The state of an authentication flow after a step has been completed.
struct FlowResult {
    /// The stages in the flow that are yet to be completed.
    let missingStages: [Stage]
    /// The stages in the flow that have been completed.
    let completedStages: [Stage]
    
    /// A stage in the authentication flow.
    enum Stage {
        /// The stage with the type `m.login.recaptcha`.
        case reCaptcha(isMandatory: Bool, siteKey: String)
        
        /// The stage with the type `m.login.email.identity`.
        case email(isMandatory: Bool)
        
        /// The stage with the type `m.login.msisdn`.
        case msisdn(isMandatory: Bool)
        
        /// The stage with the type `m.login.dummy`.
        ///
        /// This stage can be mandatory if there is no other stages. In this case the account cannot
        /// be created by just sending a username and a password, the dummy stage has to be completed.
        case dummy(isMandatory: Bool)
        
        /// The stage with the type `m.login.terms`.
        case terms(isMandatory: Bool, terms: MXLoginTerms?)
        
        /// A stage of an unknown type.
        case other(isMandatory: Bool, type: String, params: [AnyHashable: Any])
        
        /// Whether the stage is mandatory.
        var isMandatory: Bool {
            switch self {
            case .reCaptcha(let isMandatory, _):
                return isMandatory
            case .email(let isMandatory):
                return isMandatory
            case .msisdn(let isMandatory):
                return isMandatory
            case .dummy(let isMandatory):
                return isMandatory
            case .terms(let isMandatory, _):
                return isMandatory
            case .other(let isMandatory, _, _):
                return isMandatory
            }
        }
        
        /// Whether the stage is the dummy stage.
        var isDummy: Bool {
            guard case .dummy = self else { return false }
            return true
        }
    }
    
    /// Determines the next stage to be completed in the flow.
    var nextUncompletedStage: Stage? {
        if let emailStage = missingStages.first(where: { if case .email = $0 { return true } else { return false } }) {
            return emailStage
        }
        if let termsStage = missingStages.first(where: { if case .terms = $0 { return true } else { return false } }) {
            return termsStage
        }
        if let reCaptchaStage = missingStages.first(where: { if case .reCaptcha = $0 { return true } else { return false } }) {
            return reCaptchaStage
        }
        if let msisdnStage = missingStages.first(where: { if case .msisdn = $0 { return true } else { return false } }) {
            return msisdnStage
        }
        
        MXLog.failure("[FlowResult.Stage] nextUncompletedStage: The dummy stage should be handled silently and any other stages should trigger the fallback flow.")
        return missingStages.first
    }
    
    var needsFallback : Bool {
        missingStages.filter { $0.isMandatory }.contains { stage in
            if case .other = stage { return true } else { return false }
        }
    }
}

extension MXAuthenticationSession {
    /// The flows from the session mapped as a `FlowResult` value.
    var flowResult: FlowResult {
        let allFlowTypes = Set(flows.flatMap { $0.stages ?? [] }) // Using a Set here loses the order, but an order is forced during presentation anyway.
        var missingStages = [FlowResult.Stage]()
        var completedStages = [FlowResult.Stage]()
        
        allFlowTypes.forEach { flow in
            let isMandatory = flows.allSatisfy { $0.stages.contains(flow) }
            
            let stage: FlowResult.Stage
            switch flow {
            case kMXLoginFlowTypeRecaptcha:
                let parameters = params[flow] as? [AnyHashable: Any]
                let publicKey = parameters?["public_key"] as? String
                stage = .reCaptcha(isMandatory: isMandatory, siteKey: publicKey ?? "")
            case kMXLoginFlowTypeDummy:
                stage = .dummy(isMandatory: isMandatory)
            case kMXLoginFlowTypeTerms:
                let parameters = params[flow] as? [AnyHashable: Any]
                let terms = MXLoginTerms(fromJSON: parameters)
                stage = .terms(isMandatory: isMandatory, terms: terms)
            case kMXLoginFlowTypeMSISDN:
                stage = .msisdn(isMandatory: isMandatory)
            case kMXLoginFlowTypeEmailIdentity:
                stage = .email(isMandatory: isMandatory)
            default:
                let parameters = params[flow] as? [AnyHashable: Any]
                stage = .other(isMandatory: isMandatory, type: flow, params: parameters ?? [:])
            }
            
            if let completed = completed, completed.contains(flow) {
                completedStages.append(stage)
            } else {
                missingStages.append(stage)
            }
        }
        
        return FlowResult(missingStages: missingStages, completedStages: completedStages)
    }
}