GoogleAuthenticationService.swift

//
//  GoogleAuthenticationService.swift
//  DevLog
//
//  Created by opfic on 6/4/25.
//

import FirebaseAuth
import FirebaseFirestore
import FirebaseFunctions
import FirebaseMessaging
import Foundation
import GoogleSignIn

final class GoogleAuthenticationService: AuthenticationService {
    private let store = Firestore.firestore()
    private let functions = Functions.functions(region: "asia-northeast3")
    private let messaging = Messaging.messaging()
    private var user: User? { Auth.auth().currentUser }
    private let provider = TopViewControllerProvider()
    private let logger = Logger(category: "GoogleAuthService")

    @MainActor
    func signIn() async throws -> AuthDataResponse {
        logger.info("Starting Google sign in")
        
        guard let topViewController = provider.topViewController() else {
            logger.error("Top view controller not found")
            throw UIError.notFoundTopViewController
        }

        do {
            let signIn = try await GIDSignIn.sharedInstance.signIn(withPresenting: topViewController)

            guard let idToken = signIn.user.idToken?.tokenString else {
                logger.error("ID token not found")
                throw URLError(.badServerResponse)
            }
            
            let accessToken = signIn.user.accessToken.tokenString
            let credential = GoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)
            
            logger.debug("Signing in with Google credential")
            let result = try await Auth.auth().signIn(with: credential)
            
            if let photoURL = signIn.user.profile?.imageURL(withDimension: 200) {
                let changeRequest = result.user.createProfileChangeRequest()
                changeRequest.photoURL = photoURL
                changeRequest.displayName = signIn.user.profile?.name

                try await changeRequest.commitChanges()
            }

            let fcmToken = try await messaging.token()

            logger.info("Successfully signed in with Google")
            return result.user.makeResponse(providerID: .google, fcmToken: fcmToken)
        } catch {
            logger.error("Failed to sign in with Google", error: error)
            throw error
        }
    }

    func signOut(_ uid: String) async throws {
        let infoRef = store.document("users/\(uid)/userData/tokens")
        let doc = try await infoRef.getDocument()

        if doc.exists {
            try await infoRef.updateData(["fcmToken": FieldValue.delete()])
        }

        GIDSignIn.sharedInstance.signOut()
        try await GIDSignIn.sharedInstance.disconnect()

        try await messaging.deleteToken()

        try Auth.auth().signOut()
    }

    func deleteAuth(_ uid: String) async throws {
        GIDSignIn.sharedInstance.signOut()
        try await GIDSignIn.sharedInstance.disconnect()
    }

    func link(uid: String, email: String) async throws {
        let topViewController = await MainActor.run {
            provider.topViewController()
        }
        guard let topViewController = topViewController else {
            throw UIError.notFoundTopViewController
        }

        if GIDSignIn.sharedInstance.hasPreviousSignIn() {
            GIDSignIn.sharedInstance.signOut()
        }

        let signIn = try await GIDSignIn.sharedInstance.signIn(withPresenting: topViewController)

        guard let googleEmail = signIn.user.profile?.email else {
            throw EmailFetchError.emailNotFound
        }

        if googleEmail != email {
            throw EmailFetchError.emailMismatch
        }

        guard let idToken = signIn.user.idToken?.tokenString else {
            throw URLError(.badServerResponse)
        }

        let accessToken = signIn.user.accessToken.tokenString
        let credential = GoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)

        try await user?.link(with: credential)
    }

    func unlink(_ uid: String) async throws {
        do {
            logger.info("Starting Google disconnect for unlink. uid: \(uid)")
            GIDSignIn.sharedInstance.signOut()
            try await GIDSignIn.sharedInstance.disconnect()

            logger.info("Starting Firebase Google provider unlink. uid: \(uid)")
            _ = try await user?.unlink(fromProvider: AuthProviderID.google.rawValue)
        } catch {
            logger.error("Failed to unlink Google account", error: error)
            throw error
        }
    }

}