import UIKit
import Firebase
import FirebaseStorage
import FirebaseDatabase

class NetworkDataManager {

    // MARK: - Singleton
    static let instance = NetworkDataManager()
    private init() {}

    // MARK: - Private properties
    fileprivate let referance = FIRDatabase.database().reference(fromURL: "https://socialapp-9d146.firebaseio.com/")
}

extension NetworkDataManager {
    // MARK: - Fetching data from Firebase
    func fetchUsers(_ completion: @escaping (([User]) -> Void)) {
        referance.child("users").observeSingleEvent(of: .value, with: { snapshot in
            var users = [User]()
            if let data = snapshot.value as? [String: AnyObject] {

                let sessionUserEmail = SessionDataManager.instance.sessionUser?.email
                let sessionUserKey = Utils.convertToKey(string: sessionUserEmail!)

                for index in 0..<data.count {
                    let currentKey = data.keys.sorted()[index]
                    if currentKey == sessionUserKey { continue }

                    let currentUser = data[currentKey]

                    let id = currentUser?["id"] as! String
                    let imageUrl = URL(string: currentUser?["imageUrl"] as! String)!
                    let firstName = currentUser?["firstName"] as! String
                    let lastName = currentUser?["lastName"] as! String
                    let email = currentUser?["email"] as! String
                    let password = currentUser?["password"] as! String

                    let user = User(id: id, imageUrl: imageUrl, firstName: firstName, lastName: lastName, email: email, password: password, signedOnList: nil, postsID: nil, likedNews: nil)

                    users.append(user)
                }
            }
            completion(users)
        })
    }

    func getUrl(fromImage image: UIImage, withEmail email: String, _ completion: @escaping ((URL?) -> Void)) {
        let key = Utils.convertToKey(string: email)
        var imageUrl: URL?

        let storageRef = FIRStorage.storage().reference(forURL: "gs://socialapp-9d146.appspot.com").child("\(key).png")

        let group = DispatchGroup()
        group.enter()
        if let uploadData = UIImagePNGRepresentation(image) {
            storageRef.put(uploadData, metadata: nil) { (metadata, error) in
                if error != nil {
                    print(error as Any)
                    return
                }
                imageUrl = metadata?.downloadURL()
                group.leave()
            }
        }
        group.notify(queue: DispatchQueue.main) {
            completion(imageUrl)
        }
    }
}

// MARK: - Session Methods
extension NetworkDataManager {
    func getUserData(withEmail email: String, password: String, _ completion: @escaping ((User?) -> Void)) {
        let key = Utils.convertToKey(string: email)

        referance.child("users").observeSingleEvent(of: .value, with: { snapshot in
            var user: User?
            if snapshot.hasChild(key) {
                if let currentUser = snapshot.childSnapshot(forPath: key).value as? [String: AnyObject] {
                    let userPassword = currentUser["password"] as? String

                    if password != userPassword {
                        completion(nil)
                        return
                    }

                    guard let id = currentUser["id"] as? String,
                        let imageUrlText = currentUser["imageUrl"] as? String,
                        let imageUrl = URL(string: imageUrlText),

                        let firstName = currentUser["firstName"] as? String,
                        let lastName = currentUser["lastName"] as? String,
                        let email = currentUser["email"] as? String else {
                            print("Invalid user data")
                            return
                    }

                    user = User(id: id, imageUrl: imageUrl, firstName: firstName, lastName: lastName, email: email, password: password, signedOnList: nil, postsID: nil, likedNews: nil)
                }
            }
            completion(user)
        })
    }

    func signUp(user: User, _ completion: @escaping ((User?) -> Void)) {
        let key = Utils.convertToKey(string: user.email!)
        referance.child("users").observeSingleEvent(of: .value, with: { [weak self] snapshot in
            if snapshot.hasChild(key) {
                completion(nil)
                return
            }

            self?.referance.child("users/\(key)").setValue(["id": user.id!,
                                                            "imageUrl": "\(user.imageUrl!)",
                "firstName": user.firstName!,
                "lastName": user.lastName!,
                "email": user.email!,
                "password": user.password!])
            completion(user)
        })


    }

    func getSignedOnList(forUser user: User, _ completion: @escaping (([User]?) -> Void)) {
        guard let email = user.email else { return }
        let key = Utils.convertToKey(string: email)
        let signedOnUsersIdReferance = referance.child("users/\(key)/signedOnList")

        signedOnUsersIdReferance.observeSingleEvent(of: .value, with: { [weak self] snapshot in
            var userList = [User]()

            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in dictionary.keys.sorted() {
                    if let currentUserKey = dictionary[index] as? String {
                        let currentUserRef = self?.referance.child("users/\(currentUserKey)")

                        let group = DispatchGroup()
                        group.enter()

                        currentUserRef?.observeSingleEvent(of: .value, with: { userSnapshot in

                            if let currentUserDictionary = userSnapshot.value as? [String: AnyObject] {
                                let id = currentUserDictionary["id"] as? String
                                let email = currentUserDictionary["email"] as? String
                                let imageUrlStrign = currentUserDictionary["imageUrl"] as! String
                                let imageUrl = URL(string: imageUrlStrign)

                                let firstName = currentUserDictionary["firstName"] as? String
                                let lastName = currentUserDictionary["lastName"] as? String
                                let password = currentUserDictionary["password"] as? String

                                let user = User(id: id, imageUrl: imageUrl, firstName: firstName, lastName: lastName, email: email, password: password, signedOnList: nil, postsID: nil, likedNews: nil)
                                userList.append(user)

                                group.leave()
                            }
                        })
                        group.notify(queue: DispatchQueue.main, execute: {
                            completion(userList)
                        })
                    }
                }
            }
        })
    }

    func getPostList(forUser user: User, _ completion: @escaping ((_ userNews: [Post]?,_ followedUsersNews: [Post]?) -> Void)) {
        guard let sessionUserEmail = user.email else { return }
        let sessionUserKey = Utils.convertToKey(string: sessionUserEmail)

        var userPostsList = [Post]()
        let sessionUserPostsRef = referance.child("posts/\(sessionUserKey)")
        sessionUserPostsRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in 0..<dictionary.count {
                    let currentPostIndex = dictionary.keys.sorted()[index]
                    let currentPost = dictionary[currentPostIndex]

                    guard let id =  currentPost?["id"] as? String,
                        let text = currentPost?["text"] as? String else {
                            print("Invalid post data")
                            return
                    }

                    let post = Post(id: id, text: text)

                    userPostsList.append(post)
                }
            }
        })

        let signedOnUsersIdsRef = referance.child("users/\(sessionUserKey)/signedOnList")
        var followedPostsList = [Post]()
        signedOnUsersIdsRef.observeSingleEvent(of: .value, with: { snapshot in

            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in 0..<dictionary.count {
                    let currentUserIndex = dictionary.keys.sorted()[index]
                    if let currentUserKey = dictionary[currentUserIndex] {
                        let postsReferance = FIRDatabase.database().reference().child("posts/\(currentUserKey)")

                        let group = DispatchGroup()
                        group.enter()

                        postsReferance.observeSingleEvent(of: .value, with: { postSnapshot in
                            if let postDictionary = postSnapshot.value as? [String: AnyObject] {
                                for postIndex in postDictionary.keys.sorted() {
                                    let currentPost = postDictionary[postIndex]
                                    guard let id = currentPost?["id"] as? String,
                                        let text = currentPost?["text"] as? String else {
                                            print("Invalid post data")
                                            return
                                    }
                                    let post = Post(id: id, text: text)
                                    followedPostsList.append(post)
                                }
                                group.leave()
                            }
                        })
                        group.notify(queue: DispatchQueue.main, execute: {
                            completion(userPostsList, followedPostsList)
                        })
                    }
                }
            }
        })
    }

    func getLikedPostList(forUser user: User, _ completion: @escaping (([Post]?) -> Void)) {
        guard let email = user.email else { return }
        let key = Utils.convertToKey(string: email)
        let likedPostsRef = referance.child("users/\(key)/likedPosts")

        likedPostsRef.observeSingleEvent(of: .value, with: { [weak self] likedPostsSnapshot in
            var likedPosts = [Post]()

            if let likedPostsDictionary = likedPostsSnapshot.value as? [String: AnyObject] {
                let likedPostsKeys = likedPostsDictionary.keys.sorted()
                for currentPostKey in likedPostsKeys {
                    let currentPostId = likedPostsDictionary[currentPostKey] as? String

                    let postsRef = self?.referance.child("posts")

                    let group = DispatchGroup()
                    group.enter()

                    postsRef?.observeSingleEvent(of: .value, with: { postSnapshot in
                        if let postDictionary = postSnapshot.value as? [String: AnyObject] {
                            let postsKeys = postDictionary.keys.sorted()
                            for currentPostKey in postsKeys {
                                let currentPostList = postDictionary[currentPostKey] as? [String: AnyObject]
                                if (currentPostList?.keys.contains(currentPostId!))! {
                                    let currentPost = currentPostList?[currentPostId!] as? [String: AnyObject]

                                    guard let id = currentPost?["id"] as? String,
                                        let text = currentPost?["text"] as? String else { return }
                                    let post = Post(id: id, text: text)

                                    likedPosts.append(post)
                                    group.leave()
                                }
                            }
                        }
                        group.notify(queue: .main, execute: {
                            completion(likedPosts)
                        })
                    })
                }
            }
        })
    }

    // MARK: - Follow methods
    func follow(user: User) {
        guard let sessionUser = SessionDataManager.instance.sessionUser,
            let sessionUserEmail = sessionUser.email,
            let followedUserEmail = user.email else { return }

        let currentUserkey = Utils.convertToKey(string: sessionUserEmail)
        let followedUserKey = Utils.convertToKey(string: followedUserEmail)

        let signedOnListRef = FIRDatabase.database().reference().child("users/\(currentUserkey)/signedOnList")

        signedOnListRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                let lastUserId = dictionary.keys.sorted()[dictionary.count - 1]

                let substringStartIndex = lastUserId.index(lastUserId.startIndex, offsetBy: +2)
                guard let lastUserNumber = Int(lastUserId.substring(from: substringStartIndex)) else { return }

                let userIndex = lastUserNumber + 1
                signedOnListRef.child("id\(userIndex)").setValue(followedUserKey)
            } else {
                signedOnListRef.child("id0").setValue(followedUserKey)
            }

        })

    }

    func unFollow(user: User) {
        guard let sessionUser = SessionDataManager.instance.sessionUser,
            let sessionUserEmail = sessionUser.email,
            let followedUserEmail = user.email else { return }

        let key = Utils.convertToKey(string: sessionUserEmail)
        let followedUserKey = Utils.convertToKey(string: followedUserEmail)

        let signedOnIdList = FIRDatabase.database().reference().child("users/\(key)/signedOnList")

        signedOnIdList.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in 0..<dictionary.count {
                    let currentKey = dictionary.keys.sorted()[index]
                    let currentUserKey = dictionary[currentKey] as? String

                    if currentUserKey == followedUserKey {
                        signedOnIdList.child(currentKey).removeValue()
                    }
                }
            }
        })
    }
}

// MARK: - UserInteraction Methods
extension NetworkDataManager: UserInteraction {
    func edit(user: User) {

        let key = Utils.convertToKey(string: user.email!)
        let currentUserRef = referance.child("users/\(key)")

        currentUserRef.child("imageUrl").setValue("\(user.imageUrl!)")
        currentUserRef.child("firstName").setValue(user.firstName!)
        currentUserRef.child("lastName").setValue(user.lastName!)
    }

    func delete(user: User) {

    }
}

// MARK: - PostInteraction Methods
extension NetworkDataManager: PostInteraction {
    func add(post: Post) {
        guard let user = SessionDataManager.instance.sessionUser, let email = user.email else { return }
        let key = Utils.convertToKey(string: email)

        let postsRef = FIRDatabase.database().reference().child("posts/\(key)/\(post.id)")
        postsRef.setValue(["id": post.id,
                           "text": post.text])

        let idPostsRef = FIRDatabase.database().reference().child("users/\(key)/postsID")
        idPostsRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                let lastPostId = dictionary.keys.sorted()[dictionary.count - 1]

                let substringStartIndex = lastPostId.index(lastPostId.startIndex, offsetBy: +2)
                guard let lastPostNumber = Int(lastPostId.substring(from: substringStartIndex)) else { return }

                let index = lastPostNumber + 1
                idPostsRef.child("id\(index)").setValue(post.id)
            } else {
                idPostsRef.child("id0").setValue(post.id)
            }

        })
    }

    func edit(post: Post) {
        guard let user = SessionDataManager.instance.sessionUser, let email = user.email else { return }
        let key = Utils.convertToKey(string: email)

        let currentPostRef = referance.child("posts/\(key)/\(post.id)")
        currentPostRef.child("text").setValue(post.text)
    }

    func delete(post: Post) {
        guard let user = SessionDataManager.instance.sessionUser, let email = user.email else { return }
        let key = Utils.convertToKey(string: email)

        referance.child("posts/\(key)/\(post.id)").removeValue()

        let idPostsRef = referance.child("users/\(key)/postsID")
        idPostsRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in 0..<dictionary.count {
                    let currentKey = dictionary.keys.sorted()[index]
                    let currentPostId = dictionary[currentKey] as? String

                    if currentPostId == post.id {
                        idPostsRef.child(currentKey).removeValue()
                    }
                }
            }
        })
    }

    func like(post: Post) {
        guard let sessionUser = SessionDataManager.instance.sessionUser, let email = sessionUser.email else { return }
        let key = Utils.convertToKey(string: email)

        let likedPostsRef = referance.child("users/\(key)/likedPosts")

        likedPostsRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                let lastPostId = dictionary.keys.sorted()[dictionary.count - 1]

                let substringStartIndex = lastPostId.index(lastPostId.startIndex, offsetBy: +2)
                guard let lastPostNumber = Int(lastPostId.substring(from: substringStartIndex)) else { return }

                let index = lastPostNumber + 1
                likedPostsRef.child("id\(index)").setValue(post.id)
            } else {
                likedPostsRef.child("id0").setValue(post.id)
            }

        })
    }

    func dislike(post: Post) {
        guard let sessionUser = SessionDataManager.instance.sessionUser, let email = sessionUser.email else { return }
        let key = Utils.convertToKey(string: email)

        let likedPostsRef = referance.child("users/\(key)/likedPosts")
        likedPostsRef.observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: AnyObject] {
                for index in 0..<dictionary.count {
                    let currentKey = dictionary.keys.sorted()[index]
                    let currentPostId = dictionary[currentKey] as? String

                    if currentPostId == post.id {
                        likedPostsRef.child(currentKey).removeValue()
                    }
                }
            }
        })
    }
}