class User < ApplicationRecord
has_many :microposts, dependent: :destroy
has_many :active_relationships, class_name:  "Relationship",
                                  foreign_key: "follower_id",
                                  dependent:   :destroy
has_many :passive_relationships, class_name:  "Relationship",
                                   foreign_key: "followed_id",
                                   dependent:   :destroy

                                 
has_many :following, through: :active_relationships, source: :followed          
has_many :followers, through: :passive_relationships, source: :follower                      
attr_accessor :remember_token, :activation_token, :reset_token
before_save :downcase_email
before_create :create_activation_digest
validates :name, presence: true, length: {maximum: 50}
VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i
validates :email, presence: true, length: {maximum: 255}, format: {with: VALID_EMAIL_REGEX}, uniqueness: true
has_secure_password
validates :password, presence: true, length: {minimum: 6}, allow_nil: true


# Returns the hash digest of the given string.
    def User.digest(string)
        cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST : 
        BCrypt::Engine.cost 
        BCrypt::Password.create(string, cost: cost)
    end

# Returns a random token
    def User.new_token
        SecureRandom.urlsafe_base64
    end

    # Returns true if the given token matches the digest.
  def authenticated?(attribute, token)
    digest = send("#{attribute}_digest")
    return false if digest.nil?
    BCrypt::Password.new(digest).is_password?(token)
  end

# Remembers a user in the database for use in persistent sessions.
    def remember
        self.remember_token = User.new_token
        update_attribute(:remember_digest, User.digest(remember_token))
    end

# Forgets a  user.
    def forget
        update_attribute(:remember_digest, nil)
    end 

# Activates an account.   
    def activate
        update_attribute(:activated, true)
        update_attribute(:activated_at, Time.zone.now)
    end

# Sends activation email.
    def send_activation_email
        UserMailer.account_activation(self).deliver_now
    end

# Sets the password reset attributes.
 def create_reset_digest
   self.reset_token = User.new_token
   update_attribute(:reset_digest, User.digest(reset_token))
   update_attribute(:reset_sent_at, Time.zone.now)
 end

 # Sends password reset email.
 def send_password_reset_email
   UserMailer.password_reset(self).deliver_now
 end 

 # Returns true if a password reset has expired.
 def password_reset_expired?
    reset_sent_at < 2.hours.ago
 end 

 # Defines a proto-feed.
 # see "Following users" for the fill implementation. 

 def feed
 following_ids = "SELECT followed_id FROM relationships
                     WHERE follower_id = :user_id"
    Micropost.where("user_id IN (#{following_ids})
                     OR user_id = :user_id", user_id: id) 
 end

 # Follows a user. 
 def follow(other_user)
    following << other_user
 end

# Unfollow a user.
def unfollow(other_user) 
    following.delete(other_user)
end

# Reutns true if the current use is following the other user. 
def following?(other_user) 
    following.include?(other_user)
end

private

# Converts email to all lower-case.
    def downcase_email
        self.email = email.downcase
    end

# Creates and assigns the activation token and digest.
    def create_activation_digest
        self.activation_token = User.new_token
        self.activation_digest = User.digest(activation_token)
    end 

end
