Finished phase005

app/models/user_session.rb

@@ -0,0 +1,28 @@
+class UserSession < ApplicationRecord
+  TOKEN_LENGTH = 32
+
+  belongs_to :user
+
+  validates :token_digest, presence: true, uniqueness: true
+
+  def self.create_for!(user)
+    raw_token = generate_raw_token
+    user_session = create!(user: user, token_digest: digest(raw_token), last_used_at: Time.current)
+
+    [ user_session, raw_token ]
+  end
+
+  def self.find_by_token(raw_token)
+    return if raw_token.blank?
+
+    find_by(token_digest: digest(raw_token))
+  end
+
+  def self.generate_raw_token
+    SecureRandom.urlsafe_base64(TOKEN_LENGTH)
+  end
+
+  def self.digest(raw_token)
+    Digest::SHA256.hexdigest(raw_token.to_s)
+  end
+end