Initial commit

lib/json_web_token.rb

@@ -0,0 +1,32 @@
+require "jwt"
+
+# this class handles all the jwt token thing
+# we use it to encode user data into a token, and decode it back
+# it's simple, clean, and reusable, no need to overcomplicate it
+
+class JsonWebToken
+  # secret key used to sign the token
+  # make sure to keep this secret in .env (never hardcode and check before pushing to github)
+  # will crash if JWT_SECRET_KEY is not set - this is intentional for security
+  SECRET_KEY = ENV.fetch("JWT_SECRET_KEY")
+
+  # encode payload into a jwt
+  # payload is usually like: { user_id: 1 }
+  # exp = token expiration (default: 1 hour from now for better security)
+  # jti = unique token identifier for blacklisting
+  def self.encode(payload, exp = 1.hour.from_now)
+    payload[:exp] = exp.to_i
+    payload[:jti] ||= SecureRandom.uuid
+    JWT.encode(payload, SECRET_KEY, "HS256")
+  end
+
+  # decode jwt back into original payload
+  # returns the payload if token is valid, else it throws error
+  def self.decode(token)
+    decoded = JWT.decode(token, SECRET_KEY, true, algorithm: "HS256")
+    HashWithIndifferentAccess.new(decoded[0])
+  rescue JWT::DecodeError => e
+    # if decoding fails, basic error raises so you can add yours as well
+    raise StandardError.new("Invalid token: #{e.message}")
+  end
+end