require "rails_helper"

RSpec.describe JwtService do
  describe ".encode" do
    it "returns a JWT string" do
      token = described_class.encode(user_id: 1)
      expect(token).to be_a(String)
      expect(token.split(".").size).to eq(3)
    end

    it "sets a default expiration about 7 days in the future" do
      token = described_class.encode(user_id: 1)
      payload = JWT.decode(token, described_class::SECRET_KEY, true, algorithm: described_class::ALGORITHM).first
      expect(payload["exp"]).to be_within(60).of(7.days.from_now.to_i)
    end

    it "keeps a custom expiration if provided" do
      custom_exp = 1.hour.from_now.to_i
      token = described_class.encode(user_id: 1, exp: custom_exp)
      payload = JWT.decode(token, described_class::SECRET_KEY, true, algorithm: described_class::ALGORITHM).first
      expect(payload["exp"]).to eq(custom_exp)
    end
  end

  describe ".decode" do
    it "round-trips the user_id" do
      token = described_class.encode(user_id: 42)
      expect(described_class.decode(token)[:user_id]).to eq(42)
    end

    it "returns nil for a tampered token" do
      token = described_class.encode(user_id: 42)
      expect(described_class.decode(token + "x")).to be_nil
    end

    it "returns nil for a token signed with a different secret" do
      token = JWT.encode({ user_id: 42 }, "wrong-secret", "HS256")
      expect(described_class.decode(token)).to be_nil
    end

    it "returns nil for an expired token" do
      token = described_class.encode(user_id: 42, exp: 1.minute.ago.to_i)
      expect(described_class.decode(token)).to be_nil
    end

    it "returns nil for garbage input" do
      expect(described_class.decode("not-a-token")).to be_nil
    end
  end
end