# frozen_string_literal: true

require "uri"
require "faraday"

module Fiken
  # OAuth2 authorization-code helper.
  #
  #   oauth = Fiken::OAuth.new(client_id:, client_secret:, redirect_uri:)
  #   redirect_to oauth.authorize_url(state: "abc")
  #   token = oauth.exchange_code(params[:code])
  #   client = Fiken::Client.new(access_token: token.access_token)
  #   refreshed = oauth.refresh(token.refresh_token)
  class OAuth
    AUTHORIZE_URL = "https://fiken.no/oauth/authorize"
    TOKEN_URL = "https://fiken.no/oauth/token"

    attr_reader :client_id, :client_secret, :redirect_uri

    def initialize(client_id:, client_secret:, redirect_uri: nil)
      @client_id = client_id
      @client_secret = client_secret
      @redirect_uri = redirect_uri
    end

    # Build the URL to send the user to in order to authorize the app.
    def authorize_url(state:, redirect_uri: self.redirect_uri, scope: nil)
      params = {
        response_type: "code",
        client_id: client_id,
        redirect_uri: redirect_uri,
        state: state,
        scope: scope
      }.compact
      "#{AUTHORIZE_URL}?#{URI.encode_www_form(params)}"
    end

    # Exchange the authorization code from the callback for tokens.
    def exchange_code(code, redirect_uri: self.redirect_uri)
      token_request(grant_type: "authorization_code", code: code, redirect_uri: redirect_uri)
    end

    # Use a refresh token to obtain a fresh access token.
    def refresh(refresh_token)
      token_request(grant_type: "refresh_token", refresh_token: refresh_token)
    end

    private

    def token_request(params)
      response = token_connection.post(TOKEN_URL, params.compact)
      raise Error.from_response(response.status, response.body) if response.status >= 400

      Object.new(response.body)
    end

    def token_connection
      @token_connection ||= Faraday.new do |f|
        f.request :url_encoded
        f.request :authorization, :basic, client_id, client_secret
        f.response :json, content_type: /\bjson$/
        f.adapter Faraday.default_adapter
      end
    end
  end
end