# frozen_string_literal: true
require 'base64'
require 'rack'
require 'openssl'

module DiscourseApi
  class SingleSignOn
    class ParseError < RuntimeError; end
    class MissingConfigError < RuntimeError; end

    ACCESSORS = [
      :add_groups,
      :admin,
      :avatar_force_update,
      :avatar_url,
      :bio,
      :card_background_url,
      :confirmed_2fa,
      :email,
      :external_id,
      :groups,
      :locale,
      :locale_force_update,
      :moderator,
      :name,
      :no_2fa_methods,
      :nonce,
      :profile_background_url,
      :remove_groups,
      :require_2fa,
      :require_activation,
      :return_sso_url,
      :suppress_welcome_message,
      :title,
      :username,
    ]

    FIXNUMS = []

    BOOLS = [
      :admin,
      :avatar_force_update,
      :confirmed_2fa,
      :locale_force_update,
      :moderator,
      :no_2fa_methods,
      :require_2fa,
      :require_activation,
      :suppress_welcome_message,
    ]
    ARRAYS = [:groups]
    #NONCE_EXPIRY_TIME = 10.minutes # minutes is a rails method and is causing an error. Is this needed in the api?

    attr_accessor(*ACCESSORS)
    attr_writer :custom_fields, :sso_secret, :sso_url

    def self.sso_secret
      raise MissingConfigError, "sso_secret not implemented on class, be sure to set it on instance"
    end

    def self.sso_url
      raise MissingConfigError, "sso_url not implemented on class, be sure to set it on instance"
    end

    def self.parse_hash(payload)
      sso = new

      sso.sso_secret = payload.delete(:sso_secret)
      sso.sso_url = payload.delete(:sso_url)

      ACCESSORS.each do |k|
        val = payload[k]

        val = val.to_i if FIXNUMS.include? k
        if BOOLS.include? k
          val = ["true", "false"].include?(val) ? val == "true" : nil
        end
        val = val.split(",") if ARRAYS.include?(k) && !val.nil?
        sso.send("#{k}=", val)
      end

      # Set custom_fields
      sso.custom_fields = payload[:custom_fields]

      # Add custom_fields (old format)
      payload.each do |k, v|
        if field = k[/^custom\.(.+)$/, 1]
          # Maintain adding of .custom bug
          sso.custom_fields["custom.#{field}"] = v
        end
      end

      sso
    end

    def self.parse(payload, sso_secret = nil)
      sso = new
      sso.sso_secret = sso_secret if sso_secret

      parsed = Rack::Utils.parse_query(payload)
      if sso.sign(parsed["sso"]) != parsed["sig"]
        diags = "\n\nsso: #{parsed["sso"]}\n\nsig: #{parsed["sig"]}\n\nexpected sig: #{sso.sign(parsed["sso"])}"
        if parsed["sso"] =~ /[^a-zA-Z0-9=\r\n\/+]/m
          raise ParseError, "The SSO field should be Base64 encoded, using only A-Z, a-z, 0-9, +, /, and = characters. Your input contains characters we don't understand as Base64, see http://en.wikipedia.org/wiki/Base64 #{diags}"
        else
          raise ParseError, "Bad signature for payload #{diags}"
        end
      end

      decoded = Base64.decode64(parsed["sso"])
      decoded_hash = Rack::Utils.parse_query(decoded)

      ACCESSORS.each do |k|
        val = decoded_hash[k.to_s]
        val = val.to_i if FIXNUMS.include? k
        if BOOLS.include? k
          val = ["true", "false"].include?(val) ? val == "true" : nil
        end
        val = val.split(",") if ARRAYS.include?(k) && !val.nil?
        sso.send("#{k}=", val)
      end

      decoded_hash.each do |k, v|
        if field = k[/^custom\.(.+)$/, 1]
          sso.custom_fields[field] = v
        end
      end

      sso
    end

    def diagnostics
      DiscourseApi::SingleSignOn::ACCESSORS.map { |a| "#{a}: #{send(a)}" }.join("\n")
    end

    def sso_secret
      @sso_secret || self.class.sso_secret
    end

    def sso_url
      @sso_url || self.class.sso_url
    end

    def custom_fields
      @custom_fields ||= {}
    end

    def sign(payload)
      OpenSSL::HMAC.hexdigest("sha256", sso_secret, payload)
    end

    def to_url(base_url = nil)
      base = "#{base_url || sso_url}"
      "#{base}#{base.include?('?') ? '&' : '?'}#{payload}"
    end

    def payload
      payload = Base64.strict_encode64(unsigned_payload)
      "sso=#{CGI::escape(payload)}&sig=#{sign(payload)}"
    end

    def unsigned_payload
      payload = {}

      ACCESSORS.each do |k|
        next if (val = send k) == nil
        payload[k] = val
      end

      if @custom_fields
        @custom_fields.each do |k, v|
          payload["custom.#{k}"] = v.to_s
        end
      end

      Rack::Utils.build_query(payload)
    end
  end
end