require "msgpack"

module Immunio
  # Holds the status of a plugin.
  #
  # A plugin can have one of four statuses:
  #
  # - pending: initial state, waiting to be loaded
  # - loaded: successfully loaded
  # - failed: error while loading
  # - disabled: disabled in config, will never be loaded
  #
  # Each registered plugin is reported to the backend via the `EnvironmentReporter`.
  class Plugin
    attr_reader :status
    attr_accessor :version
    attr_accessor :hooks

    def initialize(name, hooks = [])
      @name = name
      @status = 'pending'
      @version = nil
      @hooks = hooks
    end

    def loaded!(version)
      @status = 'loaded'
      @version = version
      Immunio.logger.debug "Plugin #{@name} v#{version} loaded successfully"
    end

    def disabled!
      @status = 'disabled'
      Immunio.logger.debug "Plugin #{@name} is disabled"
    end

    def failed!(error)
      @status = 'failed'
      Immunio.logger.error "Plugin #{@name} failed to load: #{error}"
    end

    def inspect
      "<#{self.class} name=#{@name.inspect} status=#{@status.inspect} version=#{@version.inspect} hooks=#{@hooks.inspect}>"
    end

    def to_msgpack(packer)
      packer.write_map_header 3
      # `name` is provided as the key in `registered`
      packer.write('status').write(@status)
      packer.write('version').write(@version)
      packer.write('hooks').write(@hooks)
    end

    def self.registered
      @registered ||= {}
    end

    # DSL to register a plugin, its status and version.
    #
    # A `feature` name can be passed to determine if the plugin should be enabled. If the
    # plugin is disabled, the block will not run.
    #
    # You MUST explicitly call `plugin.loaded!` in the block to indicate that the plugin was
    # loaded successfully, or else it will be kept as 'pending'.
    #
    # Eg.:
    #
    #   Immunio::Plugin.load 'SomePluginName', feature: 'xss' do |plugin|
    #     if defined? SomePlugin
    #       # Your loading code here ...
    #       plugin.loaded! SomePluginName::VERSION
    #     end
    #   end
    #
    def self.load(name, options = {})
      if options.key? :feature
        enabled = Immunio.agent.plugin_enabled?(options[:feature])
      else
        enabled = true
      end

      plugin = registered[name] = new(name, options.fetch(:hooks, []))

      unless enabled # plugin is disabled
        plugin.disabled!
        return
      end

      Immunio.logger.debug "Loading plugin #{name} ..."
      begin
        yield plugin
      rescue StandardError, LoadError => e
        plugin.failed! e
      end
    end
  end
end