# frozen_string_literal: true

module Praxis
  class FieldExpander
    def self.expand(object, fields = true, displayable_filter = nil)
      # check the displayability of the whole type/attr object at the top as well, not just the inner ones
      if (privs = object.options[:displayable])
        raise 'Attempting to expand fields for a type that uses :displayable, but the system (or at least this controller) does not have a displayable_filter setup.' unless privs && displayable_filter
        return {} unless displayable_filter.call(Array(privs))

      end
      new(displayable_filter: displayable_filter).expand(object, fields)
    end

    attr_reader :stack, :history

    # displayable_filter is a proc that takes a set of strings (representing privileges of sort) and returns true if it should be displayed
    def initialize(displayable_filter: nil)
      @stack = Hash.new do |hash, key|
        hash[key] = Set.new
      end
      @history = Hash.new do |hash, key|
        hash[key] = {}
      end
      @displayable_filter = displayable_filter
    end

    def expand(object, fields = true)
      if stack[object].include? fields
        return history[object][fields] if history[object].include? fields

        # We should probably never get here, since we should have a record
        # of the history of an expansion if we're trying to redo it,
        # but we should also be conservative and raise here just in case.
        raise "Circular expansion detected for object #{object.inspect} with fields #{fields.inspect}"
      else
        stack[object] << fields
      end

      result = if object.is_a? Attributor::Attribute
                 expand_type(object.type, fields)
               else
                 expand_type(object, fields)
               end

      result
    ensure
      stack[object].delete fields
    end

    def expand_fields(attributes, fields)
      raise ArgumentError, 'expand_fields must be given a block' unless block_given?

      unless fields == true
        attributes = attributes.select do |k, _v|
          fields.key?(k)
        end
      end

      attributes.each_with_object({}) do |(name, dumpable), hash|
        # Filter out attributes that are not displayable (if a filter is provided and there is a displayable option)
        if (privs = dumpable.options[:displayable])
          raise "Found field named #{name} using :displayable, but the system (or at least this controller) does not have a displayable_filter setup." unless privs && @displayable_filter
          next unless @displayable_filter.call(Array(privs))

        end

        sub_fields = case fields
                     when true
                       true
                     when Hash
                       fields[name] || true
                     end
        hash[name] = yield(dumpable, sub_fields)
      end
    end

    def expand_type(object, fields = true)
      unless object.respond_to?(:attributes)
        return expand_type(object.member_attribute.type, fields) if object.respond_to?(:member_attribute)

        return true
      end

      # just include the full thing if it has no attributes
      return fields if object.attributes.empty?

      # True, expands to the default fieldset for blueprints
      fields = object.default_fieldset if object < Praxis::Blueprint && fields == true

      return history[object][fields] if history[object].include? fields

      history[object][fields] = {}
      result = expand_fields(object.attributes, fields) do |dumpable, sub_fields|
        expand(dumpable.type, sub_fields)
      end
      unless fields == true
        non_matching = fields.keys - object.attributes.keys
        raise "FieldExpansion error: attribute(s) #{non_matching} do not exist in #{object}" unless non_matching.empty?
      end
      history[object][fields].merge!(result)
    end
  end
end