require "dry-initializer"
require "i18n"

# Top-level scope for Tram collection of gems
module Tram
  # Base class for policy objects with composable validation errors
  class Policy
    require_relative "policy/validation_error"
    require_relative "policy/inflector"
    require_relative "policy/error"
    require_relative "policy/errors"
    require_relative "policy/validator"
    require_relative "policy/dsl"

    extend Dry::Initializer
    extend DSL

    # The scope used for translating error messages
    #
    # @return [Array<String>]
    #
    def scope
      Array self.class.scope
    end

    # @!method t(message, options)
    # Translates a message in the scope of current policy
    #
    # @param  [#to_s] message
    # @param  [Hash<Symbol, Object>] options
    # @return [String]
    #
    def t(message, **options)
      return message.to_s unless message.is_a? Symbol
      I18n.t message, scope: scope, **options
    end

    # The collection of validation errors
    #
    # @return [Tram::Policy::Errors]
    #
    def errors
      @errors ||= Errors.new(scope: scope)
    end

    # The array of error items for lazy translation
    #
    # @return [Array<Array>]
    #
    def items
      errors.items
    end

    # The array of error messages translated for the current locale
    #
    # @return [Array<String>]
    #
    def messages
      errors.messages
    end

    # Checks whether the policy is valid
    #
    # @param  [Proc, nil] filter Block describing **errors to be skipped**
    # @return [Boolean]
    #
    def valid?(&filter)
      filter ? errors.reject(&filter).empty? : errors.empty?
    end

    # Checks whether the policy is invalid
    #
    # @param  [Proc, nil] filter Block describing **the only errors to count**
    # @return [Boolean]
    #
    def invalid?(&filter)
      filter ? errors.any?(&filter) : errors.any?
    end

    # Raises exception if the policy is not valid
    #
    # @param  (see #valid?)
    # @raise  [Tram::Policy::ValidationError] if the policy isn't valid
    # @return [nil] if the policy is valid
    #
    def validate!(&filter)
      raise ValidationError.new(self, filter) unless valid?(&filter)
    end

    # Human-readable representation of the policy
    #
    # @example Displays policy name and its attributes
    #   UserPolicy[name: "Andy"].inspect
    #   # => #<UserPolicy["name" => "Andy"]>
    #
    # @return [String]
    #
    def inspect
      "#<#{self.class.name}[#{__attributes__}]>"
    end

    private

    def initialize(*)
      super

      self.class.validators.each do |validator|
        size = errors.count
        validator.check(self)
        break if (errors.count > size) && validator.stop_on_failure
      end
    end

    def __attributes__
      @__attributes__ ||= self.class.dry_initializer.attributes(self)
    end
  end
end