require 'ostruct'

module Spree
  class Shipment < ActiveRecord::Base
    belongs_to :order, class_name: 'Spree::Order', touch: true
    belongs_to :address, class_name: 'Spree::Address'
    belongs_to :stock_location, class_name: 'Spree::StockLocation'

    has_many :shipping_rates, dependent: :delete_all
    has_many :shipping_methods, through: :shipping_rates
    has_many :state_changes, as: :stateful
    has_many :inventory_units, dependent: :delete_all
    has_one :adjustment, as: :source, dependent: :destroy

    after_save :ensure_correct_adjustment, :update_order

    attr_accessor :special_instructions

    accepts_nested_attributes_for :address
    accepts_nested_attributes_for :inventory_units

    make_permalink field: :number, length: 11, prefix: 'H'

    scope :shipped, -> { with_state('shipped') }
    scope :ready,   -> { with_state('ready') }
    scope :pending, -> { with_state('pending') }
    scope :with_state, ->(*s) { where(state: s) }
    scope :trackable, -> { where("tracking IS NOT NULL AND tracking != ''") }

    # shipment state machine (see http://github.com/pluginaweek/state_machine/tree/master for details)
    state_machine initial: :pending, use_transactions: false do
      event :ready do
        transition from: :pending, to: :ready, if: lambda { |shipment|
          # Fix for #2040
          shipment.determine_state(shipment.order) == 'ready'
        }
      end

      event :pend do
        transition from: :ready, to: :pending
      end

      event :ship do
        transition from: :ready, to: :shipped
      end
      after_transition to: :shipped, do: :after_ship

      event :cancel do
        transition to: :canceled, from: [:pending, :ready]
      end
      after_transition to: :canceled, do: :after_cancel

      event :resume do
        transition from: :canceled, to: :ready, if: lambda { |shipment|
          shipment.determine_state(shipment.order) == :ready
        }
        transition from: :canceled, to: :pending, if: lambda { |shipment|
          shipment.determine_state(shipment.order) == :ready
        }
        transition from: :canceled, to: :pending
      end
      after_transition from: :canceled, to: [:pending, :ready], do: :after_resume
    end

    def to_param
      number
    end

    def backordered?
      inventory_units.any? { |inventory_unit| inventory_unit.backordered? }
    end

    def shipped=(value)
      return unless value == '1' && shipped_at.nil?
      self.shipped_at = Time.now
    end

    def shipping_method
      selected_shipping_rate.try(:shipping_method) || shipping_rates.first.try(:shipping_method)
    end

    def add_shipping_method(shipping_method, selected = false)
      shipping_rates.create(shipping_method: shipping_method, selected: selected)
    end

    def selected_shipping_rate
      shipping_rates.where(selected: true).first
    end

    def selected_shipping_rate_id
      selected_shipping_rate.try(:id)
    end

    def selected_shipping_rate_id=(id)
      shipping_rates.update_all(selected: false)
      shipping_rates.update(id, selected: true)
      self.save!
    end

    def refresh_rates
      return shipping_rates if shipped?
      return [] unless can_get_rates?

      # StockEstimator.new assigment below will replace the current shipping_method
      original_shipping_method_id = shipping_method.try(:id)

      self.shipping_rates = Stock::Estimator.new(order).shipping_rates(to_package)

      if shipping_method
        selected_rate = shipping_rates.detect { |rate|
          rate.shipping_method_id == original_shipping_method_id
        }
        self.selected_shipping_rate_id = selected_rate.id if selected_rate
      end

      shipping_rates
    end

    def currency
      order ? order.currency : Spree::Config[:currency]
    end

    # The adjustment amount associated with this shipment (if any.)  Returns only the first adjustment to match
    # the shipment but there should never really be more than one.
    def cost
      adjustment ? adjustment.amount : 0
    end

    alias_method :amount, :cost

    def display_cost
      Spree::Money.new(cost, { currency: currency })
    end

    alias_method :display_amount, :display_cost

    def item_cost
      line_items.map(&:amount).sum
    end

    def display_item_cost
      Spree::Money.new(item_cost, { currency: currency })
    end

    def total_cost
      cost + item_cost
    end

    def display_total_cost
      Spree::Money.new(total_cost, { currency: currency })
    end

    def editable_by?(user)
      !shipped?
    end

    def manifest
      inventory_units.group_by(&:variant).map do |variant, units|
        states = {}
        units.group_by(&:state).each { |state, iu| states[state] = iu.count }
        OpenStruct.new(variant: variant, quantity: units.length, states: states)
      end
    end

    def line_items
      if order.complete? and Spree::Config.track_inventory_levels
        order.line_items.select { |li| !li.should_track_inventory? || inventory_units.pluck(:variant_id).include?(li.variant_id) }
      else
        order.line_items
      end
    end

    def finalize!
      InventoryUnit.finalize_units!(inventory_units)
      manifest.each { |item| manifest_unstock(item) }
    end

    def after_cancel
      manifest.each { |item| manifest_restock(item) }
    end

    def after_resume
      manifest.each { |item| manifest_unstock(item) }
    end

    # Updates various aspects of the Shipment while bypassing any callbacks.  Note that this method takes an explicit reference to the
    # Order object.  This is necessary because the association actually has a stale (and unsaved) copy of the Order and so it will not
    # yield the correct results.
    def update!(order)
      old_state = state
      new_state = determine_state(order)
      update_column :state, new_state
      after_ship if new_state == 'shipped' and old_state != 'shipped'
    end

    # Determines the appropriate +state+ according to the following logic:
    #
    # pending    unless order is complete and +order.payment_state+ is +paid+
    # shipped    if already shipped (ie. does not change the state)
    # ready      all other cases
    def determine_state(order)
      return 'canceled' if order.canceled?
      return 'pending' unless order.can_ship?
      return 'pending' if inventory_units.any? &:backordered?
      return 'shipped' if state == 'shipped'
      order.paid? ? 'ready' : 'pending'
    end

    def tracking_url
      @tracking_url ||= shipping_method.build_tracking_url(tracking)
    end

    def include?(variant)
      inventory_units_for(variant).present?
    end

    def inventory_units_for(variant)
      inventory_units.group_by(&:variant_id)[variant.id] || []
    end

    def to_package
      package = Stock::Package.new(stock_location, order)
      inventory_units.includes(:variant).each do |inventory_unit|
        package.add inventory_unit.variant, 1, inventory_unit.state_name
      end
      package
    end

    def set_up_inventory(state, variant, order)
      self.inventory_units.create(variant_id: variant.id, state: state, order_id: order.id)
    end

    private

      def manifest_unstock(item)
        stock_location.unstock item.variant, item.quantity, self
      end

      def manifest_restock(item)
        if item.states["on_hand"].to_i > 0
         stock_location.restock item.variant, item.states["on_hand"], self
        end

        if item.states["backordered"].to_i > 0
          stock_location.restock_backordered item.variant, item.states["backordered"]
        end
      end

      def description_for_shipping_charge
        "#{Spree.t(:shipping)} (#{shipping_method.name})"
      end

      def after_ship
        inventory_units.each &:ship!
        adjustment.finalize!
        send_shipped_email
        touch :shipped_at
      end

      def send_shipped_email
        ShipmentMailer.shipped_email(self.id).deliver
      end

      def ensure_correct_adjustment
        if adjustment
          adjustment.originator = shipping_method
          adjustment.label = shipping_method.adjustment_label
          adjustment.amount = selected_shipping_rate.cost if adjustment.open?
          adjustment.save!
          adjustment.reload
        elsif selected_shipping_rate_id
          shipping_method.create_adjustment shipping_method.adjustment_label, order, self, true, "open"
          reload #ensure adjustment is present on later saves
        end
      end

      def update_order
        order.update!
      end

      def can_get_rates?
        order.ship_address && order.ship_address.valid?
      end
  end
end