class Price < ActiveRecord::Base
  belongs_to :group
  belongs_to :plan
  belongs_to :priceable, polymorphic: true

  validates :priceable, :group_id, :amount, presence: true
  validates :priceable_id, uniqueness: { scope: [:priceable_type, :plan_id, :group_id] }

  ##
  # @param admin {Boolean} true if the current user (ie.the user who requests the price) is an admin
  # @param user {User} The user who's reserving (or selected if an admin is reserving)
  # @param reservable {Machine|Training|Event} what the reservation is targeting
  # @param slots {Array<Slot>} when did the reservation will occur
  # @param [plan_id] {Number} if the user is subscribing to a plan at the same time of his reservation, specify the plan's ID here
  # @param [nb_places] {Number} for _reservable_ of type Event, pass here the number of booked places
  # @param [nb_reduced_places] {Number} for _reservable_ of type Event, pass here the number of booked places at reduced price
  # @return {Hash} total and price detail
  ##
  def self.compute(admin, user, reservable, slots, plan_id = nil, nb_places = nil, nb_reduced_places = nil)
    _amount = 0
    _elements = Hash.new
    _elements[:slots] = Array.new

    # initialize Plan
    if user.subscribed_plan
      plan = user.subscribed_plan
      new_plan_being_bought = false
    elsif plan_id
      plan = Plan.find(plan_id)
      new_plan_being_bought = true
    else
      plan = nil
    end

    # === compute reservation price ===

    case reservable

      # Machine reservation
      when Machine
        base_amount = reservable.prices.find_by(group_id: user.group_id, plan_id: plan.try(:id)).amount
        if plan
          machine_credit = plan.machine_credits.select {|credit| credit.creditable_id == reservable.id}.first
          if machine_credit
            hours_available = machine_credit.hours
            if !new_plan_being_bought
              user_credit = user.users_credits.find_by_credit_id(machine_credit.id)
              if user_credit
                hours_available = machine_credit.hours - user_credit.hours_used
              end
            end
            slots.each_with_index do |slot, index|
              _amount += get_slot_price(base_amount, slot, admin, _elements, (index < hours_available))
            end
          else
            slots.each do |slot|
              _amount += get_slot_price(base_amount, slot, admin, _elements)
            end
          end
        else
          slots.each do |slot|
            _amount += get_slot_price(base_amount, slot, admin, _elements)
          end
        end

      # Training reservation
      when Training
        amount = reservable.amount_by_group(user.group_id).amount
        if plan
          # Return True if the subscription link a training credit for training reserved by the user
          training_is_creditable = plan.training_credits.select {|credit| credit.creditable_id == reservable.id}.size > 0

          # Training reserved by the user is free when :
          
          # |-> the user already has a current subscription and if training_is_creditable is true and has at least one credit available.
          if !new_plan_being_bought
            if user.training_credits.size < plan.training_credit_nb and training_is_creditable
              amount = 0
            end
          # |-> the user buys a new subscription and if training_is_creditable is true.
          else
            if training_is_creditable
              amount = 0
            end
          end
        end
        slots.each do |slot|
          _amount += get_slot_price(amount, slot, admin, _elements)
        end

      # Event reservation
      when Event
        if reservable.reduced_amount and nb_reduced_places
          amount = reservable.amount * nb_places + (reservable.reduced_amount * nb_reduced_places)
        else
          amount = reservable.amount * nb_places
        end
        slots.each do |slot|
          _amount += get_slot_price(amount, slot, admin, _elements)
        end

      # Unknown reservation type
      else
        raise NotImplementedError
    end

    # === compute Plan price if any ===
    unless plan_id.nil?
      _elements[:plan] = plan.amount
      _amount += plan.amount
    end

    # return result
    {elements: _elements, total: _amount}
  end

  private
  ##
  # Compute the price of a single slot, according to the base price and the ability for an admin
  # to offer the slot.
  # @param base_amount {Number} base price of a slot
  # @param slot {Hash} Slot object
  # @param is_admin {Boolean} true if the current user has the 'admin' role
  # @param [elements] {Array} optional, if provided the resulting price will be append into elements.slots
  # @param [has_credits] {Boolean} true if the user still has credits for the given slot
  # @return {Number} price of the slot
  ##
  def self.get_slot_price(base_amount, slot, is_admin, elements = nil, has_credits = false)
    ii_amount = (((has_credits) or (slot[:offered] and is_admin)) ? 0 : base_amount)
    elements[:slots].push({start_at: slot[:start_at], price: ii_amount, promo: (ii_amount != base_amount)}) unless elements.nil?
    ii_amount
  end
end