# frozen_string_literal: true

require "forwardable"

require_relative "em"
require_relative "plan"

class CustomerPlan
	extend Forwardable

	attr_reader :expires_at, :auto_top_up_amount, :monthly_overage_limit

	def_delegator :@plan, :name, :plan_name
	def_delegators :@plan, :currency, :merchant_account, :monthly_price,
	               :minute_limit, :message_limit

	def self.for(customer_id, plan_name: nil, **kwargs)
		new(customer_id, plan: plan_name&.then(&Plan.method(:for)), **kwargs)
	end

	def initialize(
		customer_id,
		plan: nil,
		expires_at: Time.now,
		auto_top_up_amount: 0,
		monthly_overage_limit: 0
	)
		@customer_id = customer_id
		@plan = plan || OpenStruct.new
		@expires_at = expires_at
		@auto_top_up_amount = auto_top_up_amount || 0
		@monthly_overage_limit = monthly_overage_limit || 0
	end

	def active?
		plan_name && @expires_at > Time.now
	end

	def with_plan_name(plan_name)
		self.class.new(
			@customer_id,
			plan: Plan.for(plan_name),
			expires_at: @expires_at
		)
	end

	def save_plan!
		DB.exec_defer(<<~SQL, [@customer_id, plan_name])
			INSERT INTO plan_log
				(customer_id, plan_name, date_range)
			VALUES (
				$1,
				$2,
				tsrange(
					LOCALTIMESTAMP - '2 seconds'::interval,
					LOCALTIMESTAMP - '1 second'::interval
				)
			)
		SQL
	end

	def bill_plan
		EM.promise_fiber do
			DB.transaction do
				charge_for_plan
				add_one_month_to_current_plan unless activate_plan_starting_now
			end
		end
	end

	def activate_plan_starting_now
		activated = DB.exec(<<~SQL, [@customer_id, plan_name]).cmd_tuples.positive?
			INSERT INTO plan_log (customer_id, plan_name, date_range)
			VALUES ($1, $2, tsrange(LOCALTIMESTAMP, LOCALTIMESTAMP + '1 month'))
			ON CONFLICT DO NOTHING
		SQL
		return false unless activated

		DB.exec(<<~SQL, [@customer_id])
			DELETE FROM plan_log WHERE customer_id=$1 AND date_range << '[now,now]'
				AND upper(date_range) - lower(date_range) < '2 seconds'
		SQL
	end

	def activation_date
		dates = DB.query_defer(<<~SQL, [@customer_id])
			SELECT
				MIN(LOWER(date_range)) AS start_date
			FROM plan_log WHERE customer_id = $1;
		SQL

		dates.then do |r|
			r.first["start_date"]
		end
	end

protected

	def charge_for_plan
		params = [
			@customer_id,
			"#{@customer_id}-bill-#{plan_name}-at-#{Time.now.to_i}",
			-@plan.monthly_price
		]
		DB.exec(<<~SQL, params)
			INSERT INTO transactions
				(customer_id, transaction_id, created_at, amount)
			VALUES ($1, $2, LOCALTIMESTAMP, $3)
		SQL
	end

	def add_one_month_to_current_plan
		DB.exec(<<~SQL, [@customer_id])
			UPDATE plan_log SET date_range=range_merge(
				date_range,
				tsrange(
					LOCALTIMESTAMP,
					GREATEST(upper(date_range), LOCALTIMESTAMP) + '1 month'
				)
			)
			WHERE
				customer_id=$1 AND
				date_range && tsrange(LOCALTIMESTAMP, LOCALTIMESTAMP + '1 month')
		SQL
	end
end