class MaintenanceScheduleStatus
  UPCOMING_PERCENT = 0.05

  attr_reader :schedule, :latest_entry, :status, :due_odometer, :due_date

  def initialize(schedule, latest_entry, current_odometer:)
    @schedule = schedule
    @latest_entry = latest_entry
    @current_odometer = current_odometer
    @due_odometer = baseline_odometer + schedule.mileage_interval
    @due_date = baseline_date + schedule.time_interval.days
    @status = calculate_status
  end

  def overdue?
    status == "overdue"
  end

  def upcoming?
    status == "upcoming"
  end

  def no_history?
    status == "no_history"
  end

  def current?
    status == "current"
  end

  def status_label
    case status
    when "overdue" then "Overdue"
    when "upcoming" then "Upcoming"
    when "no_history" then "No history"
    else "Current"
    end
  end

  def reason
    case status
    when "overdue"
      overdue_reasons.join(" and ")
    when "upcoming"
      upcoming_reasons.join(" and ")
    when "no_history"
      "No matching maintenance entry has been recorded."
    else
      "Maintenance is current."
    end
  end

  private

  attr_reader :current_odometer

  def calculate_status
    return "overdue" if mileage_overdue? || time_overdue?
    return "upcoming" if mileage_upcoming? || time_upcoming?
    return "no_history" if latest_entry.blank?

    "current"
  end

  def baseline_odometer
    latest_entry&.odometer || schedule.baseline_odometer
  end

  def baseline_date
    latest_entry&.date || schedule.baseline_date
  end

  def mileage_overdue?
    current_odometer >= due_odometer
  end

  def time_overdue?
    Date.current >= due_date
  end

  def mileage_upcoming?
    current_odometer >= due_odometer - mileage_upcoming_window
  end

  def time_upcoming?
    Date.current >= due_date - time_upcoming_window.days
  end

  def mileage_upcoming_window
    (schedule.mileage_interval * UPCOMING_PERCENT).ceil
  end

  def time_upcoming_window
    (schedule.time_interval * UPCOMING_PERCENT).ceil
  end

  def overdue_reasons
    reasons = []
    reasons << "mileage interval reached" if mileage_overdue?
    reasons << "time interval reached" if time_overdue?
    reasons
  end

  def upcoming_reasons
    reasons = []
    reasons << "within #{mileage_upcoming_window} miles of due odometer" if mileage_upcoming?
    reasons << "within #{time_upcoming_window} days of due date" if time_upcoming?
    reasons
  end
end