import { addDays } from '../common/dates';
import type { SeasonAutopilotConfig } from '../automation/rule-config/rule-config.types';
import type { SeasonState } from './season-types';

export interface VarroaDue {
  dueOn: string;
  kind: 'INTERVAL' | 'WINTER_WINDOW';
  /** Changes with every new measurement (or winter), so one due date stays one reminder. */
  anchor: string;
}

/*
 * Invariant: the winter window (SEASON_AUTOPILOT.winterVarroaWindow, default
 * 11-15) lies inside WINTERRUHE, i.e. it does not begin before the WINTER
 * date of PHENOLOGY.calendarFallback (default 11-15). Before WINTER the
 * interval rule applies instead.
 */

/** A measurement from this day on counts for the winter window of the year. */
const WINTER_MEASUREMENT_FROM = '11-01';

/**
 * The day a varroa measurement is due. Outside WINTERRUHE: the last
 * measurement (else the creation of the colony) plus the interval. In
 * WINTERRUHE only inside the winter window, once, if there was no
 * measurement since 11-01.
 */
export function varroaMeasurementDue(
  input: {
    createdOn: string;
    lastMeasuredOn: string | null;
    lastMeasurementId: string | null;
  },
  season: Pick<SeasonState, 'segment' | 'springSince'>,
  config: SeasonAutopilotConfig,
  today: string,
): VarroaDue | null {
  if (season.segment !== 'WINTERRUHE') {
    const base = input.lastMeasuredOn ?? input.createdOn;
    const intervalDue = addDays(base, config.varroaMeasureIntervalDays);
    // A due day that fell into the winter is taken up at the start of
    // FRUEHJAHR, like the first inspection of the year.
    const dueOn =
      season.springSince !== null && intervalDue < season.springSince
        ? season.springSince
        : intervalDue;
    return {
      dueOn,
      kind: 'INTERVAL',
      anchor: input.lastMeasurementId ?? 'none',
    };
  }
  const year = today.slice(0, 4);
  const { from, to } = config.winterVarroaWindow;
  const inWindow = today >= `${year}-${from}` && today <= `${year}-${to}`;
  const measuredThisWinter =
    input.lastMeasuredOn !== null &&
    input.lastMeasuredOn >= `${year}-${WINTER_MEASUREMENT_FROM}`;
  if (!inWindow || measuredThisWinter) {
    return null;
  }
  return {
    dueOn: `${year}-${from}`,
    kind: 'WINTER_WINDOW',
    anchor: `winter-${year}`,
  };
}