import { daysBetween } from '../../common/dates';
import type { SuggestionEvidence } from '../suggestion.types';
import {
  formatDayDe,
  type SuggestionTextRegister,
  type SuggestionTextTemplate,
} from '../suggestion-texts';

const MAX_PRODUCT_LENGTH = 40;

const SEGMENT_PHRASES: Readonly<Record<string, string>> = {
  FRUEHJAHR: 'Im Frühjahr',
  SCHWARMZEIT: 'In der Schwarmzeit',
  SOMMER: 'Im Sommer',
  SPAETSOMMER: 'Im Spätsommer',
  HERBST: 'Im Herbst',
};

function text(evidence: SuggestionEvidence, key: string): string | null {
  const value = evidence[key];
  return typeof value === 'string' ? value : null;
}

function count(evidence: SuggestionEvidence, key: string): number | null {
  const value = evidence[key];
  return typeof value === 'number' ? value : null;
}

/** 'vor 8 Tagen', 'vor 1 Tag', 'heute'. */
function agoDe(from: string, today: string): string {
  const days = Math.max(0, daysBetween(from, today));
  if (days === 0) {
    return 'heute';
  }
  return `vor ${days} ${days === 1 ? 'Tag' : 'Tagen'}`;
}

function lastInspectionReason(
  evidence: SuggestionEvidence,
  today: string,
): string {
  const last = text(evidence, 'lastInspectedOn');
  return last === null
    ? 'Noch keine Durchsicht erfasst.'
    : `Letzte Durchsicht ${agoDe(last, today)}.`;
}

function intervalReason(evidence: SuggestionEvidence): string[] {
  const phrase = SEGMENT_PHRASES[text(evidence, 'segment') ?? ''];
  const days = count(evidence, 'intervalDays');
  return phrase !== undefined && days !== null
    ? [`${phrase} alle ${days} Tage.`]
    : [];
}

const INSPECTION_DUE: SuggestionTextTemplate = {
  ruleKey: 'INSPECTION_INTERVAL',
  example: {
    colonyId: 'c1',
    inspectionId: 'i1',
    lastInspectedOn: '2026-05-04',
    dueOn: '2026-05-11',
    intervalDays: 7,
    segment: 'SCHWARMZEIT',
  },
  render: (evidence, _lookup, today) => ({
    title: 'Durchsicht',
    reasons: [
      lastInspectionReason(evidence, today),
      ...intervalReason(evidence),
    ],
  }),
};

const INSPECTION_FIRST_OF_YEAR: SuggestionTextTemplate = {
  ruleKey: 'INSPECTION_INTERVAL',
  example: {
    colonyId: 'c1',
    inspectionId: 'i1',
    lastInspectedOn: '2025-09-20',
    dueOn: '2026-03-20',
    intervalDays: 14,
    segment: 'FRUEHJAHR',
  },
  render: (evidence) => {
    const last = text(evidence, 'lastInspectedOn');
    return {
      title: 'Erste Durchsicht im Jahr',
      reasons: [
        'Die Saison hat begonnen.',
        last === null
          ? 'Noch keine Durchsicht erfasst.'
          : `Letzte Durchsicht am ${formatDayDe(last, true)}.`,
      ],
    };
  },
};

const VARROA_MEASURE_DUE: SuggestionTextTemplate = {
  ruleKey: 'SEASON_AUTOPILOT',
  example: {
    colonyId: 'c1',
    measurementId: 'm1',
    lastMeasuredOn: '2026-05-06',
    dueOn: '2026-06-03',
    intervalDays: 28,
  },
  render: (evidence, _lookup, today) => {
    const last = text(evidence, 'lastMeasuredOn');
    const days = count(evidence, 'intervalDays');
    return {
      title: 'Varroa messen',
      reasons: [
        last === null
          ? 'Noch keine Messung erfasst.'
          : `Letzte Messung ${agoDe(last, today)}.`,
        ...(days === null ? [] : [`Alle ${days} Tage messen.`]),
      ],
    };
  },
};

const VARROA_WINTER_MEASURE: SuggestionTextTemplate = {
  ruleKey: 'SEASON_AUTOPILOT',
  example: {
    colonyId: 'c1',
    measurementId: 'm1',
    lastMeasuredOn: '2026-09-01',
    dueOn: '2026-11-15',
    intervalDays: 28,
  },
  render: () => ({
    title: 'Varroa messen',
    reasons: ['Vor der Winterbehandlung den Milbenfall messen.'],
  }),
};

const VARROA_RECHECK_DUE: SuggestionTextTemplate = {
  ruleKey: 'SEASON_AUTOPILOT',
  example: {
    colonyId: 'c1',
    treatmentId: 't1',
    endedOn: '2026-08-02',
    recheckOn: '2026-08-16',
  },
  render: (evidence, lookup) => {
    const treatmentId = text(evidence, 'treatmentId');
    const product =
      (treatmentId === null ? null : lookup.treatmentProduct(treatmentId)) ??
      'Behandlung';
    const name = product.slice(0, MAX_PRODUCT_LENGTH);
    const ended = text(evidence, 'endedOn');
    const recheck = text(evidence, 'recheckOn');
    return {
      title: 'Behandlungserfolg messen',
      reasons: [
        ended === null
          ? `Behandlung mit ${name} beendet.`
          : `Behandlung mit ${name} endete am ${formatDayDe(ended)}`,
        ...(recheck === null
          ? []
          : [`Nachkontrolle ab ${formatDayDe(recheck)}`]),
      ],
    };
  },
};

/** Texts of the season autopilot suggestions, by reason code. */
export const AUTOPILOT_TEXTS: SuggestionTextRegister = {
  INSPECTION_DUE,
  INSPECTION_FIRST_OF_YEAR,
  VARROA_MEASURE_DUE,
  VARROA_WINTER_MEASURE,
  VARROA_RECHECK_DUE,
};