import type { AssistantMessage, TrekCardKind } from '@trek/shared';

import { messageBlocks } from './assistantParts';
import { CARD_LOOKS } from './cards/cardLooks';
import type { CardEntry, CardFollowUp, CardLook } from './cards/cardTypes';

/**
 * The next questions an answer suggests, as one tap each: read from what the
 * answer holds, not asked from the model, so they cost nothing and come at
 * once. Cards ask what their kind offers, places found ask to narrow them, a
 * plan asks to go on, a forecast asks for the other weather. Three at most;
 * the first kind the answer holds wins.
 */

export interface FollowUp {
  id: string;
  labelKey: string;
  /** Asks for a change, so only someone who may edit the trip is offered it. */
  edits?: boolean;
}

const PLACES: readonly FollowUp[] = [
  { id: 'cheaper', labelKey: 'assistant.followUp.cheaper' },
  { id: 'closer', labelKey: 'assistant.followUp.closer' },
  { id: 'openNow', labelKey: 'assistant.followUp.openNow' },
];

const PLAN: readonly FollowUp[] = [
  { id: 'nextDay', labelKey: 'assistant.followUp.nextDay' },
  { id: 'relaxed', labelKey: 'assistant.followUp.relaxed' },
  { id: 'dinners', labelKey: 'assistant.followUp.dinners' },
];

const WEATHER: readonly FollowUp[] = [
  { id: 'rain', labelKey: 'assistant.followUp.rain' },
  { id: 'sun', labelKey: 'assistant.followUp.sun' },
];

const GENERAL: readonly FollowUp[] = [
  { id: 'more', labelKey: 'assistant.followUp.more' },
  { id: 'next', labelKey: 'assistant.followUp.next' },
];

/** What a kind offers to ask next, typed for any kind. */
function offeredBy(kind: TrekCardKind): readonly CardFollowUp<TrekCardKind>[] {
  return (CARD_LOOKS[kind] as CardLook<TrekCardKind>).followUps ?? [];
}

/**
 * The follow-ups of the cards an answer ends on (past its closing words): what
 * the first card's kind offers, laid out as the chat lays it out, without the
 * ones that ask for a change when the user may not make one, and without the
 * ones none of the answer's cards of that kind calls for.
 */
function cardFollowUps(message: AssistantMessage, canEdit: boolean): readonly FollowUp[] {
  const blocks = messageBlocks(message, false).filter((block) => block.kind !== 'text');
  const last = blocks[blocks.length - 1];
  const entries: readonly CardEntry[] = last?.kind === 'cards' ? last.entries : [];
  const kind = entries[0]?.card.kind;
  if (!kind) return [];
  const cards = entries.filter((entry) => entry.card.kind === kind).map((entry) => entry.card);
  return offeredBy(kind).filter(
    (followUp) => (canEdit || !followUp.edits) && (!followUp.when || cards.some((card) => followUp.when?.(card)))
  );
}

/** What an answer offers to ask next; changes are offered only to someone who may make them. */
export function followUpsFor(message: AssistantMessage, canEdit: boolean): readonly FollowUp[] {
  const fromCards = cardFollowUps(message, canEdit);
  if (fromCards.length > 0) return fromCards;
  const types = new Set(message.parts.map((part) => part.type));
  if (canEdit && (types.has('data-trek-change') || types.has('data-trek-applied'))) return PLAN;
  if (types.has('data-trek-places')) return PLACES;
  if (types.has('data-trek-weather')) return WEATHER;
  return types.has('text') ? GENERAL : [];
}