"use client";

import { useEffect, useMemo, useState } from "react";
import { buildFacetQueryString } from "../../../../lib/create/buildFacetQueryString";
import type { MethodFacetApiSectionId } from "../../../../lib/create/customRuleFacets";
import {
  buildFacetRecommendationRequestKey,
  getCachedFacetScores,
  loadFacetScores,
} from "../../../../lib/create/facetRecommendationsLoad";
import { useCreateFlow } from "../context/CreateFlowContext";
import { groupAnswersFromCreateFlowState } from "../../../../lib/create/groupAnswers";
import {
  deckData,
  recommendDeck,
} from "../../../../lib/create/deckRecommend";
import type { GroupAnswers } from "../../../../lib/create/deckTypes";

/**
 * Card-deck section ids served by `/api/create-flow/methods` (CR-88 §9.2).
 * Same tuple as {@link METHOD_FACET_API_SECTION_IDS} (`CUSTOM_RULE_FACETS`, CR-92).
 */
export type RecommendationSection = MethodFacetApiSectionId;

export type FacetRecommendationsResult = {
  /** `true` once the network call completes (or short-circuits with no facets). */
  isReady: boolean;
  /** `slug → score`; missing slug means `0`. */
  scoresBySlug: Record<string, number>;
  /**
   * `true` iff the user has selected at least one community facet. When
   * `false`, callers should preserve authoring order rather than reranking.
   */
  hasAnyFacets: boolean;
};

const EMPTY_SCORES: Record<string, number> = {};

function initialFacetRecommendationsResult(
  section: RecommendationSection,
  queryString: string,
): FacetRecommendationsResult {
  const hasAnyFacets = queryString.length > 0;
  if (!hasAnyFacets) {
    return {
      isReady: true,
      scoresBySlug: EMPTY_SCORES,
      hasAnyFacets: false,
    };
  }
  const requestKey = buildFacetRecommendationRequestKey(section, queryString);
  const cached = getCachedFacetScores(requestKey);
  if (cached) {
    return {
      isReady: true,
      scoresBySlug: cached,
      hasAnyFacets: true,
    };
  }
  return {
    isReady: false,
    scoresBySlug: EMPTY_SCORES,
    hasAnyFacets: true,
  };
}

/**
 * Calls `GET /api/create-flow/methods?section=<section>&facet.*=...` for the
 * card-deck step `section` and returns a `slug → score` map for re-ranking
 * the messages-file `methods[]` array (CR-88 §10).
 *
 * Returns `{ isReady: true, scoresBySlug: {} }` when the user has not selected
 * any community facets — callers fall back to the authoring order.
 *
 * Network failures resolve to `scoresBySlug: {}` so the wizard is never
 * blocked on the recommendation backend.
 */
export function useFacetRecommendations(
  section: RecommendationSection,
): FacetRecommendationsResult {
  const { state } = useCreateFlow();
  const queryString = useMemo(
    () => buildFacetQueryString(state),
    [state],
  );
  const hasAnyFacets = queryString.length > 0;

  const [result, setResult] = useState<FacetRecommendationsResult>(() =>
    initialFacetRecommendationsResult(section, queryString),
  );

  useEffect(() => {
    if (!hasAnyFacets) {
      setResult({
        isReady: true,
        scoresBySlug: EMPTY_SCORES,
        hasAnyFacets: false,
      });
      return;
    }

    const requestKey = buildFacetRecommendationRequestKey(section, queryString);
    const cached = getCachedFacetScores(requestKey);
    if (cached) {
      setResult({
        isReady: true,
        scoresBySlug: cached,
        hasAnyFacets: true,
      });
      return;
    }

    let cancelled = false;
    setResult((prev) =>
      prev.isReady && prev.hasAnyFacets
        ? { ...prev, isReady: false }
        : { isReady: false, scoresBySlug: EMPTY_SCORES, hasAnyFacets: true },
    );

    void loadFacetScores(section, queryString).then((scoresBySlug) => {
      if (cancelled) return;
      setResult({ isReady: true, scoresBySlug, hasAnyFacets: true });
    });

    return () => {
      cancelled = true;
    };
  }, [section, queryString, hasAnyFacets]);

  return result;
}

/**
 * One card per job, then the display rule for the top `limit` cards.
 * Cards marked every-rule carry no Recommended tag. With no facets, the
 * first `limit` cards in deck order show and nothing is tagged.
 */
export function deriveCompactCards(
  section: RecommendationSection,
  answers: GroupAnswers,
  limit: number,
): {
  compactCardIds: string[];
  recommendedIds: Set<string>;
  orderedIds: string[];
} {
  const recommendation = recommendDeck(deckData(section), answers, { limit });
  const orderedIds = recommendation.fallback
    ? recommendation.seeAll
    : [
        ...recommendation.shown.map((card) => card.id),
        ...recommendation.seeAll,
      ];
  if (recommendation.fallback) {
    return {
      compactCardIds: orderedIds.slice(0, limit),
      recommendedIds: new Set<string>(),
      orderedIds,
    };
  }
  return {
    compactCardIds: recommendation.shown.map((card) => card.id),
    recommendedIds: new Set(
      recommendation.recommended
        .filter((card) => card.tag === "recommended")
        .map((card) => card.id),
    ),
    orderedIds,
  };
}

export function groupAnswersForRecommendations(
  state: Parameters<typeof groupAnswersFromCreateFlowState>[0],
): GroupAnswers {
  return groupAnswersFromCreateFlowState(state);
}