/**
 * Reference engine for RECOMMENDED and the seven, as agreed on 24 and 27 October 2026.
 *
 * Pure functions with no I/O, written to be ported into
 * useFacetRecommendations.ts (deriveCompactCards) and methodRecommendations.ts.
 * The README in this package states the same rule in words.
 */
import communicationFacets from "../../data/create/customRule/communication.json";
import conflictFacets from "../../data/create/customRule/conflictManagement.json";
import decisionFacets from "../../data/create/customRule/decisionApproaches.json";
import jobsFile from "../../data/create/customRule/_jobs.json";
import membershipFacets from "../../data/create/customRule/membership.json";
import type {
  CardEngineEntry,
  DeckEngine,
  DeckId,
  DeckRecommendation,
  FacetFile,
  GroupAnswers,
  JobsFile,
  Kind,
  MatchedFacet,
  RankTier,
  RecommendedCard,
  RecommendationReason,
  SizeBand,
  TraitKey,
} from "./deckTypes";

export interface DeckData {
  deck: DeckId;
  facets: FacetFile;
  engine: DeckEngine;
  config: Pick<
    JobsFile,
    "displayLimit" | "maxAddedInSeven" | "tierOrder" | "traitKeys" | "sizeAnswers"
  >;
}

export interface RecommendOptions {
  /** How many recommended cards show before See all. A screen that shows five passes 5. */
  limit?: number;
}

interface Evaluated {
  id: string;
  entry: CardEngineEntry;
  eligible: boolean;
  matched: MatchedFacet[];
  fitsAnswer?: TraitKey;
  openedBy?: TraitKey;
  score: number;
  otherKindHits: number;
}

/** Normalizes setup answers. A group with other kinds and no main kind gets the first as main. */
export function normalizeAnswers(answers: GroupAnswers): Required<GroupAnswers> {
  const others = [...(answers.otherKinds ?? [])];
  const mainKind = answers.mainKind ?? others.shift() ?? null;
  return {
    size: answers.size ?? null,
    mainKind,
    otherKinds: others.filter((k) => k !== mainKind),
    scale: [...new Set(answers.scale ?? [])],
    stage: answers.stage ?? null,
    traits: answers.traits ?? {},
  };
}

function sizeBandOf(size: string | null, data: DeckData): SizeBand | null {
  if (!size) return null;
  const band = data.config.sizeAnswers[size];
  if (!band) throw new Error(`Unknown size answer ${size}`);
  return band;
}

function evaluate(
  id: string,
  data: DeckData,
  a: Required<GroupAnswers>,
  band: SizeBand | null,
  ticked: Set<TraitKey>,
): Evaluated {
  const f = data.facets[id];
  const entry = data.engine.cards[id];
  if (!f || !entry) throw new Error(`Card ${id} is missing from the facet or jobs file`);
  const traits = entry.traits ?? {};
  const fitsSize = band ? f.size[band] : true;
  const fitsKind = a.mainKind ? f.orgType[a.mainKind] : true;
  const openedBy = (traits.opens ?? []).find((k) => ticked.has(k));
  const isBeside = (traits.beside ?? []).length > 0;
  // Each facet group counts once. Scale earns its point only if the card fits
  // every scale the group ticked (27 Oct, call 2).
  const fitsScale = a.scale.length > 0 && a.scale.every((s) => f.scale[s]);
  const fitsStage = a.stage !== null && f.maturity[a.stage];
  const fitsAnswer = (traits.fits ?? []).find((k) => ticked.has(k));
  const matched: MatchedFacet[] = [];
  if (band && fitsSize) matched.push("size");
  if (a.mainKind && fitsKind) matched.push("kind");
  if (fitsScale) matched.push("scale");
  if (fitsStage) matched.push("stage");
  return {
    id,
    entry,
    // Size and the main kind decide eligibility, or a ticked answer opens the card.
    // A card an answer adds never competes for a job.
    eligible: !isBeside && fitsSize && (fitsKind || openedBy !== undefined),
    matched,
    fitsAnswer,
    openedBy,
    // Inside a job, scale, stage and the one point from answers decide (27 Oct, call 1).
    score: (fitsScale ? 1 : 0) + (fitsStage ? 1 : 0) + (fitsAnswer ? 1 : 0),
    otherKindHits: a.otherKinds.filter((k: Kind) => f.orgType[k]).length,
  };
}

/** Best first. Score, then other kinds, then row order inside the job. */
function compareCandidates(x: Evaluated, y: Evaluated): number {
  return (
    y.score - x.score ||
    y.otherKindHits - x.otherKindHits ||
    x.entry.priority - y.entry.priority
  );
}

/** What separated the winner from the runner-up. */
function decidedBy(c: Evaluated[]): RecommendedCard["decidedBy"] {
  if (c.length < 2) return "only";
  if (c[0].score !== c[1].score) return "score";
  if (c[0].otherKindHits !== c[1].otherKindHits) return "otherKinds";
  return "rowOrder";
}

export function recommendDeck(
  data: DeckData,
  answers: GroupAnswers,
  options: RecommendOptions = {},
): DeckRecommendation {
  const limit = options.limit ?? data.config.displayLimit;
  const a = normalizeAnswers(answers);
  const band = sizeBandOf(a.size, data);
  const ticked = new Set<TraitKey>(data.config.traitKeys.filter((k) => a.traits[k] === true));
  const jobs = data.engine.jobs;
  const jobIndex = new Map(jobs.map((j, i) => [j.id, i]));
  const allInDeckOrder = deckOrder(data);

  const anyFacet = band !== null || a.mainKind !== null || a.scale.length > 0 || a.stage !== null;
  const fallback = (): DeckRecommendation => ({
    deck: data.deck,
    fallback: true,
    recommended: [],
    shown: [],
    waiting: [],
    seeAll: allInDeckOrder,
  });
  if (!anyFacet) return fallback();

  const cardIds = Object.keys(data.engine.cards);
  const evaluated = new Map(cardIds.map((id) => [id, evaluate(id, data, a, band, ticked)]));
  const tierRank = (t: RankTier) => data.config.tierOrder.indexOf(t);
  const recommended: (RecommendedCard & { sortKey: number[]; showKey: number[] })[] = [];

  // One card per job that has an eligible card. The runner-up is its alternative.
  for (const job of jobs) {
    if (job.displayTier === "none") continue;
    const candidates = [...evaluated.values()]
      .filter((e) => e.entry.job === job.id && e.eligible)
      .sort(compareCandidates);
    const winner = candidates[0];
    if (!winner) continue;
    const reason: RecommendationReason =
      winner.openedBy && !winner.matched.includes("kind")
        ? { kind: "opened", matched: winner.matched, answer: winner.openedBy }
        : { kind: "fit", matched: winner.matched, ...(winner.fitsAnswer ? { answer: winner.fitsAnswer } : {}) };
    recommended.push({
      id: winner.id,
      job: job.id,
      showsWith: job.id,
      tier: job.displayTier as RankTier,
      tag: winner.entry.everyRuleHas ? "everyRuleHas" : "recommended",
      reason,
      ...(candidates[1] ? { alternative: candidates[1].id } : {}),
      score: winner.score,
      decidedBy: decidedBy(candidates),
      sortKey: [tierRank(job.displayTier as RankTier), job.rank ?? 0, 0],
      showKey: [jobIndex.get(job.id)!, 0, 0],
    });
  }

  // Cards a ticked answer adds beside a job, whatever the group's size or kind.
  const added = data.engine.addedOrder.filter((id) => {
    const e = evaluated.get(id)!;
    return (e.entry.traits?.beside ?? []).some((k) => ticked.has(k));
  });
  added.forEach((id, i) => {
    const e = evaluated.get(id)!;
    const besideJob = e.entry.traits!.besideJob!;
    const answer = e.entry.traits!.beside!.find((k) => ticked.has(k))!;
    const inSevenSlot = i < data.config.maxAddedInSeven;
    recommended.push({
      id,
      job: e.entry.job,
      showsWith: besideJob,
      tier: "answers",
      tag: e.entry.everyRuleHas ? "everyRuleHas" : "recommended",
      reason: { kind: "added", answer },
      // The first added cards rank right after the safety jobs, any more rank last.
      sortKey: inSevenSlot ? [tierRank("answers"), 0, i] : [data.config.tierOrder.length, 0, i],
      showKey: [jobIndex.get(besideJob)!, 1, i],
    });
  });

  if (recommended.length === 0) return fallback();

  const compareKeys = (x: number[], y: number[]) => {
    for (let i = 0; i < x.length; i++) if (x[i] !== y[i]) return x[i] - y[i];
    return 0;
  };
  // Rank decides which cards show. Deck order decides where they show.
  const ranked = [...recommended].sort((x, y) => compareKeys(x.sortKey, y.sortKey));
  const shownIds = new Set(ranked.slice(0, limit).map((r) => r.id));
  const strip = ({ sortKey: _s, showKey: _w, ...card }: (typeof recommended)[number]): RecommendedCard => card;
  const inShowOrder = [...recommended].sort((x, y) => compareKeys(x.showKey, y.showKey));
  const shown = inShowOrder.filter((r) => shownIds.has(r.id)).map(strip);
  const waiting = inShowOrder.filter((r) => !shownIds.has(r.id)).map(strip);
  const recommendedIds = new Set(recommended.map((r) => r.id));

  return {
    deck: data.deck,
    fallback: false,
    recommended: ranked.map(strip),
    shown,
    waiting,
    seeAll: [...waiting.map((r) => r.id), ...allInDeckOrder.filter((id) => !recommendedIds.has(id))],
  };
}

/** Every card in deck order, job by job, then by priority inside each job. */
export function deckOrder(data: DeckData): string[] {
  const jobIndex = new Map(data.engine.jobs.map((j, i) => [j.id, i]));
  const key = (id: string) => {
    const e = data.engine.cards[id];
    return (jobIndex.get(e.job) ?? data.engine.jobs.length) * 1000 + e.priority;
  };
  return Object.keys(data.engine.cards).sort((x, y) => key(x) - key(y));
}

/**
 * The template path (27 Oct). A group that starts from a template answers no setup
 * question and gets no recommendations. Each deck shows the template's cards first,
 * in the template's order, with no tag and no seven-card cut, then the rest of the
 * deck in deck order. templateCardIds come from templateChips.json.
 */
const jobs = jobsFile as JobsFile;
const FACETS: Record<DeckId, FacetFile> = {
  decisionApproaches: decisionFacets as FacetFile,
  membership: membershipFacets as FacetFile,
  conflictManagement: conflictFacets as FacetFile,
  communication: communicationFacets as FacetFile,
};

/** One deck's facets, jobs and display config, ready for {@link recommendDeck}. */
export function deckData(deck: DeckId): DeckData {
  return {
    deck,
    facets: FACETS[deck],
    engine: jobs.decks[deck],
    config: {
      displayLimit: jobs.displayLimit,
      maxAddedInSeven: jobs.maxAddedInSeven,
      tierOrder: jobs.tierOrder,
      traitKeys: jobs.traitKeys,
      sizeAnswers: jobs.sizeAnswers,
    },
  };
}

export function templateDeck(data: DeckData, templateCardIds: string[]): { deck: DeckId; first: string[]; rest: string[] } {
  const live = new Set(Object.keys(data.engine.cards));
  const first = [...new Set(templateCardIds)].filter((id) => live.has(id));
  const chosen = new Set(first);
  return { deck: data.deck, first, rest: deckOrder(data).filter((id) => !chosen.has(id)) };
}