import type { ExploreQuery } from "@dci/core";
import { CONFIDENCE_LEVELS, FACILITY_STATUSES, FACILITY_TYPES, GEO_PRECISIONS, PROJECT_CLASSES } from "@dci/core";

/** URL search params ↔ ExploreQuery (/explore). Unknown values are dropped so the API never sees an invalid key. */

export type ExploreParamsInput = Record<string, string | string[] | undefined> | URLSearchParams;

export const EXPLORE_PER_PAGE = 24;
export const EXPLORE_SORTS = ["updated", "name", "mw", "opened", "completeness", "announced", "opening"] as const;
export const EXPLORE_VIEWS = ["table", "map", "charts"] as const;
export const AI_FILTERS = ["any", "confirmed", "likely", "associated"] as const;

function get(sp: ExploreParamsInput, key: string): string | undefined {
  if (sp instanceof URLSearchParams) return sp.get(key) ?? undefined;
  const v = sp[key];
  const s = Array.isArray(v) ? v[0] : v;
  return s === undefined || s === "" ? undefined : s;
}

const num = (v: string | undefined): number | undefined => {
  if (v === undefined) return undefined;
  const n = Number(v);
  return Number.isFinite(n) ? n : undefined;
};
const int = (v: string | undefined): number | undefined => {
  const n = num(v);
  return n === undefined ? undefined : Math.trunc(n);
};
const bool = (v: string | undefined): boolean | undefined => (v === "1" || v === "true" ? true : v === "0" || v === "false" ? false : undefined);
const csv = (v: string | undefined, allowed: ReadonlySet<string>): string | undefined => {
  if (!v) return undefined;
  const out = v
    .split(",")
    .map((s) => s.trim())
    .filter((s) => s && allowed.has(s));
  return out.length ? out.join(",") : undefined;
};

const STATUS_SET = new Set<string>(FACILITY_STATUSES);
const TYPE_SET = new Set<string>(FACILITY_TYPES);
const CONF_SET = new Set<string>(CONFIDENCE_LEVELS);
const PREC_SET = new Set<string>(GEO_PRECISIONS);
const CLASS_SET = new Set<string>(PROJECT_CLASSES);

export function parseExploreQuery(sp: ExploreParamsInput): ExploreQuery {
  const q: ExploreQuery = {};
  const entity = get(sp, "entity");
  q.entity = entity === "projects" ? "projects" : "facilities";
  const status = csv(get(sp, "status"), STATUS_SET);
  if (status) q.status = status;
  const country = get(sp, "country");
  if (country) {
    const cc = country
      .toUpperCase()
      .split(",")
      .map((s) => s.trim())
      .filter((s) => /^[A-Z]{2}$/.test(s));
    if (cc.length) q.country = cc.join(",");
  }
  const metro = get(sp, "metro");
  if (metro && /^[a-z0-9-]+$/i.test(metro)) q.metro = metro;
  const operator = get(sp, "operator");
  if (operator && /^[a-z0-9-]+$/i.test(operator)) q.operator = operator;
  if (q.entity === "facilities") {
    const type = csv(get(sp, "type"), TYPE_SET);
    if (type) q.type = type;
    const of = int(get(sp, "opened_from"));
    if (of !== undefined) q.opened_from = of;
    const ot = int(get(sp, "opened_to"));
    if (ot !== undefined) q.opened_to = ot;
    const hs = bool(get(sp, "hyperscale"));
    if (hs !== undefined) q.hyperscale = hs;
    const lp = csv(get(sp, "location_precision"), PREC_SET);
    if (lp) q.location_precision = lp;
  } else {
    const eb = int(get(sp, "expected_before"));
    if (eb !== undefined) q.expected_before = eb;
    const ea = int(get(sp, "expected_after"));
    if (ea !== undefined) q.expected_after = ea;
    const as = get(sp, "announced_since");
    if (as && /^\d{4}(-\d{2}(-\d{2})?)?$/.test(as)) q.announced_since = as;
    const pc = csv(get(sp, "project_class"), CLASS_SET);
    if (pc) q.project_class = pc;
  }
  const minMw = num(get(sp, "min_mw"));
  if (minMw !== undefined && minMw >= 0) q.min_mw = minMw;
  const maxMw = num(get(sp, "max_mw"));
  if (maxMw !== undefined && maxMw >= 0) q.max_mw = maxMw;
  const ai = get(sp, "ai");
  if (ai && (AI_FILTERS as readonly string[]).includes(ai)) q.ai = ai as ExploreQuery["ai"];
  const conf = csv(get(sp, "confidence"), CONF_SET);
  if (conf) q.confidence = conf;
  const hasMw = bool(get(sp, "has_mw"));
  if (hasMw !== undefined) q.has_mw = hasMw;
  const text = get(sp, "q");
  if (text) q.q = text.slice(0, 120);
  const sort = get(sp, "sort");
  if (sort && (EXPLORE_SORTS as readonly string[]).includes(sort)) q.sort = sort;
  const order = get(sp, "order");
  if (order === "asc" || order === "desc") q.order = order;
  const page = int(get(sp, "page"));
  if (page && page > 1) q.page = page;
  const per = int(get(sp, "per_page"));
  if (per && per > 0 && per !== EXPLORE_PER_PAGE) q.per_page = Math.min(100, per);
  const view = get(sp, "view");
  if (view && (EXPLORE_VIEWS as readonly string[]).includes(view)) q.view = view as ExploreQuery["view"];
  return q;
}

/** Serialize (defaults skipped: entity=facilities, view=table, page=1, per_page=24). */
export function exploreToParams(q: ExploreQuery, patch?: Partial<ExploreQuery> & Record<string, unknown>): URLSearchParams {
  const merged: Record<string, unknown> = { ...q, ...(patch ?? {}) };
  const sp = new URLSearchParams();
  for (const [k, v] of Object.entries(merged)) {
    if (v === undefined || v === null || v === "" || v === false) continue;
    if (k === "entity" && v === "facilities") continue;
    if (k === "view" && v === "table") continue;
    if (k === "page" && Number(v) <= 1) continue;
    if (k === "per_page" && Number(v) === EXPLORE_PER_PAGE) continue;
    sp.set(k, v === true ? "1" : String(v));
  }
  return sp;
}

export function exploreHref(q: ExploreQuery, patch?: Partial<ExploreQuery> & Record<string, unknown>): string {
  const s = exploreToParams(q, patch).toString();
  return `/explore${s ? `?${s}` : ""}`;
}

/** Keys that count as active filters (not paging / view / sort). */
export const EXPLORE_FILTER_KEYS: Array<keyof ExploreQuery> = ["status", "country", "metro", "operator", "type", "min_mw", "max_mw", "ai", "hyperscale", "expected_before", "expected_after", "opened_from", "opened_to", "announced_since", "confidence", "location_precision", "has_mw", "project_class", "q"];

export function countExploreFilters(q: ExploreQuery): number {
  return EXPLORE_FILTER_KEYS.filter((k) => q[k] !== undefined && q[k] !== "" && q[k] !== false).length;
}

/** Toggle a member in a csv key. */
export function toggleCsv(current: string | undefined, member: string): string | undefined {
  const set = new Set((current ?? "").split(",").filter(Boolean));
  if (set.has(member)) set.delete(member);
  else set.add(member);
  return set.size ? Array.from(set).join(",") : undefined;
}