// Serialize feed filters to/from a compact, human-readable URL query string, so a
// pasted URL reproduces exactly what's on screen (handy for "here's the URL, I see
// this bug"). Only non-default values are emitted to keep URLs clean.
import type { FeedFilters } from "./api";

const KEYS = [
  "q",
  "show",
  "sort",
  "normal",
  "shorts",
  "live",
  "tags",
  "tagmode",
  "channel",
  "maxage",
  "from",
  "to",
  "mindur",
  "maxdur",
] as const;

export function filtersToParams(f: FeedFilters): URLSearchParams {
  const p = new URLSearchParams();
  if (f.q) p.set("q", f.q);
  if (f.show && f.show !== "unwatched") p.set("show", f.show);
  if (f.sort && f.sort !== "newest") p.set("sort", f.sort);
  if (!f.includeNormal) p.set("normal", "0");
  if (f.includeShorts) p.set("shorts", "1");
  if (f.includeLive) p.set("live", "1");
  if (f.tags.length) p.set("tags", f.tags.join(","));
  if (f.tagMode === "and") p.set("tagmode", "and");
  if (f.channelId) p.set("channel", f.channelId);
  if (f.maxAgeDays) p.set("maxage", String(f.maxAgeDays));
  if (f.dateFrom) p.set("from", f.dateFrom);
  if (f.dateTo) p.set("to", f.dateTo);
  if (f.minDuration != null) p.set("mindur", String(f.minDuration));
  if (f.maxDuration != null) p.set("maxdur", String(f.maxDuration));
  return p;
}

/** Merge URL params onto a base filter set (typically the defaults). */
export function paramsToFilters(params: URLSearchParams, base: FeedFilters): FeedFilters {
  const f: FeedFilters = { ...base };
  const num = (v: string | null): number | undefined => {
    if (v == null || v === "") return undefined;
    const n = Number(v);
    return Number.isFinite(n) ? n : undefined;
  };

  if (params.has("q")) f.q = params.get("q") ?? "";
  if (params.has("show")) f.show = params.get("show") || "unwatched";
  if (params.has("sort")) f.sort = params.get("sort") || "newest";
  if (params.has("normal")) f.includeNormal = params.get("normal") !== "0";
  if (params.has("shorts")) f.includeShorts = params.get("shorts") === "1";
  if (params.has("live")) f.includeLive = params.get("live") === "1";
  if (params.has("tags"))
    f.tags = (params.get("tags") ?? "")
      .split(",")
      .map((s) => Number(s))
      .filter((n) => Number.isInteger(n));
  if (params.has("tagmode")) f.tagMode = params.get("tagmode") === "and" ? "and" : "or";
  f.channelId = params.get("channel") || undefined;
  f.maxAgeDays = num(params.get("maxage"));
  f.dateFrom = params.get("from") || undefined;
  f.dateTo = params.get("to") || undefined;
  f.minDuration = num(params.get("mindur"));
  f.maxDuration = num(params.get("maxdur"));
  return f;
}

/** True if the query string carries any filter param we recognize. */
export function hasFilterParams(params: URLSearchParams): boolean {
  return KEYS.some((k) => params.has(k));
}

/** Reflect the current filters into the address bar without adding history entries. */
export function syncUrl(f: FeedFilters): void {
  const qs = filtersToParams(f).toString();
  const url = qs ? `${window.location.pathname}?${qs}` : window.location.pathname;
  window.history.replaceState(null, "", url);
}