"use client";

import { useMemo, useSyncExternalStore } from "react";

// SearchMode is defined in `lib/searchQuery.ts`, which interprets it.
// Re-exported here so every existing `from "./urlState"` import site is
// unchanged.
export type { SearchMode } from "../lib/searchQuery";
import type { SearchMode } from "../lib/searchQuery";
import { isTagId } from "../lib/curatedTags";

// Per-video modal content mode. Independent from the search page's `mode` so
// the modal can be toggled without disturbing search state. Absence on the
// URL means "transcript" — every other value is persisted verbatim.
//
// "digest" and NOT "summary", deliberately: `DisplaySummary` is already a video
// LISTING CARD (common/lib/transcripts.ts) and `/summaries/` is already the
// browse-index page tree the search index serves. A third meaning of "summary"
// is exactly the naming hazard PLAN.md warns about. "digest" matches the
// artifact, the generation stage, the settings section and the page tree.
export type ModalMode = "transcript" | "chat" | "post" | "digest";

export type UrlParams = {
  q: string;
  re: boolean;
  v: string | null;
  t: number | null;
  vm: ModalMode;
  // The transcript TRACK the reader shows (lib/captionTracks.ts) when it is
  // not the record's primary — a viewer's choice, never a data change. Absent
  // (null) for the primary, which is the default and stays off the URL.
  vt: string | null;
  ch: string[];
  nov: boolean;
  nol: boolean;
  naa: boolean;
  nar: boolean;
  nav: boolean;
  nd: boolean;
  nu: boolean;
  mode: SearchMode;
  // Subs-mode track exclusion filter; empty array means "all tracks" (no
  // exclusions). Mirrors the channel-exclusion convention. Persisted on the
  // URL as repeated `tk=` params (e.g. ?m=subs&tk=live_chat to hide live
  // chat results).
  tracks: string[];
  // Curated tag ids selected in the filter panel, as repeated `tg=` params
  // (e.g. ?tg=eva-collab&tg=eva-in-chat). ORed: a video carrying ANY of them
  // passes. `tg` and not `tag`, following `tk`'s two-letter convention, and
  // deliberately nowhere near the `tags` SEARCH SCOPE, which is yt-dlp
  // keywords — a different thing wearing the same English word (see
  // lib/curatedTags.ts).
  //
  // NOT a share-v1 key: unlike ch/nov/…, `tg` IS the live representation of
  // the committed selection, so stripAllFilterParamsFromUrl leaves it alone
  // and it round-trips through a reload on its own.
  tags: string[];
};

const listeners = new Set<() => void>();

function subscribe(cb: () => void) {
  listeners.add(cb);
  window.addEventListener("popstate", cb);
  return () => {
    listeners.delete(cb);
    window.removeEventListener("popstate", cb);
  };
}

function getSnapshot() {
  return window.location.search;
}

function getServerSnapshot() {
  return "";
}

function parse(search: string): UrlParams {
  const p = new URLSearchParams(search);
  const tRaw = p.get("t");
  const t = tRaw !== null && tRaw !== "" ? Number(tRaw) : null;
  const modeRaw = p.get("m");
  const mode: SearchMode =
    modeRaw === "subs" ? "subs" : modeRaw === "posts" ? "posts" : "transcripts";
  const vmRaw = p.get("vm");
  const vm: ModalMode =
    vmRaw === "chat"
      ? "chat"
      : vmRaw === "post"
        ? "post"
        : vmRaw === "digest"
          ? "digest"
          : "transcript";
  return {
    q: p.get("q") ?? "",
    re: p.get("re") === "1",
    v: p.get("v"),
    t: t !== null && Number.isFinite(t) ? t : null,
    vm,
    vt: p.get("vt") || null,
    ch: p.getAll("ch"),
    nov: p.get("nov") === "1",
    nol: p.get("nol") === "1",
    naa: p.get("naa") === "1",
    nar: p.get("nar") === "1",
    nav: p.get("nav") === "1",
    nd: p.get("nd") === "1",
    nu: p.get("nu") === "1",
    mode,
    tracks: p.getAll("tk"),
    // Validated against TAG_ID_RE, so this entry point agrees with the MCP's
    // parseSearchArgs: a lowercase [a-z0-9._-] id or nothing. A malformed
    // token is DROPPED rather than carried, because the only thing a
    // never-matching id can do downstream is turn a filter into a silent
    // empty result. (A well-formed id this site does not publish is a
    // different case and is kept — the chip row renders it so it can be
    // cleared.)
    tags: p.getAll("tg").filter((t) => isTagId(t)),
  };
}

export function useUrlParams(): UrlParams {
  const search = useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot);
  return useMemo(() => parse(search), [search]);
}

type Patch = Partial<{
  q: string;
  re: boolean;
  v: string | null;
  t: number | null;
  vm: ModalMode;
  vt: string | null;
  ch: string[];
  nov: boolean;
  nol: boolean;
  naa: boolean;
  nar: boolean;
  nav: boolean;
  nd: boolean;
  nu: boolean;
  mode: SearchMode;
  tracks: string[];
  tags: string[];
}>;

export function writeUrlParams(patch: Patch) {
  const params = new URLSearchParams(window.location.search);
  if (patch.q !== undefined) {
    if (patch.q) params.set("q", patch.q);
    else params.delete("q");
  }
  if (patch.re !== undefined) {
    if (patch.re) params.set("re", "1");
    else params.delete("re");
  }
  if (patch.v !== undefined) {
    if (patch.v) params.set("v", patch.v);
    else params.delete("v");
  }
  if (patch.t !== undefined) {
    if (patch.t !== null) params.set("t", String(patch.t));
    else params.delete("t");
  }
  if (patch.vm !== undefined) {
    if (patch.vm === "chat") params.set("vm", "chat");
    else if (patch.vm === "post") params.set("vm", "post");
    else if (patch.vm === "digest") params.set("vm", "digest");
    // "transcript" is the fallthrough and DELETES the param rather than
    // setting vm=transcript — the default must stay absent from the URL.
    else params.delete("vm");
  }
  if (patch.vt !== undefined) {
    if (patch.vt) params.set("vt", patch.vt);
    else params.delete("vt");
  }
  if (patch.ch !== undefined) {
    params.delete("ch");
    for (const v of patch.ch) params.append("ch", v);
  }
  if (patch.nov !== undefined) {
    if (patch.nov) params.set("nov", "1");
    else params.delete("nov");
  }
  if (patch.nol !== undefined) {
    if (patch.nol) params.set("nol", "1");
    else params.delete("nol");
  }
  if (patch.naa !== undefined) {
    if (patch.naa) params.set("naa", "1");
    else params.delete("naa");
  }
  if (patch.nar !== undefined) {
    if (patch.nar) params.set("nar", "1");
    else params.delete("nar");
  }
  if (patch.nav !== undefined) {
    if (patch.nav) params.set("nav", "1");
    else params.delete("nav");
  }
  if (patch.nd !== undefined) {
    if (patch.nd) params.set("nd", "1");
    else params.delete("nd");
  }
  if (patch.nu !== undefined) {
    if (patch.nu) params.set("nu", "1");
    else params.delete("nu");
  }
  if (patch.mode !== undefined) {
    if (patch.mode === "subs") params.set("m", "subs");
    else if (patch.mode === "posts") params.set("m", "posts");
    else params.delete("m");
  }
  if (patch.tracks !== undefined) {
    params.delete("tk");
    for (const v of patch.tracks) params.append("tk", v);
  }
  if (patch.tags !== undefined) {
    params.delete("tg");
    for (const v of patch.tags) if (isTagId(v)) params.append("tg", v);
  }
  const qs = params.toString();
  const next = `${window.location.pathname}${qs ? `?${qs}` : ""}`;
  if (next === window.location.pathname + window.location.search) return;
  window.history.replaceState(window.history.state, "", next);
  for (const l of listeners) l();
}