// Talking to Plex.
//
// Plex spreads what looks like one product over four hosts, and which one
// answers depends on what is being asked:
//
//   <server>:32400          the library itself, on the LAN
//   plex.tv                 accounts, sharing, and the PIN sign-in flow
//   discover.provider…      the owner's watchlist, with external ids attached
//   community.plex.tv       everybody else's watchlist, over GraphQL
//
// Only the owner's token is ever used. Linking a user proves who they are and
// then discards their token; see plexAccounts in the schema for why.

import { APP_URL } from "@/lib/app-url";

const PLEX_TOKEN = process.env.PLEX_AUTH_TOKEN ?? "";
const MACHINE_ID = process.env.PLEX_MACHINE_IDENTIFIER ?? "";

// Identifies Ampelos to Plex. Stable on purpose: the PIN flow ties a sign-in to
// the client that started it, so a value that changed per request would make
// every link fail at the last step.
export const CLIENT_IDENTIFIER = "ampelos";

function ownerHeaders(extra: Record<string, string> = {}) {
  return {
    "X-Plex-Token": PLEX_TOKEN,
    "X-Plex-Client-Identifier": CLIENT_IDENTIFIER,
    "X-Plex-Product": "Ampelos",
    Accept: "application/json",
    ...extra,
  };
}

/** The LAN address of the server, with the scheme the env may omit. */
export function serverUrl() {
  let base = (process.env.PLEX_URL ?? "").replace(/\/$/, "");
  if (!base) return null;
  if (!/^https?:\/\//.test(base)) base = `http://${base}`;
  const port = process.env.PLEX_PORT;
  return /:\d+$/.test(base) || !port ? base : `${base}:${port}`;
}

export type PlexSection = {
  /** plex.tv's id, which is what sharing takes -- NOT the local section key. */
  id: string;
  key: string;
  type: string;
  title: string;
};

/**
 * Sections as plex.tv sees them.
 *
 * Sharing is keyed on plex.tv's section id and the local server calls the same
 * library something else entirely: Movies is key 1 on the LAN and 140184388 to
 * plex.tv. Reading them from the server would produce numbers the sharing API
 * silently ignores.
 */
export async function listSections(): Promise<PlexSection[]> {
  const response = await fetch(`https://plex.tv/api/servers/${MACHINE_ID}`, {
    headers: ownerHeaders({ Accept: "application/xml" }),
    signal: AbortSignal.timeout(20000),
  });
  if (!response.ok) throw new Error(`Plex returned HTTP ${response.status} listing sections`);
  const xml = await response.text();

  const sections = new Map<string, PlexSection>();
  for (const element of xml.match(/<Section\b[^>]*>/g) ?? []) {
    const attr = (name: string) => element.match(new RegExp(`${name}="([^"]*)"`))?.[1] ?? "";
    const id = attr("id");
    // The same section is repeated once per existing share; first wins.
    if (id && !sections.has(id)) {
      sections.set(id, { id, key: attr("key"), type: attr("type"), title: attr("title") });
    }
  }
  return [...sections.values()];
}

/**
 * What a linked user gets: everything except Adult and Pictures.
 *
 * Matched on what the section IS rather than on a list of ids, so a library
 * added later is shared without anyone remembering to update a constant --
 * and, more importantly, so a RENAMED adult library cannot quietly become
 * shareable because its id was never on an exclusion list.
 */
export function isShareable(section: PlexSection) {
  if (section.type === "photo") return false;
  return !/\b(adult|xxx|porn)\b/i.test(section.title);
}

// --- linking ---------------------------------------------------------------

export type PlexPin = { id: number; code: string };

/**
 * Start a sign-in. The user takes the code to plex.tv; we poll for the result.
 *
 * THE ORIGIN HEADER IS LOAD-BEARING AND IS WHY THIS USED TO FAIL.
 *
 * Plex records an `origin` against the PIN, taken from the Origin header on
 * this request, and the sign-in page at app.plex.tv reads it back through
 * /api/v2/pins/info before it will honour `forwardUrl`. A PIN with a null
 * origin gets the user signed in and then stranded on plex.tv instead of
 * returned here.
 *
 * Everything else creates its PIN from the BROWSER, where the header is sent
 * automatically and nobody has to know this. Ampelos creates it in a server
 * action, where fetch sends no Origin at all -- so it has to be stated.
 * Measured against the live API: without it origin is null, with it origin is
 * "ampelos.sticknife.com".
 */
export async function createPin(): Promise<PlexPin> {
  const response = await fetch("https://plex.tv/api/v2/pins?strong=true", {
    method: "POST",
    headers: {
      "X-Plex-Client-Identifier": CLIENT_IDENTIFIER,
      "X-Plex-Product": "Ampelos",
      Origin: new URL(APP_URL).origin,
      Accept: "application/json",
    },
    signal: AbortSignal.timeout(20000),
  });
  if (!response.ok) throw new Error(`Plex would not issue a sign-in code (HTTP ${response.status})`);
  const body = await response.json();
  return { id: body.id, code: body.code };
}

/** Where to send the user. Plex returns them to `returnTo` when they are done. */
export function authUrl(pin: PlexPin, returnTo: string) {
  const params = new URLSearchParams({
    clientID: CLIENT_IDENTIFIER,
    code: pin.code,
    "context[device][product]": "Ampelos",
    forwardUrl: returnTo,
  });
  return `https://app.plex.tv/auth#?${params}`;
}

export type PlexIdentity = {
  plexUserId: string;
  plexUuid: string | null;
  username: string;
  email: string | null;
};

/**
 * Has the user finished signing in, and if so who are they?
 *
 * Returns null while the PIN is still unclaimed. The token that comes back is
 * used once, to ask Plex whose it is, and is never stored or returned to the
 * caller.
 */
export async function claimPin(pinId: number): Promise<PlexIdentity | null> {
  const response = await fetch(`https://plex.tv/api/v2/pins/${pinId}`, {
    headers: {
      "X-Plex-Client-Identifier": CLIENT_IDENTIFIER,
      Accept: "application/json",
    },
    signal: AbortSignal.timeout(20000),
  });
  if (!response.ok) throw new Error(`Plex would not confirm the sign-in (HTTP ${response.status})`);
  const body = await response.json();
  const token: string | null = body.authToken ?? null;
  if (!token) return null;

  const who = await fetch("https://plex.tv/api/v2/user", {
    headers: {
      "X-Plex-Token": token,
      "X-Plex-Client-Identifier": CLIENT_IDENTIFIER,
      Accept: "application/json",
    },
    signal: AbortSignal.timeout(20000),
  });
  if (!who.ok) throw new Error("Plex accepted the sign-in but would not say who it was");
  const account = await who.json();
  return {
    plexUserId: String(account.id),
    plexUuid: account.uuid ?? null,
    username: account.username ?? account.title ?? "unknown",
    email: account.email ?? null,
  };
}

/**
 * Who owns this server, according to the token Ampelos holds.
 *
 * Needed because the owner cannot be invited to their own libraries -- Plex
 * answers a share request naming them with HTTP 400 "You cannot send an
 * invitation to yourself." That is not a failure to handle, it is a state to
 * recognise: the owner already has every library, so there is nothing to grant.
 *
 * Asked rather than pattern-matched on that error text, because the wording is
 * Plex's to change and being wrong here would mean telling the owner their
 * libraries had failed to share forever.
 */
export async function ownerAccountId(): Promise<string | null> {
  const response = await fetch("https://plex.tv/api/v2/user", {
    headers: ownerHeaders(),
    signal: AbortSignal.timeout(20000),
  });
  if (!response.ok) return null;
  const account = await response.json();
  return account?.id != null ? String(account.id) : null;
}

// --- sharing ---------------------------------------------------------------

/**
 * The human-readable half of a Plex error.
 *
 * Plex answers failures with XML whose only useful content is the `status`
 * attribute. Surfacing the raw document instead put `<?xml version="1.0"...`
 * in front of the sentence and pushed the sentence itself past the point where
 * the message got truncated -- which is how "You cannot send an invitation to
 * yourself." reached a person as "You cannot send a".
 */
function plexErrorText(body: string) {
  return body.match(/status="([^"]*)"/)?.[1] ?? body.trim().slice(0, 200);
}

/**
 * Invite an account to the shareable libraries.
 *
 * The v2 endpoint only accepts POST and rejects a read, so the shape below is
 * the v1 one that Plex's own clients use. Sharing is idempotent from our side:
 * re-inviting somebody who already has access is answered with a conflict,
 * which is reported as success because the desired state is what matters.
 */
export async function shareLibraries(identity: { email: string | null; plexUserId: string }) {
  const sections = (await listSections()).filter(isShareable);
  if (!sections.length) throw new Error("no shareable Plex libraries found");

  const invited = identity.email ?? identity.plexUserId;
  const response = await fetch(`https://plex.tv/api/servers/${MACHINE_ID}/shared_servers`, {
    method: "POST",
    headers: ownerHeaders({ "Content-Type": "application/json" }),
    body: JSON.stringify({
      server_id: MACHINE_ID,
      shared_server: {
        library_section_ids: sections.map((s) => Number(s.id)),
        invited_email: invited,
      },
      sharing_settings: {},
    }),
    signal: AbortSignal.timeout(30000),
  });

  // 400 with an "already sharing" body is the ordinary outcome of linking an
  // account that was already invited by hand, and is not a failure.
  const text = await response.text();
  const alreadyShared = /already/i.test(text) && /shar/i.test(text);
  if (!response.ok && !alreadyShared) {
    throw new Error(`Plex refused the share: ${plexErrorText(text)}`);
  }

  return {
    sectionIds: sections.map((s) => s.id),
    sectionTitles: sections.map((s) => s.title),
    alreadyShared,
  };
}