import type { Place, PlaceList } from "../types.ts";

const XSSI_PREFIX = ")]}'\n";

export async function fetchList(listId: string): Promise<PlaceList> {
  const pb = `!1m1!1s${listId}!2e2!3e2!4i10000!16b1`;
  const url = `https://www.google.com/maps/preview/entitylist/getlist?authuser=0&hl=en&pb=${pb}`;

  const response = await fetch(url, {
    headers: {
      "User-Agent":
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36",
    },
  });

  if (!response.ok) {
    throw new Error(
      `Google Maps returned HTTP ${response.status}. The list may be private or the URL may be invalid.`,
    );
  }

  const text = await response.text();
  const json = text.startsWith(XSSI_PREFIX)
    ? text.slice(XSSI_PREFIX.length)
    : text;

  let data: unknown;
  try {
    data = JSON.parse(json);
  } catch {
    throw new Error(
      "Failed to parse Google Maps response. The list may be private or the URL may be invalid.",
    );
  }

  if (!Array.isArray(data) || !Array.isArray(data[0])) {
    throw new Error("List not found or not publicly shared");
  }

  const root = data[0] as unknown[];

  return {
    id: listId,
    name: getString(root, 4) ?? "Untitled",
    description: getString(root, 5) ?? "",
    owner: getNestedString(root, 3, 0) ?? "Unknown",
    totalCount: getNumber(root, 12) ?? 0,
    places: parsePlaces(root),
    createdAt: parseTimestamp(root, 10),
    updatedAt: parseTimestamp(root, 11),
  };
}

function parsePlaces(root: unknown[]): Place[] {
  const rawPlaces = root[8];
  if (!Array.isArray(rawPlaces)) return [];

  const places: Place[] = [];

  for (const raw of rawPlaces) {
    if (!Array.isArray(raw)) continue;

    const info = raw[1] as unknown[] | undefined;
    if (!Array.isArray(info)) continue;

    const coords = info[5] as unknown[] | undefined;
    const lat =
      Array.isArray(coords) && typeof coords[2] === "number"
        ? coords[2]
        : null;
    const lng =
      Array.isArray(coords) && typeof coords[3] === "number"
        ? coords[3]
        : null;

    if (lat === null || lng === null) continue;

    const name = typeof raw[2] === "string" ? raw[2] : "Unknown";

    places.push({
      name,
      lat,
      lng,
      address: typeof info[4] === "string" && info[4] !== "" ? info[4] : null,
      fullAddress:
        typeof info[2] === "string" && info[2] !== "" ? info[2] : null,
      placeRef: typeof info[7] === "string" ? info[7] : null,
      note: typeof raw[3] === "string" ? raw[3] : "",
      addedAt: parseTimestamp(raw as unknown[], 9),
      modifiedAt: parseTimestamp(raw as unknown[], 10),
    });
  }

  return places;
}

function getString(arr: unknown[], index: number): string | null {
  const val = arr[index];
  return typeof val === "string" ? val : null;
}

function getNumber(arr: unknown[], index: number): number | null {
  const val = arr[index];
  return typeof val === "number" ? val : null;
}

function getNestedString(
  arr: unknown[],
  index: number,
  subIndex: number,
): string | null {
  const nested = arr[index];
  if (!Array.isArray(nested)) return null;
  const val = nested[subIndex];
  return typeof val === "string" ? val : null;
}

function parseTimestamp(arr: unknown[], index: number): Date | null {
  const ts = arr[index];
  if (!Array.isArray(ts)) return null;
  const seconds = ts[0];
  if (typeof seconds !== "number") return null;
  return new Date(seconds * 1000);
}