import type { InstrumentId } from "./instruments";
import {
  goldKeys,
  type Direction,
  type GoldRow,
  type MarketSnapshot,
  type MarketSource,
  type Quote,
  type Session,
  type SessionKey,
} from "./types";

const SOURCE_URL = "https://livedata.ir/";

/* ── shared helpers ─────────────────────────────────────────────────────── */

const stripTags = (value: string) => value.replace(/<[^>]*>/g, "").trim();

function directionOf(change: string): Direction {
  const value = Number.parseFloat(change.replace(/,/g, ""));
  if (!Number.isFinite(value) || value === 0) return "flat";
  return value > 0 ? "up" : "down";
}

/* ── 1. id-anchored figures ─────────────────────────────────────────────── */

function readSpan(html: string, prefix: string, id: string) {
  const match = html.match(new RegExp(`id="${prefix}_${id}"[^>]*>([^<]*)<`));
  return match ? match[1].trim() : null;
}

function parseQuotes(html: string, ids: readonly InstrumentId[]): Quote[] {
  const quotes: Quote[] = [];
  for (const id of ids) {
    const price = readSpan(html, "s", id);
    // An instrument that moved or vanished upstream is skipped, not fatal.
    if (!price) continue;
    const change = readSpan(html, "c", id) ?? "0";
    quotes.push({
      id,
      price,
      change,
      changePercent: readSpan(html, "cp", id) ?? "0%",
      direction: directionOf(change),
    });
  }
  return quotes;
}

/* ── 2. gold purities ───────────────────────────────────────────────────── */

/**
 * This table carries no ids, so it is anchored on its section heading and then
 * on each row's fixed Persian label. More brittle than the id-based figures —
 * if upstream renames a row, that row drops out and the rest survive.
 */
const GOLD_ROW_LABELS: Record<string, (typeof goldKeys)[number]> = {
  "هر گرم 24": "g24",
  "هر گرم 22": "g22",
  "هر گرم 18": "g18",
};

/** Upstream id for the world gold ounce, shown as the table's last row. */
const GOLD_OUNCE_ID = "300106";

function parseGold(html: string): GoldRow[] {
  const start = html.indexOf("قیمت عیارهای مختلف طلا");
  if (start === -1) return [];
  const table = html.slice(start, html.indexOf("</table>", start));

  const rows: GoldRow[] = [];
  const pattern = /<td class="tabna">([^<]+)<\/td>\s*<td[^>]*>([^<]*)<\/td>\s*<td[^>]*>([^<]*)<\/td>/g;

  for (const match of table.matchAll(pattern)) {
    const key = GOLD_ROW_LABELS[stripTags(match[1])];
    if (!key) continue;
    rows.push({ key, toman: match[2].trim(), usd: match[3].trim() });
  }

  // The world ounce lives elsewhere on the page, under its own id.
  const ouncePrice = readSpan(html, "s", GOLD_OUNCE_ID);
  if (ouncePrice) rows.push({ key: "ounce", toman: null, usd: ouncePrice });

  // Keep our declared order rather than the upstream's.
  return goldKeys
    .map((key) => rows.find((row) => row.key === key))
    .filter((row): row is GoldRow => Boolean(row));
}

/* ── 3. exchange sessions ───────────────────────────────────────────────── */

const SESSION_NAMES: Record<string, SessionKey> = {
  نیویورک: "newYork",
  لندن: "london",
  توکیو: "tokyo",
};

function parseSessions(html: string): Session[] {
  const start = html.indexOf("ساعت و وضعیت کاری");
  if (start === -1) return [];
  const block = html.slice(start, html.indexOf("</ul>", start));

  const sessions: Session[] = [];
  // name, then the status icon class, then optional reopening date after the text
  const pattern =
    /<span class="nma">([^<]+)<\/span>\s*<span class="sp ([^"]*)"><\/span>\s*<span>[^<]*<\/span>\s*([^<]*)/g;

  for (const match of block.matchAll(pattern)) {
    const key = SESSION_NAMES[stripTags(match[1])];
    if (!key) continue;
    const closed = /close/i.test(match[2]);
    const reopensOn = match[3].trim();
    sessions.push({ key, open: !closed, reopensOn: closed && reopensOn ? reopensOn : null });
  }

  return sessionKeysOrder(sessions);
}

function sessionKeysOrder(sessions: Session[]) {
  const order: SessionKey[] = ["newYork", "london", "tokyo"];
  return order
    .map((key) => sessions.find((session) => session.key === key))
    .filter((session): session is Session => Boolean(session));
}

/* ── source ─────────────────────────────────────────────────────────────── */

/**
 * livedata.ir publishes no API — the figures sit in a static page its server
 * regenerates once a minute, on the minute. We read only the numbers and label
 * them ourselves, in our own three languages.
 */
export const livedataSource: MarketSource = {
  name: "livedata.ir",
  url: SOURCE_URL,

  async fetchSnapshot(ids: readonly InstrumentId[]): Promise<MarketSnapshot> {
    const response = await fetch(SOURCE_URL, {
      // One upstream request per minute for the whole site, not one per visitor.
      // Matches their regeneration cadence — polling faster gains nothing.
      next: { revalidate: 60 },
      headers: { "User-Agent": "majdtrading.com market widget" },
    });

    if (!response.ok) throw new Error(`livedata.ir responded ${response.status}`);

    const html = await response.text();
    const quotes = parseQuotes(html, ids);
    const gold = parseGold(html);
    const sessions = parseSessions(html);

    if (quotes.length === 0 && gold.length === 0 && sessions.length === 0) {
      throw new Error("livedata.ir markup produced nothing — parsers need updating");
    }

    return {
      quotes,
      gold,
      sessions,
      fetchedAt: new Date().toISOString(),
      source: { name: livedataSource.name, url: SOURCE_URL },
    };
  },
};