// Share links: a minted slug names one turn of one game, and anyone
// holding it may watch that turn — spectator-redacted, nothing else of
// the game visible. Shares persist beside the rooms and survive restarts.

import { appendFileSync, existsSync, readFileSync } from "node:fs";
import { join } from "node:path";
import { randomInt } from "node:crypto";
import { statsDir } from "./store";

export interface Share {
  id: string;
  roomId: string;
  turn: number;
  createdAt: string;
}

const SHARE_ALPHABET = "abcdefghjkmnpqrstuvwxyz23456789";
const SHARE_ID_LENGTH = 10; // 31^10 ≈ 8×10^14 — unguessable, typeable

const shares = new Map<string, Share>();

function sharesFile(): string {
  return join(statsDir(), "shares.jsonl");
}

export function loadShares(): void {
  const file = sharesFile();
  if (!existsSync(file)) return;
  for (const line of readFileSync(file, "utf8").trim().split("\n")) {
    if (!line) continue;
    try {
      const s = JSON.parse(line) as Share;
      if (s.id) shares.set(s.id, s);
    } catch {
      // A torn tail line loses one share, never the server.
    }
  }
}

export function mintShare(roomId: string, turn: number): Share {
  // One link per (room, turn): sharing the same turn twice hands back
  // the same slug, so a re-share never splits an audience.
  for (const s of shares.values()) {
    if (s.roomId === roomId && s.turn === turn) return s;
  }
  let id = "";
  for (let i = 0; i < SHARE_ID_LENGTH; i++) {
    id += SHARE_ALPHABET[randomInt(SHARE_ALPHABET.length)];
  }
  const share: Share = { id, roomId, turn, createdAt: new Date().toISOString() };
  shares.set(id, share);
  appendFileSync(sharesFile(), JSON.stringify(share) + "\n", "utf8");
  return share;
}

export function getShare(id: string): Share | undefined {
  return shares.get(id);
}