"use node";

import crypto from "crypto";
import type { ActionCtx } from "./_generated/server";
import { internal } from "./_generated/api";
import type { Id } from "./_generated/dataModel";

const MAX_CLOCK_SKEW_MS = 5 * 60 * 1000;

/**
 * Detached Ed25519 check: caller must sign `canonicalMessage` with the
 * Ed25519 private key that pairs with the userProfile's stored
 * `publicSigningKey`. Matches `voice.getToken` and
 * `recovery.resetPasswordAction` — same window, same SPKI/PEM encoding,
 * same hex signature format — so client-side signing code looks
 * identical across every sensitive call.
 *
 * Throws on failure. Sensitive mutations that previously trusted a raw
 * `userId` arg should now route through a "use node" action that calls
 * this helper before running the internal mutation.
 */
export async function requireAuth(
  ctx: ActionCtx,
  userId: Id<"userProfiles">,
  timestamp: number,
  signature: string,
  canonicalMessage: string,
): Promise<void> {
  if (
    !Number.isFinite(timestamp) ||
    Math.abs(Date.now() - timestamp) > MAX_CLOCK_SKEW_MS
  ) {
    throw new Error("Request expired. Please try again.");
  }

  const user = await ctx.runQuery(internal.auth.getUserForVoiceToken, {
    userId,
  });
  if (!user) {
    throw new Error("User not found");
  }

  let isValid = false;
  try {
    const publicKeyObj = crypto.createPublicKey({
      key: user.publicSigningKey,
      format: "pem",
      type: "spki",
    });
    isValid = crypto.verify(
      null,
      Buffer.from(canonicalMessage),
      publicKeyObj,
      Buffer.from(signature, "hex"),
    );
  } catch {
    throw new Error("Signature verification failed");
  }

  if (!isValid) {
    throw new Error("Invalid signature");
  }
}