onsight.ts

// Tiny client helper for the Onsight agent API.
//
// The one piece worth not reimplementing: the owner-action signature. Onsight
// gates money IN with x402, but every owner action afterwards (pick a winner,
// refund, edit the brief) is authorized by signing a canonical message with the
// same wallet. The message is action-, time-, AND body-bound, so a captured
// signature can't be replayed with a swapped body (e.g. a different photoId to
// redirect a payout). Get the format wrong and the server rejects you — or worse,
// you sign something you didn't mean to. This encodes it exactly once.

import { createHash } from "node:crypto";

/** Public base URL of the Onsight API. */
export const DEFAULT_BASE_URL = "https://onsight.photo";

/** Hash a request body exactly as the server does: sha256 of its JSON, hex. */
export function bodyHash(body?: unknown): string {
  return createHash("sha256")
    .update(JSON.stringify(body ?? {}))
    .digest("hex");
}

/**
 * The exact message an agent signs to authorize an owner action. Mirrors the
 * server's WalletSigGuard byte-for-byte.
 *
 * @param method    HTTP method, e.g. "POST"
 * @param path      full request path incl. query, as sent (the server's originalUrl)
 * @param timestamp ms since epoch (Date.now()) — the value of X-Wallet-Timestamp
 * @param body      the JSON request body ({} / omit for none)
 */
export function ownerActionMessage(
  method: string,
  path: string,
  timestamp: number,
  body?: unknown,
): string {
  return `Onsight agent: ${method.toUpperCase()} ${path} @ ${timestamp} body=${bodyHash(body)}`;
}

/** Minimal wallet — a viem LocalAccount (`privateKeyToAccount`) satisfies this. */
export interface WalletSigner {
  address: string;
  signMessage(args: { message: string }): Promise<`0x${string}`>;
}

/**
 * Sign an owner action and return the `X-Wallet-*` headers to send with it.
 * Pass the SAME body object you send in the request — the server rehashes the
 * received body and rejects the call if it doesn't match what was signed.
 */
export async function signOwnerActionHeaders(
  signer: WalletSigner,
  method: string,
  path: string,
  body?: unknown,
  timestamp: number = Date.now(),
): Promise<Record<string, string>> {
  const message = ownerActionMessage(method, path, timestamp, body);
  const signature = await signer.signMessage({ message });
  return {
    "X-Wallet-Address": signer.address,
    "X-Wallet-Signature": signature,
    "X-Wallet-Timestamp": String(timestamp),
  };
}

/** URL to post + fund a mission — the x402-gated photo order. */
export function missionOrderUrl(
  rewardUsd: number,
  baseUrl: string = DEFAULT_BASE_URL,
): string {
  if (!Number.isFinite(rewardUsd) || rewardUsd <= 0) {
    throw new Error(`rewardUsd must be a positive number, got ${rewardUsd}`);
  }
  return `${baseUrl}/agent/missions?rewardUsd=${rewardUsd}`;
}