// Validate + build a dev.at-intent.usage record. Written into a USER's repo by
// an app when the person uses it — the discovery footprint a consumer scans.

import { USAGE_NSID } from "./nsid.mjs";

const RECORD_FIELDS = ["app", "capability", "config", "lastSeenAt", "createdAt"];

export function validateUsage(u) {
  const errors = [];
  const warnings = [];
  if (!u || typeof u !== "object") return { errors: ["usage is not an object"], warnings };

  if (!u.app || typeof u.app !== "string") errors.push("app: required DID of the handler");
  else if (!u.app.startsWith("did:")) errors.push("app: must be a DID (did:plc:... or did:web:...)");

  if (u.capability && !u.capability.startsWith("at://")) errors.push("capability: must be an AT-URI");
  if (u.lastSeenAt && Number.isNaN(Date.parse(u.lastSeenAt))) errors.push("lastSeenAt: not a valid datetime");

  return { errors, warnings };
}

export function buildUsageRecord(u, now) {
  const record = { $type: USAGE_NSID };
  for (const f of RECORD_FIELDS) {
    if (u[f] !== undefined) record[f] = u[f];
  }
  if (!record.createdAt) record.createdAt = now || new Date().toISOString();
  return record;
}