/**
 * Pure, disk-read helpers for the standalone Studio Vite middleware.
 *
 * `readManifest` / `foldTopology` are the Studio-side manifest readers (raw
 * string + parse). The telemetry-run readers are re-exported from `@nwire/scan`
 * (the shared home — see the re-export below), so the CLI dev host and Studio
 * run identical code without either package importing the other.
 *
 * All functions are synchronous, have no side effects beyond filesystem reads,
 * and accept an explicit `cwd` so callers can target any project root without
 * touching process state.
 */

import { existsSync, readFileSync } from "node:fs";
import { resolve } from "node:path";

// Telemetry-run readers live in `@nwire/scan` so the standalone Studio Vite
// middleware and the CLI dev host share one implementation (both depend on
// scan; neither imports the other). Re-exported here so the local callers keep
// a single `nwire-read` import.
export { listTelemetryRuns, readTelemetryRun, type TelemetryRunMeta } from "@nwire/scan";

// ── readManifest ─────────────────────────────────────────────────────────────

/**
 * Read `.nwire/manifest.json` from `cwd` and return the raw JSON string.
 *
 * Returns `null` when the file does not exist or cannot be read. Callers that
 * need the parsed object can `JSON.parse` the result; returning the raw string
 * lets the Vite middleware forward bytes without a round-trip through JSON.
 */
export function readManifest(cwd: string): string | null {
  const manifestPath = resolve(cwd, ".nwire", "manifest.json");
  if (!existsSync(manifestPath)) return null;
  try {
    return readFileSync(manifestPath, "utf8");
  } catch {
    return null;
  }
}

// ── foldTopology ─────────────────────────────────────────────────────────────

/**
 * Parse the manifest JSON from disk and (in future increments) fold in live
 * runtime topology data from the running app.
 *
 * Today: parses and returns the disk manifest as-is. The "fold" step — merging
 * live handler registrations from a running runtime so the manifest stays
 * accurate during HMR — is reserved for a future increment. The function
 * signature is sealed now so both callers can adopt it without a breaking
 * change later.
 *
 * Returns `null` when no manifest is present or the file is not valid JSON.
 */
export function foldTopology(manifest: string | null, _cwd: string): unknown | null {
  if (manifest === null) return null;
  try {
    return JSON.parse(manifest) as unknown;
  } catch {
    return null;
  }
}