import { z } from "zod";

/**
 * Runner process configuration, sourced from the environment by the
 * provisioner (walking-skeleton story 06) or by the integration tests
 * that spawn the runner directly.
 *
 * - `RUNNER_TOKEN` (required) — the workspace-scoped auth token every
 *   protocol envelope is gated on. A secret: env only, never argv.
 * - `RUNNER_WORKSPACE_DIR` (required) — the directory this runner owns;
 *   the clone lands at `<workspaceDir>/repo`.
 * - `RUNNER_PORT` (default `0`) — WS listen port; `0` binds an ephemeral
 *   port which `main.ts` announces on stdout (`event: "listening"`).
 * - `RUNNER_HOST` (default `127.0.0.1`) — WS listen host.
 * - `RUNNER_HEARTBEAT_MS` (default `1000`) — staged-progress heartbeat
 *   interval while a stage is running.
 */
const runnerConfigSchema = z
  .object({
    host: z.string().min(1),
    port: z.number().int().min(0).max(65535),
    token: z.string().min(1),
    workspaceDir: z.string().min(1),
    heartbeatMs: z.number().int().positive(),
  })
  .strict();

export type RunnerConfig = z.infer<typeof runnerConfigSchema>;

function parseIntegerEnv(
  name: string,
  raw: string | undefined,
  fallback: number,
): number {
  if (raw === undefined || raw === "") return fallback;
  const value = Number(raw);
  if (!Number.isInteger(value)) {
    throw new Error(`${name} must be an integer, received "${raw}"`);
  }
  return value;
}

export function loadConfigFromEnv(env: NodeJS.ProcessEnv): RunnerConfig {
  const token = env.RUNNER_TOKEN;
  if (token === undefined || token === "") {
    throw new Error("RUNNER_TOKEN is required (workspace-scoped auth token)");
  }
  const workspaceDir = env.RUNNER_WORKSPACE_DIR;
  if (workspaceDir === undefined || workspaceDir === "") {
    throw new Error("RUNNER_WORKSPACE_DIR is required");
  }
  return runnerConfigSchema.parse({
    host:
      env.RUNNER_HOST === undefined || env.RUNNER_HOST === ""
        ? "127.0.0.1"
        : env.RUNNER_HOST,
    port: parseIntegerEnv("RUNNER_PORT", env.RUNNER_PORT, 0),
    token,
    workspaceDir,
    heartbeatMs: parseIntegerEnv(
      "RUNNER_HEARTBEAT_MS",
      env.RUNNER_HEARTBEAT_MS,
      1000,
    ),
  });
}