nEngine/apps/editor/src/renderer/playtest-session.ts

import type { ContentBundle } from "@nengine/core";
import { arrowDirection } from "@nengine/render";

/**
 * A pending save produced by an open editor model. `content` is the
 * stringified YAML to persist; `error` models a model that cannot serialize
 * (invalid edits never write — the playtest must fail loudly before boot).
 */
export type PlaytestFlush = { path: string; content: string } | { path: string; error: string };

/** Collects the dirty models currently open in the editor (empty = nothing to save). */
export type PlaytestFlushCollector = () => PlaytestFlush[];

export interface SaveAllResult {
  flushed: string[];
  failures: { path: string; error: string }[];
}

/** Persist every dirty model; a rejecting write or an un-serializable model is
 * recorded as a failure (never thrown), so a single bad file cannot half-save. */
export async function saveAllFlushes(
  flushes: PlaytestFlush[],
  write: (path: string, content: string) => Promise<void>,
): Promise<SaveAllResult> {
  const flushed: string[] = [];
  const failures: { path: string; error: string }[] = [];
  for (const flush of flushes) {
    if ("error" in flush) {
      failures.push({ path: flush.path, error: flush.error });
      continue;
    }
    try {
      await write(flush.path, flush.content);
      flushed.push(flush.path);
    } catch (err) {
      failures.push({ path: flush.path, error: err instanceof Error ? err.message : String(err) });
    }
  }
  return { flushed, failures };
}

export type PlaytestPhase = "idle" | "saving" | "compiling" | "booting" | "playing" | "stopping";

export interface PlaytestSessionDeps {
  collectFlushes: PlaytestFlushCollector;
  write: (path: string, content: string) => Promise<void>;
  compile: () => Promise<ContentBundle>;
  boot: (bundle: ContentBundle) => Promise<void>;
  teardown: () => Promise<void> | void;
  onPhase?: (phase: PlaytestPhase) => void;
}

export interface PlaytestStartResult {
  ok: boolean;
  saved: string[];
  error?: string;
}

export interface PlaytestSession {
  readonly phase: PlaytestPhase;
  start(): Promise<PlaytestStartResult>;
  stop(): Promise<void>;
}

/** The playtest lifecycle (E5): save-all → compile → boot → playing, with
 * stop() destroying the booted instance. Pure orchestration — every I/O side
 * is an injected dep, so the whole sequence is node-testable. */
export function createPlaytestSession(deps: PlaytestSessionDeps): PlaytestSession {
  let phase: PlaytestPhase = "idle";

  function setPhase(next: PlaytestPhase): void {
    phase = next;
    deps.onPhase?.(next);
  }

  async function start(): Promise<PlaytestStartResult> {
    if (phase !== "idle") {
      return { ok: false, saved: [], error: "playtest already running" };
    }
    setPhase("saving");
    const result = await saveAllFlushes(deps.collectFlushes(), deps.write);
    if (result.failures.length > 0) {
      setPhase("idle");
      const lines = result.failures.map((f) => `- ${f.path}: ${f.error}`).join("\n");
      return { ok: false, saved: result.flushed, error: `save-all failed:\n${lines}` };
    }
    setPhase("compiling");
    let bundle: ContentBundle;
    try {
      bundle = await deps.compile();
    } catch (err) {
      setPhase("idle");
      return { ok: false, saved: result.flushed, error: err instanceof Error ? err.message : String(err) };
    }
    setPhase("booting");
    try {
      await deps.boot(bundle);
    } catch (err) {
      setPhase("idle");
      return { ok: false, saved: result.flushed, error: err instanceof Error ? err.message : String(err) };
    }
    setPhase("playing");
    return { ok: true, saved: result.flushed };
  }

  async function stop(): Promise<void> {
    if (phase === "idle") return;
    setPhase("stopping");
    try {
      await deps.teardown();
    } finally {
      setPhase("idle");
    }
  }

  return { get phase() { return phase; }, start, stop };
}

/** Map a keydown key to a raw `"key:Arrow*"` input string, or undefined for
 * non-arrow keys (the local-sync input mapping, D25). */
export function keydownInput(key: string): string | undefined {
  const input = `key:${key}`;
  return arrowDirection(input) ? input : undefined;
}