/* ============================================================
   The two save-format DECISIONS, factored out of saveload.js as pure functions:
   no DOM, no engine, no imports — so they're directly unit-testable under Node and
   can't drift from the branches the real save/load paths take. Getting either wrong
   is a data-loss bug (an Odyssey loaded as a skirmish, a scenario silently
   checkpointed), so they're worth pinning down on their own.
   ============================================================ */

"use strict";

// A parsed save file is an Odyssey GALAXY iff it carries a `planets` array; otherwise it's a
// single-world skirmish. This is exactly the fork the file-import path takes before handing the
// object to the matching deserializer.
export function isGalaxySave(parsed) {
  return !!parsed && Array.isArray(parsed.planets);
}

// Given the session's game handle ({ state, galaxy, spectateMatch }), what the autosave/checkpoint
// should write — or null when there's nothing resumable: no state at all, a finished match, a
// scripted scenario (scenarios can't be saved), or a SPECTATED AI-vs-AI exhibition match. Returns
// the MODE only; the caller pairs it with the storage key and serializer.
//
// The spectate rule (docs/competitions-and-elo.md Phase 5) is the same call a scenario gets, for a
// stronger reason: a watched match isn't the player's game at all. Both seats are AI-driven, and
// what makes the "player" seat AI-driven is game.spectateMatch — a session flag, not save data.
// Checkpointing one would let "Continue" resume it as an ordinary skirmish whose player seat is
// suddenly unmanned, which is worse than having nothing to continue.
export function resumableMode({ state, galaxy, spectateMatch } = {}) {
  if (!state || state.over || state.scenario || spectateMatch) return null;
  return galaxy ? "galaxy" : "skirmish";
}