// Game variants offered on New Game, and the gating of that choice by the
// languages the sign-in service supports. Kept out of the .svelte screen so the
// gating is unit-testable (the project's node-env Vitest layer).

import type { MessageKey } from './i18n/index.svelte';
import type { Variant } from './model';

// VariantOption is a selectable game variant with its i18n label key.
export interface VariantOption {
  id: Variant;
  label: MessageKey;
}

// ALL_VARIANTS lists every variant in display order. The labels are display names keyed by
// the game's alphabet, not the interface language: the English-alphabet game is always
// "Scrabble" and the Russian-alphabet Scrabble always "Скрэббл" (both unlocalized, so the
// two never collide whatever the UI language); Erudit is localized "Erudite"/"Эрудит".
export const ALL_VARIANTS: VariantOption[] = [
  { id: 'scrabble_en', label: 'new.english' },
  { id: 'scrabble_ru', label: 'new.russian' },
  { id: 'erudit_ru', label: 'new.erudit' },
];

// variantNameKey returns the i18n key for a variant's display name (used by the in-game
// title and the lobby cards).
export function variantNameKey(v: Variant): MessageKey {
  return ALL_VARIANTS.find((o) => o.id === v)?.label ?? 'new.english';
}

// VARIANT_RULES is the i18n key for each variant's one-line rules summary on the New Game
// buttons (bag size, the ё rule, bonus differences), sourced from the engine rulesets.
export const VARIANT_RULES: Record<Variant, MessageKey> = {
  scrabble_en: 'new.rulesEnglish',
  scrabble_ru: 'new.rulesRussian',
  erudit_ru: 'new.rulesErudit',
};

// VARIANT_FLAG is the flag shown on a variant button: an emoji for the Scrabble variants;
// Erudit uses the bundled USSR flag SVG (public/flag-ussr.svg), so its entry is empty.
export const VARIANT_FLAG: Record<Variant, string> = {
  scrabble_en: '🇺🇸',
  scrabble_ru: '🇷🇺',
  erudit_ru: '',
};

// VARIANT_LANGUAGE maps each variant to its game language. en -> English;
// ru -> Russian + Эрудит.
export const VARIANT_LANGUAGE: Record<Variant, 'en' | 'ru'> = { scrabble_en: 'en', scrabble_ru: 'ru', erudit_ru: 'ru' };

// availableVariants gates ALL_VARIANTS by the session's supported languages. An empty
// or absent set is ungated (a web/legacy session without a declared set), returning
// every variant.
export function availableVariants(supportedLanguages: string[] | undefined): VariantOption[] {
  const langs = supportedLanguages ?? [];
  if (langs.length === 0) return ALL_VARIANTS;
  return ALL_VARIANTS.filter((v) => langs.includes(VARIANT_LANGUAGE[v.id]));
}

// supportsMultipleWordsToggle reports whether the New Game "multiple words per turn" toggle
// applies to a variant. Only Russian games choose the rule; English is always standard, so
// its toggle is not shown.
export function supportsMultipleWordsToggle(v: Variant): boolean {
  return VARIANT_LANGUAGE[v] === 'ru';
}

// multipleWordsForRequest resolves the per-turn word rule sent when starting a game of the
// variant: Russian games carry the toggle's value, English games are silently standard
// (true), so matchmaking and game creation stay one uniform path.
export function multipleWordsForRequest(v: Variant, toggle: boolean): boolean {
  return supportsMultipleWordsToggle(v) ? toggle : true;
}