// Region-key data access (server). Loads the deterministic region-key manifest
// (region-keys.json: stable feature id -> region key) and the sub-national geo
// (regions.geo.json: feature id -> { name, parent }) — from public/ in dev (Vite
// serves it) or dist/ in prod (Vite copies public/* -> dist/ at build, and the
// Docker image keeps only dist/) — and joins them into the lookups the
// region-level ownership model (v0.19, #16 P1) needs:
//
//   - expand a nation's ISO_A3 country list -> the region keys of all its sub-regions
//   - build the LLM "regions" reference table (key -> "name (parent ISO_A3)")
//   - the set of all valid region keys (to ignore hallucinated keys in applyTurnResult)
//
// Deliberately turf-free: it reads the two JSON files with plain JSON.parse and
// never imports @turf/@types/geojson (importing one pulls @types/geojson into the
// tsc program and breaks WorldMap.tsx; see the v0.17 changelog note). Loaded once
// at boot; the accessors below are pure data reads thereafter.
import { existsSync, readFileSync } from 'node:fs';
import path from 'node:path';
import type { GameState } from '../shared/types';

/** { name, parent } for one sub-region, where parent is the ISO_A3 country. */
interface RegionInfo {
  name: string;
  parent: string;
}

interface RegionData {
  /** stable feature id -> region key (from public/region-keys.json). */
  idToKey: Record<string, string>;
  /** region key -> { name, parent }. */
  keyToInfo: Record<string, RegionInfo>;
  /** ISO_A3 parent -> region keys of its sub-regions (file order, stable). */
  keysByCountry: Record<string, string[]>;
  /** the set of all region keys. */
  validKeys: Set<string>;
}

let data: RegionData | null = null;

/**
 * Load (or reload) the region-key manifest + geo. Idempotent. The two files are
 * served to the client from `public/` in dev (Vite serves it directly) and from
 * `dist/` in prod (Vite copies `public/*` → `dist/` at build and the Docker image
 * keeps only `dist/`), so probe `public/` then `dist/` (plus the root as a last
 * resort) and use the first directory that holds both files. Returns true when
 * both loaded cleanly; a missing/broken pair clears the data and returns false
 * so the server still boots and degrades gracefully (expansion becomes a no-op,
 * ownership falls back to the raw input keys).
 */
export function loadRegions(root: string): boolean {
  const keyFile = 'region-keys.json';
  const geoFile = 'regions.geo.json';
  const base = [
    path.join(root, 'public'), // dev: Vite serves public/ at /
    path.join(root, 'dist'), // prod: Vite copies public/* -> dist/ (== clientDir)
    root, // last resort
  ].find((d) => existsSync(path.join(d, keyFile)) && existsSync(path.join(d, geoFile)));
  if (!base) {
    data = null;
    return false;
  }
  const keyPath = path.join(base, keyFile);
  const geoPath = path.join(base, geoFile);
  try {
    const idToKey = JSON.parse(readFileSync(keyPath, 'utf8')) as Record<string, string>;
    const geo = JSON.parse(readFileSync(geoPath, 'utf8')) as {
      features?: Array<{ id?: string | number; properties?: { name?: string; parent?: string } }>;
    };
    const keyToInfo: Record<string, RegionInfo> = {};
    const keysByCountry: Record<string, string[]> = {};
    const validKeys = new Set<string>();
    for (const f of geo.features ?? []) {
      const id = f.id == null ? '' : String(f.id);
      const key = idToKey[id];
      if (!key) continue; // a geo feature with no manifest entry is skipped
      const name = typeof f.properties?.name === 'string' ? f.properties.name : '';
      const parent = typeof f.properties?.parent === 'string' ? f.properties.parent : '';
      keyToInfo[key] = { name, parent };
      validKeys.add(key);
      if (parent) (keysByCountry[parent] ??= []).push(key);
    }
    data = { idToKey, keyToInfo, keysByCountry, validKeys };
    return validKeys.size > 0;
  } catch (err) {
    console.error('[regions] failed to load region data', err);
    data = null;
    return false;
  }
}

/** Test/dev seam: drop the loaded data (the next accessors behave as "no data"). */
export function resetRegions(): void {
  data = null;
}

/** True when the manifest + geo loaded cleanly. */
export function hasRegionData(): boolean {
  return data !== null;
}

/**
 * Expand a nation's ISO_A3 country list to the region keys of all its sub-regions
 * (file order, deduped). This is what turns a preset's country-level territory
 * into region-level ownership at game creation. Returns the input unchanged when
 * no region data is loaded (graceful degradation — behaves like the old model).
 */
export function expandCountriesToKeys(countries: string[]): string[] {
  if (!data) return countries;
  const out: string[] = [];
  const seen = new Set<string>();
  for (const c of countries) {
    for (const key of data.keysByCountry[c] ?? []) {
      if (!seen.has(key)) {
        seen.add(key);
        out.push(key);
      }
    }
  }
  return out;
}

/**
 * Build the LLM reference table: region key -> "<name> (<parent ISO_A3>)", e.g.
 * `moselle-rygy -> "Moselle (FRA)"`. Only the given keys are included (the caller
 * passes the game's owned-region universe) so the prompt stays bounded.
 */
export function referenceForKeys(keys: Iterable<string>): Record<string, string> {
  const out: Record<string, string> = {};
  if (!data) return out;
  for (const key of keys) {
    const info = data.keyToInfo[key];
    if (info) out[key] = info.parent ? `${info.name} (${info.parent})` : info.name;
  }
  return out;
}

/** The region key's human name (for the dossier), or undefined if unknown. */
export function regionName(key: string): string | undefined {
  return data?.keyToInfo[key]?.name;
}

/** The union of every nation's territory region keys (the game's region universe). */
export function allTerritoryKeys(state: GameState): Set<string> {
  const out = new Set<string>();
  for (const n of Object.values(state.nations)) {
    for (const key of n.territory) out.add(key);
  }
  return out;
}

/** The set of all valid region keys (to ignore hallucinated keys in applyTurnResult). */
export function validKeys(): ReadonlySet<string> {
  return data ? data.validKeys : new Set<string>();
}