// SQLite persistence for games (one row per game id; the full GameState as JSON).
import { mkdirSync } from 'node:fs';
import path from 'node:path';
import Database from 'better-sqlite3';
import type { GameState } from '../shared/types';
import { migrateTerritoryToRegions } from './regions';

export interface Db {
  save(state: GameState): void;
  load(id: string): GameState | null;
  listIds(): string[];
  delete(id: string): boolean;
  close(): void;
}

export function openDb(filePath: string): Db {
  const dir = path.dirname(filePath);
  if (dir) mkdirSync(dir, { recursive: true });
  const db = new Database(filePath);
  db.pragma('journal_mode = WAL');
  db.exec(
    `CREATE TABLE IF NOT EXISTS games (
       id TEXT PRIMARY KEY,
       data TEXT NOT NULL,
       updated_at TEXT NOT NULL
     )`,
  );
  const upsert = db.prepare(
    `INSERT INTO games (id, data, updated_at) VALUES (?, ?, ?)
     ON CONFLICT(id) DO UPDATE SET data = excluded.data, updated_at = excluded.updated_at`,
  );
  const byId = db.prepare('SELECT data FROM games WHERE id = ?');
  const all = db.prepare('SELECT id FROM games ORDER BY updated_at DESC');
  const del = db.prepare('DELETE FROM games WHERE id = ?');
  return {
    save(state) {
      upsert.run(state.id, JSON.stringify(state), new Date().toISOString());
    },
    load(id) {
      const row = byId.get(id) as { data: string } | undefined;
      if (!row) return null;
      try {
        // v0.19: migrate any pre-v0.19 (whole-country ISO_A3) territory to
        // sub-region ids on read. A no-op when the region geo is not loaded,
        // and idempotent once a state has been migrated (the next save then
        // persists the region-level territory).
        return migrateTerritoryToRegions(JSON.parse(row.data) as GameState);
      } catch {
        return null;
      }
    },
    listIds() {
      return (all.all() as { id: string }[]).map((r) => r.id);
    },
    delete(id) {
      return del.run(id).changes > 0;
    },
    close() {
      db.close();
    },
  };
}