import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';

/**
 * Agent config, resolved from (in order): env vars, a config file, defaults.
 * Config file lives at %APPDATA%\albion-agent\config.json (or ALBION_AGENT_CONFIG).
 */
export interface AgentConfig {
  serverUrl: string; // e.g. https://albion.example.com
  apiKey: string;
  gamePath: string; // folder containing the "game" directory, e.g. E:\albion
  interfaces: string[]; // tshark interface ids; empty = all
  orderFlushSeconds: number;
}

const DEFAULTS: AgentConfig = {
  serverUrl: 'http://127.0.0.1:4310',
  apiKey: '',
  gamePath: 'E:\\albion',
  interfaces: [],
  orderFlushSeconds: 15,
};

export function configPath(): string {
  if (process.env.ALBION_AGENT_CONFIG) return process.env.ALBION_AGENT_CONFIG;
  const base = process.env.APPDATA ?? path.join(os.homedir(), '.config');
  return path.join(base, 'albion-agent', 'config.json');
}

export function loadConfig(): AgentConfig {
  let fileCfg: Partial<AgentConfig> = {};
  const p = configPath();
  if (fs.existsSync(p)) {
    try {
      fileCfg = JSON.parse(fs.readFileSync(p, 'utf8'));
    } catch {
      console.warn(`Could not parse ${p}, ignoring.`);
    }
  }
  return {
    serverUrl: process.env.ALBION_SERVER_URL ?? fileCfg.serverUrl ?? DEFAULTS.serverUrl,
    apiKey: process.env.ALBION_API_KEY ?? fileCfg.apiKey ?? DEFAULTS.apiKey,
    gamePath: process.env.ALBION_GAME_PATH ?? fileCfg.gamePath ?? DEFAULTS.gamePath,
    interfaces: fileCfg.interfaces ?? DEFAULTS.interfaces,
    orderFlushSeconds: fileCfg.orderFlushSeconds ?? DEFAULTS.orderFlushSeconds,
  };
}

export function saveConfig(cfg: AgentConfig): void {
  const p = configPath();
  fs.mkdirSync(path.dirname(p), { recursive: true });
  fs.writeFileSync(p, JSON.stringify(cfg, null, 2));
}