import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'node:fs';
import { homedir } from 'node:os';
import { dirname, resolve } from 'node:path';
import { type Config, ConfigSchema } from './types.ts';

const DEFAULT_CONFIG_PATH = resolve(homedir(), '.nanobot', 'config.json');

export function getConfigPath(override?: string): string {
  return override ?? process.env['NANOBOT_CONFIG'] ?? DEFAULT_CONFIG_PATH;
}

export function loadConfig(configPath?: string): Config {
  const path = getConfigPath(configPath);

  if (!existsSync(path)) {
    return ConfigSchema.parse({});
  }

  const raw = readFileSync(path, 'utf8');
  let json: unknown;
  try {
    json = JSON.parse(raw);
  } catch {
    console.error(`Failed to parse config at ${path}`);
    return ConfigSchema.parse({});
  }

  // Apply NANOBOT_ env var overrides before validation
  const merged = applyEnvOverrides(json as Record<string, unknown>);
  return ConfigSchema.parse(merged);
}

export function saveConfig(config: Config, configPath?: string): void {
  const path = getConfigPath(configPath);
  mkdirSync(dirname(path), { recursive: true });
  writeFileSync(path, JSON.stringify(config, null, 2), 'utf8');
}

/** Resolve `~` in workspace path to the real home directory. */
export function resolveWorkspacePath(raw: string): string {
  if (raw.startsWith('~/') || raw === '~') {
    return resolve(homedir(), raw.slice(2));
  }
  return resolve(raw);
}

function applyEnvOverrides(json: Record<string, unknown>): Record<string, unknown> {
  const out = structuredClone(json);

  const model = process.env['NANOBOT_MODEL'];
  if (model) {
    const agent = (out['agent'] as Record<string, unknown> | undefined) ?? {};
    agent['model'] = model;
    out['agent'] = agent;
  }

  const workspace = process.env['NANOBOT_WORKSPACE'];
  if (workspace) {
    const agent = (out['agent'] as Record<string, unknown> | undefined) ?? {};
    agent['workspacePath'] = workspace;
    out['agent'] = agent;
  }

  return out;
}