import fs from 'fs/promises';
import path from 'path';
import { env } from '../config/env';
import { logger } from '../utils/logger';
import { AgentError } from '../middleware/error-handler';

interface SlugEntry {
  basePath: string;
  composeProject: string;
  registeredAt: string;
}

type Registry = Record<string, SlugEntry>;

const registryPath = () => path.join(env.AGENT_DATA_DIR, 'registry.json');

let cache: Registry | null = null;

async function loadRegistry(): Promise<Registry> {
  if (cache) return cache;
  try {
    const data = await fs.readFile(registryPath(), 'utf-8');
    cache = JSON.parse(data) as Registry;
    return cache;
  } catch {
    cache = {};
    return cache;
  }
}

async function saveRegistry(registry: Registry): Promise<void> {
  await fs.mkdir(env.AGENT_DATA_DIR, { recursive: true });
  await fs.writeFile(registryPath(), JSON.stringify(registry, null, 2), 'utf-8');
  cache = registry;
}

export async function registerSlug(slug: string, basePath: string, composeProject: string): Promise<void> {
  const registry = await loadRegistry();
  registry[slug] = {
    basePath,
    composeProject,
    registeredAt: new Date().toISOString(),
  };
  await saveRegistry(registry);
  logger.info(`[registry] Registered slug ${slug} → ${basePath} (project: ${composeProject})`);
}

export async function unregisterSlug(slug: string): Promise<void> {
  const registry = await loadRegistry();
  if (!registry[slug]) {
    throw new AgentError(404, `Slug ${slug} not registered`);
  }
  delete registry[slug];
  await saveRegistry(registry);
  logger.info(`[registry] Unregistered slug ${slug}`);
}

export async function getSlugEntry(slug: string): Promise<SlugEntry> {
  const registry = await loadRegistry();
  const entry = registry[slug];
  if (!entry) {
    throw new AgentError(404, `Slug ${slug} not registered`, 'SLUG_NOT_FOUND');
  }
  return entry;
}

export async function listSlugs(): Promise<Record<string, SlugEntry>> {
  return loadRegistry();
}