import { readFileSync, writeFileSync, existsSync } from 'node:fs';
import { join } from 'node:path';
import { findProjectRoot } from '../core/paths.js';
import { loadConfig } from '../core/config.js';

/**
 * Register the AgentHub MCP server with as little friction as possible.
 *
 * Default: writes/merges a project `.mcp.json` — the standard config that Claude
 * Code (and any `.mcp.json`-aware MCP client) auto-discovers, so those agents
 * register with zero hand-editing. For CLIs that use a GLOBAL config instead
 * (Codex / Kimi) it prints a ready-to-paste snippet. `--print` is a dry run.
 */
function resolveUrl(root: string): string {
  let serverUrl = process.env.AGENTHUB_SERVER || undefined;
  if (!serverUrl) {
    try {
      serverUrl = loadConfig(root).serverUrl;
    } catch {
      /* no project config */
    }
  }
  return serverUrl ?? 'http://127.0.0.1:3377';
}

export function installMcp(cwd: string, opts: { print?: boolean } = {}): void {
  const root = findProjectRoot(cwd) ?? cwd;
  const url = resolveUrl(root);
  const serverDef = { command: 'agenthub', args: ['mcp'], env: { AGENTHUB_SERVER: url } };
  const out = (s = '') => process.stdout.write(s + '\n');

  out();
  out('AgentHub MCP — registration');
  out('═══════════════════════════');
  out(`Hub URL: ${url}`);

  const mcpJsonPath = join(root, '.mcp.json');
  if (opts.print) {
    out('');
    out(`Would write ${mcpJsonPath}:`);
    out(JSON.stringify({ mcpServers: { agenthub: serverDef } }, null, 2));
  } else {
    let json: { mcpServers?: Record<string, unknown> } = { mcpServers: {} };
    if (existsSync(mcpJsonPath)) {
      try {
        json = JSON.parse(readFileSync(mcpJsonPath, 'utf-8')) as typeof json;
      } catch {
        json = { mcpServers: {} };
      }
    }
    if (!json.mcpServers) json.mcpServers = {};
    json.mcpServers.agenthub = serverDef;
    writeFileSync(mcpJsonPath, JSON.stringify(json, null, 2) + '\n', 'utf-8');
    out('');
    out(`✓ Wrote ${mcpJsonPath}`);
    out('  → Claude Code (and any .mcp.json-aware client) opened here auto-registers it.');
  }

  out('');
  out('For CLIs that use a GLOBAL config instead of project .mcp.json:');
  out('');
  out('── Codex (~/.codex/config.toml) ──');
  out('  [mcp_servers.agenthub]');
  out('  command = "agenthub"');
  out('  args = ["mcp"]');
  out(`  env = { AGENTHUB_SERVER = "${url}" }`);
  out('');
  out('── Kimi (its MCP config) ──');
  out(`  stdio server — command: agenthub  args: ["mcp"]  env: AGENTHUB_SERVER=${url}`);
  out('');
  out('On Windows use the Mac LAN IP (e.g. http://192.168.178.30:3377). Requires agenthub >= 0.7.0.');
  out('');
}