import { readFileSync, existsSync } from 'fs';
import { join } from 'path';

/**
 * Detect Node.js project type and configuration
 */
export function detectNodeJS(projectPath) {
  const packageJsonPath = join(projectPath, 'package.json');

  if (!existsSync(packageJsonPath)) {
    return null;
  }

  let pkg;
  try {
    pkg = JSON.parse(readFileSync(packageJsonPath, 'utf-8'));
  } catch (error) {
    return null;
  }

  const deps = pkg.dependencies || {};
  const devDeps = pkg.devDependencies || {};
  const scripts = pkg.scripts || {};

  // Check for Electron (not dockerizable)
  if (deps.electron || devDeps.electron) {
    return {
      type: 'nodejs-electron',
      dockerizable: false,
      reason: 'Electron apps are desktop applications and cannot be containerized',
      template: null
    };
  }

  // Detect project subtype
  const hasVite = !!devDeps.vite;
  const hasReact = !!(deps.react || devDeps.react);
  const hasExpress = !!deps.express;
  const hasSocketIO = !!(deps['socket.io'] || deps['socket.io-client']);
  const hasConcurrently = !!devDeps.concurrently;

  // Check for server-side rendering setup (Vite + React + Express with concurrent dev)
  if (hasVite && hasReact && hasExpress && (hasConcurrently || scripts.dev?.includes('concurrently'))) {
    return {
      type: 'nodejs-vite-react-ssr',
      dockerizable: true,
      template: 'nodejs/vite-react-ssr',
      port: detectPort(pkg) || 3000,
      entryPoint: detectEntryPoint(pkg, projectPath, 'ssr'),
      buildCommand: 'npm run build',
      description: 'Vite + React with Express SSR'
    };
  }

  // Vite + React SPA (no backend)
  if (hasVite && hasReact && !hasExpress) {
    return {
      type: 'nodejs-vite-react',
      dockerizable: true,
      template: 'nodejs/vite-react',
      port: 80, // Nginx serves static files on port 80
      entryPoint: null,
      buildCommand: 'npm run build',
      description: 'Vite + React SPA (served by Nginx)'
    };
  }

  // Express server (with or without Socket.io)
  if (hasExpress) {
    return {
      type: 'nodejs-express',
      dockerizable: true,
      template: 'nodejs/express',
      port: detectPort(pkg) || 3000,
      entryPoint: detectEntryPoint(pkg, projectPath, 'express'),
      buildCommand: detectBuildCommand(pkg),
      description: hasSocketIO ? 'Express + Socket.io server' : 'Express server'
    };
  }

  // Generic Node.js project (has package.json but no clear type)
  if (pkg.main || scripts.start) {
    return {
      type: 'nodejs-generic',
      dockerizable: true,
      template: 'nodejs/express',
      port: detectPort(pkg) || 3000,
      entryPoint: detectEntryPoint(pkg, projectPath, 'generic'),
      buildCommand: detectBuildCommand(pkg),
      description: 'Generic Node.js application'
    };
  }

  // Has package.json but nothing to run
  return {
    type: 'nodejs-unknown',
    dockerizable: false,
    reason: 'No start script or main entry point found',
    template: null
  };
}

/**
 * Detect the default port from package.json or environment
 */
function detectPort(pkg) {
  const scripts = pkg.scripts || {};

  // Check start script for port
  const startScript = scripts.start || '';
  const portMatch = startScript.match(/PORT[=\s]+(\d+)/i) ||
                    startScript.match(/-p\s+(\d+)/) ||
                    startScript.match(/--port\s+(\d+)/);
  if (portMatch) {
    return parseInt(portMatch[1], 10);
  }

  // Check for common port patterns in dev script
  const devScript = scripts.dev || '';
  const devPortMatch = devScript.match(/:(\d{4})/);
  if (devPortMatch) {
    return parseInt(devPortMatch[1], 10);
  }

  // Default based on common frameworks
  if (pkg.dependencies?.['next']) return 3000;
  if (pkg.devDependencies?.vite) return 5173;

  return null;
}

/**
 * Detect the entry point file
 */
function detectEntryPoint(pkg, projectPath, type) {
  // Check package.json main field
  if (pkg.main) {
    return pkg.main;
  }

  // Check for common entry points
  const commonEntries = [
    'server.js',
    'server.mjs',
    'src/server.js',
    'src/server.mjs',
    'src/index.js',
    'src/index.mjs',
    'index.js',
    'app.js',
    'src/app.js'
  ];

  for (const entry of commonEntries) {
    if (existsSync(join(projectPath, entry))) {
      return entry;
    }
  }

  // For SSR projects, look for server files
  if (type === 'ssr') {
    const ssrEntries = ['server.mjs', 'server.js', 'src/server.mjs', 'src/server.js'];
    for (const entry of ssrEntries) {
      if (existsSync(join(projectPath, entry))) {
        return entry;
      }
    }
  }

  // Default
  return 'index.js';
}

/**
 * Detect if project has a build command
 */
function detectBuildCommand(pkg) {
  const scripts = pkg.scripts || {};

  if (scripts.build) {
    return 'npm run build';
  }

  return null;
}

/**
 * Get additional info about the Node.js project
 */
export function getNodeJSInfo(projectPath) {
  const packageJsonPath = join(projectPath, 'package.json');

  if (!existsSync(packageJsonPath)) {
    return null;
  }

  const pkg = JSON.parse(readFileSync(packageJsonPath, 'utf-8'));

  return {
    name: pkg.name,
    version: pkg.version,
    hasLockFile: existsSync(join(projectPath, 'package-lock.json')),
    hasYarnLock: existsSync(join(projectPath, 'yarn.lock')),
    hasPnpmLock: existsSync(join(projectPath, 'pnpm-lock.yaml')),
    nodeVersion: pkg.engines?.node || null,
    scripts: Object.keys(pkg.scripts || {}),
    dependencies: Object.keys(pkg.dependencies || {}),
    devDependencies: Object.keys(pkg.devDependencies || {})
  };
}