import fs from 'fs';
import path from 'path';

/**
 * Page information structure
 */
export interface PageInfo {
  filePath: string;
  route: string;
  url: string;
  title: string;
  priority: number;
  changeFrequency: 'always' | 'hourly' | 'daily' | 'weekly' | 'monthly' | 'yearly' | 'never';
  lastModified: Date;
  isDynamic: boolean;
  dynamicParams?: string[];
  contentType: 'page' | 'layout' | 'api';
}

/**
 * Dynamic route information
 */
export interface DynamicRouteInfo {
  pattern: string;
  paramName: string;
  example: string;
}

/**
 * SEO analysis results
 */
export interface SEOAnalysis {
  totalPages: number;
  internalLinks: number;
  orphanedPages: string[];
  brokenLinks: string[];
  pagesWithIssues: {
    url: string;
    issues: string[];
  }[];
  averageLinkDensity: number;
  pageTypes: {
    [key: string]: number;
  };
}

/**
 * Discover all React pages in the app directory
 */
export function discoverPages(appDir: string): PageInfo[] {
  const pages: PageInfo[] = [];
  
  if (!fs.existsSync(appDir)) {
    throw new Error(`App directory not found: ${appDir}`);
  }

  // Scan the app directory
  scanDirectory(appDir, '', pages);

  return pages.sort((a, b) => a.route.localeCompare(b.route));
}

/**
 * Scan directory recursively for page files
 */
function scanDirectory(dir: string, relativePath: string, pages: PageInfo[]): void {
  const items = fs.readdirSync(dir, { withFileTypes: true });

  for (const item of items) {
    const fullPath = path.join(dir, item.name);
    const itemRelativePath = relativePath ? path.join(relativePath, item.name) : item.name;

    if (item.isDirectory()) {
      // Skip special directories
      if (['api', 'lib', 'components', 'hooks'].includes(item.name)) {
        continue;
      }

      // Scan subdirectories
      scanDirectory(fullPath, itemRelativePath, pages);
    } else if (item.isFile()) {
      // Process page files
      if (isPageFile(item.name)) {
        processPageFile(fullPath, itemRelativePath, pages);
      }
    }
  }
}

/**
 * Check if file is a page component
 */
function isPageFile(filename: string): boolean {
  const pageExtensions = ['.tsx', '.ts', '.jsx', '.js'];
  return pageExtensions.some(ext => filename.endsWith(ext)) && 
         (filename === 'page.tsx' || filename === 'page.ts' || 
          filename === 'page.jsx' || filename === 'page.js');
}

/**
 * Process a page file
 */
function processPageFile(fullPath: string, relativePath: string, pages: PageInfo[]): void {
  const route = convertPathToRoute(relativePath);
  const url = `/${route}`;
  const title = extractPageTitle(fullPath) || route;
  const priority = calculatePagePriority(route);
  const changeFrequency = calculateChangeFrequency(route);
  const isDynamic = isDynamicRoute(relativePath);
  const dynamicParams = extractDynamicParams(relativePath);
  const lastModified = getLastModifiedTime(fullPath);
  const contentType = getContentType(relativePath);

  pages.push({
    filePath: fullPath,
    route,
    url,
    title,
    priority,
    changeFrequency,
    lastModified,
    isDynamic,
    dynamicParams,
    contentType
  });
}

/**
 * Convert file path to Next.js route
 */
function convertPathToRoute(filePath: string): string {
  // Remove 'page.tsx' extension
  let route = filePath.replace(/page\.(tsx|ts|jsx|js)$/, '');
  
  // Replace backslashes with forward slashes
  route = route.replace(/\\/g, '/');
  
  // Handle index routes
  if (route === '' || route === '.') {
    return '';
  }
  
  // Handle dynamic routes
  route = route.replace(/\[(\w+)\]/g, ':$1');
  
  return route;
}

/**
 * Extract page title from file content
 */
function extractPageTitle(filePath: string): string | null {
  try {
    const content = fs.readFileSync(filePath, 'utf8');
    
    // Look for title in metadata or component
    const titleMatch = content.match(/export\s+default\s+function\s+\w*\s*\([^)]*\)\s*{[^}]*title:\s*['"`]([^'"`]+)['"`]/);
    if (titleMatch) {
      return titleMatch[1];
    }
    
    // Look for title in metadata function
    const metadataMatch = content.match(/export\s+async\s+function\s+generateMetadata\(\)\s*{[^}]*title:\s*['"`]([^'"`]+)['"`]/);
    if (metadataMatch) {
      return metadataMatch[1];
    }
    
    return null;
  } catch (error) {
    return null;
  }
}

/**
 * Calculate page priority based on route
 */
function calculatePagePriority(route: string): number {
  const priorityMap: Record<string, number> = {
    '': 1.0, // Home page
    'about-us': 0.9,
    'contact-us': 0.9,
    'services': 0.9,
    'vending-machines': 0.9,
    'manuals': 0.8
  };

  // Check exact match first
  if (priorityMap[route]) {
    return priorityMap[route];
  }

  // Check partial matches
  for (const [key, value] of Object.entries(priorityMap)) {
    if (route.startsWith(key) && route !== key) {
      return Math.max(0.1, value - 0.1); // Slightly lower priority for child pages
    }
  }

  // Default priority
  return 0.5;
}

/**
 * Calculate change frequency based on route type
 */
function calculateChangeFrequency(route: string): 'always' | 'hourly' | 'daily' | 'weekly' | 'monthly' | 'yearly' | 'never' {
  if (route === '' || route === 'about-us' || route === 'contact-us') {
    return 'monthly';
  }

  if (route.startsWith('services') || route.startsWith('vending-machines')) {
    return 'weekly';
  }

  if (route.startsWith('manuals') || route.startsWith('blog')) {
    return 'daily';
  }

  return 'monthly';
}

/**
 * Check if route is dynamic
 */
function isDynamicRoute(filePath: string): boolean {
  return filePath.includes('[') && filePath.includes(']');
}

/**
 * Extract dynamic parameters from route
 */
function extractDynamicParams(filePath: string): string[] {
  const matches = filePath.match(/\[(\w+)\]/g);
  return matches ? matches.map(match => match.slice(1, -1)) : [];
}

/**
 * Get last modified time of file
 */
function getLastModifiedTime(filePath: string): Date {
  const stats = fs.statSync(filePath);
  return stats.mtime;
}

/**
 * Determine content type based on path
 */
function getContentType(filePath: string): 'page' | 'layout' | 'api' {
  if (filePath.includes('api')) {
    return 'api';
  }
  if (filePath.includes('layout')) {
    return 'layout';
  }
  return 'page';
}

/**
 * Analyze internal links in pages
 */
export function analyzeInternalLinks(pages: PageInfo[], contentByRoute: Record<string, string>): SEOAnalysis {
  const internalLinks: { from: string; to: string; text: string }[] = [];
  const brokenLinks: string[] = [];
  const orphanedPages: string[] = [];
  const pagesWithIssues: { url: string; issues: string[] }[] = [];
  const linkCounts: Record<string, number> = {};

  // Find pages that link to other pages
  for (const [route, content] of Object.entries(contentByRoute)) {
    const links = extractLinksFromContent(content);
    
    for (const link of links) {
      if (isInternalLink(link.href)) {
        const targetRoute = convertLinkToRoute(link.href);
        
        if (pages.some(p => p.route === targetRoute)) {
          internalLinks.push({
            from: route,
            to: targetRoute,
            text: link.text
          });
          
          linkCounts[route] = (linkCounts[route] || 0) + 1;
        } else {
          brokenLinks.push(`${route} -> ${link.href}`);
        }
      }
    }
  }

  // Find orphaned pages (pages with no inbound links)
  for (const page of pages) {
    const hasInboundLinks = internalLinks.some(link => link.to === page.route);
    if (!hasInboundLinks && page.route !== '') {
      orphanedPages.push(page.route);
    }
  }

  // Analyze pages with issues
  for (const [route, issues] of Object.entries(analyzePageIssues(pages, contentByRoute))) {
    if (issues.length > 0) {
      pagesWithIssues.push({ url: route, issues });
    }
  }

  // Calculate average link density
  const totalLinks = Object.values(linkCounts).reduce((sum, count) => sum + count, 0);
  const totalPages = Object.keys(linkCounts).length;
  const averageLinkDensity = totalPages > 0 ? totalLinks / totalPages : 0;

  // Analyze page types
  const pageTypes: Record<string, number> = {};
  for (const page of pages) {
    const type = page.contentType;
    pageTypes[type] = (pageTypes[type] || 0) + 1;
  }

  return {
    totalLinks: internalLinks.length,
    totalPages: pages.length,
    internalLinks: internalLinks.length,
    orphanedPages,
    brokenLinks,
    pagesWithIssues,
    averageLinkDensity,
    pageTypes
  };
}

/**
 * Extract links from content
 */
function extractLinksFromContent(content: string): { href: string; text: string }[] {
  const links: { href: string; text: string }[] = [];
  const linkRegex = /<a[^>]+href="([^"]+)"[^>]*>([^<]+)<\/a>/g;
  
  let match;
  while ((match = linkRegex.exec(content)) !== null) {
    links.push({
      href: match[1],
      text: match[2].trim()
    });
  }
  
  return links;
}

/**
 * Check if link is internal
 */
function isInternalLink(href: string): boolean {
  return !href.startsWith('http') && !href.startsWith('mailto:') && !href.startsWith('tel:');
}

/**
 * Convert link to route
 */
function convertLinkToRoute(href: string): string {
  // Remove leading slash
  let route = href.replace(/^\//, '');
  
  // Remove query parameters and fragments
  route = route.split(/[?#]/)[0];
  
  // Handle dynamic routes
  route = route.replace(/:\w+/g, '*');
  
  return route;
}

/**
 * Analyze individual page issues
 */
function analyzePageIssues(pages: PageInfo[], contentByRoute: Record<string, string>): Record<string, string[]> {
  const issues: Record<string, string[]> = {};
  
  for (const [route, content] of Object.entries(contentByRoute)) {
    const pageIssues: string[] = [];
    
    // Check for missing title
    if (!content.match(/title:/i) && !content.match(/Head>/i)) {
      pageIssues.push('Missing title');
    }
    
    // Check for missing description
    if (!content.match(/description:/i) && !content.match(/Head>/i)) {
      pageIssues.push('Missing description');
    }
    
    // Check for too many links
    const linkCount = extractLinksFromContent(content).length;
    if (linkCount > 10) {
      pageIssues.push(`Too many internal links (${linkCount})`);
    }
    
    if (pageIssues.length > 0) {
      issues[route] = pageIssues;
    }
  }
  
  return issues;
}

/**
 * Generate sitemap XML from pages
 */
export function generateSitemapXml(pages: PageInfo[]): string {
  let xml = '<?xml version="1.0" encoding="UTF-8"?>\n';
  xml += '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">\n';
  
  const currentDate = new Date().toISOString();
  
  for (const page of pages) {
    xml += '  <url>\n';
    xml += `    <loc>${page.url}</loc>\n`;
    xml += `    <lastmod>${currentDate}</lastmod>\n`;
    xml += `    <changefreq>${page.changeFrequency}</changefreq>\n`;
    xml += `    <priority>${page.priority.toFixed(1)}</priority>\n`;
    xml += '  </url>\n';
  }
  
  xml += '</urlset>';
  return xml;
}