// Advanced sitemap generation utilities

import { MetadataRoute } from 'next';
import { getBaseUrl, getAllRoutes } from './sitemap-utils';

// Generate XML sitemap manually (alternative to Next.js built-in)
export function generateSitemapXML(): string {
    const baseUrl = getBaseUrl();
    const routes = getAllRoutes();

    const urlEntries = routes
        .map((route) => {
            const url = `${baseUrl}${route.url}`;
            const lastmod =
                route.lastModified?.toISOString().split('T')[0] ||
                new Date().toISOString().split('T')[0];
            const changefreq = route.changeFrequency || 'monthly';
            const priority = route.priority || 0.5;

            return `  <url>
    <loc>${url}</loc>
    <lastmod>${lastmod}</lastmod>
    <changefreq>${changefreq}</changefreq>
    <priority>${priority}</priority>
  </url>`;
        })
        .join('\n');

    return `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
${urlEntries}
</urlset>`;
}

// Generate sitemap index for multiple sitemaps
export function generateSitemapIndex(): string {
    const baseUrl = getBaseUrl();
    const now = new Date().toISOString();

    return `<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
    <loc>${baseUrl}/sitemap.xml</loc>
    <lastmod>${now}</lastmod>
  </sitemap>
</sitemapindex>`;
}

// Validate sitemap URLs
export function validateSitemapUrls(): { valid: boolean; errors: string[] } {
    const routes = getAllRoutes();
    const errors: string[] = [];

    routes.forEach((route, index) => {
        // Check for valid URL format
        if (!route.url.startsWith('/') && route.url !== '') {
            errors.push(`Route ${index}: URL should start with '/' or be empty for root`);
        }

        // Check priority range
        if (route.priority && (route.priority < 0 || route.priority > 1)) {
            errors.push(`Route ${index}: Priority should be between 0 and 1`);
        }

        // Check for duplicate URLs
        const duplicates = routes.filter((r) => r.url === route.url);
        if (duplicates.length > 1) {
            errors.push(`Route ${index}: Duplicate URL found: ${route.url}`);
        }
    });

    return {
        valid: errors.length === 0,
        errors,
    };
}

// Get sitemap statistics
export function getSitemapStats() {
    const routes = getAllRoutes();
    const baseUrl = getBaseUrl();

    return {
        totalUrls: routes.length,
        baseUrl,
        lastGenerated: new Date().toISOString(),
        routesByPriority: {
            high: routes.filter((r) => (r.priority || 0) >= 0.8).length,
            medium: routes.filter((r) => (r.priority || 0) >= 0.5 && (r.priority || 0) < 0.8)
                .length,
            low: routes.filter((r) => (r.priority || 0) < 0.5).length,
        },
        routesByChangeFreq: routes.reduce(
            (acc, route) => {
                const freq = route.changeFrequency || 'monthly';
                acc[freq] = (acc[freq] || 0) + 1;
                return acc;
            },
            {} as Record<string, number>,
        ),
    };
}