import { dirname, extname, join, relative, sep } from 'node:path';
import { existsSync, readdirSync, writeFileSync } from 'node:fs';
import { fileURLToPath } from 'node:url';

const MIME_TYPES: Record<string, string> = {
    '.css': 'text/css; charset=utf-8',
    '.gif': 'image/gif',
    '.html': 'text/html; charset=utf-8',
    '.ico': 'image/x-icon',
    '.jpeg': 'image/jpeg',
    '.jpg': 'image/jpeg',
    '.js': 'text/javascript; charset=utf-8',
    '.json': 'application/json; charset=utf-8',
    '.map': 'application/json; charset=utf-8',
    '.mjs': 'text/javascript; charset=utf-8',
    '.otf': 'font/otf',
    '.png': 'image/png',
    '.svg': 'image/svg+xml',
    '.ttf': 'font/ttf',
    '.txt': 'text/plain; charset=utf-8',
    '.wasm': 'application/wasm',
    '.webmanifest': 'application/manifest+json; charset=utf-8',
    '.webp': 'image/webp',
    '.woff': 'font/woff',
    '.woff2': 'font/woff2',
    '.xml': 'application/xml; charset=utf-8'
};

function toPosixPath(filePath: string): string {
    return filePath.split(sep).join('/');
}

function listFiles(rootDir: string, currentDir = rootDir): string[] {
    const entries = readdirSync(currentDir, { withFileTypes: true });
    const files: string[] = [];

    for (const entry of entries) {
        const entryPath = join(currentDir, entry.name);
        if (entry.isDirectory()) {
            files.push(...listFiles(rootDir, entryPath));
            continue;
        }
        if (entry.isFile()) {
            files.push(entryPath);
        }
    }

    return files;
}

function resolveMimeType(filePath: string): string {
    const ext = extname(filePath).toLowerCase();
    return MIME_TYPES[ext] ?? 'application/octet-stream';
}

function main(): void {
    const scriptDir = dirname(fileURLToPath(import.meta.url));
    const workspaceRoot = join(scriptDir, '..', '..');
    const webDistDir = join(workspaceRoot, 'web', 'dist');
    const outputPath = join(workspaceRoot, 'hub', 'src', 'web', 'embeddedAssets.generated.ts');
    const outputDir = dirname(outputPath);

    if (!existsSync(webDistDir)) {
        throw new Error(`Missing web/dist directory: ${webDistDir}. Run bun run build:web first.`);
    }

    const indexHtmlPath = join(webDistDir, 'index.html');
    if (!existsSync(indexHtmlPath)) {
        throw new Error(`Missing web/dist/index.html. Run bun run build:web first.`);
    }

    const files = listFiles(webDistDir).sort((a, b) => a.localeCompare(b));
    if (files.length === 0) {
        throw new Error(`No files found in web/dist: ${webDistDir}.`);
    }

    const imports: string[] = [];
    const manifestLines: string[] = [];

    files.forEach((filePath, index) => {
        const relativeToDist = toPosixPath(relative(webDistDir, filePath));
        const requestPath = `/${relativeToDist}`;
        const importPath = toPosixPath(relative(outputDir, filePath));
        const importName = `asset${index}`;
        const mimeType = resolveMimeType(filePath);

        imports.push(`import ${importName} from '${importPath}' assert { type: 'file' };`);
        manifestLines.push(`    { path: '${requestPath}', sourcePath: ${importName}, mimeType: '${mimeType}' },`);
    });

    const output = [
        '// This file is generated by hub/scripts/generate-embedded-web-assets.ts.',
        '// Do not edit by hand.',
        '',
        ...imports,
        '',
        'export interface EmbeddedWebAsset {',
        '    path: string;',
        '    sourcePath: string;',
        '    mimeType: string;',
        '}',
        '',
        'export const embeddedAssets: EmbeddedWebAsset[] = [',
        ...manifestLines,
        '];',
        ''
    ].join('\n');

    writeFileSync(outputPath, output, 'utf-8');
    console.log(`[embedded-assets] Wrote ${files.length} assets to ${outputPath}`);
}

main();