#!/usr/bin/env node
/**
 * CSS Build Script
 * Concatenates modular CSS files from src/styles/ into style.css
 *
 * Usage:
 *   node scripts/build-css.js          # Development build (readable)
 *   node scripts/build-css.js --minify # Production build (minified)
 *
 * File order matters! Files are concatenated in alphabetical order.
 * Prefix files with numbers to control order: _01_variables.css, _02_panel.css, etc.
 */

import fs from 'fs-extra';
import path from 'path';
import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
const rootDir = path.resolve(__dirname, '..');
const stylesDir = path.join(rootDir, 'src', 'styles');
const outputFile = path.join(rootDir, 'style.css');

const shouldMinify = process.argv.includes('--minify');

/**
 * Minify CSS by removing comments, unnecessary whitespace, and redundant characters.
 * Safe for CSS custom properties, strings, and data URIs.
 */
function minifyCSS(css) {
    let result = css;

    // Remove CSS comments (/* ... */) — but not inside strings
    result = result.replace(/\/\*[\s\S]*?\*\//g, '');

    // Remove lines that are only whitespace after comment removal
    result = result.replace(/^\s*[\r\n]/g, '\n');

    // Collapse multiple newlines into one
    result = result.replace(/\n{2,}/g, '\n');

    // Remove spaces around structural characters outside of strings
    result = result.replace(/(\{|\}|;|:|,)/g, '$1');

    // Remove space before {
    result = result.replace(/\s+\{/g, '{');

    // Remove space after {
    result = result.replace(/\{\s+/g, '{');

    // Remove space before }
    result = result.replace(/\s+\}/g, '}');

    // Remove space after }
    result = result.replace(/\}\s+/g, '}');

    // Remove space around :
    result = result.replace(/\s*:\s*/g, ':');

    // Remove space around ;
    result = result.replace(/;\s*/g, ';');

    // Remove space around ,
    result = result.replace(/,\s*/g, ',');

    // Remove trailing semicolon before }
    result = result.replace(/;\}/g, '}');

    // Collapse multiple spaces into one (preserves spaces inside strings roughly)
    result = result.replace(/[ \t]+/g, ' ');

    // Remove leading/trailing whitespace
    result = result.trim();

    return result;
}

async function buildCSS() {
    console.log(`Building CSS from src/styles/...${shouldMinify ? ' (minified)' : ' (readable)'}`);

    // Read all CSS files from src/styles/
    const files = await fs.readdir(stylesDir);
    const cssFiles = files
        .filter(f => f.endsWith('.css'))
        .sort() // Alphabetical order (use _01_, _02_ prefix for control)
        .map(f => path.join(stylesDir, f));

    if (cssFiles.length === 0) {
        console.error('No CSS files found in src/styles/');
        process.exit(1);
    }

    console.log(`Found ${cssFiles.length} CSS files:`);
    cssFiles.forEach(f => console.log(`  - ${path.basename(f)}`));

    // Read and concatenate all files
    const contents = [];
    for (const file of cssFiles) {
        const content = await fs.readFile(file, 'utf-8');
        const basename = path.basename(file);

        if (shouldMinify) {
            // In minified mode, skip comment separators
            contents.push(content);
        } else {
            contents.push(`/* ============================================ */`);
            contents.push(`/* ${basename} */`);
            contents.push(`/* ============================================ */`);
            contents.push('');
            contents.push(content);
            contents.push('');
        }
    }

    let combined = contents.join('\n');

    // Apply minification if requested
    if (shouldMinify) {
        const beforeSize = combined.length;
        combined = minifyCSS(combined);
        const afterSize = combined.length;
        const reduction = (((beforeSize - afterSize) / beforeSize) * 100).toFixed(1);
        console.log(`\n🗜️  Minification: ${beforeSize.toLocaleString()} → ${afterSize.toLocaleString()} bytes (${reduction}% reduction)`);
    }

    // Write to style.css
    await fs.writeFile(outputFile, combined, 'utf-8');

    const stats = await fs.stat(outputFile);
    const lines = combined.split('\n').length;
    const sizeKB = (stats.size / 1024).toFixed(1);

    console.log(`\n✅ Built ${outputFile}`);
    console.log(`   Lines: ${lines}`);
    console.log(`   Size: ${sizeKB} KB`);
}

buildCSS().catch(err => {
    console.error('Build failed:', err);
    process.exit(1);
});