#!/usr/bin/env node
/**
 * Site Generator
 *
 * Reads markdown summaries from summaries/{id}.md and embeds them into
 * data/books.json, then creates a dist directory with all static assets.
 *
 * Usage: node build.js
 *
 * Run this after editing any summary markdown files.
 */

const fs = require('fs');
const path = require('path');

const ROOT_DIR = __dirname;
const SUMMARIES_DIR = path.join(ROOT_DIR, 'summaries');
const BOOKS_JSON = path.join(ROOT_DIR, 'data', 'books.json');
const DIST_DIR = path.join(ROOT_DIR, 'dist');

function readSummary(id) {
  const filePath = path.join(SUMMARIES_DIR, `${id}.md`);

  if (!fs.existsSync(filePath)) {
    return null;
  }

  const content = fs.readFileSync(filePath, 'utf8').trim();
  const lines = content.split('\n');

  // Skip the title line (# Title) and return the rest
  const summaryLines = lines.slice(1).join('\n').trim();
  return summaryLines || null;
}

/**
 * Recursively copies a directory from src to dest.
 */
function copyDir(src, dest) {
  fs.mkdirSync(dest, { recursive: true });
  const entries = fs.readdirSync(src, { withFileTypes: true });

  for (const entry of entries) {
    const srcPath = path.join(src, entry.name);
    const destPath = path.join(dest, entry.name);

    if (entry.isDirectory()) {
      copyDir(srcPath, destPath);
    } else {
      fs.copyFileSync(srcPath, destPath);
    }
  }
}

/**
 * Embeds summaries from markdown files into books.json.
 * Returns the updated books data.
 */
function embedSummaries() {
  console.log('Embedding summaries...\n');

  const booksData = JSON.parse(fs.readFileSync(BOOKS_JSON, 'utf8'));

  let updated = 0;
  let missing = [];

  for (const book of booksData.books) {
    const summary = readSummary(book.id);

    if (summary) {
      book.summary = summary;
      updated++;
      console.log(`✓ ${book.title}`);
    } else {
      delete book.summary;
      missing.push(book.title);
      console.log(`✗ ${book.title} (no summary file)`);
    }
  }

  fs.writeFileSync(BOOKS_JSON, JSON.stringify(booksData, null, 2));

  console.log(`\nSummaries embedded: ${updated}`);
  console.log(`Missing summaries: ${missing.length}`);

  if (missing.length > 0) {
    console.log('\nCreate these files to add summaries:');
    missing.forEach(title => {
      const book = booksData.books.find(b => b.title === title);
      console.log(`  summaries/${book.id}.md`);
    });
  }

  return booksData;
}

/**
 * Creates the dist directory with all static assets for distribution.
 */
function createDist() {
  console.log('\n--- Creating dist directory ---\n');

  // Remove existing dist directory
  if (fs.existsSync(DIST_DIR)) {
    fs.rmSync(DIST_DIR, { recursive: true });
  }
  fs.mkdirSync(DIST_DIR);

  // Copy static files
  fs.copyFileSync(path.join(ROOT_DIR, 'index.html'), path.join(DIST_DIR, 'index.html'));
  console.log('✓ index.html');

  // Copy directories
  copyDir(path.join(ROOT_DIR, 'css'), path.join(DIST_DIR, 'css'));
  console.log('✓ css/');

  copyDir(path.join(ROOT_DIR, 'js'), path.join(DIST_DIR, 'js'));
  console.log('✓ js/');

  copyDir(path.join(ROOT_DIR, 'data'), path.join(DIST_DIR, 'data'));
  console.log('✓ data/');

  copyDir(path.join(ROOT_DIR, 'images'), path.join(DIST_DIR, 'images'));
  console.log('✓ images/');

  console.log('\nDist directory created at: dist/');
}

function build() {
  console.log('=== Building Site ===\n');

  embedSummaries();
  createDist();

  console.log('\n=== Build Complete ===');
  console.log('Site is ready. Open dist/index.html in a browser.');
}

build();