/**
 * ============================================================
 * SVGarden — https://www.svgarden.dev
 * Author : Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 * File   : src/lib/snippets.mjs
 * Desc   : Build-time snippet bank loader — parses snippets/** frontmatter
 * ============================================================
 */
import { readFile, readdir } from 'node:fs/promises';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import YAML from 'yaml';

const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..', '..');
export const SNIPPETS_DIR = path.join(ROOT, 'snippets');

export const CATEGORIES = [
  'loaders',
  'stroke-draw',
  'hover',
  'gauges',
  'text',
  'text-fx',
  'morph',
  'motion-path',
  'filters',
  'scroll',
  'charts',
  'interactive',
  'backgrounds',
  'buttons',
];

export const DIFFICULTIES = ['beginner', 'intermediate', 'advanced'];

const AUTHOR_HEADER_RE =
  /^<!--\s*\n\s*=+\s*\n\s*SVGarden — https:\/\/www\.svgarden\.dev\s*\n\s*Author : Simon-Pierre Boucher\s*\n\s*Contact: contact@spboucher\.ai\s*\n\s*File {3}: (.+)\s*\n\s*Desc {3}: (.+)\s*\n\s*=+\s*\n-->/;

const FRONTMATTER_RE = /<!--svgarden\n([\s\S]*?)\n-->/;

/** Builds the attribution header that travels with every copied snippet. */
export function attributionHeader(relPath, desc) {
  return [
    '<!--',
    '  ============================================================',
    '  SVGarden — https://www.svgarden.dev',
    '  Author : Simon-Pierre Boucher',
    '  Contact: contact@spboucher.ai',
    `  File   : ${relPath}`,
    `  Desc   : ${desc}`,
    '  ============================================================',
    '-->',
  ].join('\n');
}

/**
 * Parses one snippet file into its metadata + raw code.
 * Throws with a descriptive message on any structural violation,
 * so both the build and validate-snippets.mjs fail loudly.
 */
export function parseSnippetSource(source, relPath) {
  const headerMatch = source.match(AUTHOR_HEADER_RE);
  if (!headerMatch) {
    throw new Error(`${relPath}: missing or malformed SVGarden author header`);
  }
  const desc = headerMatch[2].trim();

  const fmMatch = source.match(FRONTMATTER_RE);
  if (!fmMatch) {
    throw new Error(`${relPath}: missing <!--svgarden ...--> frontmatter block`);
  }

  let meta;
  try {
    meta = YAML.parse(fmMatch[1]);
  } catch (err) {
    throw new Error(`${relPath}: invalid YAML frontmatter — ${err.message}`);
  }

  for (const field of ['title', 'slug', 'category', 'tags', 'difficulty', 'techniques', 'how_it_works', 'created']) {
    if (meta[field] === undefined || meta[field] === null || meta[field] === '') {
      throw new Error(`${relPath}: frontmatter missing required field "${field}"`);
    }
  }

  const code = source.slice(source.indexOf(fmMatch[0]) + fmMatch[0].length).trim();
  if (!code) {
    throw new Error(`${relPath}: no snippet code after frontmatter`);
  }

  const customizable = Array.isArray(meta.customizable) ? meta.customizable : [];

  return {
    title: String(meta.title),
    slug: String(meta.slug),
    category: String(meta.category),
    tags: (meta.tags ?? []).map(String),
    difficulty: String(meta.difficulty),
    techniques: (meta.techniques ?? []).map(String),
    howItWorks: String(meta.how_it_works).trim(),
    customizable,
    created: String(meta.created),
    support: meta.support ? String(meta.support).trim() : null,
    desc,
    relPath,
    code,
    header: attributionHeader(relPath, desc),
  };
}

/** The full snippet text a visitor gets from Copy / Download. */
export function copyText(snippet, code = snippet.code) {
  return `${snippet.header}\n${code}\n`;
}

/** Loads, parses and sorts the whole bank. Cached per process (one build). */
let cache = null;
export async function loadSnippets() {
  if (cache) return cache;
  const files = [];
  for (const dirent of await readdir(SNIPPETS_DIR, { withFileTypes: true })) {
    if (!dirent.isDirectory()) continue;
    for (const f of await readdir(path.join(SNIPPETS_DIR, dirent.name))) {
      if (f.endsWith('.html')) files.push(path.join(dirent.name, f));
    }
  }
  files.sort();

  const snippets = [];
  const slugs = new Set();
  for (const rel of files) {
    const relPath = path.posix.join('snippets', ...rel.split(path.sep));
    const source = await readFile(path.join(SNIPPETS_DIR, rel), 'utf8');
    const snippet = parseSnippetSource(source, relPath);
    const dirCategory = rel.split(path.sep)[0];
    if (snippet.category !== dirCategory) {
      throw new Error(`${relPath}: frontmatter category "${snippet.category}" ≠ directory "${dirCategory}"`);
    }
    if (slugs.has(snippet.slug)) {
      throw new Error(`${relPath}: duplicate slug "${snippet.slug}"`);
    }
    slugs.add(snippet.slug);
    snippets.push(snippet);
  }

  snippets.sort((a, b) => a.category.localeCompare(b.category) || a.title.localeCompare(b.title));
  cache = snippets;
  return snippets;
}

/** Categories that actually contain snippets, with counts. */
export async function loadCategories() {
  const snippets = await loadSnippets();
  const counts = new Map();
  for (const s of snippets) counts.set(s.category, (counts.get(s.category) ?? 0) + 1);
  return CATEGORIES.filter((c) => counts.has(c)).map((c) => ({ name: c, count: counts.get(c) }));
}

/** Standalone HTML document used inside the sandboxed preview iframes. */
export function previewDocument(snippet, { padding = '1rem' } = {}) {
  return `<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
  html, body { margin: 0; height: 100%; }
  body { display: grid; place-items: center; padding: ${padding}; box-sizing: border-box; overflow: hidden; background: var(--sg-preview-bg, #ffffff); transition: background .2s ease; }
</style>
</head>
<body>
${snippet.code}
</body>
</html>`;
}