/**
 * Mini-renderer markdown sans dépendance externe.
 *
 * Volontairement minimal et stable : pas de plugins, pas d'extension HTML
 * arbitraire. Couvre les besoins des pages CMS Karbé (À propos, FAQ, CGV,
 * etc.) sans introduire de surface d'attaque XSS.
 *
 * Supporte :
 *   # H1 / ## H2 / ### H3
 *   paragraphes (séparés par ligne vide)
 *   **gras** et *italique*
 *   [texte](https://lien)
 *   - liste à puces
 *   1. liste numérotée
 *   ---  (séparateur)
 *   > citation (blockquote)
 *
 * Toute autre balise HTML dans le markdown est échappée.
 */

function escapeHtml(s: string): string {
  return s
    .replace(/&/g, "&")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;")
    .replace(/'/g, "&#39;");
}

function inline(text: string): string {
  let out = escapeHtml(text);
  // **bold**
  out = out.replace(/\*\*([^*]+)\*\*/g, "<strong>$1</strong>");
  // *italic*
  out = out.replace(/(^|[^*])\*([^*\n]+)\*/g, "$1<em>$2</em>");
  // [text](url)
  out = out.replace(
    /\[([^\]]+)\]\(((?:https?:\/\/|\/|mailto:)[^)\s]+)\)/g,
    (_m, label: string, href: string) => {
      const safe = href.replace(/[&<>"']/g, (c) => `&#${c.charCodeAt(0)};`);
      const isExternal = /^https?:/.test(href);
      const extra = isExternal ? ' target="_blank" rel="noopener noreferrer"' : "";
      return `<a href="${safe}" class="text-[var(--color-karbe-canopy-700)] underline hover:text-[var(--color-karbe-laterite-700)]"${extra}>${label}</a>`;
    },
  );
  return out;
}

export function renderMarkdown(md: string): string {
  const lines = md.replace(/\r\n?/g, "\n").split("\n");
  const out: string[] = [];
  let paragraph: string[] = [];
  let listType: "ul" | "ol" | null = null;
  let inBlockquote = false;
  const blockquote: string[] = [];

  function flushParagraph() {
    if (paragraph.length) {
      out.push(`<p class="my-4 leading-relaxed">${inline(paragraph.join(" "))}</p>`);
      paragraph = [];
    }
  }
  function flushList() {
    if (listType) {
      out.push(`</${listType}>`);
      listType = null;
    }
  }
  function flushBlockquote() {
    if (inBlockquote) {
      out.push(
        `<blockquote class="my-4 border-l-4 border-[var(--color-karbe-laterite-500)] pl-4 italic text-[var(--color-karbe-ink)]/75">${blockquote
          .map((l) => inline(l))
          .join(" ")}</blockquote>`,
      );
      blockquote.length = 0;
      inBlockquote = false;
    }
  }

  for (const rawLine of lines) {
    const line = rawLine.trimEnd();

    if (!line.trim()) {
      flushParagraph();
      flushList();
      flushBlockquote();
      continue;
    }

    if (/^---+$/.test(line.trim())) {
      flushParagraph();
      flushList();
      flushBlockquote();
      out.push(`<hr class="my-6 border-[var(--color-karbe-canopy-100)]" />`);
      continue;
    }

    let m: RegExpExecArray | null;
    if ((m = /^(#{1,3})\s+(.+)$/.exec(line))) {
      flushParagraph();
      flushList();
      flushBlockquote();
      const level = m[1].length;
      const sizes = ["", "text-3xl mt-8 mb-4 font-medium font-serif", "text-2xl mt-7 mb-3 font-medium font-serif", "text-xl mt-6 mb-2 font-semibold"];
      out.push(`<h${level} class="${sizes[level]}">${inline(m[2])}</h${level}>`);
      continue;
    }

    if ((m = /^[-*]\s+(.+)$/.exec(line))) {
      flushParagraph();
      flushBlockquote();
      if (listType !== "ul") {
        flushList();
        out.push(`<ul class="my-4 list-disc space-y-1 pl-6">`);
        listType = "ul";
      }
      out.push(`<li>${inline(m[1])}</li>`);
      continue;
    }
    if ((m = /^\d+\.\s+(.+)$/.exec(line))) {
      flushParagraph();
      flushBlockquote();
      if (listType !== "ol") {
        flushList();
        out.push(`<ol class="my-4 list-decimal space-y-1 pl-6">`);
        listType = "ol";
      }
      out.push(`<li>${inline(m[1])}</li>`);
      continue;
    }

    if ((m = /^>\s?(.*)$/.exec(line))) {
      flushParagraph();
      flushList();
      inBlockquote = true;
      blockquote.push(m[1]);
      continue;
    }

    flushList();
    flushBlockquote();
    paragraph.push(line);
  }

  flushParagraph();
  flushList();
  flushBlockquote();

  return out.join("\n");
}