/* =============================================================================
 * ui_template_help.ts
 * [?] 설명서(54-2) — 좌측 패널 아래 단추 묶음 맨 왼쪽 단추 + 모달(왼쪽 차례 · 오른쪽 글). B02~B09 공용.
 * 글 = `resources/help/<페이지>/*.md` — 서버가 열 때마다 읽음(파일만 고치면 다음에 열 때 바뀜).
 * 페이지 = 주소(#/b05-…)의 B0N · 먼저 여는 항목 = 좌측 패널에서 보이는 `[data-help-topic]` 중 마지막
 * (지금 연 상자 · 구조물 종류) · 없으면 첫 파일(00_설명서).
 * 단추 자리 = `.ui-sidebar-actions` 안 `[data-help-row]`(없으면 그 줄 자신)의 맨 앞.
 * ========================================================================== */

import "./ui_template_help.css";
import { API_BASE_URL } from "@config/config_frontend";
import { createButton, el } from "./ui_template_elements";
import { openModal } from "./ui_template_modal";

interface HelpItem {
  key: string;
  title: string;
  text: string;
}

const TEXT = { button: "?", tip: "설명서", title: "설명서", close: "닫기", empty: "설명 글 없음" };

function currentPage(): string {
  const n = /^#\/b0(\d)/i.exec(location.hash)?.[1];
  return n ? `B0${n}` : "";
}

function escapeHtml(text: string): string {
  return text.replace(
    /[&<>"]/g,
    (c) => `&${{ "&": "amp", "<": "lt", ">": "gt", '"': "quot" }[c]};`,
  );
}

function inline(text: string): string {
  return escapeHtml(text)
    .replace(/\*\*(.+?)\*\*/g, "<strong>$1</strong>")
    .replace(/`(.+?)`/g, "<code>$1</code>");
}

/** 메모장 글에 쓸 만큼만 — 제목(#) · 목록(- · 1.) · 문단 · **굵게** · `코드` */
export function renderHelpMarkdown(text: string): string {
  const out: string[] = [];
  let list: "ul" | "ol" | null = null;
  let para: string[] = [];
  const flush = (): void => {
    if (para.length) out.push(`<p>${para.map(inline).join("<br>")}</p>`);
    para = [];
    if (list) out.push(`</${list}>`);
    list = null;
  };
  for (const raw of text.split(/\r?\n/)) {
    const line = raw.trim();
    const head = /^(#{1,4})\s+(.*)$/.exec(line);
    const item = /^(?:([-*])|\d+\.)\s+(.*)$/.exec(line);
    if (!line) flush();
    else if (head) {
      flush();
      out.push(`<h${head[1].length + 1}>${inline(head[2])}</h${head[1].length + 1}>`);
    } else if (item) {
      const kind = item[1] ? "ul" : "ol";
      if (para.length || list !== kind) flush();
      if (!list) out.push(`<${kind}>`);
      list = kind;
      out.push(`<li>${inline(item[2])}</li>`);
    } else {
      if (list) flush();
      para.push(line);
    }
  }
  flush();
  return out.join("");
}

function visibleTopics(): string[] {
  const panel = document.querySelector(".ui-workflow-overlay__panel--title") ?? document;
  return [...panel.querySelectorAll<HTMLElement>("[data-help-topic]")]
    .filter((node) => node.offsetParent !== null)
    .map((node) => node.dataset.helpTopic ?? "");
}

async function fetchItems(page: string): Promise<HelpItem[]> {
  const response = await fetch(`${API_BASE_URL}/help/${page}`, {
    credentials: "include",
    cache: "no-store",
  });
  return response.ok ? ((await response.json()) as { items: HelpItem[] }).items : [];
}

/** B05 · B06 = 한 페이지(구조물 폼 공유) — 제 폴더 뒤에 짝 폴더 항목(짝의 설명서는 뺌)도 보임 */
const PAIR: Record<string, string> = { B05: "B06", B06: "B05" };

async function openHelp(): Promise<void> {
  const page = currentPage();
  const pair = PAIR[page];
  const [own, other] = await Promise.all([fetchItems(page), pair ? fetchItems(pair) : []]);
  const items = [...own, ...other.filter((item) => !own.some((o) => o.key === item.key))];
  const topics = visibleTopics();
  const first = [...topics].reverse().find((key) => items.some((item) => item.key === key));
  openModal({
    title: `${TEXT.title} · ${page}`,
    closeLabel: TEXT.close,
    dialogClass: "ui-help",
    mount: (body) => {
      const article = el("article", { className: "ui-help__text" });
      const toc = el("nav", { className: "ui-help__toc" });
      const show = (key: string): void => {
        const item = items.find((entry) => entry.key === key);
        article.innerHTML = item ? renderHelpMarkdown(item.text) : `<p>${TEXT.empty}</p>`;
        article.dataset.helpKey = key;
        toc
          .querySelectorAll("button")
          .forEach((b) => b.classList.toggle("is-active", b.dataset.helpKey === key));
      };
      for (const item of items) {
        const link = el("button", {
          className: "ui-help__link",
          text: item.title,
          attrs: { type: "button" },
        });
        link.dataset.helpKey = item.key;
        link.addEventListener("click", () => show(item.key));
        toc.append(link);
      }
      body.append(el("div", { className: "ui-help__grid", children: [toc, article] }));
      show(first ?? items[0]?.key ?? "");
    },
  });
}

export function createHelpButton(): HTMLButtonElement {
  const button = createButton({
    label: TEXT.button,
    variant: "ghost",
    onClick: () => void openHelp(),
  });
  button.classList.add("ui-help-btn");
  button.title = button.ariaLabel = TEXT.tip;
  return button;
}

/** 아래 단추 묶음에 [?] 를 한 번 — `[data-help-row]` 가 있으면 그 줄 · 없으면 묶음 자신의 맨 앞 */
export function placeHelpButton(actions: HTMLElement): void {
  if (actions.querySelector(".ui-help-btn")) return;
  (actions.querySelector<HTMLElement>("[data-help-row]") ?? actions).prepend(createHelpButton());
}