/* =============================================================================
 * ui_template_side_panels.ts
 * 본문 오른쪽 접는 패널 여럿 — 나란히 · 하나만 열림 · 모두 접힘 됨 · 폭 공유
 * 접힌 패널 = 제목 세로 글 띠(누르면 폄) · 편 패널 = 머리(제목 · 접기 ▸) + 몸 · 왼쪽 경계 끌기(화살표 키)
 * 열린 패널 · 폭 = 부르는 쪽 취향 키(`aislo:pref:{prefKey}`)
 * 부르기: const sp = createSidePanels({ prefKey, panels: [{ id, title, body }] }) →
 *         본문과 함께 `.ui-side-panels-row` 칸에 [본문, sp.root] 로 넣음
 * ========================================================================== */

import { readByKey, writeByKey } from "../A00_Common/b_page_state";
import { el } from "./ui_template_elements";
import { currentLanguageIndex } from "./ui_template_locale";
import "./ui_template_side_panels.css";

const TEXT = {
  Open: ["{v} 펴기", "Open {v}"],
  Close: ["{v} 접기", "Collapse {v}"],
  Grip: ["패널 너비 — 끌거나 화살표 키", "Panel width — drag or arrow keys"],
} as const;

const ts = (key: keyof typeof TEXT, v: string): string =>
  TEXT[key][currentLanguageIndex === 1 ? 1 : 0].replace("{v}", v);

export interface SidePanelDef {
  id: string;
  title: string;
  body: HTMLElement;
}

export interface SidePanelsOpts {
  panels: SidePanelDef[];
  /** 취향 키 이름 — `aislo:pref:` 뒤에 붙음 */
  prefKey: string;
  /** 기억이 없을 때 열 패널(null = 모두 접힘) · 기본 첫 패널 */
  defaultOpen?: string | null;
  /** 기억이 없을 때 폭(px) · 기본 420 */
  defaultWidth?: number;
  /** 가장 좁은 폭(px) · 기본 280 · 가장 넓게 = 화면의 85% */
  minWidth?: number;
  /** 열린 패널이 바뀜(누름 · open 모두) */
  onChange?(open: string | null): void;
  /** 폭이 바뀜(끌기 · 화살표) */
  onResize?(px: number): void;
}

export interface SidePanels {
  root: HTMLElement;
  /** 열 패널(null = 모두 접음) — 기억함 */
  open(id: string | null): void;
  current(): string | null;
  width(): number;
}

interface Pref {
  open?: string | null;
  width?: number;
}

/** 끌어 정한 폭 — 가장 작게 min · 가장 크게 화면의 85% */
export function clampSideWidth(px: number, min: number, viewport: number): number {
  return Math.round(Math.min(Math.max(min, viewport * 0.85), Math.max(min, px)));
}

export function createSidePanels(opts: SidePanelsOpts): SidePanels {
  const key = `aislo:pref:${opts.prefKey}`;
  const min = opts.minWidth ?? 280;
  const ids = opts.panels.map((p) => p.id);
  let pref: Pref = {};
  try {
    pref = JSON.parse(readByKey(key) ?? "{}") as Pref;
  } catch {
    /* 깨진 기억 — 기본값 */
  }
  let now: string | null =
    pref.open === null || ids.includes(pref.open ?? "")
      ? (pref.open ?? null)
      : opts.defaultOpen === undefined
        ? (ids[0] ?? null)
        : opts.defaultOpen;
  let width = clampSideWidth(pref.width ?? opts.defaultWidth ?? 420, min, window.innerWidth);
  const save = (): void => writeByKey(key, JSON.stringify({ open: now, width }));

  const root = el("div", { className: "ui-side-panels" });
  root.style.setProperty("--ui-side-panels-width", `${width}px`);
  const setWidth = (px: number, keep: boolean): void => {
    width = clampSideWidth(px, min, window.innerWidth);
    root.style.setProperty("--ui-side-panels-width", `${width}px`);
    opts.onResize?.(width);
    if (keep) save();
  };

  const views = opts.panels.map((p) => {
    const bodyId = `ui-side-panel-${opts.prefKey}-${p.id}`;
    const strip = el("button", {
      className: "ui-side-panels__strip",
      text: p.title,
      attrs: { type: "button", "aria-expanded": "false", "aria-controls": bodyId },
    });
    strip.title = ts("Open", p.title);
    strip.addEventListener("click", () => {
      open(p.id);
      fold.focus();
    });
    const fold = el("button", {
      className: "ui-side-panels__fold",
      text: "▸",
      attrs: { type: "button", "aria-expanded": "true", "aria-controls": bodyId },
    });
    fold.title = ts("Close", p.title);
    fold.setAttribute("aria-label", fold.title);
    fold.addEventListener("click", () => {
      open(null);
      strip.focus();
    });
    const grip = el("div", {
      className: "ui-side-panels__grip",
      attrs: {
        role: "separator",
        "aria-orientation": "vertical",
        "aria-label": ts("Grip", ""),
        tabindex: "0",
      },
    });
    const box = el("section", {
      className: "ui-side-panels__panel",
      attrs: { "data-panel": p.id, "aria-label": p.title },
      children: [
        grip,
        el("header", {
          className: "ui-side-panels__head",
          children: [el("strong", { className: "ui-side-panels__title", text: p.title }), fold],
        }),
        el("div", { className: "ui-side-panels__body", attrs: { id: bodyId }, children: [p.body] }),
      ],
    });
    grip.addEventListener("pointerdown", (ev) => {
      if (ev.button !== 0) return;
      ev.preventDefault();
      const start = box.getBoundingClientRect().width;
      const x0 = ev.clientX;
      root.classList.add("is-resizing");
      const move = (m: PointerEvent): void => setWidth(start + x0 - m.clientX, false);
      const up = (u: PointerEvent): void => {
        window.removeEventListener("pointermove", move);
        window.removeEventListener("pointerup", up);
        root.classList.remove("is-resizing");
        setWidth(start + x0 - u.clientX, true);
      };
      window.addEventListener("pointermove", move);
      window.addEventListener("pointerup", up);
    });
    grip.addEventListener("keydown", (ev) => {
      const step = ev.shiftKey ? 80 : 20;
      const d = ev.key === "ArrowLeft" ? step : ev.key === "ArrowRight" ? -step : 0;
      if (!d) return;
      ev.preventDefault();
      setWidth(width + d, true);
    });
    root.append(strip, box);
    return { id: p.id, strip, box };
  });

  const draw = (): void => {
    for (const v of views) {
      const on = v.id === now;
      v.strip.hidden = on;
      v.box.hidden = !on;
    }
  };

  function open(id: string | null): void {
    const next = id !== null && ids.includes(id) ? id : null;
    const was = now;
    now = next;
    draw();
    save();
    if (next !== was) opts.onChange?.(next);
  }

  draw();
  return { root, open, current: () => now, width: () => width };
}