/* =============================================================================
 * ui_template_range_bar.ts
 * 부품 「범위 바」(631 · 부품 모음 `#/b01-account?view=ui-kit`) — 가로 한 줄 칸(범위) · 칸 사이 경계값 하나 · 칸 눌러 고름 · 색 상자로 칸 색
 *
 *   꼴   = 칸(넓이 = 경계 차 비례 · 아주 좁으면 최소 넓이) · 칸 사이 = 수 입력 · 두 끝 = 고정 글 · 아래 = 색 상자 줄(+ 칠 안 함 = 빗금)
 *   크기 = data-size 24 · 28(기본 28)
 *   상태 = 마우스 `:hover` · 눌림 `:active` · 고름 = aria-pressed · 막힘 `disabled` · 오류 = 경계 칸 aria-invalid(`setError`)
 *   쓰기 = `createRangeBar({ edges: [0, 20, 250], colors: ["a", "b"], palette: [{ value: "a", name: "노랑", color: "var(--…)" }], onChange })`
 *   나눔 · 합침 · 검사는 부르는 쪽(급경사 = `A00_Common/map/logic/map_slope_bands.ts`)
 * ========================================================================== */

import { setUiSize, type UiSize } from "./ui_template_button";
import { createInputField } from "./ui_template_input";
import "./ui_template_range_bar.css";

export interface RangeBarColor {
  value: string;
  name: string;
  /** CSS 색(`var(--…)`) */
  color: string;
}

export interface RangeBarState {
  /** 경계 — 처음 · 끝은 고정 · 칸 i = [경계 i, 경계 i+1) */
  edges: number[];
  /** 칸 색 값(빈 글 = 칠 안 함) */
  colors: string[];
}

export interface RangeBarHandle {
  root: HTMLDivElement;
  get: () => RangeBarState;
  /** 칸을 새로 그림(onChange 는 안 부름) */
  set: (state: RangeBarState, selected?: number) => void;
  selected: () => number;
  /** 경계 i(1 ~ 끝 − 1)를 틀림으로 · 없으면 모두 풂 */
  setError: (edge?: number) => void;
}

export function createRangeBar(opts: {
  edges: number[];
  colors: string[];
  palette: RangeBarColor[];
  /** 있으면 색 상자 줄 끝에 칠 안 함(값 빈 글) */
  noneLabel?: string;
  unit?: string;
  /** 두 끝 글(없음 = 경계값 + 단위) */
  ends?: [string, string];
  /** 경계 아래 작은 글(예 ° 환산) */
  hint?: (value: number) => string;
  onChange?: (state: RangeBarState) => void;
  onSelect?: (index: number) => void;
  size?: UiSize;
  ariaLabel?: string;
}): RangeBarHandle {
  const root = document.createElement("div");
  root.className = "ui-range-bar";
  setUiSize(root, opts.size ?? 28);
  if (opts.ariaLabel) root.setAttribute("aria-label", opts.ariaLabel);
  const track = document.createElement("div");
  track.className = "ui-range-bar__track";
  const swatchRow = document.createElement("div");
  swatchRow.className = "ui-range-bar__colors";
  root.append(track, swatchRow);

  let state: RangeBarState = { edges: [...opts.edges], colors: [...opts.colors] };
  let current = 0;
  let segs: HTMLButtonElement[] = [];
  let inputs: HTMLInputElement[] = [];
  const unit = opts.unit ? ` ${opts.unit}` : "";
  const colorOf = (value: string): string =>
    opts.palette.find((p) => p.value === value)?.color ?? "";
  const nameOf = (value: string): string =>
    opts.palette.find((p) => p.value === value)?.name ?? opts.noneLabel ?? "";
  const changed = (): void => opts.onChange?.(get());
  const get = (): RangeBarState => ({ edges: [...state.edges], colors: [...state.colors] });

  const swatches = [
    ...opts.palette,
    ...(opts.noneLabel !== undefined ? [{ value: "", name: opts.noneLabel, color: "" }] : []),
  ].map((p) => {
    const b = document.createElement("button");
    b.type = "button";
    b.className = "ui-range-bar__swatch";
    b.dataset.value = p.value;
    if (p.color) b.style.setProperty("--ui-range-bar-color", p.color);
    else b.dataset.empty = "";
    b.append(p.name);
    b.addEventListener("click", () => {
      if (state.colors[current] === p.value) return;
      state.colors[current] = p.value;
      paint();
      changed();
    });
    swatchRow.append(b);
    return b;
  });

  /** 칸 넓이 = 경계 차(경계가 틀리면 그대로 둠) */
  function layout(): void {
    const e = state.edges;
    if (!e.every((v, i) => Number.isFinite(v) && (i === 0 || v > e[i - 1]))) return;
    segs.forEach((seg, i) => {
      seg.style.flexGrow = String(e[i + 1] - e[i]);
      seg.title = `${e[i]} ~ ${e[i + 1]}${unit} · ${nameOf(state.colors[i])}`;
    });
  }

  function paint(): void {
    segs.forEach((seg, i) => {
      const color = colorOf(state.colors[i]);
      if (color) {
        seg.style.setProperty("--ui-range-bar-color", color);
        delete seg.dataset.empty;
      } else {
        seg.style.removeProperty("--ui-range-bar-color");
        seg.dataset.empty = "";
      }
      seg.setAttribute("aria-pressed", String(i === current));
    });
    const picked = state.colors[current];
    for (const b of swatches) b.setAttribute("aria-pressed", String(b.dataset.value === picked));
    layout();
  }

  const endText = (text: string): HTMLSpanElement => {
    const span = document.createElement("span");
    span.className = "ui-range-bar__end";
    span.textContent = text;
    return span;
  };

  function render(): void {
    const e = state.edges;
    segs = [];
    inputs = [];
    track.replaceChildren(endText(opts.ends?.[0] ?? `${e[0]}${unit}`));
    state.colors.forEach((_, i) => {
      const seg = document.createElement("button");
      seg.type = "button";
      seg.className = "ui-range-bar__seg";
      seg.dataset.index = String(i);
      seg.addEventListener("click", () => {
        current = i;
        paint();
        opts.onSelect?.(i);
      });
      segs.push(seg);
      track.append(seg);
      if (i === state.colors.length - 1) return;
      const field = createInputField({
        type: "number",
        size: opts.size ?? 28,
        value: String(e[i + 1]),
        min: e[0],
        max: e.at(-1),
      });
      field.root.classList.add("ui-range-bar__edge");
      field.input.dataset.edge = String(i + 1);
      const hint = document.createElement("span");
      hint.className = "ui-range-bar__hint";
      const showHint = (): void => {
        const v = state.edges[i + 1];
        hint.textContent = opts.hint && Number.isFinite(v) ? opts.hint(v) : "";
      };
      field.input.addEventListener("input", () => {
        const raw = field.input.value.trim();
        state.edges[i + 1] = raw === "" ? NaN : Number(raw);
        showHint();
        layout();
        changed();
      });
      showHint();
      if (opts.hint) field.root.append(hint);
      inputs.push(field.input);
      track.append(field.root);
    });
    track.append(endText(opts.ends?.[1] ?? `${e.at(-1)}${unit}`));
    paint();
  }

  const set = (next: RangeBarState, selected = current): void => {
    state = { edges: [...next.edges], colors: [...next.colors] };
    current = Math.max(0, Math.min(selected, state.colors.length - 1));
    render();
  };

  const setError = (edge?: number): void => {
    inputs.forEach((input, k) => {
      const bad = k + 1 === edge;
      input.classList.toggle("ui-input--error", bad);
      if (bad) input.setAttribute("aria-invalid", "true");
      else input.removeAttribute("aria-invalid");
    });
  };

  render();
  return { root, get, set, selected: () => current, setError };
}