/* =============================================================================
 * line_stack_tex.ts
 * 줄 쌓기 산출근거 수식 조판(PLAN 804-2 · 요구 677) — 식 나무 → TeX → KaTeX(MIT) · 분수 · 첨자 · 괄호
 *   기호 식(side "sym") = 기호(첨자) · 값 식(side "val") = 값(모르면 기호 빨강) · 만약 = 탄 갈래만 · 반올림 · 올림 · 버림 감싸개 숨김
 *   금액 줄 꼴(`inline`) = ÷ 한 줄(경쟁사 「노무비 : 59,020 ÷ Q」) · 공식 줄 = 분수
 *   규칙은 수식 탭 그림(`formula_doc_render.ts` renderNode)과 같음 — 셈 정본은 계산기
 * ========================================================================== */

import katex from "katex";
import "../config/node_modules/katex/dist/katex.min.css";
import { eqText } from "@ui/ui_template_equation";
import { splitId, type Node } from "../common_util/common_util_formula_doc";
import { isNum } from "../common_util/common_util_formula_doc_calc";
import { leafNum, takenOf, type Values } from "../common_util/common_util_formula_doc_view";

export interface TexCtx {
  side: "sym" | "val";
  vals: Values;
  inline?: boolean;
  /** 묶음 값의 비목(기계 · 단가산출 줄 노 · 재 · 경) */
  cost?: string;
}

const HIDE = new Set(["반올림", "올림", "버림"]);
const OPS: Record<string, string> = {
  "+": "+",
  "-": "-",
  "*": "\\times",
  "/": "\\div",
  "<": "<",
  "<=": "\\le",
  ">": ">",
  ">=": "\\ge",
  "==": "=",
  "!=": "\\ne",
  그리고: "\\;\\text{그리고}\\;",
  또는: "\\;\\text{또는}\\;",
};
const PREC: Record<string, number> = {
  또는: 1,
  그리고: 2,
  "<": 3,
  "<=": 3,
  ">": 3,
  ">=": 3,
  "==": 3,
  "!=": 3,
  "+": 4,
  "-": 4,
  "*": 5,
  "/": 5,
};
const prec = (n: Node): number => (n[0] === "bin" ? PREC[n[1]] : n[0] === "neg" ? 6 : 9);

/** TeX 글 안전 — \text{} 안 */
const txt = (s: string): string => `\\text{${s.replace(/[\\{}$&#^_%~]/g, (c) => `\\${c}`)}}`;
const word = (s: string): string =>
  /^[A-Za-z]$/.test(s) ? s : /^[A-Za-z]+$/.test(s) ? `\\mathit{${s}}` : txt(s);

/** 기호 글(`Q_작업^표`) → TeX(첨자) */
export function symTex(id: string): string {
  const [s, lo, up] = splitId(id);
  return `${word(s)}${lo ? `_{${word(lo)}}` : ""}${up ? `^{${word(up)}}` : ""}`;
}

/** 값 → TeX(천 자리 쉼표) */
export const valTex = (v: unknown): string => {
  const t = eqText(v);
  return isNum(v) ? t.replace(/,/g, "{,}") : txt(t);
};

const paren = (t: string): string => `\\left(${t}\\right)`;
const miss = (t: string): string => `\\htmlClass{lstk-miss}{${t}}`;

export function tex(n: Node, c: TexCtx): string {
  const go = (x: Node): string => tex(x, c);
  switch (n[0]) {
    case "num":
      return valTex(n[1]);
    case "str":
      return txt(`'${n[1]}'`);
    case "var": {
      if (c.side === "sym") return symTex(n[1]);
      let v = c.vals[n[1]];
      if (v && typeof v === "object" && c.cost) v = (v as Values)[c.cost];
      return v === null || v === undefined || typeof v === "object"
        ? miss(symTex(n[1]))
        : valTex(v);
    }
    case "field": {
      if (c.side === "val" && n[1][0] === "var") {
        const v = c.vals[n[1][1]];
        const got = v && typeof v === "object" ? (v as Values)[n[2]] : undefined;
        if (isNum(got)) return valTex(got);
      }
      return `${n[1][0] === "var" ? symTex(n[1][1]) : go(n[1])}.${txt(n[2])}`;
    }
    case "neg":
      return `-${n[1][0] === "bin" ? paren(go(n[1])) : go(n[1])}`;
    case "pct":
      return `${prec(n[1]) < 9 ? paren(go(n[1])) : go(n[1])}\\,\\%`;
    case "call": {
      const [, name, items] = n;
      if (name === "만약") {
        const pick = takenOf(n, c.vals);
        if (pick) return go(items[pick]);
      }
      if (HIDE.has(name) && items.length >= 1 && items.length <= 2) return go(items[0]);
      const fn = name === "최소" ? "\\min" : name === "최대" ? "\\max" : txt(name);
      return `${fn}${paren(items.map(go).join(",\\,"))}`;
    }
    case "bin": {
      const [, o, a, b] = n;
      const na = leafNum(a, c.vals);
      const nb = leafNum(b, c.vals);
      if ((o === "+" || o === "-") && nb === 0) return go(a);
      if ((o === "*" || o === "/") && nb === 1) return go(a);
      if ((o === "+" && na === 0) || (o === "*" && na === 1)) return go(b);
      if (o === "/" && !c.inline) return `\\dfrac{${go(a)}}{${go(b)}}`;
      const mine = PREC[o];
      const left = prec(a) < mine || (mine === 3 && prec(a) === 3) ? paren(go(a)) : go(a);
      const right = prec(b) <= mine ? paren(go(b)) : go(b);
      return `${left} ${OPS[o] ?? txt(o)} ${right}`;
    }
  }
}

/** TeX → 조판 요소(못 그리면 글 그대로) */
export function katexNode(t: string): HTMLElement {
  const box = document.createElement("span");
  box.className = "lstk-tex";
  katex.render(t, box, {
    throwOnError: false,
    strict: "ignore",
    trust: (x) => x.command === "\\htmlClass",
    output: "html",
  });
  return box;
}