// SPDX-License-Identifier: GPL-2.0-only

"use strict";

(async () => {
  if (await subEnabled()) {
    console.log("TeX Type started.");

    function cmdToUnicode(name, args) {
      if (name === "^")
        return Array.from(args[0]).reduce(
          (acc, c) => acc + (window.unicodeMaps.toSuperscript[c] ?? "^" + c),
          ""
        );
      if (name === "_")
        return Array.from(args[0]).reduce(
          (acc, c) => acc + (window.unicodeMaps.toSubscript[c] ?? "_" + c),
          ""
        );

      let sym = {
        "\\x": "×",
        "\\times": "×",
        "\\.": "⋅",
        "\\cdot": "⋅",
        "\\pm": "±",
        "\\mp": "∓",
        "\\in": "∈",
        "\\/in": "∉",
        "\\\\": "\u200b\\",
        "\\{": "\u200b{",
        "\\}": "\u200b}",
        "\\^": "\u200b^",
        "\\_": "\u200b_",
        "<===": "⇐",
        "==>": "⇒",
        "<=>": "⇔",
        "<==": "⟸",
        "=>": "⟹",
        "\\implies": "⟹",
        "<>": "⟺",
        "\\iff": "⟺",
        "<=": "⩽",
        "\\le": "⩽",
        ">=": "⩾",
        "\\ge": "⩾",
      }[name];
      if (sym) return sym;

      if (["\\bf", "\\mathbf"].includes(name))
        return Array.from(args[0]).reduce(
          (acc, chr) => acc + (window.unicodeMaps.toBold[chr] ?? chr),
          ""
        );

      console.error("unreachable");
    }

    function getArgs(input, i, count) {
      const args = [];
      for (let argI = 0; argI < count; argI++) {
        while (input.value[i] === " ") i++;

        if (!input.value[i]) break;

        if (input.value[i] === "\\") {
          const start = i;
          i = handleCmd(input, i);
          if (failed) break;
          args.push(input.value.slice(start, i));
        } else if (input.value[i] === "{") {
          const argStart = ++i;
          i = subCmds(input, i);
          if (i === input.value.length) break;
          const arg = input.value.slice(argStart, i++);
          args.push(arg);
        } else {
          args.push(input.value[i++]);
        }
      }
      return { args, argsEnd: i };
    }

    function trySubCmd(input, nameStart) {
      let nameEnd;
      if (input.value[nameStart] === "\\") {
        const offset = input.value.slice(nameStart + 2).search(/\W/);
        nameEnd = nameStart + 2 + (offset < 0 ? 0 : offset);
      } else if ("^_".includes(input.value[nameStart])) nameEnd = nameStart + 1;
      else if (
        "<>=".includes(input.value[nameStart]) &&
        ">=".includes(input.value[nameStart + 1])
      )
        if ("<>=".includes(input.value[nameStart + 2]))
          if ("<>=".includes(input.value[nameStart + 3]))
            nameEnd = nameStart + 4;
          else if (/\s/.test(input.value[nameStart + 3]))
            nameEnd = nameStart + 3;
          else return { end: nameStart + 1, success: false };
        else if (/\s/.test(input.value[nameStart + 2])) nameEnd = nameStart + 2;
        else return { end: nameStart + 1, success: false };
      else if (input.value[nameStart] === "\u200b")
        return { end: nameStart + 2, success: true };
      else return { end: nameStart + 1, success: false };
      const name = input.value.slice(nameStart, nameEnd);

      const argsCount = {
        "\\x": 0,
        "\\times": 0,
        "\\.": 0,
        "\\cdot": 0,
        "\\pm": 0,
        "\\mp": 0,
        "\\in": 0,
        "\\/in": 0,
        "\\\\": 0,
        "\\{": 0,
        "\\}": 0,
        "\\^": 0,
        "\\_": 0,
        "<==": 0,
        "=>": 0,
        "<=>": 0,
        "<===": 0,
        "==>": 0,
        "\\implies": 0,
        "<>": 0,
        "\\iff": 0,
        "<=": 0,
        "\\le": 0,
        ">=": 0,
        "\\ge": 0,
        "\\bf": 1,
        "\\mathbf": 1,
        "^": 1,
        _: 1,
      }[name];
      if (argsCount == null) return { end: nameEnd, success: false };

      const argsRet = getArgs(input, nameEnd, argsCount);
      const args = argsRet.args;
      const argsEnd = argsRet.argsEnd;
      if (args.length < argsCount) return { end: argsEnd, success: false };

      const unicode = cmdToUnicode(name, args);
      input.value =
        input.value.slice(0, nameStart) + unicode + input.value.slice(argsEnd);

      const caret = input.caret;
      if (caret > nameStart)
        input.caret = caret + nameStart - argsEnd + unicode.length;

      return { end: nameStart + unicode.length, success: true };
    }

    function subCmds(input, i) {
      const starts = [];
      const ends = [];
      if (i == null) i = 0;
      while (i < input.value.length) {
        if (input.value[i] === "}") return i;
        else i = trySubCmd(input, i).end;
      }
      return input.value.length;
    }

    window.addEventListener("input", (event) => {
      if (event.target.selectionStart != null) {
        const input = {
          value: event.target.value,
          caret: event.target.selectionStart,
        };
        subCmds(input);
        event.target.value = input.value;
        event.target.selectionStart = event.target.selectionEnd = input.caret;
      } else if (event.target.contentEditable === "true") {
        const textNode = window.getSelection().anchorNode;
        const input = {
          value: textNode.textContent,
          caret: window.getSelection().getRangeAt(0).startOffset,
        };
        subCmds(input);
        textNode.textContent = input.value;
        window
          .getSelection()
          .setBaseAndExtent(textNode, input.caret, textNode, input.caret);
      }
    });
  }
})();