import React, { useState, useEffect, useRef } from "react";
import DataGrid, {Column} from "devextreme-react/data-grid";
import {Alert} from "./AlertDialog.js";
import {addNumbersToGrid, numbersToArrOfArr, afterCommaLen} from "./helpers.js";
import "./App.css";

let imdtRes;
let imdtResIdx;
let resArr = [];
let noOfDigits = 0;

function Addition() {
  const [input, setInput] = useState(""); // initial user input like 34+56.7
  const [realResult, setRealResult] = useState(0); // real result of calculation
  const [carryArr, setCarryArr] = useState([]); // array of carries ["1","0"]
  const [commaIdx, setCommaIdx] = useState(0); // int: comma position
  const [numbers, setNumbers] = useState(0); // array of arrays with input numbers
  const [showAlert, setShowAlert] = useState(false);
  const [numbersGrid, setNumbersGrid] = useState([{id: 1, number: ""}]);
  const [resultsGrid, setResultsGrid] = useState([{id: 1, number: ""}]);
  const [stepsGrid, setStepsGrid] = useState([{id: 1, step: ""}]);

  // focus the input field
  let calculationInput = useRef(null);
  useEffect(()=>{
    if(calculationInput.current && calculationInput.current.value === ""){
      calculationInput.current.focus();
    }
  },[])

  const handleInput = (e) => {
    setInput(e.target.value);
  }

  const handleResChange = (e, nosLeft) => {
    if(typeof e === "string"){
      imdtRes = e;
    }else{
      imdtRes = e.target.value;
    }

    // remove deleted input
    if(imdtRes === ""){
      resArr.shift();
    }else{
      // add input number to result array
      resArr.unshift(imdtRes);
    }
  }

  const handleCarryChange = (e, noOfDigits, nosLeft) => {
    let carryArrCopy = [...carryArr];
    carryArrCopy.unshift(e.target.value);
    setCarryArr(carryArrCopy);
    let noCarry = carryArrCopy[0] === "0" || carryArrCopy[0] === undefined

    if((nosLeft === 1 && noCarry) ||
       // if stop after first iteration, numbers left is undefined at first
       (nosLeft !== nosLeft && realResult.toString().length === 1 && noCarry)){
      nosLeft = 0;
      handleResChange(" ", 0)
    }

    if(nosLeft === 0){
      createIdmtResults()
      setShowAlert(true);
    }
  }

  const handleSubmit = (e) => {
    startCalculation();
    e.preventDefault(); // avoid page reload
  }

  const startCalculation = () => {
    if (input.includes("+")){
      let numbers = input.split("+").map(x => parseFloat(x.replace(",",".")));
      let realRes = numbers.reduce((x,y) => x+y, 0);
      let afterComma = Math.max(...numbers.map(x => afterCommaLen(x)));
      realRes = parseFloat(realRes.toFixed(afterComma));
      setRealResult(realRes);
      console.log("real result: ", realRes);

      let [numbersArr, commaIdx] = numbersToArrOfArr(numbers);
      setNumbers(numbersArr);
      setCommaIdx(commaIdx);

      setNumbersGrid(addNumbersToGrid(numbersArr, "+"));
    }
  }

  const ResultCarryForm = ({handleResChange, handleCarryChange}) => {
    let resInputField = useRef(null);
    let carryInputField = useRef(null);
    let labelText = "";
    let nosLeft = imdtResIdx + 1;
    let carryText = "Übertrag = ";

    if(typeof numbers === "object" && imdtResIdx !== -1){
      // set the digit index, start with the last digit
      if(typeof imdtResIdx === "undefined" || imdtResIdx === null){
        noOfDigits = Math.min(...numbers.map(n => n.length));
        imdtResIdx = noOfDigits - 1;
      }

      // skip over comma
      if(imdtResIdx === commaIdx){
        if(!resArr.includes(".")){
          handleResChange(".", nosLeft);
        }
        imdtResIdx = imdtResIdx - 1;
        nosLeft = nosLeft - 1;
      }

      // iterate numbers for this digit index
      for (let n in numbers){
        // skip last empty number if no carry
        if(nosLeft === 1 && carryArr[0] === "0"){
          nosLeft = 0;
          imdtResIdx = -1;
          return <></>
        }

        // create label text like: d + d + .. = input
        let digit = numbers[parseInt(n)][imdtResIdx];
        if(digit === "" || digit === "&nbsp;"){
          digit = 0;
        }
        labelText += digit;
        if (parseInt(n) === numbers.length - 1){
          if(carryArr[0] !== undefined && carryArr[0] > 0){
            labelText += " + " + carryArr[0].toString();
          }
          labelText += " = ";
        }else{
          labelText += " + ";
        }
      }

      imdtResIdx -= 1;
      nosLeft -= 1;

      return (
        <form>
          <label htmlFor="input_result" id="input_result_label">
            {labelText}
          </label>
          <input
            onChange={(e) => handleResChange(e, nosLeft)}
            type="text" id="input_result" size="2" maxLength="1"
            aria-labelledby="input_result_label" aria-required="true"
            ref={resInputField} autoFocus/>
          <br/>
          <label htmlFor="input_carry" id="input_carry_label">
            {carryText}
          </label>
          <input
            onChange={(e) => handleCarryChange(e, noOfDigits, nosLeft)}
            type="text" id="input_carry" size="2" maxLength="1"
            aria-labelledby="input_carry_label" aria-required="true"
            ref={carryInputField}/>
        </form>
      );
    }else{
      return (
        <>
        </>
      );
    }
  }

  const addButtonsToImdtSteps = () => {
    if(stepsGrid[0]["step"]!==""){
      let table = document.getElementById("idmtResultSteps").getElementsByTagName("table")[0]
      let trs = table.getElementsByTagName("tr");
      for(let trIdx in trs){
        let tr = trs[trIdx];
        if(tr instanceof HTMLElement && trIdx < trs.length-1){
          let td = tr.getElementsByTagName("td")[0];
          let btn = document.createElement("button");
          btn.innerHTML = "hier starten";
          btn.classList = "btn btn-secondary btn-sm";
          btn.id = "btn-" + trIdx;
          btn.addEventListener("click", () => startOver(trIdx));
          td.appendChild(btn);
        }
      }
    }
  }

  const showIdmtResults = () => {
    setShowAlert(false);
    document.getElementById("idmtResultSteps").style.display = "inline-block";
    addButtonsToImdtSteps()
  }

  const createIdmtResults = () => {
    let realResArr = realResult.toString().split("");
    while(realResArr.length < resArr.length){
      realResArr.unshift("&nbsp;"); // add " " before
    }

    let carries = carryArr.map(x => x || "0")
    carries.push("0");
    while(carries.length < resArr.length){
      carries.unshift("0"); // add "0" before
    }

    let foundComma = false;
    let stepsGridCopy = [];
    for (let i=0; i<resArr.length; i++) {
      let text = "";
      let trueNumbers = false;
      let idxNumbers = resArr.length - i - 1;
      let idxCarry = carries.length - i - 1;
      let realSum = 0;
      for (let j=0; j<numbers.length; j++) {
        let no = numbers[j][idxNumbers];
        if (no!=="." && no!=="&nbsp;"){
          trueNumbers = true;
          realSum += parseInt(no);
        }
        text += no
        if (j<numbers.length-1){
          text += " + "
        }
      }

      // ignore indexes without real digits
      if (resArr[idxNumbers]!=="&nbsp;" || (carries[idxCarry]!=="&nbsp;" & carries[idxCarry]!=="0")){
        trueNumbers = true;
      }

      // carry array has no "."
      if (resArr[idxNumbers] === "."){
        foundComma = true;
        trueNumbers = false;
      }
      if (foundComma){
        idxCarry += 1;
      }

      // add carry only if > 0
      if (carries[idxCarry]!=="0"){
        realSum += parseInt(carries[idxCarry]);
        text += " + " + carries[idxCarry] // + " Übertrag"
      }

      let realCarry = parseInt(realSum/10).toString()
      realSum = (realSum % 10).toString()
      text += " = "
      if (trueNumbers){
        text += resArr[idxNumbers]
        text += " und " + carries[idxCarry-1] + " Übertrag "
        text = text.replace(/&nbsp;/g, "0")
        text += resArr[idxNumbers]===realSum && carries[idxCarry-1]===realCarry ? "(Richtig) " : "(Falsch) ";

        stepsGridCopy.push({step: text});
      }
    }

    document.getElementById("stepsParagraph").innerHTML = "Rechenschritte: ";
    setStepsGrid(stepsGridCopy);

    let btnSubmit = document.createElement("button");
    btnSubmit.innerHTML = "Ergebnis abgeben";
    btnSubmit.addEventListener("click", finishCalculation);
    btnSubmit.classList = "btn btn-secondary btn-sm";
    btnSubmit.id = "btnSubmitSteps";
    document.getElementById("idmtResultSteps").appendChild(btnSubmit);

    document.getElementById("idmtResultSteps").tabIndex = 0;
    document.getElementById("idmtResultSteps").focus();

    document.getElementById("idmtResultSteps").style.display = "none";
  }

  const startOver = (idx) => {
    let invertedIdx = numbers[0].length - idx - 1;
    imdtResIdx = invertedIdx;

    let carryArrCopy = [...carryArr];
    let slicer = invertedIdx;
    if(resArr[0] !== "&nbsp;" && !resArr.includes(".")){
      slicer += 1;
    }else if(resArr[0] === "&nbsp;" && resArr.includes(".")){
      slicer -= 1;
    }
    carryArrCopy = carryArrCopy.slice(slicer);

    // reset result and carries until the chosen step
    let commaPos = resArr.indexOf(".");
    if(resArr.includes(".") && commaPos >= invertedIdx){
      imdtResIdx -= 1;
      resArr = resArr.slice(invertedIdx);
    }else{
      resArr = resArr.slice(invertedIdx + 1);
    }

    setCarryArr(carryArrCopy);

    document.getElementById("btnSubmitSteps").remove();
    document.getElementById("idmtResultSteps").style.display = "none";
  }

  const finishCalculation = () => {
    setShowAlert(false);
    document.getElementById("idmtResultSteps").innerHTML = "";
    let resCalc = resArr.filter(n => n !== "&nbsp;").join("");
    setResultsGrid([{number: resCalc}]);
    resCalc = parseFloat(resCalc);

    let message = ""
    if(resCalc === realResult){
      message = "Richtig!"
    }else{
      message = "Das ist leider falsch."
    }
    message = "<p>" + message + "</p>"
    document.getElementById("finishCalculation").innerHTML = message
  }

  return (
    <main>

      <h1>Addition</h1>

      <form onSubmit={(e) => handleSubmit(e)}>
        <label htmlFor="calculationInput">
          Rechnung:
        </label>
        <input
          type="text"
          id="calculationInput"
          onChange={(e) => handleInput(e)}
          aria-label="Rechnung"
          aria-required="true"
          ref={calculationInput}/>
        <input type="submit" value="berechnen"/>
      </form>

      <div id="overview">
        <DataGrid
          dataSource={numbersGrid}
          keyExpr="id"
          focusedRowEnabled={true}
          showBorders={true}
          showColumnHeaders={false}
        >
          <Column dataField="number" />
        </DataGrid>

        <hr></hr>

        <DataGrid
          dataSource={resultsGrid}
          focusedRowEnabled={true}
          showBorders={true}
          showColumnHeaders={false}
        >
          <Column dataField="number" />
        </DataGrid>
      </div>

      <div id="calculation">
        <ResultCarryForm
          handleResChange={handleResChange}
          handleCarryChange={handleCarryChange}/>
      </div>

      <div id="finishCalculation"></div>

      <div id="idmtResultSteps">
        <p id="stepsParagraph"></p>
        <DataGrid
          dataSource={stepsGrid}
          focusedRowEnabled={true}
          showBorders={true}
          showColumnHeaders={false}
          noDataText=""
        >
          <Column dataField="step" />
        </DataGrid>
      </div>

      <Alert
        showAlert={showAlert}
        finishCalc={finishCalculation}
        showIdmtResults={showIdmtResults}
      />

    </main>
  );
}

export default Addition;