// main flow
var og = [
  // example
  [0, 0, 2, 4, 2, 8],
  [1, 2, 4, 5, 3, -9],
  [-2, -4, -5, -4, 3, 6],
];

addMatrix(og, 3, 6, "step");
var ogMatrix = document.querySelector("div.ERO div.step");
ogMatrix.setAttribute("contentEditable", "true");
gaussianElimination(og, 3, 6);
document.getElementById("updateMatrix").addEventListener(
  "click",
  function () {
    console.log("input event fired");
    var thatTable = document.querySelector("table");
    var containerERO = document.querySelector("div.ERO");
    var oldstuff = document.querySelectorAll("div.step");
    oldstuff.forEach((x) => x.parentNode.removeChild(x));

    var newMatrix = tableToArray(thatTable);
    addMatrix(newMatrix, 3, 6, "step");
    var ogMatrix = document.querySelector("div.ERO div.step");
    ogMatrix.setAttribute("contentEditable", "true");
    gaussianElimination(newMatrix, 3, 6);
  },
  false
);

function tableToArray(table) {
  // for retrieving new array from html
  var result = [];
  var rows = table.rows;
  var cells, t;

  // Iterate over rows
  for (var i = 0, iLen = rows.length; i < iLen; i++) {
    cells = rows[i].cells;
    t = [];

    // Iterate over cells
    for (var j = 0, jLen = cells.length; j < jLen; j++) {
      t.push(parseInt(cells[j].textContent));
    }
    result.push(t);
  }
  return result;
}
function gaussianElimination(matrix, row, col) {
  var nonzeroFlag;
  var currRow = 0;
  var factor;
  // step 1 locate the leftmost column that does not consist entirely of zero
  for (var i = 0; i < col; i++) {
    nonzeroFlag = false;
    for (let j = currRow; j < row; j++) {
      var curr = matrix[j][i];
      if (curr != 0) {
        nonzeroFlag = true;
      }
    }

    if (!nonzeroFlag) {
      // if entire column is zero, move to next column
      continue;
    } else {
      // step 2 interchange top row with another row to get top row to nonzero
      for (let k = currRow; k < row; k++) {
        if (matrix[currRow][i] != 0) {
          // if top row is already nonzero, do nothing
          break;
        }
        if (matrix[k][i] == 0) {
          // if current row is zero, do nothing
          continue;
        }
        let temp = matrix[k];
        matrix[k] = matrix[currRow];
        matrix[currRow] = temp;
        addMatrix(matrix, 3, 6, "step");
        break;
      }
      // console.log(JSON.parse(JSON.stringify(matrix)));
      // step 3 for each row below the top row, add a suitable multiple of the top row to it,
      // so that the entry below the leading entry of the top row becomes zero
      for (var a = currRow + 1; a < row; a++) {
        if (matrix[a][i] == 0) {
          // leading column is already zero, do nothing
          continue;
        }
        if (
          (matrix[a][i] < 0 && matrix[currRow][i] > 0) ||
          (matrix[a][i] > 0 && matrix[currRow][i] < 0)
        ) {
          factor = Math.abs(matrix[a][i] / matrix[currRow][i]);
        } else {
          factor = matrix[a][i] / matrix[currRow][i];
          factor = -factor;
        }
        for (var u = i; u < col; u++) {
          matrix[a][u] = matrix[a][u] + matrix[currRow][u] * factor;
        }
        addMatrix(matrix, 3, 6, "step");
      }
      currRow++;

      // console.log(JSON.parse(JSON.stringify(matrix)));
    }
  }
}

function createAugmentedMatrix(row, column) {
  const reducer = (accumulator, currentValue) => accumulator + currentValue;
  var items = Array(row);
  for (var i = 0; i < row; i++) {
    var temp = Array(column);
    for (var j = 0; j < column - 1; j++) {
      temp[j] = getRandomInt(-10, 10);
    }
    temp[column - 1] = 0;
    temp[column - 1] = temp.reduce(reducer);
    items[i] = temp;
  }
  return items;
}

function addMatrix(items, row, col, which) {
  // add matrix into dom
  var table = document.createElement("div");
  table.setAttribute("class", which);
  var innerTable = document.createElement("table");
  for (var i = 0; i < row; i++) {
    var innerRow = document.createElement("tr");
    for (var j = 0; j < col; j++) {
      var innerCell = document.createElement("td");
      var temp = items[i][j];
      innerCell.innerHTML = temp;
      innerRow.appendChild(innerCell);
    }
    innerTable.appendChild(innerRow);
  }
  table.appendChild(innerTable);
  var containerERO = document.querySelector("div.ERO");
  containerERO.appendChild(table);
}