// target equation: Z = √(R^2 + (X_L - X_C)^2)
var xl = 0; // constant
var xc = 0; // constant
var r = new Array(); // independent variable
var z = new Array(); // dependent variable

function calcZ(r, xl, xc) {
  var x = xl - xc; // (X_L - X_C)
  var temp = r * r + x * x; // (R^2 + (X_L - X_C)^2)
  return Math.sqrt(temp);
}

function calculate() {
  xl = Number($("#xl").val());
  xc = Number($("#xc").val());
  var minr = Number($("#minr").val());
  var maxr = Number($("#maxr").val());
  var rval = 0;

  var valid = true;
  valid = validDeci(xl, "X<sub>L</sub>");
  valid = validDeci(xc, "X<sub>C</sub>");
  valid = validWhole(minr, "R's minimum");
  valid = validWhole(maxr, "R's maximum");
  if (maxr < minr) {
    //extra check, are the boundaries valid?
    valid = false;
    alert("The maximum cannot be less than the minimum!");
  }
  if (!valid) {
    return false;
  }

  var i = 0
  for (rval = minr; rval <= maxr; rval++) {
    r[i] = rval;
    z[i] = calcZ(rval, xl, xc);
    i++;
  }
  return true;
}

function validDeci(entry, label) {
  if (entry == "" || entry == null) {
  alert("Please enter a value for " + label + ".")
  return false;
  }
  if (/^\d+\.?\d*$/.test(entry)) {
    if (/\.{0,3}/) { // separated to provide more specific error messages 
      return true;
    } else {
      alert("Please round " + label + " to 3 places and try again."); 
      return false;
    }
  } else {
    alert("Please enter a numeric value for " + label + " and try again.");
    return false;
  }
}

function validWhole(entry, label) { // The max and min should be whole.
  if (entry == "" || entry == null) {
  alert("Please enter a value for " + label + ".")
  return false;
  }
  if (/^\d+$/.test(entry)) {
      return true;
    } else {
      alert(label + " must be a whole number. Please try again.");
      return false;
   }
}

function display() {
  var s = "";
  var match = false;
  s = "Z = &radic;((R)<sup>2</sup> + (" + xl + " - " + xc + ")<sup>2</sup><br>)";

  for (var i = 0; i < r.length; i++) {
    s += "When R = " + r[i] + ", Z = " + z[i].toFixed(3) + "<br>";
    if (r[i] == (xl - xc)) {
    match = true;
    }
  }
  if (match == true) {  // explains the topic further if the user set R correctly
  s += "You might have noticed that the formula for Z is simply the Pythagorean theorem. " +
  "R, X, and Z can be represented as sides of a right triangle, so when R = X, Z is always equal to R&radic;2. ";
  }
  values.innerHTML = s;
}

function plotVals() {
  var trace1 = {
    x: r,
    y: z,
    mode: "scatter",
    name: "Resistance (R)",
  }
  var data = [trace1]
  var layout = {
    title: "Effect of Resistance on Impedance",
    showlegend: true,
    width: 500,
    height: 500,
    paper_bgcolor: "#c4ffa7",
    plot_bgcolor: "#97EB9E",
    xaxis: {
      title: "R (ohms)",
    },
    yaxis: {
      title: "Z (ohms)",
    },
  }
  Plotly.newPlot("container", data, layout, {displayModeBar: false});
}

$(document).ready(function() {
 $("#calc").click(function () {
  if (calculate()) {
  display();
  }
 })

 $("#plot").click(function () {
  if (calculate()) {
  plotVals();
  }
})})