// NOTE: SHEET IS UNDER BERKELEY ACC

/**
 * Calculate GPA given grades & units 
 * @param {*} grades Grades column
 * @param {*} units Class units (weights) column
 */
function GRADEPOINTS(grades, units) {

  if (grades.length != units.length) {
    throw Error("Grades & Units columns must have the same length")
  }
  else if (grades[0].length != 1 || units[0].length != 1) {
    throw Error("Grades & Units each must be single columns")
  }

  let gradeMap = {
    "A+": 4.0,
    "A": 4.0,
    "A-": 3.7,
    "B+": 3.3,
    "B": 3,
    "B-": 2.7,
    "C+": 2.3,
    "C": 2.0,
    "C-": 1.7,
    "D+": 1.3,
    "D": 1,
    "D-": 0.7,
    "F": 0.0,
  }

  let gpSum = 0;
  let denom = 0;
  for (let i = 0; i < grades.length; i++) {
    let grade = grades[i][0];
    let unitCount = units[i][0]
    if (Object.keys(gradeMap).includes(grade)) {
      gpSum += gradeMap[grade] * unitCount;
      denom += unitCount;
    }
  }

  if (denom == 0) {
    throw Error("No valid values found in grades col")
  }

  return gpSum / denom;
}