/**
 * Main draw routine.
 *
 * This routine draws about the lines representing the data, about 27500 
 * points at once and represents the main critical section.  Previous
 * drawn values are remembered and used, together with the increment
 * paramenter, to render frames of animation.
 *
 * Optimizations include precalculating the data, array access vs. 
 * refinement, and using a single path and stroke.
 */
function draw (type, increment) {

  var
    year    = C_MAP[YEAR],
    index   = C_MAP[type],
    pIndex  = C_MAP[PREVIOUS],
    names   = F500.names,
    values  = F500.values,
    length1 = values.length,
    dec     = 1 - increment,
    length2,
    data,
    nameWidth,
    i, j,
    x, y;

  context.clearRect(0, 0, width, height);
  context.beginPath();

  for (i = 0; i < length1; i++) {

    data      = values[i];
    length2   = data.length;
    nameWidth = names[i].length / 4;

    for (j = 0; j < length2; j++) {
      x = data[j][year];
      data[j][pIndex] = y =
        increment * data[j][index] + dec * (data[j][pIndex] || data[j][index]);
      context.moveTo(x - nameWidth, y);
      context.lineTo(x + nameWidth, y);
    }
  }

  context.closePath();
  context.stroke();

  if (selected !== null)
    drawCompany(type, selected, increment);
}

/**
 * Precalculate revenue, price and inflation.
 *
 * Revenue and profit are stored as actual values (in millions).  This value
 * is displayed to the user in the company popup.  To draw the data, these
 * values need to be translated to their y coordinates in the log scale.
 *
 * This translation is precalculated for speed at draw time and calculated
 * client-side to keep the data size down.
 *
 * Run after first draw.
 */
function calculate() {

  var
    rBase     = height / Math.log(6e5),
    pBase     = height / ( 2 * Math.log(1e6) ),
    rIndex    = D_MAP[REVENUE],
    pIndex    = D_MAP[PROFIT],
    yIndex    = D_MAP[YEAR],
    values    = F500.values,
    inflation = F500.inflation,
    half      = height / 2,
    length1   = values.length,
    length2,
    data,
    datum,
    year,
    v,
    i, j;

  for (i = 0; i < length1; i++) {

    data = values[i];
    length2 = data.length;

    for (j = 0; j < length2; j++) {
      datum = data[j];
      year = datum[yIndex];
      datum.push(Math.round(height - Math.log(datum[rIndex] - 40) * rBase));
      datum.push(Math.round(height - Math.log(datum[rIndex] * inflation[year] - 40) * rBase));
      v = datum[pIndex];
      if (v < 0) {
        datum.push(Math.round(half + Math.log(-10 * v) * pBase));
        datum.push(Math.round(half + Math.log(-10 * v * inflation[year]) * pBase));
      } else {
        datum.push(Math.round(half - Math.log(10 * v) * pBase));
        datum.push(Math.round(half - Math.log(10 * v * inflation[year]) * pBase));
      }
    }
  }
}