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package spire.example

import spire.implicits._
import spire.math._

import scala.annotation.tailrec

object MandelbrotDemo {
  /**
   * Compute whether the complex number c stays contained within a radius-2
   * circle after 'limit' iterations.
   */
  def mandelbrot(c: Complex[Double], limit: Int): Int = {
    @tailrec def loop(z: Complex[Double], n: Int): Int =
      if (n >= limit) n
      else if (z.abs > 2.0) n - 1
      else loop(z * z + c, n + 1)

    loop(c, 1)
  }

  /**
   * Print an ASCII approximation of the 4x4 box from -2-2i to 2+2i.
   */
  def main(args: Array[String]) {
    val res = 26 // number of iterations to try before including pt in the set
    val rows = if (args.isEmpty) 20 else args(0).toInt // rows to print
    val cols = rows * 2 // cols to print. most fonts are roughly 1:2

    val h = 4.0 / rows // height per pixel character
    val w = 4.0 / cols // width per pixel character
    val x0 = -2.0 // starting x value (x offset)
    val y0 = -2.0 // starting y value (y offset)

    def pt(x: Int, y: Int) = Complex(x * w + x0, y * h + y0)
    def display(s: String, n: Int) = print(Xterm.rainbow(n) + s)

    // render the area in ASCII, using o's and spaces.
    cfor(0)(_ <= rows, _ + 1) { y =>
      cfor(0)(_ <= cols, _ + 1) { x =>
        // if n