defmodule EctoPSQLExtras.Mandelbrot do
  @behaviour EctoPSQLExtras

  def info do
    %{
      title: "The mandelbrot set",
      columns: [
        %{name: :art, type: :string}
      ]
    }
  end

  def query(_args \\ []) do
    """
    /* ECTO_PSQL_EXTRAS: The mandelbrot set */

    WITH RECURSIVE Z(IX, IY, CX, CY, X, Y, I) AS (
              SELECT IX, IY, X::float, Y::float, X::float, Y::float, 0
              FROM (select -2.2 + 0.031 * i, i from generate_series(0,101) as i) as xgen(x,ix),
                   (select -1.5 + 0.031 * i, i from generate_series(0,101) as i) as ygen(y,iy)
              UNION ALL
              SELECT IX, IY, CX, CY, X * X - Y * Y + CX AS X, Y * X * 2 + CY, I + 1
              FROM Z
              WHERE X * X + Y * Y < 16::float
              AND I < 100
        )
    SELECT array_to_string(array_agg(SUBSTRING(' .,,,-----++++%%%%@@@@#### ', LEAST(GREATEST(I,1),27), 1)),'') AS art
    FROM (
          SELECT IX, IY, MAX(I) AS I
          FROM Z
          GROUP BY IY, IX
          ORDER BY IY, IX
         ) AS ZT
    GROUP BY IY
    ORDER BY IY;
    """
  end
end
