#!/usr/bin/python

"""
Output the Well-Known-Text[1] representation of an n-gon, centered at
(0,0).

The parameter n is passed as a required command-line option. The
radius of the n-gon is an optional argument.

[1] http://en.wikipedia.org/wiki/Well-known_text
"""

import math
import site
import sys
from optparse import OptionParser
import os

# Basically, add '../src' to our path.
# Needed for the imports that follow.
site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')

import CLI
import ExitCodes
import Geometry
import StringUtils

usage = '%prog [options] <number of sides>'
fmtr = CLI.VerbatimHelpFormatter()
parser = OptionParser(usage, formatter=fmtr)

# Use this module's docstring as the description.
parser.description = __doc__


parser.add_option('-r',
                  '--radius',
                  type="float",
                  help="The radius of the n-gon. Defaults to 1.0.",
                  default=1.0)


(options, args) = parser.parse_args()

if (len(args) < 1) or (not StringUtils.is_integer(args[0])):
    print "\nERROR: You must supply the number of sides, n.\n"
    parser.print_help()
    print '' # Print a newline.
    raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)

# The conversion of n to int is safe, since it passed is_integer
# above.
n = int(args[0])
r = options.radius

# Each new coordinate is going to be separated from the previous by
# angle_delta radians.
angle_delta = 2*math.pi / float(n)

# The set of coordinates, as two-tuples. We already know the first
# one--it's just cos/sin of 0.
coords = [(r, 0)]

for coord_idx in range(1, n):
    angle = coord_idx * angle_delta    
    x = r * math.cos(angle)
    y = r * math.sin(angle)
    coords.append((x, y))

# A well-known-text polygon must be closed, i.e. the last coordinate
# must equal the first. So, we're missing a coordinate, but the
# Polygon class will handle it for us.
p = Geometry.Polygon(coords)
print p.wkt()