#!/usr/bin/python
# -*- coding: utf8 -*-

try:
    import svgwrite as svg
except ImportError:
    print 'You need to install svgwrite: http://pypi.python.org/pypi/svgwrite/'
    exit(1)

from math import *

size = 220, 180
rx, ry = size[0] / 2 - 3, 50
v = float(ry) / float(rx)
l = 40
lw = 2

# document
doc = svg.Drawing('ehrenfest-paradox-disk.svg', size=size)
doc['stroke-width'] = lw
doc['fill'] = 'white'
doc['stroke'] = 'black'
doc['stroke-linejoin'] = 'miter'

# background
doc.add(doc.rect(id='background', insert=(0, 0), size=size, stroke='none'))

# disk
grad = doc.defs.add(doc.linearGradient(id='grad', start=('0%',0), end=('100%',0), gradientUnits='objectBoundingBox'))
grad.add_stop_color(offset=0, color='#f7f7f7')
grad.add_stop_color(offset=0.5, color='#dddddd')
grad.add_stop_color(offset=1, color='#999999')
disk = doc.add(doc.g(id='disk', transform='translate(' + str(size[0]/2) + ',' + str(ry+3) + ')'))
path = 'M ' + str(-rx) + ',0 V ' + str(l)
path += ' A ' + str(rx) + ',' + str(ry) + ' 0 1 0 ' + str(rx) + ',' + str(l)
path += ' V 0 Z'
disk.add(doc.path(d=path, fill='url(#grad)', stroke_linejoin='bevel'))
disk.add(doc.ellipse(center=(0, 0), r=(rx, ry), fill='#d8d8d8'))
disk.add(doc.ellipse(center=(0, 0), r=(2, 2.0*v), fill='black'))
radius_angle = radians(-40.0)
csr = cos(radius_angle), sin(radius_angle)
disk.add(doc.line(start=(0,0), end=(rx*csr[0], ry*csr[1]),
    stroke_width=lw*sqrt(csr[0]**2 + (v*csr[1])**2)))
# round arrow
ar, aw, ah, ab, al, a0, a1 = 0.7*rx, 7, 2, 1, 3, radians(160), radians(100)
apath = 'M ' + str(ar*cos(a0)) + ',' + str(ar*sin(a0))
apath += ' A %f,%f 0 0 0 %f,%f' % (ar, ar, ar*cos(a1), ar*sin(a1))
arrowhead = doc.defs.add(doc.marker(id='arrowhead', orient='auto', overflow='visible'))
arrowhead.add(doc.path(fill='black', stroke='none',
    d='M 0.0,0.0 L %f,%f L %f,0 L %f,%f L 0,0 z'%(-ab, -ah, al, -ab, ah)))
arrow = doc.path(d=apath, fill='none', stroke_width=aw, transform='scale(1,' + str(v) + ')')
arrow['marker-end'] = arrowhead.get_funciri()
disk.add(arrow)

# ruler
ruler = doc.defs.add(doc.g(id='ruler'))
rw, rh, rn = 32, 14, 4
ruler.add(doc.path(d='M 0,0 H %f V %f H 0 V 0 Z'%(rw+3, rh),
    fill='white', stroke='none'))
squares = ''
for i in range(rn/2):
    squares += 'M %f,0 H %f V %f H %f V 0 Z '%(i*rw*2./rn, (1+i*2.)*rw/rn, rh, i*rw*2./rn)
ruler.add(doc.path(d=squares, fill='red', stroke='none'))
ruleredge = 'M %f,0 H %f V %f H 0 V 0 H %f V %f'%(rw, 3+rw, rh, rw, rh)
for i in range(1, rn):
    ruleredge += ' M %f,0 V %f'%(i*rw/float(rn), rh/2.)
ruler.add(doc.path(d=ruleredge, fill='none', stroke='black', stroke_width=lw, stroke_linecap='round'))
rulers = doc.add(doc.g(id='rulers'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(0.89, 0.42, 0, 1, 17, 134)'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(1.00, 0.16, 0, 1, 54, 150)'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(1.00, 0.00, 0, 1, 95, 156)'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(0.53, 0.33, 0, 1, 16.53, 91)'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(0.57, 0.19, 0, 1, 39, 104)'))
rulers.add(doc.use(ruler, insert=(0, 0), transform='matrix(0.60, 0.10, 0, 1, 63, 112)'))
doc.add(doc.path(d='M 16.5,106 V 133', fill='none', stroke_width=1, stroke_dasharray='4,2'))
doc.add(doc.path(d='M 84.5,130 V 154', fill='none', stroke_width=1, stroke_dasharray='4,2'))

# text
doc.add(doc.path(id='omega', stroke='none', fill='black',
transform='translate(70,70) scale(0.03,-0.03)',
d='M 13 0 m 251 82 c 9 -63 43 -93 94 -93 c 59 0 113 38 153 93 c 75 104 94 \
255 94 289 c 0 71 -37 71 -43 71 c -25 0 -50 -26 -50 -48 c 0 -13 6 -19 15 -27 \
c 32 -33 35 -65 35 -87 c 0 -85 -85 -219 -190 -219 c -9 0 -37 0 -55 23 c -12 \
16 -20 35 -20 55 c 0 3 0 5 6 16 c 19 45 33 100 33 113 c 0 12 -7 23 -21 23 c \
-11 0 -20 -9 -28 -25 c -2 -5 -14 -49 -21 -101 c -2 -18 -2 -20 -9 -27 c -44 \
-61 -90 -77 -124 -77 c -66 0 -88 55 -88 114 c 0 75 37 158 84 225 c 10 14 10 \
16 10 19 c 0 8 -6 12 -12 12 c -16 0 -62 -88 -76 -120 c -37 -89 -38 -171 -38 \
-180 c 0 -80 30 -142 106 -142 c 65 0 113 46 145 93 z'))
doc.add(doc.path(id='r', stroke='none', fill='black',
transform='translate(152,60) scale(0.03,-0.03)',
d='M 29 0 m 59 59 c -3 -15 -9 -38 -9 -43 c 0 -18 14 -27 29 -27 c 12 0 30 8 \
37 28 c 2 4 36 140 40 158 c 8 33 26 103 32 130 c 4 13 32 60 56 82 c 8 7 37 33 \
80 33 c 26 0 41 -12 42 -12 c -30 -5 -52 -29 -52 -55 c 0 -16 11 -35 38 -35 c \
27 0 55 23 55 59 c 0 35 -32 65 -83 65 c -65 0 -109 -49 -128 -77 c -8 45 -44 \
77 -91 77 c -46 0 -65 -39 -74 -57 c -18 -34 -31 -94 -31 -97 c 0 -10 10 -10 12 \
-10 c 10 0 11 1 17 23 c 17 71 37 119 73 119 c 17 0 31 -8 31 -46 c 0 -21 -3 \
-32 -16 -84 z'))

doc.save()