import urllib
import json
import copy
from collections import OrderedDict

import matplotlib.pyplot as plt
from matplotlib.ticker import FuncFormatter

import dateutil.parser
from datetime import datetime, timedelta

cache = '_pr_cache.txt'

# Obtain release dates using, e.g.,
#
#  git log v0.4 -n 1 --format='%ai'
#
# The first two releases are commented out.
# This was in the era before PRs.
#
releases = OrderedDict([
    #('0.1', u'2009-10-07 13:52:19 +0200'),
    #('0.2', u'2009-11-12 14:48:45 +0200'),
    ('0.3', u'2011-10-10 03:28:47 -0700'),
    ('0.4', u'2011-12-03 14:31:32 -0800')])

for r in releases:
    releases[r] = dateutil.parser.parse(releases[r])

def fetch_PRs(user='scikits-image', repo='scikits-image', state='open'):
    params = {'state': state,
              'per_page': 100,
              'page': 1}

    data = []
    page_data = True

    while page_data:
        config = {'user': user,
                  'repo': repo,
                  'params': urllib.urlencode(params)}

        fetch_status = 'Fetching page %(page)d (state=%(state)s)' % params + \
                       ' from %(user)s/%(repo)s...' % config
        print fetch_status

        f = urllib.urlopen(
            'https://api.github.com/repos/%(user)s/%(repo)s/pulls?%(params)s' \
            % config
        )

        params['page'] += 1

        page_data = json.loads(f.read())

        if 'message' in page_data and page_data['message'] == "Not Found":
            page_data = []
            print 'Warning: Repo not found (%(user)s/%(repo)s)' % config
        else:
            data.extend(page_data)

    return data

try:
    PRs = json.loads(open(cache, 'r').read())
    print 'Loaded PRs from cache...'

except IOError:
    PRs = fetch_PRs(user='stefanv', repo='scikits.image', state='closed')
    PRs.extend(fetch_PRs(state='open'))
    PRs.extend(fetch_PRs(state='closed'))

    cf = open(cache, 'w')
    cf.write(json.dumps(PRs))
    cf.flush()

nrs = [pr['number'] for pr in PRs]
print 'Processing %d pull requests...' % len(nrs)

dates = [dateutil.parser.parse(pr['created_at']) for pr in PRs]

epoch = datetime(2009, 1, 1, tzinfo=dates[0].tzinfo)

def seconds_from_epoch(dates):
    seconds = [(dt - epoch).total_seconds() for dt in dates]
    return seconds

dates_f = seconds_from_epoch(dates)

def date_formatter(value, _):
    dt = epoch + timedelta(seconds=value)
    return dt.strftime('%Y/%m/%d')

plt.figure(figsize=(7, 5))
plt.hist(dates_f, bins=80)

ax = plt.gca()
ax.xaxis.set_major_formatter(FuncFormatter(date_formatter))

labels = ax.get_xticklabels()
for l in labels:
    l.set_rotation(40)


for version, date in releases.items():
    date = seconds_from_epoch([date])[0]
    plt.axvline(date, color='r', label=version)

plt.title('Pull request activity').set_y(1.05)
plt.xlabel('Date')
plt.ylabel('PRs created')
plt.legend(loc=2, title='Release')
plt.subplots_adjust(top=0.875, bottom=0.225)

plt.savefig('PRs.png')

plt.show()

Add script to plot GitHub pull-request activity.