#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# committer_parser.py
#
# Simple script to parse the output of 'git log' and generate some statistics.
# May leverage GitHub API in the future
#
'''
To use this commit parser script pipe git log into the stdin:

    git log | committer_parser.py -c -
'''
# pylint: disable=resource-leakage

# Import python libs
from __future__ import absolute_import
from __future__ import print_function
import sys
import getopt
import re
import email.utils
import datetime


class Usage(Exception):
    def __init__(self, msg):  # pylint: disable=W0231
        self.msg = 'committer_parser.py [-c | --contributor-detail] - |' \
                    ' <logfilename>\n'
        self.msg += '   : Parse commit log from git and print number of ' \
                    'commits and unique committers\n'
        self.msg += '   : by month.  Accepts a filename or reads from stdin.\n'
        self.msg += '   : -c | --contributor-detail generates output by ' \
                    'contributor, by month, in a tab-separated table\n'
        if msg:
            self.msg += '\n'
            self.msg += msg


def parse_date(datestr):
    d = email.utils.parsedate(datestr)
    return datetime.datetime(d[0], d[1], d[2], d[3], d[4], d[5], d[6])


def parse_gitlog(filename=None):
    '''
    Parse out the gitlog cli data
    '''
    results = {}
    commits = {}
    commits_by_contributor = {}

    if not filename or filename == '-':
        fh = sys.stdin
    else:
        fh = open(filename, 'r+')

    try:
        commitcount = 0
        for line in fh.readlines():
            line = line.rstrip()
            if line.startswith('commit '):
                new_commit = True
                commitcount += 1
                continue

            if line.startswith('Author:'):
                author = re.match(r'Author:\s+(.*)\s+<(.*)>', line)
                if author:
                    email = author.group(2)
                continue

            if line.startswith('Date:'):

                isodate = re.match(r'Date:\s+(.*)', line)
                d = parse_date(isodate.group(1))
                continue

            if len(line) < 2 and new_commit:
                new_commit = False
                key = '{0}-{1}'.format(d.year, str(d.month).zfill(2))

                if key not in results:
                    results[key] = []

                if key not in commits:
                    commits[key] = 0

                if email not in commits_by_contributor:
                    commits_by_contributor[email] = {}

                if key not in commits_by_contributor[email]:
                    commits_by_contributor[email][key] = 1
                else:
                    commits_by_contributor[email][key] += 1

                    if email not in results[key]:
                        results[key].append(email)

                    commits[key] += commitcount
                    commitcount = 0
    finally:
        fh.close()
    return (results, commits, commits_by_contributor)


def counts_by_contributor(commits_by_contributor, results):
    output = ''
    dates = sorted(results.keys())
    for d in dates:
        output += '\t{0}'.format(d)

    output += '\n'

    for email in sorted(commits_by_contributor.keys()):
        output += '\'{0}'.format(email)
        for d in dates:
            if d in commits_by_contributor[email]:
                output += '\t{0}'.format(commits_by_contributor[email][d])
            else:
                output += '\t'
        output += '\n'
    return output


def count_results(results, commits):
    result_str = ''
    print('Date\tContributors\tCommits')
    for k in sorted(results.keys()):
        result_str += '{0}\t{1}\t{2}'.format(k, len(results[k]), commits[k])
        result_str += '\n'
    return result_str


def main(argv=None):
    if argv is None:
        argv = sys.argv
    try:
        try:
            opts, args = getopt.getopt(argv[1:], 'hc', ['help', 'contributor-detail'])
            if not args:
                raise Usage('committer_parser.py needs a filename or \'-\' to read from stdin')
        except getopt.error as msg:
            raise Usage(msg)
    except Usage as err:
        print(err.msg, file=sys.stderr)
        return 2

    if opts:
        if '-h' in opts[0] or '--help' in opts[0]:
            return 0

    data, counts, commits_by_contributor = parse_gitlog(filename=args[0])

    if opts:
        if '-c' or '--contributor-detail':
            print(counts_by_contributor(commits_by_contributor, data))
    else:
        print(count_results(data, counts))


if __name__ == "__main__":
    sys.exit(main())