import cStringIO
import csv
import codecs
import decimal
import datetime
import json
import re


def slugify(s):
    return re.sub('[^a-z0-9_\-]+', '-', s.lower())


class JSONEncoder(json.JSONEncoder):
    """Custom JSON encoding class, to handle Decimal and datetime.date instances.
    """

    def default(self, o):
        if isinstance(o, decimal.Decimal):
            return float(o)

        if isinstance(o, datetime.date):
            return o.isoformat()

        super(JSONEncoder, self).default(o)


def json_dumps(data):
    return json.dumps(data, cls=JSONEncoder)


class UnicodeWriter:
    """
    A CSV writer which will write rows to CSV file "f",
    which is encoded in the given encoding.
    """

    def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
        # Redirect output to a queue
        self.queue = cStringIO.StringIO()
        self.writer = csv.writer(self.queue, dialect=dialect, **kwds)
        self.stream = f
        self.encoder = codecs.getincrementalencoder(encoding)()

    def _encode_utf8(self, val):
        if isinstance(val, (unicode, str)):
            return val.encode('utf-8')

        return val

    def writerow(self, row):
        self.writer.writerow([self._encode_utf8(s) for s in row])
        # Fetch UTF-8 output from the queue ...
        data = self.queue.getvalue()
        data = data.decode("utf-8")
        # ... and reencode it into the target encoding
        data = self.encoder.encode(data)
        # write to the target stream
        self.stream.write(data)
        # empty queue
        self.queue.truncate(0)

    def writerows(self, rows):
        for row in rows:
            self.writerow(row)