#!/usr/bin/env python

"""
serialization
"""

import argparse
import csv
import json
import sys
from StringIO import StringIO
from .cast import isstring
from .cast import unify


def dictlist2csv(list_of_dicts, header=None, fp=None):
    """
    convert a `list_of_dicts` to CSV

    `fp` should be a file-like object or  a path to a file
    that will be overwritten.  If `fp` is not provided, a
    string will be returned
    """

    if isstring(fp):
        with open(fp, 'w') as _fp:
            return dictlist2csv(list_of_dicts, _fp)

    return_string = False
    if fp is None:
        return_string = True
        fp = StringIO()

    # get the header
    if not list_of_dicts:
        return   # XXX what about return_string?  Good or bad?
    header = header or list_of_dicts[0].keys()

    # instantiate a writer
    writer = csv.DictWriter(fp, fieldnames=header)
    writer.writeheader()
    for row in list_of_dicts:
        row = {key: unify(value)
               for key, value in row.items()}
        try:
            writer.writerow(row)
        except (UnicodeDecodeError, UnicodeEncodeError) as e:
            print (row )
            print(e)
            raise

    if return_string:
        return fp.getvalue()


def dump_json(_json):
    """general purpose JSON front-end"""
    return json.dumps(_json, indent=2, sort_keys=True)


def append(filename, item):
    """append line-`item` to `filename`"""

    with open(filename, 'a') as f:
        f.write('{}\n'.format(item))


def main(args=sys.argv[1:]):
    """CLI"""

    # parse command line
    description = "convert a list of dicts in JSON format to CSV"
    parser = argparse.ArgumentParser(description=description)
    parser.add_argument('input',
                        type=argparse.FileType('r'),
                        help="path to file containing a list of flat dicts")
    parser.add_argument('-o', '--output', dest='output',
                        type=argparse.FileType('w'), default=sys.stdout,
                        help="file to write the CSV to [DEFAULT: stdout]")
    options = parser.parse_args(args)

    # parse input
    data = json.loads(options.input.read())
    assert type(data) == list

    # write output
    dictlist2csv(data, options.output)


if __name__ == '__main__':
    main()