"""
This file contains functions to deal with Bibtex files and edit them.
"""
import bibtexparser
import re

from codecs import open
from libbmc import tools


default_papers_filename_mask = "{first}_{last}-{journal}-{year}{arxiv_version}"
default_books_filename_mask = "{authors} - {title}"


def dict2BibTeX(data):
    """
    Convert a single BibTeX entry dict to a BibTeX string.

    :param data: A dict representing BibTeX entry, as the ones from \
            ``bibtexparser`` output.
    :return: A formatted BibTeX string.
    """
    """Convert a single bibtex entry dict to bibtex string"""
    bibtex = '@' + data['ENTRYTYPE'] + '{' + data['ID'] + ",\n"

    for field in [i for i in sorted(data) if i not in ['ENTRYTYPE', 'ID']]:
        bibtex += "\t" + field + "={" + data[field] + "},\n"
    bibtex += "}\n"
    return bibtex


def write(filename, data):
    """
    Create a new BibTeX file.

    :param filename: The name of the BibTeX file to write.
    :param data: A list of dict representing BibTeX entries, as the ones from \
            ``bibtexparser`` output.
    """
    bibtex = "\n".join([dict2BibTeX(i) for i in data])
    with open(filename, 'w', encoding='utf-8') as fh:
        fh.write(bibtex)


def append(filename, data):
    """
    Append some entries to a bibtex file.

    :param filename: The name of the BibTeX file to edit.
    :param data: A list of dict representing BibTeX entries, as the ones from \
            ``bibtexparser`` output.
    """
    with open(filename, 'a', encoding="utf-8") as fh:
        fh.write("\n".join([dict2BibTeX(i) for i in data]))


def edit(filename, identifier, data):
    """
    Update an entry in a BibTeX file.

    :param filename: The name of the BibTeX file to edit.
    :param identifier: The id of the entry to update, in the BibTeX file.
    :param data: A dict associating fields and updated values. Fields present \
            in the BibTeX file but not in this dict will be kept as is.
    """
    # Get current bibtex
    with open(filename, 'r', encoding="utf-8") as fh:
        bibtex = bibtexparser.load(fh)
    bibtex = bibtex.entries_dict

    # Update it
    for k in data:
        bibtex[identifier][k] = data[k]

    # Write the resulting BibTeX
    write(filename, bibtex)


def replace(filename, identifier, data):
    """
    Replace an entry in a BibTeX file.

    :param filename: The name of the BibTeX file to edit.
    :param identifier: The id of the entry to replace, in the BibTeX file.
    :param data: A dict representing a BibTeX entry, as the one from \
            ``bibtexparser`` output.
    """
    # Get current bibtex
    with open(filename, 'r', encoding="utf-8") as fh:
        bibtex = bibtexparser.load(fh)
    bibtex = bibtex.entries_dict

    # Update the bibtex
    bibtex[identifier] = data

    # Write the resulting BibTeX
    write(filename, bibtex)


def delete(filename, identifier):
    """
    Delete an entry in a BibTeX file.

    :param filename: The name of the BibTeX file to edit.
    :param identifier: The id of the entry to delete, in the BibTeX file.
    """
    # Get current bibtex
    with open(filename, 'r', encoding="utf-8") as fh:
        bibtex = bibtexparser.load(fh)
    bibtex = bibtex.entries_dict

    # Delete the bibtex entry
    del(bibtex[identifier])

    # Write the resulting BibTeX
    write(filename, bibtex)


def get(filename, ignore_fields=[]):
    """
    Get all entries from a BibTeX file.

    :param filename: The name of the BibTeX file.
    :param ignore_fields: An optional list of fields to strip from the BibTeX \
            file.

    :returns: A list of ``bibtexparser`` dicts representing the fetched \
            entries.
    """
    # Open bibtex file
    with open(filename, 'r', encoding="utf-8") as fh:
        bibtex = bibtexparser.load(fh)
    bibtex = bibtex.entries_dict

    # Clean the entry dict if necessary
    bibtex = [{k: entry[k] for k in entry if k not in ignore_fields}
              for entry in bibtex]

    return bibtex


def get_entry(filename, identifier, ignore_fields=[]):
    """
    Get an entry from a BibTeX file.

    :param filename: The name of the BibTeX file.
    :param identifier: An id of the entry to fetch, in the BibTeX file.
    :param ignore_fields: An optional list of fields to strip from the BibTeX \
            file.

    :returns: A ``bibtexparser`` dict representing the fetched entry. \
            ``None`` if entry was not found.
    """
    # Open bibtex file
    with open(filename, 'r', encoding="utf-8") as fh:
        bibtex = bibtexparser.load(fh)
    bibtex = bibtex.entries_dict

    try:
        # Try to fetch the matching entry dict
        entry = bibtex[identifier]
    except KeyError:
        # If none found, return None
        return None

    # Clean the entry dict if necessary
    entry = {k: entry[k] for k in entry if k not in ignore_fields}

    return entry


def to_filename(bibtex, mask=default_papers_filename_mask):
    """
    Convert a bibtex entry to a formatted filename according to a given mask.

    :param bibtex: A dict representing a BibTeX entry, as the one from \
            ``bibtexparser`` output.
    :param mask: A Python format string.

    :returns: A formatted filename.
    """
    authors = re.split(' and ', bibtex['author'])

    filename = mask
    filename = filename.format(journal=bibtex.get("journal", default=""))
    filename = filename.format(title=bibtex.get("title", default=""))
    filename = filename.format(year=bibtex.get("year", default=""))

    filename = filename.format(first=authors[0].split(',')[0].strip())
    filename = filename.format(last=authors[-1].split(',')[0].strip())
    filename = filename.format(authors=", ".join(
        [i.split(',')[0].strip() for i in authors]))

    arxiv_version = ""
    if "eprint" in bibtex:
        arxiv_version = '-' + bibtex['eprint'][bibtex['eprint'].rfind('v'):]
    filename = filename.format(arxiv_version=arxiv_version)

    return tools.slugify(filename)