import os
import io
import json
import re
import os.path
import pathlib

import six
from .attrs import TAG, HEAD, DEP, ENT_IOB, ENT_TYPE


LANGUAGES = {}
_data_path = pathlib.Path(__file__).parent / 'data'


def set_lang_class(name, cls):
    global LANGUAGES
    LANGUAGES[name] = cls


def get_lang_class(name):
    lang = re.split('[^a-zA-Z0-9]', name, 1)[0]
    if lang not in LANGUAGES:
        raise RuntimeError('Language not supported: %s' % lang)
    return LANGUAGES[lang]


def get_data_path():
    return _data_path


def set_data_path(path):
    global _data_path
    if isinstance(path, basestring):
        path = pathlib.Path(path)
    _data_path = path



def match_best_version(target_name, target_version, path):
    path = path if not isinstance(path, basestring) else pathlib.Path(path)
    matches = []
    for data_name in path.iterdir():
        name, version = split_data_name(data_name.parts[-1])
        if name == target_name and constraint_match(target_version, version):
            matches.append((tuple(float(v) for v in version.split('.')), data_name))
    if matches:
        return pathlib.Path(max(matches)[1])
    else:
        return None


def split_data_name(name):
    return name.split('-', 1) if '-' in name else (name, '')


def constraint_match(constraint_string, version):
    # From http://github.com/spacy-io/sputnik
    if not constraint_string:
        return True

    constraints = [c.strip() for c in constraint_string.split(',') if c.strip()]

    for c in constraints:
        if not re.match(r'[><=][=]?\d+(\.\d+)*', c):
            raise ValueError('invalid constraint: %s' % c)

    return all(semver.match(version, c) for c in constraints)


def read_regex(path):
    path = path if not isinstance(path, basestring) else pathlib.Path(path)
    with path.open() as file_:
        entries = file_.read().split('\n')
    expression = '|'.join(['^' + re.escape(piece) for piece in entries if piece.strip()])
    return re.compile(expression)


def read_prefix_regex(path):
    path = path if not isinstance(path, basestring) else pathlib.Path(path)
    with path.open() as file_:
        entries = file_.read().split('\n')
    expression = '|'.join(['^' + re.escape(piece) for piece in entries if piece.strip()])
    return re.compile(expression)


def read_suffix_regex(path):
    path = path if not isinstance(path, basestring) else pathlib.Path(path)
    with path.open() as file_:
        entries = file_.read().split('\n')
    expression = '|'.join([piece + '$' for piece in entries if piece.strip()])
    return re.compile(expression)


def read_infix_regex(path):
    path = path if not isinstance(path, basestring) else pathlib.Path(path)
    with path.open() as file_:
        entries = file_.read().split('\n')
    expression = '|'.join([piece for piece in entries if piece.strip()])
    return re.compile(expression)


def normalize_slice(length, start, stop, step=None):
    if not (step is None or step == 1):
        raise ValueError("Stepped slices not supported in Span objects."
                         "Try: list(tokens)[start:stop:step] instead.")
    if start is None:
       start = 0
    elif start < 0:
       start += length
    start = min(length, max(0, start))

    if stop is None:
       stop = length
    elif stop < 0:
       stop += length
    stop = min(length, max(start, stop))

    assert 0 <= start <= stop <= length
    return start, stop


def utf8open(loc, mode='r'):
    return io.open(loc, mode, encoding='utf8')