from six import BytesIO, text_type
from six.moves.urllib.parse import urlparse, urlencode, urlunparse
import copy
import json
import zlib

from .util import CaseInsensitiveDict


def replace_headers(request, replacements):
    """
    Replace headers in request according to replacements. The replacements
    should be a list of (key, value) pairs where the value can be any of:
      1. A simple replacement string value.
      2. None to remove the given header.
      3. A callable which accepts (key, value, request) and returns a string
         value or None.
    """
    new_headers = request.headers.copy()
    for k, rv in replacements:
        if k in new_headers:
            ov = new_headers.pop(k)
            if callable(rv):
                rv = rv(key=k, value=ov, request=request)
            if rv is not None:
                new_headers[k] = rv
    request.headers = new_headers
    return request


def remove_headers(request, headers_to_remove):
    """
    Wrap replace_headers() for API backward compatibility.
    """
    replacements = [(k, None) for k in headers_to_remove]
    return replace_headers(request, replacements)


def replace_query_parameters(request, replacements):
    """
    Replace query parameters in request according to replacements. The
    replacements should be a list of (key, value) pairs where the value can be
    any of:
      1. A simple replacement string value.
      2. None to remove the given header.
      3. A callable which accepts (key, value, request) and returns a string
         value or None.
    """
    query = request.query
    new_query = []
    replacements = dict(replacements)
    for k, ov in query:
        if k not in replacements:
            new_query.append((k, ov))
        else:
            rv = replacements[k]
            if callable(rv):
                rv = rv(key=k, value=ov, request=request)
            if rv is not None:
                new_query.append((k, rv))
    uri_parts = list(urlparse(request.uri))
    uri_parts[4] = urlencode(new_query)
    request.uri = urlunparse(uri_parts)
    return request


def remove_query_parameters(request, query_parameters_to_remove):
    """
    Wrap replace_query_parameters() for API backward compatibility.
    """
    replacements = [(k, None) for k in query_parameters_to_remove]
    return replace_query_parameters(request, replacements)


def replace_post_data_parameters(request, replacements):
    """
    Replace post data in request--either form data or json--according to
    replacements. The replacements should be a list of (key, value) pairs where
    the value can be any of:
      1. A simple replacement string value.
      2. None to remove the given header.
      3. A callable which accepts (key, value, request) and returns a string
         value or None.
    """
    replacements = dict(replacements)
    if request.method == 'POST' and not isinstance(request.body, BytesIO):
        if request.headers.get('Content-Type') == 'application/json':
            json_data = json.loads(request.body.decode('utf-8'))
            for k, rv in replacements.items():
                if k in json_data:
                    ov = json_data.pop(k)
                    if callable(rv):
                        rv = rv(key=k, value=ov, request=request)
                    if rv is not None:
                        json_data[k] = rv
            request.body = json.dumps(json_data).encode('utf-8')
        else:
            if isinstance(request.body, text_type):
                request.body = request.body.encode('utf-8')
            splits = [p.partition(b'=') for p in request.body.split(b'&')]
            new_splits = []
            for k, sep, ov in splits:
                if sep is None:
                    new_splits.append((k, sep, ov))
                else:
                    rk = k.decode('utf-8')
                    if rk not in replacements:
                        new_splits.append((k, sep, ov))
                    else:
                        rv = replacements[rk]
                        if callable(rv):
                            rv = rv(key=rk, value=ov.decode('utf-8'),
                                    request=request)
                        if rv is not None:
                            new_splits.append((k, sep, rv.encode('utf-8')))
            request.body = b'&'.join(k if sep is None else b''.join([k, sep, v])
                                     for k, sep, v in new_splits)
    return request


def remove_post_data_parameters(request, post_data_parameters_to_remove):
    """
    Wrap replace_post_data_parameters() for API backward compatibility.
    """
    replacements = [(k, None) for k in post_data_parameters_to_remove]
    return replace_post_data_parameters(request, replacements)


def decode_response(response):
    """
    If the response is compressed with gzip or deflate:
      1. decompress the response body
      2. delete the content-encoding header
      3. update content-length header to decompressed length
    """
    def is_compressed(headers):
        encoding = headers.get('content-encoding', [])
        return encoding and encoding[0] in ('gzip', 'deflate')

    def decompress_body(body, encoding):
        """Returns decompressed body according to encoding using zlib.
        to (de-)compress gzip format, use wbits = zlib.MAX_WBITS | 16
        """
        if encoding == 'gzip':
            return zlib.decompress(body, zlib.MAX_WBITS | 16)
        else:  # encoding == 'deflate'
            return zlib.decompress(body)

    # Deepcopy here in case `headers` contain objects that could
    # be mutated by a shallow copy and corrupt the real response.
    response = copy.deepcopy(response)
    headers = CaseInsensitiveDict(response['headers'])
    if is_compressed(headers):
        encoding = headers['content-encoding'][0]
        headers['content-encoding'].remove(encoding)
        if not headers['content-encoding']:
            del headers['content-encoding']

        new_body = decompress_body(response['body']['string'], encoding)
        response['body']['string'] = new_body
        headers['content-length'] = [str(len(new_body))]
        response['headers'] = dict(headers)
    return response
