from contextlib import contextmanager
from dataclasses import dataclass
from email.encoders import encode_noop
from json import loads
import logging
import os
import re
from typing import TYPE_CHECKING
from typing import Any  # noqa:F401
from typing import Callable  # noqa:F401
from typing import ContextManager  # noqa:F401
from typing import Dict  # noqa:F401
from typing import Generator  # noqa:F401
from typing import List  # noqa:F401
from typing import Optional  # noqa:F401
from typing import Pattern  # noqa:F401
from typing import Tuple  # noqa:F401
from typing import Union  # noqa:F401
from urllib import parse

from ddtrace.constants import _USER_ID_KEY
from ddtrace.internal._unpatched import unpatched_open as open  # noqa: A004
from ddtrace.internal.constants import BLOCKED_RESPONSE_HTML
from ddtrace.internal.constants import BLOCKED_RESPONSE_JSON
from ddtrace.internal.constants import DEFAULT_TIMEOUT
from ddtrace.internal.constants import SAMPLING_DECISION_TRACE_TAG_KEY
from ddtrace.internal.constants import W3C_TRACESTATE_ORIGIN_KEY
from ddtrace.internal.constants import W3C_TRACESTATE_PARENT_ID_KEY
from ddtrace.internal.constants import W3C_TRACESTATE_SAMPLING_PRIORITY_KEY
from ddtrace.internal.utils import _get_metas_to_propagate
from ddtrace.internal.utils.cache import cached


_W3C_TRACESTATE_INVALID_CHARS_REGEX_VALUE = re.compile(r",|;|~|[^\x20-\x7E]+")
_W3C_TRACESTATE_INVALID_CHARS_REGEX_KEY = re.compile(r",| |=|[^\x20-\x7E]+")


if TYPE_CHECKING:
    import http.client as httplib

    from ddtrace.internal.http import HTTPConnection
    from ddtrace.internal.http import HTTPSConnection
    from ddtrace.internal.uds import UDSHTTPConnection

ConnectionType = Union["HTTPSConnection", "HTTPConnection", "UDSHTTPConnection"]
Connector = Callable[[], ContextManager["httplib.HTTPConnection"]]


log = logging.getLogger(__name__)


@cached()
def normalize_header_name(header_name):
    # type: (Optional[str]) -> Optional[str]
    """
    Normalizes an header name to lower case, stripping all its leading and trailing white spaces.
    :param header_name: the header name to normalize
    :type header_name: str
    :return: the normalized header name
    :rtype: str
    """
    return header_name.strip().lower() if header_name is not None else None


def strip_query_string(url):
    # type: (str) -> str
    """
    Strips the query string from a URL for use as tag in spans.
    :param url: The URL to be stripped
    :return: The given URL without query strings
    """
    hqs, fs, f = url.partition("#")
    h, _, _ = hqs.partition("?")
    if not f:
        return h
    return h + fs + f


def redact_query_string(query_string, query_string_obfuscation_pattern):
    # type: (str, re.Pattern) -> Union[bytes, str]
    bytes_query = query_string if isinstance(query_string, bytes) else query_string.encode("utf-8")
    return query_string_obfuscation_pattern.sub(b"<redacted>", bytes_query)


def redact_url(url, query_string_obfuscation_pattern, query_string=None):
    # type: (str, re.Pattern, Optional[str]) -> Union[str,bytes]
    parts = parse.urlparse(url)
    redacted_query = None

    if query_string:
        redacted_query = redact_query_string(query_string, query_string_obfuscation_pattern)
    elif parts.query:
        redacted_query = redact_query_string(parts.query, query_string_obfuscation_pattern)

    if redacted_query is not None and len(parts) >= 5:
        redacted_parts = parts[:4] + (redacted_query,) + parts[5:]  # type: Tuple[Union[str, bytes], ...]
        bytes_redacted_parts = tuple(x if isinstance(x, bytes) else x.encode("utf-8") for x in redacted_parts)
        return urlunsplit(bytes_redacted_parts, url)

    # If no obfuscation is performed, return original url
    return url


def urlunsplit(components, original_url):
    # type: (Tuple[bytes, ...], str) -> bytes
    """
    Adaptation from urlunsplit and urlunparse, using bytes components
    """
    scheme, netloc, url, params, query, fragment = components
    if params:
        url = b"%s;%s" % (url, params)
    if netloc or (scheme and url[:2] != b"//"):
        if url and url[:1] != b"/":
            url = b"/" + url
        url = b"//%s%s" % ((netloc or b""), url)
    if scheme:
        url = b"%s:%s" % (scheme, url)
    if query or (original_url and original_url[-1] in ("?", b"?")):
        url = b"%s?%s" % (url, query)
    if fragment or (original_url and original_url[-1] in ("#", b"#")):
        url = b"%s#%s" % (url, fragment)
    return url


def connector(url, **kwargs):
    # type: (str, Any) -> Connector
    """Create a connector context manager for the given URL.

    This function returns a context manager that wraps a connection object to
    perform HTTP requests against the given URL. Extra keyword arguments can be
    passed to the underlying connection object, if needed.

    Example::
        >>> connect = connector("http://localhost:8080")
        >>> with connect() as conn:
        ...     conn.request("GET", "/")
        ...     ...
    """

    @contextmanager
    def _connector_context():
        # type: () -> Generator[Union[httplib.HTTPConnection, httplib.HTTPSConnection], None, None]
        connection = get_connection(url, **kwargs)
        yield connection
        connection.close()

    return _connector_context


def w3c_get_dd_list_member(context):
    # Context -> str
    tags = []
    if context.sampling_priority is not None:
        tags.append("{}:{}".format(W3C_TRACESTATE_SAMPLING_PRIORITY_KEY, context.sampling_priority))
    if context.dd_origin:
        tags.append(
            "{}:{}".format(
                W3C_TRACESTATE_ORIGIN_KEY,
                w3c_encode_tag((_W3C_TRACESTATE_INVALID_CHARS_REGEX_VALUE, "_", context.dd_origin)),
            )
        )

    sampling_decision = context._meta.get(SAMPLING_DECISION_TRACE_TAG_KEY)
    if sampling_decision:
        tags.append(
            "t.dm:{}".format((w3c_encode_tag((_W3C_TRACESTATE_INVALID_CHARS_REGEX_VALUE, "_", sampling_decision))))
        )
    # since this can change, we need to grab the value off the current span
    usr_id = context._meta.get(_USER_ID_KEY)
    if usr_id:
        tags.append("t.usr.id:{}".format(w3c_encode_tag((_W3C_TRACESTATE_INVALID_CHARS_REGEX_VALUE, "_", usr_id))))

    current_tags_len = sum(len(i) for i in tags)
    for k, v in _get_metas_to_propagate(context):
        if k not in [SAMPLING_DECISION_TRACE_TAG_KEY, _USER_ID_KEY]:
            # for key replace ",", "=", and characters outside the ASCII range 0x20 to 0x7E
            # for value replace ",", ";", "~" and characters outside the ASCII range 0x20 to 0x7E
            k = k.replace("_dd.p.", "t.")
            next_tag = "{}:{}".format(
                w3c_encode_tag((_W3C_TRACESTATE_INVALID_CHARS_REGEX_KEY, "_", k)),
                w3c_encode_tag((_W3C_TRACESTATE_INVALID_CHARS_REGEX_VALUE, "_", v)),
            )
            # we need to keep the total length under 256 char
            potential_current_tags_len = current_tags_len + len(next_tag)
            if not potential_current_tags_len > 256:
                tags.append(next_tag)
                current_tags_len += len(next_tag)
            else:
                log.debug("tracestate would exceed 256 char limit with tag: %s. Tag will not be added.", next_tag)

    return ";".join(tags)


@cached()
def w3c_encode_tag(args):
    # type: (Tuple[Pattern, str, str]) -> str
    pattern, replacement, tag_val = args
    tag_val = pattern.sub(replacement, tag_val)
    # replace = with ~ if it wasn't already replaced by the regex
    return tag_val.replace("=", "~")


def w3c_tracestate_add_p(tracestate, span_id):
    # Adds last datadog parent_id to tracestate. This tag is used to reconnect a trace with non-datadog spans
    p_member = "{}:{:016x}".format(W3C_TRACESTATE_PARENT_ID_KEY, span_id)
    if "dd=" in tracestate:
        return tracestate.replace("dd=", f"dd={p_member};")
    elif tracestate:
        return f"dd={p_member},{tracestate}"
    return f"dd={p_member}"


class Response(object):
    """
    Custom API Response object to represent a response from calling the API.

    We do this to ensure we know expected properties will exist, and so we
    can call `resp.read()` and load the body once into an instance before we
    close the HTTPConnection used for the request.
    """

    __slots__ = ["status", "body", "reason", "msg"]

    def __init__(self, status=None, body=None, reason=None, msg=None):
        self.status = status
        self.body = body
        self.reason = reason
        self.msg = msg

    @classmethod
    def from_http_response(cls, resp):
        """
        Build a ``Response`` from the provided ``HTTPResponse`` object.

        This function will call `.read()` to consume the body of the ``HTTPResponse`` object.

        :param resp: ``HTTPResponse`` object to build the ``Response`` from
        :type resp: ``HTTPResponse``
        :rtype: ``Response``
        :returns: A new ``Response``
        """
        return cls(
            status=resp.status,
            body=resp.read(),
            reason=getattr(resp, "reason", None),
            msg=getattr(resp, "msg", None),
        )

    def get_json(self):
        """Helper to parse the body of this request as JSON"""
        try:
            body = self.body
            if not body:
                log.debug("Empty reply from Datadog Agent, %r", self)
                return

            if not isinstance(body, str) and hasattr(body, "decode"):
                body = body.decode("utf-8")

            if hasattr(body, "startswith") and body.startswith("OK"):
                # This typically happens when using a priority-sampling enabled
                # library with an outdated agent. It still works, but priority sampling
                # will probably send too many traces, so the next step is to upgrade agent.
                log.debug("Cannot parse Datadog Agent response. This occurs because Datadog agent is out of date")
                return

            return loads(body)
        except (ValueError, TypeError):
            log.debug("Unable to parse Datadog Agent JSON response: %r", body, exc_info=True)

    def __repr__(self):
        return "{0}(status={1!r}, body={2!r}, reason={3!r}, msg={4!r})".format(
            self.__class__.__name__,
            self.status,
            self.body,
            self.reason,
            self.msg,
        )


def get_connection(url: str, timeout: float = DEFAULT_TIMEOUT) -> ConnectionType:
    """Return an HTTP connection to the given URL."""
    parsed = verify_url(url)
    hostname = parsed.hostname or ""
    path = parsed.path or "/"

    from ddtrace.internal.http import HTTPConnection
    from ddtrace.internal.http import HTTPSConnection
    from ddtrace.internal.uds import UDSHTTPConnection

    if parsed.scheme == "https":
        return HTTPSConnection.with_base_path(hostname, parsed.port, base_path=path, timeout=timeout)
    elif parsed.scheme == "http":
        return HTTPConnection.with_base_path(hostname, parsed.port, base_path=path, timeout=timeout)
    elif parsed.scheme == "unix":
        return UDSHTTPConnection(path, hostname, parsed.port, timeout=timeout)

    raise ValueError("Unsupported protocol '%s'" % parsed.scheme)


def verify_url(url: str) -> parse.ParseResult:
    """Validates that the given URL can be used as an intake
    Returns a parse.ParseResult.
    Raises a ``ValueError`` if the URL cannot be used as an intake
    """
    parsed = parse.urlparse(url)
    schemes = ("http", "https", "unix")
    if parsed.scheme not in schemes:
        raise ValueError(
            "Unsupported protocol '%s' in intake URL '%s'. Must be one of: %s"
            % (parsed.scheme, url, ", ".join(schemes))
        )
    elif parsed.scheme in ["http", "https"] and not parsed.hostname:
        raise ValueError("Invalid hostname in intake URL '%s'" % url)
    elif parsed.scheme == "unix" and not parsed.path:
        raise ValueError("Invalid file path in intake URL '%s'" % url)

    return parsed


_HTML_BLOCKED_TEMPLATE_CACHE = None  # type: Optional[str]
_JSON_BLOCKED_TEMPLATE_CACHE = None  # type: Optional[str]
_RESPONSE_ID_TEMPLATE = "[security_response_id]"


def _format_template(template: str, security_response_id: str) -> str:
    return template.replace(_RESPONSE_ID_TEMPLATE, security_response_id)


def _get_blocked_template(accept_header_value: str, security_response_id: str) -> str:
    global _HTML_BLOCKED_TEMPLATE_CACHE
    global _JSON_BLOCKED_TEMPLATE_CACHE

    need_html_template = False

    if accept_header_value and "text/html" in accept_header_value.lower():
        need_html_template = True

    if need_html_template and _HTML_BLOCKED_TEMPLATE_CACHE:
        return _format_template(_HTML_BLOCKED_TEMPLATE_CACHE, security_response_id)

    if not need_html_template and _JSON_BLOCKED_TEMPLATE_CACHE:
        return _format_template(_JSON_BLOCKED_TEMPLATE_CACHE, security_response_id)

    if need_html_template:
        template_path = os.getenv("DD_APPSEC_HTTP_BLOCKED_TEMPLATE_HTML")
    else:
        template_path = os.getenv("DD_APPSEC_HTTP_BLOCKED_TEMPLATE_JSON")

    if template_path:
        try:
            with open(template_path, "r") as template_file:
                content = template_file.read()

            if need_html_template:
                _HTML_BLOCKED_TEMPLATE_CACHE = content
            else:
                _JSON_BLOCKED_TEMPLATE_CACHE = content
            return _format_template(content, security_response_id)
        except (OSError, IOError) as e:  # noqa: B014
            log.warning("Could not load custom template at %s: %s", template_path, str(e))

    # No user-defined template at this point
    if need_html_template:
        _HTML_BLOCKED_TEMPLATE_CACHE = BLOCKED_RESPONSE_HTML
        return _format_template(_HTML_BLOCKED_TEMPLATE_CACHE, security_response_id)

    _JSON_BLOCKED_TEMPLATE_CACHE = BLOCKED_RESPONSE_JSON
    return _format_template(_JSON_BLOCKED_TEMPLATE_CACHE, security_response_id)


def parse_form_params(body: str) -> Dict[str, Union[str, List[str]]]:
    """Return a dict of form data after HTTP form parsing"""
    body_params = body.replace("+", " ")
    req_body: Dict[str, Union[str, List[str]]] = dict()
    for item in body_params.split("&"):
        key, equal, val = item.partition("=")
        if equal:
            key = parse.unquote(key)
            val = parse.unquote(val)
            prev_value = req_body.get(key, None)
            if prev_value is None:
                req_body[key] = val
            elif isinstance(prev_value, list):
                prev_value.append(val)
            else:
                req_body[key] = [prev_value, val]
    return req_body


def parse_form_multipart(body: str, headers: Optional[Dict] = None) -> Dict[str, Any]:
    """Return a dict of form data after HTTP form parsing"""
    import email
    import json
    from urllib.parse import parse_qs

    def parse_message(msg):
        if msg.is_multipart():
            res = {
                part.get_param("name", failobj=part.get_filename(), header="content-disposition"): parse_message(part)
                for part in msg.get_payload()
            }
        else:
            content_type = msg.get("Content-Type")
            if content_type in ("application/json", "text/json"):
                res = json.loads(msg.get_payload())
            elif content_type in ("application/xml", "text/xml"):
                import ddtrace.vendor.xmltodict as xmltodict

                res = xmltodict.parse(msg.get_payload())
            elif content_type in ("application/x-url-encoded", "application/x-www-form-urlencoded"):
                res = parse_qs(msg.get_payload())
            elif content_type in ("text/plain", None):
                res = msg.get_payload()
            else:
                res = ""

        return res

    if headers is not None:
        content_type = headers.get("Content-Type") or headers.get("content-type")
        msg = email.message_from_string("MIME-Version: 1.0\nContent-Type: %s\n%s" % (content_type, body))
        return parse_message(msg)
    return {}


@dataclass
class FormData:
    name: str
    filename: str
    data: Union[str, bytes]
    content_type: str


def multipart(parts: List[FormData]) -> Tuple[bytes, dict]:
    from email.mime.application import MIMEApplication
    from email.mime.multipart import MIMEMultipart
    from email.policy import HTTP

    msg = MIMEMultipart("form-data")
    del msg["MIME-Version"]

    for part in parts:
        app = MIMEApplication(part.data, part.content_type, encode_noop)
        app.add_header("Content-Disposition", "form-data", name=part.name, filename=part.filename)
        del app["MIME-Version"]
        msg.attach(app)

    # Split headers and body
    headers, _, body = msg.as_bytes(policy=HTTP).partition(b"\r\n\r\n")

    return body, dict(_.split(": ") for _ in headers.decode().splitlines())
