# This file is part of Radicale Server - Calendar Server
# Copyright © 2008 Nicolas Kandel
# Copyright © 2008 Pascal Halter
# Copyright © 2008-2016 Guillaume Ayoub
#
# This library is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Radicale.  If not, see <http://www.gnu.org/licenses/>.

"""
Radicale Server module.

This module offers a WSGI application class.

To use this module, you should take a look at the file ``radicale.py`` that
should have been included in this package.

"""

import os
import pprint
import base64
import socket
import socketserver
import ssl
import wsgiref.simple_server
import re
import zlib
from http import client
from urllib.parse import unquote, urlparse

import vobject

from . import auth, rights, storage, xmlutils


VERSION = "2.0.0-pre"

# Standard "not allowed" response that is returned when an authenticated user
# tries to access information they don't have rights to
NOT_ALLOWED = (client.FORBIDDEN, {}, None)

WELL_KNOWN_RE = re.compile(r"/\.well-known/(carddav|caldav)/?$")


class HTTPServer(wsgiref.simple_server.WSGIServer):
    """HTTP server."""

    # These class attributes must be set before creating instance
    client_timeout = None

    def __init__(self, address, handler, bind_and_activate=True):
        """Create server."""
        ipv6 = ":" in address[0]

        if ipv6:
            self.address_family = socket.AF_INET6

        # Do not bind and activate, as we might change socket options
        super().__init__(address, handler, False)

        if ipv6:
            # Only allow IPv6 connections to the IPv6 socket
            self.socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1)

        if bind_and_activate:
            self.server_bind()
            self.server_activate()

    def get_request(self):
        # Set timeout for client
        _socket, address = super().get_request()
        if self.client_timeout:
            _socket.settimeout(self.client_timeout)
        return _socket, address


class HTTPSServer(HTTPServer):
    """HTTPS server."""

    # These class attributes must be set before creating instance
    certificate = None
    key = None
    protocol = None
    cyphers = None

    def __init__(self, address, handler):
        """Create server by wrapping HTTP socket in an SSL socket."""
        super().__init__(address, handler, bind_and_activate=False)

        self.socket = ssl.wrap_socket(
            self.socket, self.key, self.certificate, server_side=True,
            ssl_version=self.protocol, cyphers=self.cyphers)

        self.server_bind()
        self.server_activate()


class ThreadedHTTPServer(socketserver.ThreadingMixIn, HTTPServer):
    pass


class ThreadedHTTPSServer(socketserver.ThreadingMixIn, HTTPSServer):
    pass


class RequestHandler(wsgiref.simple_server.WSGIRequestHandler):
    """HTTP requests handler."""
    def log_message(self, *args, **kwargs):
        """Disable inner logging management."""


class Application:
    """WSGI application managing collections."""
    def __init__(self, configuration, logger):
        """Initialize application."""
        super().__init__()
        self.configuration = configuration
        self.logger = logger
        self.is_authenticated = auth.load(configuration, logger)
        self.Collection = storage.load(configuration, logger)
        self.authorized = rights.load(configuration, logger)
        self.encoding = configuration.get("encoding", "request")
        if configuration.getboolean("logging", "full_environment"):
            self.headers_log = lambda environ: environ

    # This method is overriden in __init__ if full_environment is set
    # pylint: disable=E0202
    @staticmethod
    def headers_log(environ):
        """Remove environment variables from the headers for logging."""
        request_environ = dict(environ)
        for shell_variable in os.environ:
            if shell_variable in request_environ:
                del request_environ[shell_variable]
        return request_environ
    # pylint: enable=E0202

    def decode(self, text, environ):
        """Try to magically decode ``text`` according to given ``environ``."""
        # List of charsets to try
        charsets = []

        # First append content charset given in the request
        content_type = environ.get("CONTENT_TYPE")
        if content_type and "charset=" in content_type:
            charsets.append(
                content_type.split("charset=")[1].split(";")[0].strip())
        # Then append default Radicale charset
        charsets.append(self.encoding)
        # Then append various fallbacks
        charsets.append("utf-8")
        charsets.append("iso8859-1")

        # Try to decode
        for charset in charsets:
            try:
                return text.decode(charset)
            except UnicodeDecodeError:
                pass
        raise UnicodeDecodeError

    def collect_allowed_items(self, items, user):
        """Get items from request that user is allowed to access."""
        read_last_collection_allowed = None
        write_last_collection_allowed = None
        read_allowed_items = []
        write_allowed_items = []

        for item in items:
            if isinstance(item, self.Collection):
                if self.authorized(user, item, "r"):
                    self.logger.debug(
                        "%s has read access to collection %s" %
                        (user or "Anonymous", item.path or "/"))
                    read_last_collection_allowed = True
                    read_allowed_items.append(item)
                else:
                    self.logger.debug(
                        "%s has NO read access to collection %s" %
                        (user or "Anonymous", item.path or "/"))
                    read_last_collection_allowed = False

                if self.authorized(user, item, "w"):
                    self.logger.debug(
                        "%s has write access to collection %s" %
                        (user or "Anonymous", item.path or "/"))
                    write_last_collection_allowed = True
                    write_allowed_items.append(item)
                else:
                    self.logger.debug(
                        "%s has NO write access to collection %s" %
                        (user or "Anonymous", item.path or "/"))
                    write_last_collection_allowed = False
            else:
                # item is not a collection, it's the child of the last
                # collection we've met in the loop. Only add this item
                # if this last collection was allowed.
                if read_last_collection_allowed:
                    self.logger.debug(
                        "%s has read access to item %s" %
                        (user or "Anonymous", item.href))
                    read_allowed_items.append(item)
                else:
                    self.logger.debug(
                        "%s has NO read access to item %s" %
                        (user or "Anonymous", item.href))

                if write_last_collection_allowed:
                    self.logger.debug(
                        "%s has write access to item %s" %
                        (user or "Anonymous", item.href))
                    write_allowed_items.append(item)
                else:
                    self.logger.debug(
                        "%s has NO write access to item %s" %
                        (user or "Anonymous", item.href))

        return read_allowed_items, write_allowed_items

    def __call__(self, environ, start_response):
        """Manage a request."""
        def response(status, headers={}, answer=None):
            # Start response
            status = "%i %s" % (status,
                                client.responses.get(status, "Unknown"))
            self.logger.debug("Answer status: %s" % status)
            start_response(status, list(headers.items()))
            # Return response content
            return [answer] if answer else []

        self.logger.info("%s request at %s received" % (
            environ["REQUEST_METHOD"], environ["PATH_INFO"]))
        headers = pprint.pformat(self.headers_log(environ))
        self.logger.debug("Request headers:\n%s" % headers)

        # Strip base_prefix from request URI
        base_prefix = self.configuration.get("server", "base_prefix")
        if environ["PATH_INFO"].startswith(base_prefix):
            environ["PATH_INFO"] = environ["PATH_INFO"][len(base_prefix):]
        elif self.configuration.get("server", "can_skip_base_prefix"):
            self.logger.debug(
                "Prefix already stripped from path: %s", environ["PATH_INFO"])
        else:
            # Request path not starting with base_prefix, not allowed
            self.logger.debug(
                "Path not starting with prefix: %s", environ["PATH_INFO"])
            return response(*NOT_ALLOWED)

        # Sanitize request URI
        environ["PATH_INFO"] = storage.sanitize_path(
            unquote(environ["PATH_INFO"]))
        self.logger.debug("Sanitized path: %s", environ["PATH_INFO"])

        path = environ["PATH_INFO"]

        # Get function corresponding to method
        function = getattr(self, "do_%s" % environ["REQUEST_METHOD"].upper())

        # Ask authentication backend to check rights
        authorization = environ.get("HTTP_AUTHORIZATION", None)

        if authorization and authorization.startswith("Basic"):
            authorization = authorization[len("Basic"):].strip()
            user, password = self.decode(base64.b64decode(
                authorization.encode("ascii")), environ).split(":", 1)
        else:
            user = environ.get("REMOTE_USER")
            password = None

        well_known = WELL_KNOWN_RE.match(path)
        if well_known:
            redirect = self.configuration.get(
                "well-known", well_known.group(1))
            try:
                redirect = redirect % ({"user": user} if user else {})
            except KeyError:
                status = client.UNAUTHORIZED
                realm = self.configuration.get("server", "realm")
                headers = {"WWW-Authenticate": "Basic realm=\"%s\"" % realm}
                self.logger.info(
                    "Refused /.well-known/ redirection to anonymous user")
            else:
                status = client.SEE_OTHER
                self.logger.info("/.well-known/ redirection to: %s" % redirect)
                headers = {"Location": redirect}
            return response(status, headers)

        is_authenticated = self.is_authenticated(user, password)
        is_valid_user = is_authenticated or not user

        # Get content
        content_length = int(environ.get("CONTENT_LENGTH") or 0)
        if content_length:
            max_content_length = self.configuration.getint(
                "server", "max_content_length")
            if max_content_length and content_length > max_content_length:
                self.logger.debug(
                    "Request body too large: %d", content_length)
                return response(client.REQUEST_ENTITY_TOO_LARGE)
            try:
                content = self.decode(
                    environ["wsgi.input"].read(content_length), environ)
            except socket.timeout:
                return response(client.REQUEST_TIMEOUT)
            self.logger.debug("Request content:\n%s" % content)
        else:
            content = None

        if is_valid_user:
            if function in (self.do_GET, self.do_HEAD,
                            self.do_OPTIONS, self.do_PROPFIND,
                            self.do_REPORT):
                lock_mode = "r"
            else:
                lock_mode = "w"
            with self.Collection.acquire_lock(lock_mode):
                items = self.Collection.discover(
                    path, environ.get("HTTP_DEPTH", "0"))
                read_allowed_items, write_allowed_items = (
                    self.collect_allowed_items(items, user))
                if (read_allowed_items or write_allowed_items or
                        is_authenticated and function == self.do_PROPFIND or
                        function == self.do_OPTIONS):
                    status, headers, answer = function(
                        environ, read_allowed_items, write_allowed_items,
                        content, user)
                else:
                    status, headers, answer = NOT_ALLOWED
        else:
            status, headers, answer = NOT_ALLOWED

        if (status, headers, answer) == NOT_ALLOWED and not is_authenticated:
            # Unknown or unauthorized user
            self.logger.info("%s refused" % (user or "Anonymous user"))
            status = client.UNAUTHORIZED
            realm = self.configuration.get("server", "realm")
            headers = {
                "WWW-Authenticate":
                "Basic realm=\"%s\"" % realm}
            answer = None

        # Set content length
        if answer:
            self.logger.debug("Response content:\n%s" % answer, environ)
            answer = answer.encode(self.encoding)
            accept_encoding = [
                encoding.strip() for encoding in
                environ.get("HTTP_ACCEPT_ENCODING", "").split(",")
                if encoding.strip()]
            if "deflate" in accept_encoding:
                answer = zlib.compress(answer)
                headers["Content-Encoding"] = "deflate"
            headers["Content-Length"] = str(len(answer))

        if self.configuration.has_section("headers"):
            for key in self.configuration.options("headers"):
                headers[key] = self.configuration.get("headers", key)

        return response(status, headers, answer)

    # All these functions must have the same parameters, some are useless
    # pylint: disable=W0612,W0613,R0201

    def do_DELETE(self, environ, read_collections, write_collections, content,
                  user):
        """Manage DELETE request."""
        if not write_collections:
            return NOT_ALLOWED

        collection = write_collections[0]

        if collection.path == environ["PATH_INFO"].strip("/"):
            # Path matching the collection, the collection must be deleted
            item = collection
        else:
            # Try to get an item matching the path
            name = xmlutils.name_from_path(environ["PATH_INFO"], collection)
            item = collection.get(name)

        if item:
            if_match = environ.get("HTTP_IF_MATCH", "*")
            if if_match in ("*", item.etag):
                # No ETag precondition or precondition verified, delete item
                answer = xmlutils.delete(environ["PATH_INFO"], collection)
                return client.OK, {}, answer

        # No item or ETag precondition not verified, do not delete item
        return client.PRECONDITION_FAILED, {}, None

    def do_GET(self, environ, read_collections, write_collections, content,
               user):
        """Manage GET request."""
        # Display a "Radicale works!" message if the root URL is requested
        if environ["PATH_INFO"] == "/":
            headers = {"Content-type": "text/html"}
            answer = "<!DOCTYPE html>\n<title>Radicale</title>Radicale works!"
            return client.OK, headers, answer

        if not read_collections:
            return NOT_ALLOWED

        collection = read_collections[0]

        item_name = xmlutils.name_from_path(environ["PATH_INFO"], collection)

        if item_name:
            # Get collection item
            item = collection.get(item_name)
            if item:
                answer = item.serialize()
                etag = item.etag
            else:
                return client.NOT_FOUND, {}, None
        else:
            # Get whole collection
            answer = collection.serialize()
            etag = collection.etag

        if answer:
            headers = {
                "Content-Type": storage.MIMETYPES[collection.get_meta("tag")],
                "Last-Modified": collection.last_modified,
                "ETag": etag}
        else:
            headers = {}
        return client.OK, headers, answer

    def do_HEAD(self, environ, read_collections, write_collections, content,
                user):
        """Manage HEAD request."""
        status, headers, answer = self.do_GET(
            environ, read_collections, write_collections, content, user)
        return status, headers, None

    def do_MKCALENDAR(self, environ, read_collections, write_collections,
                      content, user):
        """Manage MKCALENDAR request."""
        if not write_collections:
            return NOT_ALLOWED

        collection = write_collections[0]

        props = xmlutils.props_from_request(content)
        # TODO: use this?
        # timezone = props.get("C:calendar-timezone")
        collection = self.Collection.create_collection(
            environ["PATH_INFO"], tag="VCALENDAR")
        for key, value in props.items():
            collection.set_meta(key, value)
        return client.CREATED, {}, None

    def do_MKCOL(self, environ, read_collections, write_collections, content,
                 user):
        """Manage MKCOL request."""
        if not write_collections:
            return NOT_ALLOWED

        collection = write_collections[0]

        props = xmlutils.props_from_request(content)
        collection = self.Collection.create_collection(environ["PATH_INFO"])
        for key, value in props.items():
            collection.set_meta(key, value)
        return client.CREATED, {}, None

    def do_MOVE(self, environ, read_collections, write_collections, content,
                user):
        """Manage MOVE request."""
        if not write_collections:
            return NOT_ALLOWED

        from_collection = write_collections[0]
        from_name = xmlutils.name_from_path(
            environ["PATH_INFO"], from_collection)
        item = from_collection.get(from_name)
        if item:
            # Move the item
            to_url_parts = urlparse(environ["HTTP_DESTINATION"])
            if to_url_parts.netloc == environ["HTTP_HOST"]:
                to_url = to_url_parts.path
                to_path, to_name = to_url.rstrip("/").rsplit("/", 1)
                for to_collection in self.Collection.discover(
                        to_path, depth="0"):
                    if to_collection in write_collections:
                        to_collection.upload(to_name, item)
                        from_collection.delete(from_name)
                        return client.CREATED, {}, None
                    else:
                        return NOT_ALLOWED
            else:
                # Remote destination server, not supported
                return client.BAD_GATEWAY, {}, None
        else:
            # No item found
            return client.GONE, {}, None

    def do_OPTIONS(self, environ, read_collections, write_collections,
                   content, user):
        """Manage OPTIONS request."""
        headers = {
            "Allow": ("DELETE, HEAD, GET, MKCALENDAR, MKCOL, MOVE, "
                      "OPTIONS, PROPFIND, PROPPATCH, PUT, REPORT"),
            "DAV": "1, 2, 3, calendar-access, addressbook, extended-mkcol"}
        return client.OK, headers, None

    def do_PROPFIND(self, environ, read_collections, write_collections,
                    content, user):
        """Manage PROPFIND request."""
        if not read_collections:
            return client.NOT_FOUND, {}, None
        headers = {
            "DAV": "1, 2, 3, calendar-access, addressbook, extended-mkcol",
            "Content-Type": "text/xml"}
        answer = xmlutils.propfind(
            environ["PATH_INFO"], content, read_collections, write_collections,
            user)
        return client.MULTI_STATUS, headers, answer

    def do_PROPPATCH(self, environ, read_collections, write_collections,
                     content, user):
        """Manage PROPPATCH request."""
        if not write_collections:
            return NOT_ALLOWED

        collection = write_collections[0]

        answer = xmlutils.proppatch(environ["PATH_INFO"], content, collection)
        headers = {
            "DAV": "1, 2, 3, calendar-access, addressbook, extended-mkcol",
            "Content-Type": "text/xml"}
        return client.MULTI_STATUS, headers, answer

    def do_PUT(self, environ, read_collections, write_collections, content,
               user):
        """Manage PUT request."""
        if not write_collections:
            return NOT_ALLOWED

        collection = write_collections[0]

        content_type = environ.get("CONTENT_TYPE")
        if content_type:
            tags = {value: key for key, value in storage.MIMETYPES.items()}
            tag = tags.get(content_type.split(";")[0])
            if tag:
                collection.set_meta("tag", tag)
        headers = {}
        item_name = xmlutils.name_from_path(environ["PATH_INFO"], collection)
        item = collection.get(item_name)

        etag = environ.get("HTTP_IF_MATCH", "")
        match = environ.get("HTTP_IF_NONE_MATCH", "") == "*"
        if (not item and not etag) or (
                item and ((etag or item.etag) == item.etag) and not match):
            # PUT allowed in 3 cases
            # Case 1: No item and no ETag precondition: Add new item
            # Case 2: Item and ETag precondition verified: Modify item
            # Case 3: Item and no Etag precondition: Force modifying item
            items = list(vobject.readComponents(content or ""))
            if item:
                # PUT is modifying an existing item
                if items:
                    new_item = collection.update(item_name, items[0])
                else:
                    new_item = None
            elif item_name:
                # PUT is adding a new item
                if items:
                    new_item = collection.upload(item_name, items[0])
                else:
                    new_item = None
            else:
                # PUT is replacing the whole collection
                collection.delete()
                new_item = self.Collection.create_collection(
                    environ["PATH_INFO"], items)
            if new_item:
                headers["ETag"] = new_item.etag
            status = client.CREATED
        else:
            # PUT rejected in all other cases
            status = client.PRECONDITION_FAILED
        return status, headers, None

    def do_REPORT(self, environ, read_collections, write_collections, content,
                  user):
        """Manage REPORT request."""
        if not read_collections:
            return NOT_ALLOWED

        collection = read_collections[0]

        headers = {"Content-Type": "text/xml"}

        answer = xmlutils.report(environ["PATH_INFO"], content, collection)
        return client.MULTI_STATUS, headers, answer

    # pylint: enable=W0612,W0613,R0201