#!/usr/bin/env python3

# Libervia Web
# Copyright (C) 2011-2021 Jérôme Poisson <goffi@goffi.org>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program 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 Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


import os.path
from pathlib import Path
import urllib.error
import urllib.parse
import urllib.request

from twisted.internet import defer
from twisted.web import server
from twisted.web import static
from twisted.web import resource as web_resource
from twisted.web.util import Redirect

from libervia.web.server.constants import Const as C
from libervia.web.server.utils import quote
from libervia.backend.core import exceptions
from libervia.backend.core.i18n import D_, _
from libervia.backend.core.log import getLogger
from libervia.backend.tools.common import uri as common_uri
from libervia.backend.tools.common import data_format
from libervia.backend.tools.common.utils import OrderedSet, recursive_update

from . import proxy

log = getLogger(__name__)


class ProtectedFile(static.File):
    """A static.File class which doesn't show directory listing"""

    def __init__(self, path, *args, **kwargs):
        if "defaultType" not in kwargs and len(args) < 2:
            # defaultType is second positional argument, and Twisted uses it
            # in File.createSimilarFile, so we set kwargs only if it is missing
            # in kwargs and it is not in a positional argument
            kwargs["defaultType"] = "application/octet-stream"
        super(ProtectedFile, self).__init__(str(path), *args, **kwargs)

    def directoryListing(self):
        return web_resource.NoResource()


    def getChild(self, path, request):
        return super().getChild(path, request)

    def getChildWithDefault(self, path, request):
        return super().getChildWithDefault(path, request)

    def getChildForRequest(self, request):
        return super().getChildForRequest(request)


class LiberviaRootResource(ProtectedFile):
    """Specialized resource for Libervia root

    handle redirections declared in libervia.conf
    """

    def __init__(self, host, host_name, site_name, site_path, *args, **kwargs):
        ProtectedFile.__init__(self, *args, **kwargs)
        self.host = host
        self.host_name = host_name
        self.site_name = site_name
        self.site_path = Path(site_path)
        self.default_theme = self.config_get('theme')
        if self.default_theme is None:
            if not host_name:
                # FIXME: we use bulma theme by default for main site for now
                #   as the development is focusing on this one, and default theme may
                #   be broken
                self.default_theme = 'bulma'
            else:
                self.default_theme =  C.TEMPLATE_THEME_DEFAULT
        self.site_themes = set()
        self.named_pages = {}
        self.browser_modules = {}
        # template dynamic data used in all pages
        self.dyn_data_common = {"scripts": OrderedSet()}
        for theme, data in host.renderer.get_themes_data(site_name).items():
            # we check themes for browser metadata, and merge them here if found
            self.site_themes.add(theme)
            browser_meta = data.get('browser_meta')
            if browser_meta is not None:
                log.debug(f"merging browser metadata from theme {theme}: {browser_meta}")
                recursive_update(self.browser_modules, browser_meta)
            browser_path = data.get('browser_path')
            if browser_path is not None:
                self.browser_modules.setdefault('themes_browser_paths', set()).add(
                    browser_path)
                try:
                    next(browser_path.glob("*.py"))
                except StopIteration:
                    pass
                else:
                    log.debug(f"found brython script(s) for theme {theme}")
                    self.browser_modules.setdefault('brython', []).append(
                        {
                            "path": browser_path,
                            "url_hash": None,
                            "url_prefix": f"__t_{theme}"
                        }
                    )

        self.uri_callbacks = {}
        self.pages_redirects = {}
        self.cached_urls = {}
        self.main_menu = None
        self.login_url = None
        # map Libervia application names => data
        self.libervia_apps = {}
        self.build_path = host.get_build_path(site_name)
        self.build_path.mkdir(parents=True, exist_ok=True)
        self.dev_build_path = host.get_build_path(site_name, dev=True)
        self.dev_build_path.mkdir(parents=True, exist_ok=True)
        self.putChild(
            C.BUILD_DIR.encode(),
            ProtectedFile(
                self.build_path,
                defaultType="application/octet-stream"),
        )

    def __str__(self):
        return (
            f"Root resource for {self.host_name or 'default host'} using "
            f"{self.site_name or 'default site'} at {self.site_path} and deserving "
            f"files at {self.path}"
        )

    def config_get(self, key, default=None, value_type=None):
        """Retrieve configuration for this site

        params are the same as for [Libervia.config_get]
        """
        return self.host.config_get(self, key, default, value_type)

    def get_front_url(self, theme):
        return Path(
            '/',
            C.TPL_RESOURCE,
            self.site_name or C.SITE_NAME_DEFAULT,
            C.TEMPLATE_TPL_DIR,
            theme)

    def add_resource_to_path(self, path: str, resource: web_resource.Resource) -> None:
        """Add a resource to the given path

        A "NoResource" will be used for all intermediate segments
        """
        segments, __, last_segment = path.rpartition("/")
        url_segments = segments.split("/") if segments else []
        current = self
        for segment in url_segments:
            resource = web_resource.NoResource()
            current.putChild(segment, resource)
            current = resource

        current.putChild(
            last_segment.encode('utf-8'),
            resource
        )

    async def _start_app(self, app_name, extra=None) -> dict:
        """Start a Libervia App

        @param app_name: canonical application name
        @param extra: extra parameter to configure app
        @return: app data
            app data will not include computed exposed data, at this needs to wait for the
            app to be started
        """
        if extra is None:
            extra = {}
        log.info(_(
            "starting application {app_name}").format(app_name=app_name))
        app_data = data_format.deserialise(
            await self.host.bridge_call(
                "application_start", app_name, data_format.serialise(extra)
            )
        )
        if app_data.get("started", False):
            log.debug(f"application {app_name!r} is already started or starting")
            # we do not await on purpose, the workflow should not be blocking at this
            # point
            defer.ensureDeferred(self._on_app_started(app_name, app_data["instance"]))
        else:
            self.host.apps_cb[app_data["instance"]] = self._on_app_started
        return app_data

    async def _on_app_started(
        self,
        app_name: str,
        instance_id: str
    ) -> None:
        exposed_data = self.libervia_apps[app_name] = data_format.deserialise(
            await self.host.bridge_call("application_exposed_get", app_name, "", "")
        )
        external = exposed_data.get("web_external", False)
        if external:
            log.info(
                f"App {app_name!r} (instance {instance_id!r}) has been started."
            )
            # we don't add any resource of proxy for external apps.
            return
        try:
            web_port = int(exposed_data['ports']['web'].split(':')[1])
        except (KeyError, ValueError):
            log.warning(_(
                "no web port found for application {app_name!r}, can't use it "
                ).format(app_name=app_name))
            raise exceptions.DataError("no web port found")

        try:
            url_prefix = exposed_data['url_prefix'].strip().rstrip('/')
        except (KeyError, AttributeError) as e:
            log.warning(_(
                "no URL prefix specified for this application, we can't embed it: {msg}")
                .format(msg=e))
            raise exceptions.DataError("no URL prefix")

        if not url_prefix.startswith('/'):
            raise exceptions.DataError(
                f"invalid URL prefix, it must start with '/': {url_prefix!r}")

        res = proxy.SatReverseProxyResource(
            "localhost",
            web_port,
            url_prefix.encode()
        )
        self.add_resource_to_path(url_prefix, res)

        log.info(
            f"Resource for app {app_name!r} (instance {instance_id!r}) has been added."
        )

    async def _init_redirections(self, options):
        url_redirections = options["url_redirections_dict"]

        url_redirections = url_redirections.get(self.site_name, {})

        ## redirections
        self.redirections = {}
        self.inv_redirections = {}  # new URL to old URL map

        for old, new_data_list in url_redirections.items():
            # several redirections can be used for one path by using a list.
            # The redirection will be done using first item of the list, and all items
            # will be used for inverse redirection.
            # e.g. if a => [b, c], a will redirect to c, and b and c will both be
            # equivalent to a
            if not isinstance(new_data_list, list):
                new_data_list = [new_data_list]
            for new_data in new_data_list:
                # new_data can be a dictionary or a unicode url
                if isinstance(new_data, dict):
                    # new_data dict must contain either "url", "page" or "path" key
                    # (exclusive)
                    # if "path" is used, a file url is constructed with it
                    if ((
                        len(
                            {"path", "url", "page"}.intersection(list(new_data.keys()))
                        ) != 1
                    )):
                        raise ValueError(
                            'You must have one and only one of "url", "page" or "path" '
                            'key in your url_redirections_dict data'
                        )
                    if "url" in new_data:
                        new = new_data["url"]
                    elif "page" in new_data:
                        new = new_data
                        new["type"] = "page"
                        new.setdefault("path_args", [])
                        if not isinstance(new["path_args"], list):
                            log.error(
                                _('"path_args" in redirection of {old} must be a list. '
                                  'Ignoring the redirection'.format(old=old)))
                            continue
                        new.setdefault("query_args", {})
                        if not isinstance(new["query_args"], dict):
                            log.error(
                                _(
                                    '"query_args" in redirection of {old} must be a '
                                    'dictionary. Ignoring the redirection'
                                ).format(old=old)
                            )
                            continue
                        new["path_args"] = [quote(a) for a in new["path_args"]]
                        # we keep an inversed dict of page redirection
                        # (page/path_args => redirecting URL)
                        # so get_url can return the redirecting URL if the same arguments
                        # are used # making the URL consistent
                        args_hash = tuple(new["path_args"])
                        self.pages_redirects.setdefault(new_data["page"], {}).setdefault(
                            args_hash,
                            old
                        )

                        # we need lists in query_args because it will be used
                        # as it in request.path_args
                        for k, v in new["query_args"].items():
                            if isinstance(v, str):
                                new["query_args"][k] = [v]
                    elif "path" in new_data:
                        new = "file:{}".format(urllib.parse.quote(new_data["path"]))
                elif isinstance(new_data, str):
                    new = new_data
                    new_data = {}
                else:
                    log.error(
                        _("ignoring invalid redirection value: {new_data}").format(
                            new_data=new_data
                        )
                    )
                    continue

                # some normalization
                if not old.strip():
                    # root URL special case
                    old = ""
                elif not old.startswith("/"):
                    log.error(
                        _("redirected url must start with '/', got {value}. Ignoring")
                        .format(value=old)
                    )
                    continue
                else:
                    old = self._normalize_url(old)

                if isinstance(new, dict):
                    # dict are handled differently, they contain data
                    # which ared use dynamically when the request is done
                    self.redirections.setdefault(old, new)
                    if not old:
                        if new["type"] == "page":
                            log.info(
                                _("Root URL redirected to page {name}").format(
                                    name=new["page"]
                                )
                            )
                    else:
                        if new["type"] == "page":
                            page = self.get_page_by_name(new["page"])
                            url = page.get_url(*new.get("path_args", []))
                            self.inv_redirections[url] = old
                    continue

                # at this point we have a redirection URL in new, we can parse it
                new_url = urllib.parse.urlsplit(new)

                # we handle the known URL schemes
                if new_url.scheme == "xmpp":
                    location = self.get_page_path_from_uri(new)
                    if location is None:
                        log.warning(
                            _("ignoring redirection, no page found to handle this URI: "
                              "{uri}").format(uri=new))
                        continue
                    request_data = self._get_request_data(location)
                    self.inv_redirections[location] = old

                elif new_url.scheme in ("", "http", "https"):
                    # direct redirection
                    if new_url.netloc:
                        raise NotImplementedError(
                            "netloc ({netloc}) is not implemented yet for "
                            "url_redirections_dict, it is not possible to redirect to an "
                            "external website".format(netloc=new_url.netloc))
                    location = urllib.parse.urlunsplit(
                        ("", "", new_url.path, new_url.query, new_url.fragment)
                    )
                    request_data = self._get_request_data(location)
                    self.inv_redirections[location] = old

                elif new_url.scheme == "file":
                    # file or directory
                    if new_url.netloc:
                        raise NotImplementedError(
                            "netloc ({netloc}) is not implemented for url redirection to "
                            "file system, it is not possible to redirect to an external "
                            "host".format(
                                netloc=new_url.netloc))
                    path = urllib.parse.unquote(new_url.path)
                    if not os.path.isabs(path):
                        raise ValueError(
                            "file redirection must have an absolute path: e.g. "
                            "file:/path/to/my/file")
                    # for file redirection, we directly put child here
                    resource_class = (
                        ProtectedFile if new_data.get("protected", True) else static.File
                    )
                    res = resource_class(path, defaultType="application/octet-stream")
                    self.add_resource_to_path(old, res)
                    log.info("[{host_name}] Added redirection from /{old} to file system "
                             "path {path}".format(host_name=self.host_name,
                                                   old=old,
                                                   path=path))

                    # we don't want to use redirection system, so we continue here
                    continue

                elif new_url.scheme == "libervia-app":
                    # a Libervia application

                    app_name = urllib.parse.unquote(new_url.path).lower().strip()
                    extra = {"url_prefix": f"/{old}"}
                    try:
                        await self._start_app(app_name, extra)
                    except Exception as e:
                        log.warning(_(
                            "Can't launch {app_name!r} for path /{old}: {e}").format(
                            app_name=app_name, old=old, e=e))
                        continue

                    log.info(
                        f"[{self.host_name}] Added redirection from /{old} to "
                        f"application {app_name}"
                    )
                    # normal redirection system is not used here
                    continue
                elif new_url.scheme == "proxy":
                    # a reverse proxy
                    host, port = new_url.hostname, new_url.port
                    if host is None or port is None:
                        raise ValueError(
                            "invalid host or port in proxy redirection, please check your "
                            "configuration: {new_url.geturl()}"
                        )
                    url_prefix = (new_url.path or old).rstrip('/')
                    res = proxy.SatReverseProxyResource(
                        host,
                        port,
                        url_prefix.encode(),
                    )
                    self.add_resource_to_path(old, res)
                    log.info(
                        f"[{self.host_name}] Added redirection from /{old} to reverse proxy "
                        f"{new_url.netloc} with URL prefix {url_prefix}/"
                    )

                    # normal redirection system is not used here
                    continue
                else:
                    raise NotImplementedError(
                        "{scheme}: scheme is not managed for url_redirections_dict".format(
                            scheme=new_url.scheme
                        )
                    )

                self.redirections.setdefault(old, request_data)
                if not old:
                    log.info(_("[{host_name}] Root URL redirected to {uri}")
                        .format(host_name=self.host_name,
                                uri=request_data[1]))

        # the default root URL, if not redirected
        if not "" in self.redirections:
            self.redirections[""] = self._get_request_data(C.LIBERVIA_PAGE_START)

    async def _set_menu(self, menus):
        menus = menus.get(self.site_name, [])
        main_menu = []
        for menu in menus:
            if not menu:
                msg = _("menu item can't be empty")
                log.error(msg)
                raise ValueError(msg)
            elif isinstance(menu, list):
                if len(menu) != 2:
                    msg = _(
                        "menu item as list must be in the form [page_name, absolue URL]"
                    )
                    log.error(msg)
                    raise ValueError(msg)
                page_name, url = menu
            elif menu.startswith("libervia-app:"):
                app_name = menu[13:].strip().lower()
                app_data = await self._start_app(app_name)
                exposed_data = app_data["expose"]
                external = exposed_data.get("web_external", False)
                if external:
                    # The app is opened separately and not embedded into the Web frontend.
                    try:
                        front_url = exposed_data["front_url"]
                    except KeyError:
                        raise exceptions.DataError(
                            'Missing "front_url" in app data for external app '
                            f'{app_name!r}, it is mandatory when "external" is set. This '
                            f'must be set in {app_name!r} app configuration file.'

                        )
                else:
                    front_url = exposed_data['web_url_path']
                    options = self.host.options
                    url_redirections = options["url_redirections_dict"].setdefault(
                        self.site_name, {}
                    )
                    if front_url in url_redirections:
                        raise exceptions.ConflictError(
                            f"There is already a redirection from {front_url!r}, can't add "
                            f"{app_name!r}")

                    url_redirections[front_url] = {
                        "page": 'embed_app',
                        "path_args": [app_name]
                    }

                page_name = exposed_data.get('web_label', app_name).title()
                url = front_url

                log.debug(
                    f"Application {app_name} added to menu of {self.site_name}"
                )
            else:
                page_name = menu
                try:
                    url = self.get_page_by_name(page_name).url
                except KeyError as e:
                    log_msg = _("Can'find a named page ({msg}), please check "
                                "menu_json in configuration.").format(msg=e.args[0])
                    log.error(log_msg)
                    raise exceptions.ConfigError(log_msg)

            if page_name == "login":
                self.login_url = url
                continue
            icon = C.DEFAULT_ICONS.get(page_name, "")

            main_menu.append({
                "name": page_name,
                "url": url,
                "icon": icon
            })
        self.main_menu = main_menu

    def _normalize_url(self, url, lower=True):
        """Return URL normalized for self.redirections dict

        @param url(unicode): URL to normalize
        @param lower(bool): lower case of url if True
        @return (str): normalized URL
        """
        if lower:
            url = url.lower()
        return "/".join((p for p in url.split("/") if p))

    def _get_request_data(self, uri):
        """Return data needed to redirect request

        @param url(unicode): destination url
        @return (tuple(list[str], str, str, dict): tuple with
            splitted path as in Request.postpath
            uri as in Request.uri
            path as in Request.path
            args as in Request.args
        """
        uri = uri
        # XXX: we reuse code from twisted.web.http.py here
        #      as we need to have the same behaviour
        x = uri.split("?", 1)

        if len(x) == 1:
            path = uri
            args = {}
        else:
            path, argstring = x
            args = urllib.parse.parse_qs(argstring, True)

        # XXX: splitted path case must not be changed, as it may be significant
        #      (e.g. for blog items)
        return (
            self._normalize_url(path, lower=False).split("/"),
            uri,
            path,
            args,
        )

    def _redirect(self, request, request_data):
        """Redirect an URL by rewritting request

        this is *NOT* a HTTP redirection, but equivalent to URL rewritting
        @param request(web.http.request): original request
        @param request_data(tuple): data returned by self._get_request_data
        @return (web_resource.Resource): resource to use
        """
        # recursion check
        try:
            request._redirected
        except AttributeError:
            pass
        else:
            try:
                __, uri, __, __ = request_data
            except ValueError:
                uri = ""
            log.error(D_( "recursive redirection, please fix this URL:\n"
                          "{old} ==> {new}").format(
                          old=request.uri.decode("utf-8"), new=uri))
            return web_resource.NoResource()

        request._redirected = True  # here to avoid recursive redirections

        if isinstance(request_data, dict):
            if request_data["type"] == "page":
                try:
                    page = self.get_page_by_name(request_data["page"])
                except KeyError:
                    log.error(
                        _(
                            'Can\'t find page named "{name}" requested in redirection'
                        ).format(name=request_data["page"])
                    )
                    return web_resource.NoResource()
                path_args = [pa.encode('utf-8') for pa in request_data["path_args"]]
                request.postpath = path_args + request.postpath

                try:
                    request.args.update(request_data["query_args"])
                except (TypeError, ValueError):
                    log.error(
                        _("Invalid args in redirection: {query_args}").format(
                            query_args=request_data["query_args"]
                        )
                    )
                    return web_resource.NoResource()
                return page
            else:
                raise exceptions.InternalError("unknown request_data type")
        else:
            path_list, uri, path, args = request_data
            path_list = [p.encode('utf-8') for p in path_list]
            log.debug(
                "Redirecting URL {old} to {new}".format(
                    old=request.uri.decode('utf-8'), new=uri
                )
            )
            # we change the request to reflect the new url
            request.postpath = path_list[1:] + request.postpath
            request.args.update(args)

        # we start again to look for a child with the new url
        return self.getChildWithDefault(path_list[0], request)

    def get_page_by_name(self, name):
        """Retrieve page instance from its name

        @param name(unicode): name of the page
        @return (LiberviaPage): page instance
        @raise KeyError: the page doesn't exist
        """
        return self.named_pages[name]

    def get_page_path_from_uri(self, uri):
        """Retrieve page URL from xmpp: URI

        @param uri(unicode): URI with a xmpp: scheme
        @return (unicode,None): absolute path (starting from root "/") to page handling
            the URI.
            None is returned if no page has been registered for this URI
        """
        uri_data = common_uri.parse_xmpp_uri(uri)
        try:
            page, cb = self.uri_callbacks[uri_data["type"], uri_data["sub_type"]]
        except KeyError:
            url = None
        else:
            url = cb(page, uri_data)
        if url is None:
            # no handler found
            # we try to find a more generic one
            try:
                page, cb = self.uri_callbacks[uri_data["type"], None]
            except KeyError:
                pass
            else:
                url = cb(page, uri_data)
        return url

    def getChildWithDefault(self, name, request):
        # XXX: this method is overriden only for root url
        #      which is the only ones who need to be handled before other children
        if name == b"" and not request.postpath:
            return self._redirect(request, self.redirections[""])
        return super(LiberviaRootResource, self).getChildWithDefault(name, request)

    def getChild(self, name, request):
        resource = super(LiberviaRootResource, self).getChild(name, request)

        if isinstance(resource, web_resource.NoResource):
            # if nothing was found, we try our luck with redirections
            # XXX: we want redirections to happen only if everything else failed
            path_elt = request.prepath + request.postpath
            for idx in range(len(path_elt), -1, -1):
                test_url = b"/".join(path_elt[:idx]).decode('utf-8').lower()
                if test_url in self.redirections:
                    request_data = self.redirections[test_url]
                    request.postpath = path_elt[idx:]
                    return self._redirect(request, request_data)

        return resource

    def putChild(self, path, resource):
        """Add a child to the root resource"""
        if not isinstance(path, bytes):
            raise ValueError("path must be specified in bytes")
        if not isinstance(resource, web_resource.EncodingResourceWrapper):
            # FIXME: check that no information is leaked (c.f. https://twistedmatrix.com/documents/current/web/howto/using-twistedweb.html#request-encoders)
            resource = web_resource.EncodingResourceWrapper(
                resource, [server.GzipEncoderFactory()])

        super(LiberviaRootResource, self).putChild(path, resource)

    def createSimilarFile(self, path):
        # XXX: this method need to be overriden to avoid recreating a LiberviaRootResource

        f = LiberviaRootResource.__base__(
            path, self.defaultType, self.ignoredExts, self.registry
        )
        # refactoring by steps, here - constructor should almost certainly take these
        f.processors = self.processors
        f.indexNames = self.indexNames[:]
        f.childNotFound = self.childNotFound
        return f