# hgweb/common.py - Utility functions needed by hgweb_mod and hgwebdir_mod

#

# Copyright 21 May 2005 - (c) 2005 Jake Edge <jake@edge2.net>

# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import base64

import errno

import mimetypes

import os

from .. import (

    encoding,

    pycompat,

    util,

)

httpserver = util.httpserver

HTTP_OK = 200

HTTP_NOT_MODIFIED = 304

HTTP_BAD_REQUEST = 400

HTTP_UNAUTHORIZED = 401

HTTP_FORBIDDEN = 403

HTTP_NOT_FOUND = 404

HTTP_METHOD_NOT_ALLOWED = 405

HTTP_SERVER_ERROR = 500

def ismember(ui, username, userlist):

    """Check if username is a member of userlist.

    If userlist has a single '*' member, all users are considered members.

    Can be overridden by extensions to provide more complex authorization

    schemes.

    """

    return userlist == ['*'] or username in userlist

def checkauthz(hgweb, req, op):

    '''Check permission for operation based on request data (including

    authentication info). Return if op allowed, else raise an ErrorResponse

    exception.'''

    user = req.env.get('REMOTE_USER')

    deny_read = hgweb.configlist('web', 'deny_read')

    if deny_read and (not user or ismember(hgweb.repo.ui, user, deny_read)):

        raise ErrorResponse(HTTP_UNAUTHORIZED, 'read not authorized')

    allow_read = hgweb.configlist('web', 'allow_read')

    if allow_read and (not ismember(hgweb.repo.ui, user, allow_read)):

        raise ErrorResponse(HTTP_UNAUTHORIZED, 'read not authorized')

    if op == 'pull' and not hgweb.allowpull:

        raise ErrorResponse(HTTP_UNAUTHORIZED, 'pull not authorized')

    elif op == 'pull' or op is None: # op is None for interface requests

        return

    # enforce that you can only push using POST requests

    if req.env['REQUEST_METHOD'] != 'POST':

        msg = 'push requires POST request'

        raise ErrorResponse(HTTP_METHOD_NOT_ALLOWED, msg)

    # require ssl by default for pushing, auth info cannot be sniffed

    # and replayed

    scheme = req.env.get('wsgi.url_scheme')

    if hgweb.configbool('web', 'push_ssl') and scheme != 'https':

        raise ErrorResponse(HTTP_FORBIDDEN, 'ssl required')

    deny = hgweb.configlist('web', 'deny_push')

    if deny and (not user or ismember(hgweb.repo.ui, user, deny)):

        raise ErrorResponse(HTTP_UNAUTHORIZED, 'push not authorized')

    allow = hgweb.configlist('web', 'allow_push')

    if not (allow and ismember(hgweb.repo.ui, user, allow)):

        raise ErrorResponse(HTTP_UNAUTHORIZED, 'push not authorized')

# Hooks for hgweb permission checks; extensions can add hooks here.

# Each hook is invoked like this: hook(hgweb, request, operation),

# where operation is either read, pull or push. Hooks should either

# raise an ErrorResponse exception, or just return.

#

# It is possible to do both authentication and authorization through

# this.

permhooks = [checkauthz]

class ErrorResponse(Exception):

    def __init__(self, code, message=None, headers=None):

        if message is None:

            message = _statusmessage(code)

        Exception.__init__(self, message)

        self.code = code

        if headers is None:

            headers = []

        self.headers = headers

class continuereader(object):

    def __init__(self, f, write):

        self.f = f

        self._write = write

        self.continued = False

    def read(self, amt=-1):

        if not self.continued:

            self.continued = True

            self._write('HTTP/1.1 100 Continue\r\n\r\n')

        return self.f.read(amt)

    def __getattr__(self, attr):

        if attr in ('close', 'readline', 'readlines', '__iter__'):

            return getattr(self.f, attr)

        raise AttributeError

def _statusmessage(code):

    responses = httpserver.basehttprequesthandler.responses

    return responses.get(code, ('Error', 'Unknown error'))[0]

def statusmessage(code, message=None):

    return '%d %s' % (code, message or _statusmessage(code))

def get_stat(spath, fn):

    """stat fn if it exists, spath otherwise"""

    cl_path = os.path.join(spath, fn)

    if os.path.exists(cl_path):

        return os.stat(cl_path)

    else:

        return os.stat(spath)

def get_mtime(spath):

    return get_stat(spath, "00changelog.i").st_mtime

def ispathsafe(path):

    """Determine if a path is safe to use for filesystem access."""

    parts = path.split('/')

    for part in parts:

        if (part in ('', os.curdir, os.pardir) or

            pycompat.ossep in part or

            pycompat.osaltsep is not None and pycompat.osaltsep in part):

            return False

    return True

def staticfile(directory, fname, req):

    """return a file inside directory with guessed Content-Type header

    fname always uses '/' as directory separator and isn't allowed to

    contain unusual path components.

    Content-Type is guessed using the mimetypes module.

    Return an empty string if fname is illegal or file not found.

    """

    if not ispathsafe(fname):

        return

    fpath = os.path.join(*fname.split('/'))

    if isinstance(directory, str):

        directory = [directory]

    for d in directory:

        path = os.path.join(d, fpath)

        if os.path.exists(path):

            break

    try:

        os.stat(path)

        ct = mimetypes.guess_type(path)[0] or "text/plain"

        with open(path, 'rb') as fh:

            data = fh.read()

        req.respond(HTTP_OK, ct, body=data)

    except TypeError:

        raise ErrorResponse(HTTP_SERVER_ERROR, 'illegal filename')

    except OSError as err:

        if err.errno == errno.ENOENT:

            raise ErrorResponse(HTTP_NOT_FOUND)

        else:

            raise ErrorResponse(HTTP_SERVER_ERROR,

                                encoding.strtolocal(err.strerror))

def paritygen(stripecount, offset=0):

    """count parity of horizontal stripes for easier reading"""

    if stripecount and offset:

        # account for offset, e.g. due to building the list in reverse

        count = (stripecount + offset) % stripecount

        parity = (stripecount + offset) / stripecount & 1

    else:

        count = 0

        parity = 0

    while True:

        yield parity

        count += 1

        if stripecount and count >= stripecount:

            parity = 1 - parity

            count = 0

def get_contact(config):

    """Return repo contact information or empty string.

    web.contact is the primary source, but if that is not set, try

    ui.username or $EMAIL as a fallback to display something useful.

    """

    return (config("web", "contact") or

            config("ui", "username") or

            encoding.environ.get("EMAIL") or "")

def caching(web, req):

    tag = r'W/"%d"' % web.mtime

    if req.env.get('HTTP_IF_NONE_MATCH') == tag:

        raise ErrorResponse(HTTP_NOT_MODIFIED)

    req.headers.append(('ETag', tag))

def cspvalues(ui):

    """Obtain the Content-Security-Policy header and nonce value.

    Returns a 2-tuple of the CSP header value and the nonce value.

    First value is ``None`` if CSP isn't enabled. Second value is ``None``

    if CSP isn't enabled or if the CSP header doesn't need a nonce.

    """

    # Don't allow untrusted CSP setting since it be disable protections

    # from a trusted/global source.

    csp = ui.config('web', 'csp', untrusted=False)

    nonce = None

    if csp and '%nonce%' in csp:

        nonce = base64.urlsafe_b64encode(uuid.uuid4().bytes).rstrip('=')

        csp = csp.replace('%nonce%', nonce)

    return csp, nonce