#!/usr/bin/env python
# -*- coding:utf-8 -*-

import base64
import io
import json
import logging
import os
import sys

from jinja2 import FileSystemLoader, Environment
import nbformat
from jupyter_server.base.handlers import JupyterHandler, APIHandler
from jupyter_server.utils import url_path_join
from jupyter_server.log import log_request
import requests
from tornado import ioloop, web, escape, netutil, httpserver

from .. import __file__ as nbdime_root
from ..args import ConfigBackedParser, add_generic_args, add_web_args
from ..diffing.notebooks import diff_notebooks
from ..log import logger
from ..merging.notebooks import decide_notebook_merge
from ..nbmergeapp import _build_arg_parser as build_merge_parser
from ..utils import EXPLICIT_MISSING_FILE, is_in_repo


# TODO: See <notebook>/notebook/services/contents/handlers.py for possibly useful utilities:
#contents_manager
#ContentsHandler


# Separate logger for server entrypoint (?)
_logger = logging.getLogger(__name__)


here = os.path.abspath(os.path.dirname(__file__))
static_path = os.path.join(here, 'static')
template_path = os.path.join(here, 'templates')


class NbdimeHandler(JupyterHandler):
    def initialize(self, **params):
        self.params = params

    def base_args(self):
        fn = self.params.get('outputfilename', None)
        base = {
            'closable': self.params.get('closable', False),
            'savable': fn is not None,
            'baseUrl': self.nbdime_base_url,
            'hideUnchanged': self.params.get('hide_unchanged', True),
            'collapseIdentical': self.params.get('identical_lines_margin', 2),
        }
        if fn:
            # For reference, e.g. if user wants to download file
            base['outputfilename'] = fn
        return base

    def write_error(self, status_code, **kwargs):
        # Write error message for HTTPErrors if serve_traceback is off:
        exc_info = kwargs.get('exc_info', None)
        if exc_info and not self.settings.get('serve_traceback'):
            (etype, value, traceback) = exc_info
            if etype == web.HTTPError:
                self.set_header('Content-Type', 'text/plain')
                return self.finish(str(value))
        return super(NbdimeHandler, self).write_error(status_code, **kwargs)

    def read_notebook(self, arg, fail_on_empty=True):
        # Currently assuming arg is a filename relative to
        # where the server was started from, later we may
        # want to accept urls or full notebooks as well.
        if not isinstance(arg, str):
            raise web.HTTPError(400, 'Expecting a filename or a URL.')

        try:
            # Check that file exists
            if arg == EXPLICIT_MISSING_FILE:
                path = arg
            else:
                path = os.path.join(self.curdir, arg)
                if not os.path.exists(path):
                    if '://' not in arg:
                        raise ValueError('Supplied argument cannot be read: %r' % arg)
                    # Assume file is URI
                    r = requests.get(arg)
                    r.raise_for_status()

            # Let nbformat do the reading and validation
            if path == EXPLICIT_MISSING_FILE:
                nb = nbformat.v4.new_notebook()
            elif os.path.exists(path):
                try:
                    nb = nbformat.read(path, as_version=4)
                except nbformat.reader.NotJSONError:
                    if fail_on_empty:
                        raise
                    # Handle empty notebook file
                    if isinstance(path, str):
                        with io.open(path, encoding='utf-8') as fo:
                            if len(fo.read(10)) != 0:
                                raise
                    nb = nbformat.v4.new_notebook()
            else:
                nb = nbformat.reads(r.text, as_version=4)
        except requests.exceptions.HTTPError as e:
            self.log.exception(e)
            raise web.HTTPError(422, 'Invalid notebook: %s, received http error: %s' % (arg, str(e)))
        except Exception as e:
            self.log.exception(e)
            raise web.HTTPError(422, 'Invalid notebook: %s' % arg)

        return nb

    def get_notebook_argument(self, argname):
        # Assuming a request on the form "{'argname':arg}"
        body = json.loads(escape.to_unicode(self.request.body))
        arg = body[argname]

        return self.read_notebook(arg)

    @property
    def nbdime_base_url(self):
        relative = self.params.get('nbdime_relative_base_url', None)
        if relative is None:
            return self.base_url
        return url_path_join(self.base_url, relative)

    @property
    def curdir(self):
        return self.params.get('cwd', os.curdir)

    # Polyfill in until we can rely on Notebook 5.0 being present
    @property
    def mathjax_config(self):
        try:
            return super(NbdimeHandler, self).mathjax_config
        except AttributeError:
            return 'TeX-AMS_HTML-full,Safe'


class MainHandler(NbdimeHandler):
    def get(self):
        args = self.base_args()
        args['base'] = self.get_argument('base', '')
        args['local'] = self.get_argument('local', '')
        args['remote'] = self.get_argument('remote', '')
        self.write(self.render_template('compare.html',
                    config_data=args,
                   ))


class MainDiffHandler(NbdimeHandler):
    def get(self):
        args = self.base_args()
        args['base'] = self.get_argument('base', '')
        args['remote'] = self.get_argument('remote', '')

        self.write(self.render_template('diff.html',
                    config_data=args,
                   ))


class MainDifftoolHandler(NbdimeHandler):
    def get(self):
        args = self.base_args()
        if 'difftool_args' in self.params:
            base = self.params['difftool_args']['base']
            remote = self.params['difftool_args']['remote']
            if isinstance(base, str):
                args['base'] = base
            else:
                args['base'] = base.name
            if isinstance(remote, str):
                args['remote'] = remote
            else:
                args['remote'] = remote.name
        else:
            args['base'] = self.get_argument('base', '')
            args['remote'] = self.get_argument('remote', '')
        self.write(self.render_template('difftool.html',
                    config_data=args,
                   ))


class MainMergeHandler(NbdimeHandler):
    def get(self):
        args = self.base_args()
        args['base'] = self.get_argument('base', '')
        args['local'] = self.get_argument('local', '')
        args['remote'] = self.get_argument('remote', '')
        args['showBase'] = self.params.get('show_base', True)
        self.write(self.render_template('merge.html',
                    config_data=args,
                   ))


class MainMergetoolHandler(NbdimeHandler):
    def get(self):
        args = self.base_args()
        if 'mergetool_args' in self.params:
            args['base'] = self.params['mergetool_args']['base']
            args['local'] = self.params['mergetool_args']['local']
            args['remote'] = self.params['mergetool_args']['remote']
            args['showBase'] = self.params.get('show_base', True)
        else:
            args['base'] = self.get_argument('base', '')
            args['local'] = self.get_argument('local', '')
            args['remote'] = self.get_argument('remote', '')
            args['showBase'] = self.params.get('show_base', True)
        self.write(self.render_template('mergetool.html',
                    config_data=args,
                   ))


class ApiDiffHandler(NbdimeHandler, APIHandler):
    def post(self):
        base_nb = self.get_notebook_argument('base')
        remote_nb = self.get_notebook_argument('remote')

        try:
            thediff = diff_notebooks(base_nb, remote_nb)
        except Exception:
            logger.exception('Error diffing documents:')
            raise web.HTTPError(500, 'Error while attempting to diff documents')

        data = {
            'base': base_nb,
            'diff': thediff,
            }
        self.finish(data)

    def get_notebook_argument(self, argname):
        if 'difftool_args' in self.params:
            arg = self.params['difftool_args'][argname]
            if not isinstance(arg, str):
                # Assume arg is file-like
                arg.seek(0)
                return nbformat.read(arg, as_version=4)
            return self.read_notebook(arg)
        return super(ApiDiffHandler, self).get_notebook_argument(argname)


class ApiMergeHandler(NbdimeHandler, APIHandler):
    def post(self):
        base_nb = self.get_notebook_argument('base')
        local_nb = self.get_notebook_argument('local')
        remote_nb = self.get_notebook_argument('remote')
        merge_args = self.settings.get('merge_args')
        if merge_args is None:
            merge_args = build_merge_parser().parse_args(['', '', ''])
            merge_args.merge_strategy = 'mergetool'
            self.settings['merge_args'] = merge_args

        try:
            decisions = decide_notebook_merge(base_nb, local_nb, remote_nb,
                                              args=merge_args)
        except Exception:
            logger.exception('Error merging documents:')
            raise web.HTTPError(500, 'Error while attempting to merge documents')

        data = {
            'base': base_nb,
            'merge_decisions': decisions
            }
        self.finish(data)

    def get_notebook_argument(self, argname):
        if 'mergetool_args' in self.params:
            arg = self.params['mergetool_args'][argname]
            return self.read_notebook(arg, fail_on_empty=False)
        return super(ApiMergeHandler, self).get_notebook_argument(argname)


class ApiMergeStoreHandler(NbdimeHandler, APIHandler):
    def post(self):
        # I don't think we want to accept arbitrary filenames
        # to write to from the http request, only allowing
        # this operation if the server was run with an output
        # filename as a commandline argument:
        fn = self.params.get('outputfilename', None)
        if not fn:
            raise web.HTTPError(400, 'Server does not accept storing merge result.')
        path = os.path.join(self.curdir, fn)
        logger.info('Saving merge result in %s', path)

        body = json.loads(escape.to_unicode(self.request.body))
        merged = body['merged']
        merged_nb = nbformat.from_dict(merged)

        # Somehow store unsolved conflicts?
        # conflicts = body['conflicts']

        with io.open(path, 'w', encoding='utf8') as f:
            nbformat.write(merged_nb, f)
        self.finish()


class ApiCloseHandler(NbdimeHandler, APIHandler):
    def post(self):
        # Only allow closing, if started as tool
        if self.params.get('closable', False) is not True:
            raise web.HTTPError(
                400, 'This server cannot be closed remotely.')

        # Fail if no exit code is supplied:
        fallback = int(self.request.headers.get('exit_code', 1))
        try:
            self.application.exit_code = self.get_argument('exitCode')
        except web.MissingArgumentError:
            try:
                self.application.exit_code = json.loads(self.request.body).get('exitCode', fallback)
            except json.JSONDecodeError:
                self.application.exit_code = fallback

        if isinstance(self.application.exit_code, str):
            self.application.exit_code = int(self.application.exit_code, 10)

        _logger.info('Closing server on remote request (%d)', self.application.exit_code)
        self.finish()
        ioloop.IOLoop.current().stop()


def asyncio_patch():
    """set default asyncio policy to be compatible with tornado

    Tornado 6 (at least) is not compatible with the default
    asyncio implementation on Windows

    Pick the older SelectorEventLoopPolicy on Windows
    if the known-incompatible default policy is in use.

    do this as early as possible to make it a low priority and overrideable

    ref: https://github.com/tornadoweb/tornado/issues/2608

    FIXME: if/when tornado supports the defaults in asyncio,
            remove and bump tornado requirement for py38
    """
    if sys.platform.startswith("win") and sys.version_info >= (3, 8):
        import asyncio
        try:
            from asyncio import (
                WindowsProactorEventLoopPolicy,
                WindowsSelectorEventLoopPolicy,
            )
        except ImportError:
            pass
            # not affected
        else:
            if type(asyncio.get_event_loop_policy()) is WindowsProactorEventLoopPolicy:
                # WindowsProactorEventLoopPolicy is not compatible with tornado 6
                # fallback to the pre-3.8 default of Selector
                asyncio.set_event_loop_policy(WindowsSelectorEventLoopPolicy())


def make_app(**params):
    base_url = params.pop('base_url', '/')
    handlers = [
        (r'/', MainHandler, params),
        (r'/diff', MainDiffHandler, params),
        (r'/difftool', MainDifftoolHandler, params),
        (r'/merge', MainMergeHandler, params),
        (r'/mergetool', MainMergetoolHandler, params),
        (r'/api/diff', ApiDiffHandler, params),
        (r'/api/merge', ApiMergeHandler, params),
        (r'/api/store', ApiMergeStoreHandler, params),
        (r'/api/closetool', ApiCloseHandler, params),
        # Static handler will be added automatically
    ]
    if base_url != '/':
        prefix = base_url.rstrip('/')
        handlers = [
            (prefix + path, cls, params)
            for (path, cls, params) in handlers
        ]
    else:
        prefix = ''

    env = Environment(loader=FileSystemLoader([template_path]), autoescape=False)
    settings = {
        'log_function': log_request,
        'static_path': static_path,
        'static_url_prefix': prefix + '/static/',
        'template_path': [template_path],
        'base_url': base_url,
        'jinja2_env': env,
        'local_hostnames': ['localhost', '127.0.0.1'],
        'cookie_secret': base64.encodebytes(os.urandom(32)), # Needed even for an unsecured server.
    }

    try:
        from jupyter_server.auth import IdentityProvider
        settings['identity_provider'] = IdentityProvider()
    except ImportError:
        pass

    if is_in_repo(nbdime_root):
        # don't cache when working from repo
        settings.update({
            # 'autoreload': True,
            'compiled_template_cache': False,
            'static_hash_cache': False,
            # 'serve_traceback': True,
            })

    app = web.Application(handlers, **settings)
    app.exit_code = 0
    return app

def init_app(on_port=None, closable=False, **params):
    asyncio_patch()
    _logger.debug('Using params: %s', params)
    params.update({'closable': closable})
    port = params.pop('port', 0)
    ip = params.pop('ip', '127.0.0.1')
    app = make_app(**params)
    if ip not in {'127.0.0.1', 'localhost', '::1'}:
        # enable remote access when listening on a public ip
        app.settings['allow_remote_access'] = True
    if port != 0:
        server = app.listen(port, address=ip)
        _logger.info('Listening on %s, port %d', ip, port)
    else:
        sockets = netutil.bind_sockets(0, ip)
        server = httpserver.HTTPServer(app)
        server.add_sockets(sockets)
        for s in sockets:
            _logger.info('Listening on %s, port %d', *s.getsockname()[:2])
            port = s.getsockname()[1]
    if on_port is not None:
        on_port(port)
    return app, server


def main_server(on_port=None, closable=False, **params):
    app, server = init_app(on_port, closable, **params)
    io_loop = ioloop.IOLoop.current()
    if sys.platform.startswith('win'):
        # workaround for tornado on Windows:
        # add no-op to wake every 5s
        # to handle signals that may be ignored by the inner loop
        pc = ioloop.PeriodicCallback(lambda : None, 5000)
        pc.start()
    io_loop.start()
    # Clean up after server:
    server.stop()
    return app.exit_code


def _build_arg_parser():
    """
    Creates an argument parser that lets the user specify a port
    and displays a help message.
    """
    description = 'Web interface for Nbdime.'
    parser = ConfigBackedParser(description=description)
    add_generic_args(parser)
    add_web_args(parser)
    return parser


def main(args=None):
    if args is None:
        args = sys.argv[1:]
    arguments = _build_arg_parser().parse_args(args)
    return main_server(port=arguments.port,
                       ip=arguments.ip,
                       cwd=arguments.workdirectory,
                       base_url=arguments.base_url,
                      )


if __name__ == '__main__':
    sys.exit(main())