# SPDX-License-Identifier: AGPL-3.0-or-later

# Main repository logic.
#
# This file is part of Hydrilla
#
# Copyright (C) 2021 Wojtek Kosior
#
# 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 <https://www.gnu.org/licenses/>.
#
#
# I, Wojtek Kosior, thereby promise not to sue for violation of this
# file's license. Although I request that you do not make use this code
# in a proprietary program, I am not going to enforce this in court.

from flask import Flask, Blueprint, current_app, url_for, abort, request, \
    redirect
from jinja2 import Environment, PackageLoader
import re
from hashlib import sha256
import os
import pathlib
import json
import gettext
import logging

SCHEMA_VERSION = [0, 2]

strip_comment_re = re.compile(r'''
^ # match from the beginning of each line
( # catch the part before '//' comment
  (?: # this group matches either a string or a single out-of-string character
    [^"/] |
    "
    (?: # this group matches any in-a-string character
      [^"\\] |          # match any normal character
      \\[^u] |          # match any escaped character like '\f' or '\n'
      \\u[a-fA-F0-9]{4} # match an escape
    )*
    "
  )*
)
# expect either end-of-line or a comment:
# * unterminated strings will cause matching to fail
# * bad comment (with '/' instead of '//') will be indicated by second group
#   having length 1 instead of 2 or 0
(//?|$)
''', re.VERBOSE)

def strip_json_comments(text):
    processed = 0
    stripped_text = []
    for line in text.split('\n'):
        match = strip_comment_re.match(line)

        if match is None: # unterminated string
            # ignore this error, let json module report it
            stripped = line
        elif len(match[2]) == 1:
            raise json.JSONDecodeError('bad comment', text,
                                       processed + len(match[1]))
        else:
            stripped = match[1]

        stripped_text.append(stripped)
        processed += len(line) + 1

    return '\n'.join(stripped_text)

here = pathlib.Path(__file__).resolve().parent

bp = Blueprint('bp', __package__)

def load_config(config_path):
    config = {}
    to_load = [config_path]
    failures_ok = [False]

    while to_load:
        path = to_load.pop()
        can_fail = failures_ok.pop()

        try:
            with open(config_path) as config_file:
                new_config = json.loads(strip_json_comments(config_file.read()))
        except Exception as e:
            if can_fail:
                continue
            raise e from None

        config.update(new_config)

        for key, failure_ok in [('try_configs', True), ('use_configs', False)]:
            paths = new_config.get(key, [])
            paths.reverse()
            to_load.extend(paths)
            failures_ok.extend([failure_ok] * len(paths))

    for key in ['try_configs', 'use_configs']:
        if key in config:
            config.pop(key)

    return config

def get_content_file_path(path):
    if os.path.sep != '/':
        path.replace('/', os.path.sep)

    path = pathlib.Path(path)
    if path.is_absolute():
        raise ValueError(_('path_is_absolute_{}').format(path))

    return path

class MyNotImplError(NotImplementedError):
    '''Raised when a planned but not-yet-completed feature is used.'''
    def __init__(self, what, where):
        super().__init__(_('not_implemented_{what}_{where}')
                         .format(what=what, where=where))

def normalize_version(ver):
    '''
    ver is an array of integers. Strip right-most zeroes from ver.

    Returns a *new* array. Doesn't modify its argument.
    '''
    new_len = 0
    for i, num in enumerate(ver):
        if num != 0:
            new_len = i + 1

    return ver[:new_len]

def parse_version(ver_str):
    '''
    Convert ver_str into an array representation, e.g. for ver_str="4.6.13.0"
    return [4, 6, 13, 0].
    '''
    return [int(num) for num in ver_str.split('.')]

def version_string(ver, rev=None):
    '''
    ver is an array of integers. rev is an optional integer. Produce string
    representation of version (optionally with revision number), like:
        1.2.3-5
    No version normalization is performed.
    '''
    return '.'.join([str(n) for n in ver]) + ('' if rev is None else f'-{rev}')

class VersionedContentItem:
    '''Stores definitions of multiple versions of website content item.'''
    def __init__(self):
        self.uuid = None
        self.identifier = None
        self.by_version = {}
        self.known_versions = []

    def register_item(self, item):
        '''Make item queryable by version. Perform sanity checks for uuid.'''
        if self.identifier is None:
            self.identifier = item['identifier']
            self.uuid = item['uuid']
        elif self.uuid != item['uuid']:
            raise ValueError(_('uuid_mismatch_{identifier}')
                             .format(identifier=self.identifier))

        ver = item['version']
        ver_str = version_string(ver)

        if ver_str in self.by_version:
            raise ValueError(_('version_clash_{identifier}_{version}')
                             .format(identifier=self.identifier,
                                     version=ver_str))

        self.by_version[ver_str] = item
        self.known_versions.append(ver)

    def get_by_ver(self, ver=None):
        '''
        Find and return definition of the newest version of item.

        If ver is specified, instead find and return definition of that version
        of the item (or None is absent).
        '''
        ver = version_string(ver or self.known_versions[-1])

        return self.by_version.get(ver)

    def get_all(self):
        '''Return a list of all definitions of item, ordered by version.'''
        return [self.by_version[version_string(ver)]
                for ver in self.known_versions]

class PatternTreeNode:
    '''
    "Pattern Tree" is how we refer to the data structure used for querying
    Haketilo patterns. Those look like 'https://*.example.com/ab/***'. The goal
    is to make it possible for given URL to quickly retrieve all known patterns
    that match it.
    '''
    def __init__(self):
        self.wildcard_matches = [None, None, None]
        self.literal_match    = None
        self.children         = {}

    def search(self, segments):
        '''
        Yields all matches of this segments sequence against the tree that
        starts at this node. Results are produces in order from greatest to
        lowest pattern specificity.
        '''
        nodes = [self]

        for segment in segments:
            next_node = nodes[-1].children.get(segment)
            if next_node is None:
                break

            nodes.append(next_node)

        nsegments = len(segments)
        cond_literal = lambda: len(nodes)     == nsegments
        cond_wildcard = [
            lambda: len(nodes) + 1 == nsegments and segments[-1] != '*',
            lambda: len(nodes) + 1 <  nsegments,
            lambda: len(nodes) + 1 != nsegments or  segments[-1] != '***'
        ]

        while nodes:
            node = nodes.pop()

            for item, condition in [(node.literal_match, cond_literal),
                                    *zip(node.wildcard_matches, cond_wildcard)]:
                if item is not None and condition():
                    yield item

    def add(self, segments, item_instantiator):
        '''
        Make item queryable through (this branch of) the Pattern Tree. If there
        was not yet any item associated with the tree path designated by
        segments, create a new one using item_instantiator() function. Return
        all items matching this path (both the ones that existed and the ones
        just created).
        '''
        node = self
        segment = None

        for segment in segments:
            wildcards = node.wildcard_matches

            child = node.children.get(segment) or PatternTreeNode()
            node.children[segment] = child
            node = child

        if node.literal_match is None:
            node.literal_match = item_instantiator()

        if segment not in ('*', '**', '***'):
            return [node.literal_match]

        if wildcards[len(segment) - 1] is None:
            wildcards[len(segment) - 1] = item_instantiator()

        return [node.literal_match, wildcards[len(segment) - 1]]

proto_regex  = re.compile(r'^(?P<proto>\w+)://(?P<rest>.*)$')
user_re      = r'[^/?#@]+@' # r'(?P<user>[^/?#@]+)@' # discarded for now
query_re     = r'\??[^#]*'  # r'\??(?P<query>[^#]*)' # discarded for now
domain_re    = r'(?P<domain>[^/?#]+)'
path_re      = r'(?P<path>[^?#]*)'
http_regex   = re.compile(f'{domain_re}{path_re}{query_re}.*')
ftp_regex    = re.compile(f'(?:{user_re})?{domain_re}{path_re}.*')

class UrlError(ValueError):
    pass

class DeconstructedUrl:
    '''Represents a deconstructed URL or URL pattern'''
    def __init__(self, url):
        self.url = url

        match = proto_regex.match(url)
        if not match:
            raise UrlError(_('invalid_URL_{}').format(url))

        self.proto = match.group('proto')
        if self.proto not in ('http', 'https', 'ftp'):
            raise UrlError(_('disallowed_protocol_{}').format(proto))

        if self.proto == 'ftp':
            match = ftp_regex.match(match.group('rest'))
        elif self.proto in ('http', 'https'):
            match = http_regex.match(match.group('rest'))

        if not match:
            raise UrlError(_('invalid_URL_{}').format(url))

        self.domain = match.group('domain').split('.')
        self.domain.reverse()
        self.path = [*filter(None, match.group('path').split('/'))]

class MappingItem:
    '''
    A mapping, together with one of its patterns, as stored in Pattern Tree.
    '''
    def __init__(self, pattern, mapping):
        self.pattern = pattern
        self.mapping = mapping

    def register(self, patterns_by_proto):
        '''
        Make self queryable through the Pattern Tree that starts with the
        protocols dictionary passed in the argument.
        '''
        deco = DeconstructedUrl(self.pattern)

        domain_tree = patterns_by_proto.get(deco.proto) or PatternTreeNode()
        patterns_by_proto[deco.proto] = domain_tree

        for path_tree in domain_tree.add(deco.domain, PatternTreeNode):
            for match_list in path_tree.add(deco.path, list):
                match_list.append(self)

class Content:
    '''Stores serveable website content.'''
    def __init__(self, content_dir_path):
        '''
        When an instance of Content is constructed, it searches
        content_dir_path for custom serveable site content and loads it.
        '''
        self.resources = {}
        self.mappings  = {}
        self.licenses  = {}
        self.indexes   = {}
        self.definition_processors = {
            'resource': self._process_resource_or_mapping,
            'mapping': self._process_resource_or_mapping,
            'license': self._process_license
        }
        self.patterns_by_proto = {}
        self.file_sha256sums = {}

        self.content_dir_path = pathlib.Path(content_dir_path).resolve()

        if not self.content_dir_path.is_dir():
            raise ValueError(_('content_dir_path_not_dir'))

        for subdir_path in self.content_dir_path.iterdir():
            if not subdir_path.is_dir():
                continue
            try:
                self._load_content_from_subdir(subdir_path, subdir_path.name)
            except Exception as e:
                if current_app._pydrilla_werror:
                    raise e from None
                logging.error(_('couldnt_load_content_from_%s'), subdir_path,
                              exc_info=True)

        self._report_missing()
        self._finalize()

    def _load_content_from_subdir(self, subdir_path, source_name):
        '''
        Helper function used to load definitions from index.json of a
        subdirectory of the content direcotory.
        '''
        index_path = subdir_path / 'index.json'
        with open(index_path) as index_file:
            index = json.loads(strip_json_comments(index_file.read()))

        self._process_index(index, source_name)

    @staticmethod
    def register_item(dict, item):
        '''
        Helper function used to add a versioned item definition to content
        data structures.
        '''
        identifier = item['identifier']
        versioned_item = dict.get(identifier)
        if versioned_item is None:
            versioned_item = VersionedContentItem()
            dict[identifier] = versioned_item

        versioned_item.register_item(item)

    @staticmethod
    def _process_copyright_and_license(definition):
        '''Helper function used by other _process_*() methods.'''
        for field in ['copyright', 'licenses']:
            if definition[field] == 'auto':
                raise MyNotImplError(f'"{{field}}": "auto"',
                                     definition['source_name'])

    def _get_file_sha256sum(self, path):
        '''
        Compute sha256 of the file at path. Cache results on this Content
        object.
        '''
        path = path.resolve()
        sha256sum = self.file_sha256sums.get(path)

        if sha256sum is None:
            with open(path, mode='rb') as hashed_file:
                sha256sum = sha256(hashed_file.read()).digest().hex()
            self.file_sha256sums[path] = sha256sum

        return sha256sum

    def _add_file_sha256sum(self, source_name, file_object):
        '''
        Expect file_object to be a dict with field "file" holding a file path
        relative to content directory's subdirectory source_name. Compute or
        fetch from cache the sha256 sum of that file and put it in file_object's
        "sha256" field.
        '''
        file_path = self.content_dir_path / source_name / file_object['file']
        file_object['sha256'] = self._get_file_sha256sum(file_path)

    def _process_resource_or_mapping(self, definition, index):
        '''
        Sanitizes, autocompletes and registers serveable mapping/resource
        definition.
        '''
        definition['version'] = normalize_version(definition['version'])

        if definition['type'] == 'resource':
            self._process_copyright_and_license(definition)
            definition['dependencies'] = definition.get('dependencies', [])
            self.register_item(self.resources, definition)
            source_name = definition['source_name']
            for script in definition['scripts']:
                self._add_file_sha256sum(source_name, script)
        else:
            self.register_item(self.mappings, definition)

    def _process_license(self, license, index):
        '''Sanitizes and registers serveable license definition.'''
        identifier = license['identifier']
        if identifier in self.licenses:
            raise ValueError(_('license_clash_{}').format(identifier))

        self.licenses[identifier] = license

        source_name = license['source_name']
        for legal_text in license['legal_text']:
            self._add_file_sha256sum(source_name, legal_text)

        notice = license.get('notice')
        if notice is not None:
            self._add_file_sha256sum(source_name, notice)

    def _process_index(self, index, source_name):
        '''
        Sanitizes, autocompletes and registers data from a loaded index.json
        file.
        '''
        schema_ver = normalize_version(index['schema_version'])
        index['schema_version'] = schema_ver
        if schema_ver != SCHEMA_VERSION:
            raise ValueError('index_json_schema_mismatch_{found}_{required}'
                             .format(found=version_string(schema_ver),
                                     required=version_string(SCHEMA_VERSION)))

        if source_name in self.indexes:
            raise ValueError(_('source_name_clash_{}').format(source_name))

        index['source_name'] = source_name

        self._process_copyright_and_license(index)

        self.indexes[source_name] = index

        for definition in index['definitions']:
            try:
                definition['source_name'] = source_name
                definition['source_copyright'] = index['copyright']
                definition['source_licenses'] = index['licenses']
                processor = self.definition_processors[definition['type']]
                processor(definition, index)
            except Exception as e:
                if current_app._pydrilla_werror:
                    raise e from None
                logging.error(_('couldnt_load_definition_from_%s'), subdir_path,
                              exc_info=True)
    @staticmethod
    def all_items(versioned_items_dict):
        '''Iterator over all registered versions of all items.'''
        for versioned_item in versioned_items_dict.values():
            for item in versioned_item.by_version.values():
                yield item

    def _report_missing(self):
        '''
        Use logger to print information about items that are referenced but
        were not loaded.
        '''
        def report_missing_license(object, object_type, lic):
            if object_type == 'index':
                logging.error(_('no_index_license_%(source)s_%(lic)s'),
                              source=object['source_name'], lic=lic)
                return

            ver_str = version_string(object['version'])
            kwargs = {object_type: object['identifier'], ver: ver_str, lic: lic}
            if object_type == 'resource':
                fmt = _('no_resource_license_%(resource)s_%(ver)s_%(lic)s')
            else:
                fmt = _('no_mapping_license_%(mapping)s_%(ver)s_%(lic)s')

            logging.error(fmt, **kwargs)

        for object_type, iterable in [
                ('index',    self.indexes.values()),
                ('resource', self.all_items(self.resources))
        ]:
            for object in iterable:
                to_process = [object['licenses']]
                licenses = []
                while to_process:
                    term = to_process.pop()

                    if type(term) is str:
                        if term not in ['or', 'and'] and \
                           term not in self.licenses:
                            report_missing_license(object, object_type, lic)
                        continue

                    to_process.extend(term)

        def report_missing_dependency(resource, dep):
            logging.error(_('no_dep_%(resource)s_%(ver)s_%(dep)s'),
                          dep=dep, resource=resource['identifier'],
                          ver=version_string(resource['version']))

        for resource in self.all_items(self.resources):
            for dep in resource['dependencies']:
                if dep not in self.resources:
                    report_missing_dependency(resource, dep)

        def report_missing_payload(mapping, payload):
            logging.error(_('no_payload_%(mapping)s_%(ver)s_%(payload)s'),
                          mapping=mapping['identifier'], payload=payload,
                          ver=version_string(mapping['version']))

        for mapping in self.all_items(self.mappings):
            for payload in mapping['payloads']:
                payload = payload['payload']
                if payload not in self.resources:
                    report_missing_payload(mapping, payload)

    def _finalize(self):
        '''
        Initialize structures needed to serve queries. Called once after all
        data gets loaded.
        '''
        for dict in [self.resources, self.mappings]:
            for versioned_item in dict.values():
                versioned_item.known_versions.sort()

        for mapping in self.all_items(self.mappings):
            for payload in mapping['payloads']:
                pattern = payload['pattern']
                try:
                    MappingItem(pattern, mapping)\
                        .register(self.patterns_by_proto)
                except Exception as e:
                    if current_app._pydrilla_werror:
                        raise e from None
                    logging.error(
                        _('couldnt_register_%(mapping)s_%(ver)s_%(pattern)s'),
                        mapping=mapping['identifier'], pattern=pattern,
                        ver=version_string(mapping['version'])
                    )

    def query(self, url):
        '''
        Return a list of registered mappings that match url.

        If multiple versions of a mapping are applicable, only the most recent
        is included in the result.
        '''
        deco = DeconstructedUrl(url)

        mappings = {}

        domain_tree = self.patterns_by_proto.get(deco.proto) \
            or PatternTreeNode()

        def process_item(item):
            if url[-1] != '/' and item.pattern[-1] == '/':
                return

            identifier = item.mapping['identifier']

            if identifier not in mappings or \
               item.mapping['version'] > mappings[identifier]['version']:
                mappings[identifier] = item.mapping

        for path_tree in domain_tree.search(deco.domain):
            for item_list in path_tree.search(deco.path):
                for item in item_list:
                    process_item(item)

        return list(mappings.values())

def create_app(config_path=(here / 'config.json'), flask_config={}):
    app = Flask(__package__)
    app.config.update(flask_config)

    language = flask_config.get('lang', 'en')
    translation = gettext.translation('pydrilla', localedir=(here / 'locales'),
                                      languages=[language])

    app._pydrilla_gettext = translation.gettext

    # https://stackoverflow.com/questions/9449101/how-to-stop-flask-from-initialising-twice-in-debug-mode
    if app.debug and os.environ.get('WERKZEUG_RUN_MAIN') != 'true':
        return app

    config = load_config(config_path)
    for key in ['static_resource_uri', 'content_dir', 'hydrilla_sources_uri']:
        if key not in config:
            raise ValueError(_('config_key_absent_{}').format(key))

    app._pydrilla_static_resource_uri  = config['static_resource_uri']
    if app._pydrilla_static_resource_uri[-1] != '/':
        app._pydrilla_static_resource_uri += '/'
    app._pydrilla_hydrilla_sources_uri = config['hydrilla_sources_uri']
    app._pydrilla_werror = config.get('werror', False)
    if 'hydrilla_parent' in config:
        raise MyNotImplError('hydrilla_parent', config_path.name)

    content_dir = pathlib.Path(config['content_dir'])
    if not content_dir.is_absolute():
        content_dir = config_path.parent / content_dir
    with app.app_context():
        app._pydrilla_content = Content(content_dir.resolve())

    app.register_blueprint(bp)

    return app

def _(text_key):
    return current_app._pydrilla_gettext(text_key)

def content():
    return current_app._pydrilla_content

class MyEnvironment(Environment):
    '''
    A wrapper class around jinja2.Environment that causes GNU gettext function
    (as '_' and '__'), url_for function and 'hydrilla_sources_uri' config option
    to be passed to every call of each template's render() method.
    '''

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def get_template(self, *args, **kwargs):
        template = super().get_template(*args, **kwargs)
        old_render = template.render

        def new_render(*args, **kwargs):
            _ = current_app._pydrilla_gettext
            sources_uri = current_app._pydrilla_hydrilla_sources_uri

            def escaping_gettext(text_key):
                from markupsafe import escape

                return str(escape(_(text_key)))

            final_kwargs = {
                '_': escaping_gettext,
                '__': escaping_gettext,
                'url_for': url_for,
                'hydrilla_sources_uri' : sources_uri
            }
            final_kwargs.update(kwargs)

            return old_render(*args, **final_kwargs)

        template.render = new_render

        return template

j2env = MyEnvironment(loader=PackageLoader(__package__), autoescape=False)

indexpage = j2env.get_template('index.html')
@bp.route('/')
def index():
    return indexpage.render()

def get_resource_or_mapping(identifier, get_dict):
    ver = request.args.get('ver')
    versioned_item = get_dict().get(identifier)

    if ver == 'all':
        definition = versioned_item.get_all() if versioned_item else []
    else:
        if ver is not None:
            try:
                ver = normalize_version(parse_version(ver))
            except:
                abort(400)

        definition = versioned_item and versioned_item.get_by_ver(ver)
        if definition is None:
            abort(404)

    return json.dumps(definition)

def get_license_or_source(identifier, get_dict):
    definition = get_dict().get(identifier)
    if definition is None:
        abort(404)

    return json.dumps(definition)

for item_type, get_dict, get_item in [
        ('resource', lambda: content().resources, get_resource_or_mapping),
        ('mapping',  lambda: content().mappings,  get_resource_or_mapping),
        ('license',  lambda: content().licenses,  get_license_or_source),
        ('source',   lambda: content().indexes,   get_license_or_source)
]:
    def _get_item(identifier, get_dict=get_dict, get_item=get_item):
        return get_item(identifier, get_dict)

    bp.add_url_rule(f'/{item_type}s/<string:identifier>', item_type, _get_item)

@bp.route('/query')
def query():
    url = request.args['url']

    return json.dumps(content().query(url))

@bp.route('/sources/<string:identifier>/<path:path>')
def get_file(identifier, path):
    if identifier not in content().indexes:
        abort(404)

    new_uri = f'{current_app._pydrilla_static_resource_uri}{identifier}/{path}'

    return redirect(new_uri, code=301)