from datetime import datetime
from dateutil.parser import parse as date_parse
import re
from lxml import etree as ET

from osc.core import http_DELETE
from osc.core import http_GET
from osc.core import http_POST
from osc.core import makeurl


class CommentAPI(object):
    COMMENT_MARKER_REGEX = re.compile(r'<!-- (?P<bot>[^ ]+)(?P<info>(?: [^= ]+=[^ ]+)*) -->')

    def __init__(self, apiurl):
        self.apiurl = apiurl

    def _prepare_url(self, request_id=None, project_name=None,
                     package_name=None, query=None):
        """Prepare the URL to get/put comments in OBS.

        :param request_id: Request where to refer the comment.
        :param project_name: Project name where to refer comment.
        :param package_name: Package name where to refer the comment.
        :returns: Formated URL for the request.
        """
        url = None
        if request_id:
            url = makeurl(self.apiurl, ['comments', 'request', request_id], query)
        elif project_name and package_name:
            url = makeurl(self.apiurl, ['comments', 'package', project_name,
                                        package_name], query)
        elif project_name:
            url = makeurl(self.apiurl, ['comments', 'project', project_name], query)
        else:
            raise ValueError('Please, set request_id, project_name or / and package_name to add a comment.')
        return url

    def _comment_as_dict(self, comment_element):
        """Convert an XML element comment into a dictionary.
        :param comment_element: XML element that store a comment.
        :returns: A Python dictionary object.
        """
        comment = {
            'who': comment_element.get('who'),
            'when': datetime.strptime(comment_element.get('when'), '%Y-%m-%d %H:%M:%S %Z'),
            'id': comment_element.get('id'),
            'parent': comment_element.get('parent', None),
            'comment': comment_element.text,
        }
        return comment

    def request_as_comment_dict(self, request):
        return {
            'who': request.creator,
            'when': date_parse(request.statehistory[0].when),
            'id': '-1',
            'parent': None,
            'comment': request.description,
        }

    def get_comments(self, request_id=None, project_name=None,
                     package_name=None):
        """Get the list of comments of an object in OBS.

        :param request_id: Request where to get comments.
        :param project_name: Project name where to get comments.
        :param package_name: Package name where to get comments.
        :returns: A list of comments (as a dictionary).
        """
        url = self._prepare_url(request_id, project_name, package_name)
        root = root = ET.parse(http_GET(url)).getroot()
        comments = {}
        for c in root.findall('comment'):
            c = self._comment_as_dict(c)
            comments[c['id']] = c
        return comments

    def comment_find(self, comments, bot, info_match=None):
        """Return previous bot comments that match criteria."""
        # Case-insensitive for backwards compatibility.
        bot = bot.lower()
        for c in comments.values():
            m = self.COMMENT_MARKER_REGEX.match(c['comment'])
            if m and bot == m.group('bot').lower():
                info = {}

                # Python base regex does not support repeated subgroup capture
                # so parse the optional info using string split.
                stripped = m.group('info').strip()
                if stripped:
                    for pair in stripped.split(' '):
                        key, value = pair.split('=')
                        info[key] = value

                # Skip if info does not match.
                if info_match:
                    match = True
                    for key, value in info_match.items():
                        if not (value is None or (key in info and info[key] == value)):
                            match = False
                            break
                    if not match:
                        continue

                return c, info
        return None, None

    def command_find(self, comments, user, command=None, who_allowed=None):
        """
        Find comment commands with the optional conditions.

        Usage (in comment):
            @<user> <command> [args...]
        """
        command_re = re.compile(r'^@(?P<user>[^ ,:]+)[,:]? (?P<args>.*)$', re.MULTILINE)

        # Search for commands in the order the comment was created.
        for comment in sorted(comments.values(), key=lambda c: c['when']):
            if who_allowed and comment['who'] not in who_allowed:
                continue

            # Handle stupid line endings returned in comments.
            match = command_re.search(comment['comment'].replace('\r', ''))
            if not match:
                continue

            if match.group('user') != user:
                continue

            args = match.group('args').strip().split(' ')
            if command and (args[0] or None) != command:
                continue

            yield args, comment['who']

    def add_marker(self, comment, bot, info=None):
        """Add bot marker to comment that can be used to find comment."""

        if info:
            infos = []
            for key, value in info.items():
                infos.append('='.join((str(key), str(value))))

        marker = '<!-- {}{} -->'.format(bot, ' ' + ' '.join(infos) if info else '')
        return marker + '\n\n' + comment

    def remove_marker(self, comment):
        if comment.startswith('<!--'):
            comment = ''.join(comment.splitlines(True)[1:]).strip()

        return comment

    def add_comment(self, request_id=None, project_name=None,
                    package_name=None, comment=None, parent_id=None):
        """Add a comment in an object in OBS.

        :param request_id: Request where to write a comment.
        :param project_name: Project name where to write a comment.
        :param package_name: Package name where to write a comment.
        :param comment: Comment to be published.
        :return: Comment id.
        """
        if not comment:
            raise ValueError('Empty comment.')

        comment = self.truncate(comment.strip())

        # OBS returns unicode from some APIs, but comment API does not accept
        # when included. Rather than handle everywhere just strip here.
        comment = comment.encode('ascii', 'ignore')

        query = {}
        if parent_id:
            query['parent_id'] = parent_id
        url = self._prepare_url(request_id, project_name, package_name, query)
        return http_POST(url, data=comment)

    @staticmethod
    def truncate(comment, suffix='...', length=65535):
        # Handle very short length by dropping suffix and just chopping comment.
        if length <= len(suffix) + len('\n</pre>'):
            return comment[:length]
        if len(comment) <= length:
            return comment

        # Determine the point at which to end by leaving room for suffix.
        end = length - len(suffix)
        if comment.find('<pre>', 0, end) != -1:
            # For the sake of simplicity leave space for closing pre tag even if
            # after truncation it may no longer be necessary. Otherwise, it
            # requires recursion with some fun edge cases.
            end -= len('\n</pre>')

        # Check for the end location landing inside a pre tag and correct by
        # moving in front of the tag. Landing on the ends is a noop.
        pre_index = max(comment.rfind('<pre>', end - 4, end + 4),
                        comment.rfind('</pre>', end - 5, end + 5))
        if pre_index != -1:
            end = pre_index

        comment = comment[:end]

        # Check for unbalanced pre tag and add a closing tag.
        if comment.count('<pre>') > comment.count('</pre>'):
            suffix += '\n</pre>'

        return comment + suffix

    def delete(self, comment_id):
        """Remove a comment object.
        :param comment_id: Id of the comment object.
        """
        url = makeurl(self.apiurl, ['comment', comment_id])
        return http_DELETE(url)

    def delete_children(self, comments):
        """Removes the comments that have no childs

        :param comments dict of id->comment dict
        :return same hash without the deleted comments
        """
        parents = []
        for comment in comments.values():
            if comment['parent']:
                parents.append(comment['parent'])

        for comment in list(comments.values()):
            if comment['id'] not in parents:
                # Parent comments that have been removed are still returned
                # when children exist and are authored by _nobody_. Such
                # should not be deleted remotely, but only marked internally.
                if comment['who'] != '_nobody_':
                    self.delete(comment['id'])
                del comments[comment['id']]

        return comments

    def delete_from(self, request_id=None, project_name=None,
                    package_name=None):
        """Remove the comments related with a request, project or package.
        :param request_id: Request where to remove comments.
        :param project_name: Project name where to remove comments.
        :param package_name: Package name where to remove comments.
        :return: Number of comments removed.
        """
        comments = self.get_comments(request_id, project_name, package_name)
        while comments:
            comments = self.delete_children(comments)
        return True

    def delete_from_where_user(self, user, request_id=None, project_name=None,
                               package_name=None):
        """Remove comments where @user is mentioned.

        This method is used to remove notifications when a request is
        removed or moved to another project.
        :param user: User name where the comment will be removed.
        :param request_id: Request where to remove comments.
        :param project_name: Project name where to remove comments.
        :param package_name: Package name where to remove comments.
        :return: Number of comments removed.
        """
        for comment in self.get_comments(request_id, project_name, package_name).values():
            if comment['who'] == user:
                self.delete(comment['id'])