# -*- coding: utf-8 -*-
#
# Copyright (C) 2005 Edgewall Software
# Copyright (C) 2005 Christopher Lenz <cmlenz@gmx.de>
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://trac.edgewall.com/license.html.
#
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at http://projects.edgewall.com/trac/.
#
# Author: Christopher Lenz <cmlenz@gmx.de>

from heapq import heappop, heappush

from trac.config import Option
from trac.core import *
from trac.perm import PermissionError


class IRepositoryConnector(Interface):
    """Extension point interface for components that provide support for a
    specific version control system."""

    def get_supported_types():
        """Return the types of version control systems that are supported by
        this connector, and their relative priorities.
        
        Highest number is highest priority.
        """

    def get_repository(repos_type, repos_dir, authname):
        """Return the Repository object for the given repository type and
        directory.
        """


class RepositoryManager(Component):
    """Component that keeps track of the supported version control systems, and
    provides easy access to the configured implementation."""

    connectors = ExtensionPoint(IRepositoryConnector)

    repository_type = Option('trac', 'repository_type', 'svn',
        """Repository connector type. (''since 0.10'')""")
    repository_dir = Option('trac', 'repository_dir', '',
        """Path to local repository""")

    def __init__(self):
        self._connector = None

    # Public API methods

    def get_repository(self, authname):
        if not self._connector:
            candidates = []
            for connector in self.connectors:
                for repos_type_, prio in connector.get_supported_types():
                    if self.repository_type != repos_type_:
                        continue
                    heappush(candidates, (-prio, connector))
            if not candidates:
                raise TracError, 'Unsupported version control system "%s"' \
                                 % self.repository_type
            self._connector = heappop(candidates)[1]
        return self._connector.get_repository(self.repository_type,
                                              self.repository_dir, authname)


class NoSuchChangeset(TracError):
    def __init__(self, rev):
        TracError.__init__(self, "No changeset %s in the repository" % rev)

class NoSuchNode(TracError):
    def __init__(self, path, rev, msg=None):
        TracError.__init__(self, "%sNo node %s at revision %s" \
                           % (msg and '%s: ' % msg or '', path, rev))

class Repository(object):
    """
    Base class for a repository provided by a version control system.
    """

    def __init__(self, name, authz, log):
        self.name = name
        self.authz = authz or Authorizer()
        self.log = log

    def close(self):
        """
        Close the connection to the repository.
        """
        raise NotImplementedError

    def get_changeset(self, rev):
        """
        Retrieve a Changeset object that describes the changes made in
        revision 'rev'.
        """
        raise NotImplementedError

    def get_changesets(self, start, stop):
        """
        Generate Changeset belonging to the given time period (start, stop).
        """
        rev = self.youngest_rev
        while rev:
            if self.authz.has_permission_for_changeset(rev):
                chgset = self.get_changeset(rev)
                if chgset.date < start:
                    return
                if chgset.date < stop:
                    yield chgset
            rev = self.previous_rev(rev)

    def has_node(self, path, rev=None):
        """
        Tell if there's a node at the specified (path,rev) combination.

        When `rev` is `None`, the latest revision is implied.
        """
        try:
            self.get_node(path, rev)
            return True
        except TracError:
            return False        
    
    def get_node(self, path, rev=None):
        """
        Retrieve a Node (directory or file) from the repository at the
        given path. If the rev parameter is specified, the version of the
        node at that revision is returned, otherwise the latest version
        of the node is returned.
        """
        raise NotImplementedError

    def get_oldest_rev(self):
        """
        Return the oldest revision stored in the repository.
        """
        raise NotImplementedError
    oldest_rev = property(lambda x: x.get_oldest_rev())

    def get_youngest_rev(self):
        """
        Return the youngest revision in the repository.
        """
        raise NotImplementedError
    youngest_rev = property(lambda x: x.get_youngest_rev())

    def previous_rev(self, rev):
        """
        Return the revision immediately preceding the specified revision.
        """
        raise NotImplementedError

    def next_rev(self, rev, path=''):
        """
        Return the revision immediately following the specified revision.
        """
        raise NotImplementedError

    def rev_older_than(self, rev1, rev2):
        """
        Return True if rev1 is older than rev2, i.e. if rev1 comes before rev2
        in the revision sequence.
        """
        raise NotImplementedError

    def get_youngest_rev_in_cache(self, db):
        """
        Return the youngest revision currently cached.
        The way revisions are sequenced is version control specific.
        By default, one assumes that the revisions are sequenced in time.
        """
        cursor = db.cursor()
        cursor.execute("SELECT rev FROM revision ORDER BY time DESC LIMIT 1")
        row = cursor.fetchone()
        return row and row[0] or None

    def get_path_history(self, path, rev=None, limit=None):
        """
        Retrieve all the revisions containing this path (no newer than 'rev').
        The result format should be the same as the one of Node.get_history()
        """
        raise NotImplementedError

    def normalize_path(self, path):
        """
        Return a canonical representation of path in the repos.
        """
        return NotImplementedError

    def normalize_rev(self, rev):
        """
        Return a canonical representation of a revision in the repos.
        'None' is a valid revision value and represents the youngest revision.
        """
        return NotImplementedError

    def short_rev(self, rev):
        """
        Return a compact representation of a revision in the repos.
        """
        return self.normalize_rev(rev)
        
    def get_changes(self, old_path, old_rev, new_path, new_rev,
                    ignore_ancestry=1):
        """
        Generator that yields change tuples (old_node, new_node, kind, change)
        for each node change between the two arbitrary (path,rev) pairs.

        The old_node is assumed to be None when the change is an ADD,
        the new_node is assumed to be None when the change is a DELETE.
        """
        raise NotImplementedError


class Node(object):
    """
    Represents a directory or file in the repository.
    """

    DIRECTORY = "dir"
    FILE = "file"

    def __init__(self, path, rev, kind):
        assert kind in (Node.DIRECTORY, Node.FILE), "Unknown node kind %s" % kind
        self.path = unicode(path)
        self.rev = rev
        self.kind = kind

    def get_content(self):
        """
        Return a stream for reading the content of the node. This method
        will return None for directories. The returned object should provide
        a read([len]) function.
        """
        raise NotImplementedError

    def get_entries(self):
        """
        Generator that yields the immediate child entries of a directory, in no
        particular order. If the node is a file, this method returns None.
        """
        raise NotImplementedError

    def get_history(self, limit=None):
        """
        Generator that yields (path, rev, chg) tuples, one for each revision in which
        the node was changed. This generator will follow copies and moves of a
        node (if the underlying version control system supports that), which
        will be indicated by the first element of the tuple (i.e. the path)
        changing.
        Starts with an entry for the current revision.
        """
        raise NotImplementedError

    def get_previous(self):
        """
        Return the (path, rev, chg) tuple corresponding to the previous
        revision for that node.
        """
        skip = True
        for p in self.get_history(2):
            if skip:
                skip = False
            else:
                return p

    def get_properties(self):
        """
        Returns a dictionary containing the properties (meta-data) of the node.
        The set of properties depends on the version control system.
        """
        raise NotImplementedError

    def get_content_length(self):
        raise NotImplementedError
    content_length = property(lambda x: x.get_content_length())

    def get_content_type(self):
        raise NotImplementedError
    content_type = property(lambda x: x.get_content_type())

    def get_name(self):
        return self.path.split('/')[-1]
    name = property(lambda x: x.get_name())

    def get_last_modified(self):
        raise NotImplementedError
    last_modified = property(lambda x: x.get_last_modified())

    isdir = property(lambda x: x.kind == Node.DIRECTORY)
    isfile = property(lambda x: x.kind == Node.FILE)


class Changeset(object):
    """
    Represents a set of changes of a repository.
    """

    ADD = 'add'
    COPY = 'copy'
    DELETE = 'delete'
    EDIT = 'edit'
    MOVE = 'move'

    def __init__(self, rev, message, author, date):
        self.rev = rev
        self.message = message
        self.author = author
        self.date = date

    def get_properties(self):
        """Generator that provide additional metadata for this changeset.

        Each additional property is a 4 element tuple:
         * `name` is the name of the property,
         * `text` its value
         * `wikiflag` indicates whether the `text` should be interpreted as
            wiki text or not
         * `htmlclass` enables to attach special formatting to the displayed
            property, e.g. `'author'`, `'time'`, `'message'` or `'changeset'`.
        """
        
    def get_changes(self):
        """
        Generator that produces a (path, kind, change, base_path, base_rev)
        tuple for every change in the changeset, where change can be one of
        Changeset.ADD, Changeset.COPY, Changeset.DELETE, Changeset.EDIT or
        Changeset.MOVE, and kind is one of Node.FILE or Node.DIRECTORY.
        """
        raise NotImplementedError


class PermissionDenied(PermissionError):
    """
    Exception raised by an authorizer if the user has insufficient permissions
    to view a specific part of the repository.
    """
    def __str__(self):
        return self.action


class Authorizer(object):
    """
    Base class for authorizers that are responsible to granting or denying
    access to view certain parts of a repository.
    """

    def assert_permission(self, path):
        if not self.has_permission(path):
            raise PermissionDenied, \
                  'Insufficient permissions to access %s' % path

    def assert_permission_for_changeset(self, rev):
        if not self.has_permission_for_changeset(rev):
            raise PermissionDenied, \
                  'Insufficient permissions to access changeset %s' % rev

    def has_permission(self, path):
        return True

    def has_permission_for_changeset(self, rev):
        return True