# Copyright (C) 2009-2013  Roman Zimbelmann <hut@lavabit.com>
# This software is distributed under the terms of the GNU GPL version 3.

import string
import re
import os
ALLOWED_KEYS = string.ascii_letters + string.digits + "`'"

class Bookmarks(object):
    """Bookmarks is a container which associates keys with bookmarks.

    A key is a string with: len(key) == 1 and key in ALLOWED_KEYS.

    A bookmark is an object with: bookmark == bookmarktype(str(instance))
    Which is true for str or FileSystemObject. This condition is required
    so bookmark-objects can be saved to and loaded from a file.

    Optionally, a bookmark.go() method is used for entering a bookmark.
    """

    last_mtime = None
    autosave = True
    load_pattern = re.compile(r"^[\d\w']:.")

    def __init__(self, bookmarkfile, bookmarktype=str, autosave=False):
        """Initializes Bookmarks.

        <bookmarkfile> specifies the path to the file where
        bookmarks are saved in.
        """
        self.autosave = autosave
        self.dct = {}
        self.path = bookmarkfile
        self.bookmarktype = bookmarktype

    def load(self):
        """Load the bookmarks from path/bookmarks"""
        try:
            new_dict = self._load_dict()
        except OSError:
            return

        self._set_dict(new_dict, original=new_dict)

    def delete(self, key):
        """Delete the bookmark with the given key"""
        if key == '`':
            key = "'"
        if key in self.dct:
            del self.dct[key]
            if self.autosave: self.save()

    def enter(self, key):
        """Enter the bookmark with the given key.

        Requires the bookmark instance to have a go() method.
        """

        try:
            return self[key].go()
        except (IndexError, KeyError, AttributeError):
            return False

    def update_if_outdated(self):
        if self.last_mtime != self._get_mtime():
            self.update()

    def remember(self, value):
        """Bookmarks <value> to the key '"""
        self["'"] = value
        if self.autosave: self.save()

    def __iter__(self):
        return iter(self.dct.items())

    def __getitem__(self, key):
        """Get the bookmark associated with the key"""
        if key == '`':
            key = "'"
        if key in self.dct:
            return self.dct[key]
        else:
            raise KeyError("Nonexistant Bookmark: `%s'!" % key)

    def __setitem__(self, key, value):
        """Bookmark <value> to the key <key>.

        key is expected to be a 1-character string and element of ALLOWED_KEYS.
        value is expected to be a filesystemobject.
        """
        if key == '`':
            key = "'"
        if key in ALLOWED_KEYS:
            self.dct[key] = value
            if self.autosave: self.save()

    def __contains__(self, key):
        """Test whether a bookmark-key is defined"""
        return key in self.dct

    def update(self):
        """Update the bookmarks from the bookmark file.

        Useful if two instances are running which define different bookmarks.
        """

        try:
            real_dict = self._load_dict()
            real_dict_copy = real_dict.copy()
        except OSError:
            return

        for key in set(self.dct.keys()) | set(real_dict.keys()):
            # set some variables
            if key in self.dct:
                current = self.dct[key]
            else:
                current = None

            if key in self.original_dict:
                original = self.original_dict[key]
            else:
                original = None

            if key in real_dict:
                real = real_dict[key]
            else:
                real = None

            # determine if there have been changes
            if current == original and current != real:
                continue   # another ranger instance has changed the bookmark

            if key not in self.dct:
                del real_dict[key]   # the user has deleted it
            else:
                real_dict[key] = current   # the user has changed it

        self._set_dict(real_dict, original=real_dict_copy)

    def save(self):
        """Save the bookmarks to the bookmarkfile.

        This is done automatically after every modification if autosave is True."""
        self.update()
        if self.path is None:
            return
        if os.access(self.path, os.W_OK):
            f = open(self.path+".new", 'w')
            for key, value in self.dct.items():
                if type(key) == str\
                        and key in ALLOWED_KEYS:
                    try:
                        f.write("{0}:{1}\n".format(str(key), str(value)))
                    except:
                        pass

            f.close()
            os.rename(self.path+".new", self.path)
        self._update_mtime()

    def _load_dict(self):
        dct = {}

        if self.path is None:
            return dct

        if not os.path.exists(self.path):
            try:
                f = open(self.path, 'w')
            except:
                raise OSError('Cannot read the given path')
            f.close()

        if os.access(self.path, os.R_OK):
            f = open(self.path, 'r')
            for line in f:
                if self.load_pattern.match(line):
                    key, value = line[0], line[2:-1]
                    if key in ALLOWED_KEYS:
                        dct[key] = self.bookmarktype(value)
            f.close()
            return dct
        else:
            raise OSError('Cannot read the given path')

    def _set_dict(self, dct, original):
        if original is None:
            original = {}

        self.dct.clear()
        self.dct.update(dct)
        self.original_dict = original
        self._update_mtime()

    def _get_mtime(self):
        if self.path is None:
            return None
        try:
            return os.stat(self.path).st_mtime
        except OSError:
            return None

    def _update_mtime(self):
        self.last_mtime = self._get_mtime()
