# This file is part of the qpopplerview package.
#
# Copyright (c) 2010 - 2012 by Wilbert Berendsen
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
# See http://www.gnu.org/licenses/ for more information.


"""
Manages lists of rectangular objects and quickly finds them.
"""

import bisect


Left   = 0
Top    = 1
Right  = 2
Bottom = 3


class Rectangles(object):
    """
    Manages a list of rectangular objects and quickly finds objects at
    some point, in some rectangle or intersecting some rectangle.
    
    The implementation uses four lists of the objects sorted on either
    coordinate, so retrieval is fast.
    
    Bulk adding is done in the constructor or via the bulk_add() method (which
    clears the indexes, that are recreated on first search).  Single objects
    can be added and deleted, keeping the indexes, but that's slower.
    
    """
    _func = lambda obj: obj.rect().normalized().getCoords()
    
    def __init__(self, objects=None, func=None):
        """Initializes the Rectangles object.
        
        objects should be an iterable of rectangular objects.
        
        function(obj) should return a four-tuple (left, top, right, bottom)
        of the coordinates of the rectangle.  The coordinates should be normalized,
        i.e. top <= bottom and left <= right.
        
        The default function is: lambda obj: obj.rect().normalized().getCoords()
        
        """
        self._items = {} # maps object to the result of func(object)
        self._index = {} # maps side to indices, objects (index=coordinate of that side)
        if func:
            self._func = func
        if objects:
            self.bulk_add(objects)
    
    def add(self, obj):
        """Adds an object to our list. Keeps the index intact."""
        if obj in self._items:
            return
        self._items[obj] = coords = self._func(obj)
        for side, (indices, objects) in self._index.items():
            i = bisect.bisect_left(indices, coords[side])
            indices.insert(i, coords[side])
            objects.insert(i, obj)
    
    def bulk_add(self, objects):
        """Adds many new items to the index using the function given in the constructor.
        
        After this, the index is cleared and recreated on the first search operation.
        
        """
        self._items.update((obj, self._func(obj)) for obj in objects)
        self._index.clear()
        
    def remove(self, obj):
        """Removes an object from our list. Keeps the index intact."""
        del self._items[obj]
        for indices, objects in self._index.values():
            i = objects.index(obj)
            del objects[i]
            del indices[i]
            
    def clear(self):
        """Empties the list of items."""
        self._items.clear()
        self._index.clear()
        
    def at(self, x, y):
        """Returns a set() of objects that are touched by the given point."""
        return self._test(
            (self._smaller, Top, y),
            (self._larger, Bottom, y),
            (self._smaller, Left, x),
            (self._larger, Right, x))
         
    def inside(self, left, top, right, bottom):
        """Returns a set() of objects that are fully in the given rectangle."""
        return self._test(
            (self._larger, Top, top),
            (self._smaller, Bottom, bottom),
            (self._larger, Left, left),
            (self._smaller, Right, right))
    
    def intersecting(self, left, top, right, bottom):
        """Returns a set() of objects intersecting the given rectangle."""
        return self._test(
            (self._smaller, Top, bottom),
            (self._larger, Bottom, top),
            (self._smaller, Left, right),
            (self._larger, Right, left))

    def closest(self, obj, side):
        """Returns the object closest to the given one, going to the given side."""
        coords = self._items[obj]
        pos = coords[side^2]
        lat = (coords[side^1|2] - coords[side^1&2]) / 2.0
        direction = -1 if side < Right else 1
        indices, objects = self._sorted(side^2)
        i = objects.index(obj)
        mindist = indices[-1]
        result = []
        for other in objects[i+direction::direction]:
            coords = self._items[other]
            pos1 = coords[side^2]
            d = abs(pos1 - pos)
            if d > mindist:
                break
            lat1 = (coords[side^1|2] - coords[side^1&2]) / 2.0
            dlat = abs(lat1 - lat)
            if dlat < d:
                dist = dlat + d  # manhattan dist
                result.append((other, dist))
                mindist = min(mindist, dist)
        if result:
            result.sort(key=lambda r: r[1])
            return result[0][0]

    def __len__(self):
        return len(self._items)
        
    def __contains__(self, obj):
        return obj in self._items
        
    def __nonzero__(self):
        return bool(self._items)
        
    # private helper methods
    def _test(self, *tests):
        """Performs tests and returns objects that fulfill all of them.
        
        Every test should be a three tuple(method, side, value).
        Method is either self._smaller or self._larger.
        Returns a (possibly empty) set.
        
        """
        result = None
        for meth, side, value in tests:
            objects = meth(side, value)
            if not result:
                result = set(objects)
            else:
                result &= set(objects)
            if not result:
                break
        return result
    
    def _smaller(self, side, value):
        """Returns objects for side below value."""
        indices, objects = self._sorted(side)
        i = bisect.bisect_right(indices, value)
        return objects[:i]

    def _larger(self, side, value):
        """Returns objects for side above value."""
        indices, objects = self._sorted(side)
        i = bisect.bisect_left(indices, value)
        return objects[i:]
        
    def _sorted(self, side):
        """Returns a two-tuple (indices, objects) sorted on index for the given side.""" 
        try:
            return self._index[side]
        except KeyError:
            if self._items:
                objects = [(coords[side], obj) for obj, coords in self._items.items()]
                objects.sort()
                result = tuple(map(list, zip(*objects)))
            else:
                result = [], []
            self._index[side] = result
            return result
            

