"""

 The GDAL/OGR library uses an Envelope structure to hold the bounding

 box information for a geometry.  The envelope (bounding box) contains

 two pairs of coordinates, one for the lower left coordinate and one

 for the upper right coordinate:

                           +----------o Upper right; (max_x, max_y)

                           |          |

                           |          |

                           |          |

 Lower left (min_x, min_y) o----------+

"""

from ctypes import Structure, c_double

from types import TupleType, ListType

from django.contrib.gis.gdal.error import OGRException

# The OGR definition of an Envelope is a C structure containing four doubles.

#  See the 'ogr_core.h' source file for more information:

#   http://www.gdal.org/ogr/ogr__core_8h-source.html

class OGREnvelope(Structure):

    "Represents the OGREnvelope C Structure."

    _fields_ = [("MinX", c_double),

                ("MaxX", c_double),

                ("MinY", c_double),

                ("MaxY", c_double),

                ]

class Envelope(object):

    """

    The Envelope object is a C structure that contains the minimum and

    maximum X, Y coordinates for a rectangle bounding box.  The naming

    of the variables is compatible with the OGR Envelope structure.

    """

    def __init__(self, *args):

        """

        The initialization function may take an OGREnvelope structure, 4-element

        tuple or list, or 4 individual arguments.

        """

        if len(args) == 1:

            if isinstance(args[0], OGREnvelope):

                # OGREnvelope (a ctypes Structure) was passed in.

                self._envelope = args[0]

            elif isinstance(args[0], (TupleType, ListType)):

                # A tuple was passed in.

                if len(args[0]) != 4:

                    raise OGRException('Incorrect number of tuple elements (%d).' % len(args[0]))

                else:

                    self._from_sequence(args[0])

            else:

                raise TypeError('Incorrect type of argument: %s' % str(type(args[0])))

        elif len(args) == 4:

            # Individiual parameters passed in.

            #  Thanks to ww for the help

            self._from_sequence(map(float, args))

        else:

            raise OGRException('Incorrect number (%d) of arguments.' % len(args))

        # Checking the x,y coordinates

        if self.min_x >= self.max_x:

            raise OGRException('Envelope minimum X >= maximum X.')

        if self.min_y >= self.max_y:

            raise OGRException('Envelope minimum Y >= maximum Y.')

    def __eq__(self, other):

        """

        Returns True if the envelopes are equivalent; can compare against

        other Envelopes and 4-tuples.

        """

        if isinstance(other, Envelope):

            return (self.min_x == other.min_x) and (self.min_y == other.min_y) and \

                   (self.max_x == other.max_x) and (self.max_y == other.max_y)

        elif isinstance(other, TupleType) and len(other) == 4:

            return (self.min_x == other[0]) and (self.min_y == other[1]) and \

                   (self.max_x == other[2]) and (self.max_y == other[3])

        else:

            raise OGRException('Equivalence testing only works with other Envelopes.')

    def __str__(self):

        "Returns a string representation of the tuple."

        return str(self.tuple)

    def _from_sequence(self, seq):

        "Initializes the C OGR Envelope structure from the given sequence."

        self._envelope = OGREnvelope()

        self._envelope.MinX = seq[0]

        self._envelope.MinY = seq[1]

        self._envelope.MaxX = seq[2]

        self._envelope.MaxY = seq[3]

    @property

    def min_x(self):

        "Returns the value of the minimum X coordinate."

        return self._envelope.MinX

    @property

    def min_y(self):

        "Returns the value of the minimum Y coordinate."

        return self._envelope.MinY

    @property

    def max_x(self):

        "Returns the value of the maximum X coordinate."

        return self._envelope.MaxX

    @property

    def max_y(self):

        "Returns the value of the maximum Y coordinate."

        return self._envelope.MaxY

    @property

    def ur(self):

        "Returns the upper-right coordinate."

        return (self.max_x, self.max_y)

    @property

    def ll(self):

        "Returns the lower-left coordinate."

        return (self.min_x, self.min_y)

    @property

    def tuple(self):

        "Returns a tuple representing the envelope."

        return (self.min_x, self.min_y, self.max_x, self.max_y)

    @property

    def wkt(self):

        "Returns WKT representing a Polygon for this envelope."

        # TODO: Fix significant figures.

        return 'POLYGON((%s %s,%s %s,%s %s,%s %s,%s %s))' % \

               (self.min_x, self.min_y, self.min_x, self.max_y,

                self.max_x, self.max_y, self.max_x, self.min_y,

                self.min_x, self.min_y)