from ctypes import byref, c_int

from datetime import date, datetime, time

from django.contrib.gis.gdal.base import GDALBase

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

from django.contrib.gis.gdal.prototypes import ds as capi

# For more information, see the OGR C API source code:

#  http://www.gdal.org/ogr/ogr__api_8h.html

#

# The OGR_Fld_* routines are relevant here.

class Field(GDALBase):

    "A class that wraps an OGR Field, needs to be instantiated from a Feature object."

    #### Python 'magic' routines ####

    def __init__(self, feat, index):

        """

        Initializes on the feature pointer and the integer index of

        the field within the feature.

        """

        # Setting the feature pointer and index.

        self._feat = feat

        self._index = index

        # Getting the pointer for this field.

        fld_ptr = capi.get_feat_field_defn(feat, index)

        if not fld_ptr:

            raise OGRException('Cannot create OGR Field, invalid pointer given.')

        self.ptr = fld_ptr

        # Setting the class depending upon the OGR Field Type (OFT)

        self.__class__ = OGRFieldTypes[self.type]

        # OFTReal with no precision should be an OFTInteger.

        if isinstance(self, OFTReal) and self.precision == 0:

            self.__class__ = OFTInteger

    def __str__(self):

        "Returns the string representation of the Field."

        return str(self.value).strip()

    #### Field Methods ####

    def as_double(self):

        "Retrieves the Field's value as a double (float)."

        return capi.get_field_as_double(self._feat, self._index)

    def as_int(self):

        "Retrieves the Field's value as an integer."

        return capi.get_field_as_integer(self._feat, self._index)

    def as_string(self):

        "Retrieves the Field's value as a string."

        return capi.get_field_as_string(self._feat, self._index)

    def as_datetime(self):

        "Retrieves the Field's value as a tuple of date & time components."

        yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)]

        status = capi.get_field_as_datetime(self._feat, self._index, byref(yy), byref(mm), byref(dd),

                                            byref(hh), byref(mn), byref(ss), byref(tz))

        if status:

            return (yy, mm, dd, hh, mn, ss, tz)

        else:

            raise OGRException('Unable to retrieve date & time information from the field.')

    #### Field Properties ####

    @property

    def name(self):

        "Returns the name of this Field."

        return capi.get_field_name(self.ptr)

    @property

    def precision(self):

        "Returns the precision of this Field."

        return capi.get_field_precision(self.ptr)

    @property

    def type(self):

        "Returns the OGR type of this Field."

        return capi.get_field_type(self.ptr)

    @property

    def type_name(self):

        "Return the OGR field type name for this Field."

        return capi.get_field_type_name(self.type)

    @property

    def value(self):

        "Returns the value of this Field."

        # Default is to get the field as a string.

        return self.as_string()

    @property

    def width(self):

        "Returns the width of this Field."

        return capi.get_field_width(self.ptr)

### The Field sub-classes for each OGR Field type. ###

class OFTInteger(Field):

    @property

    def value(self):

        "Returns an integer contained in this field."

        return self.as_int()

    @property

    def type(self):

        """

        GDAL uses OFTReals to represent OFTIntegers in created

        shapefiles -- forcing the type here since the underlying field

        type may actually be OFTReal.

        """

        return 0

class OFTReal(Field):

    @property

    def value(self):

        "Returns a float contained in this field."

        return self.as_double()

# String & Binary fields, just subclasses

class OFTString(Field): pass

class OFTWideString(Field): pass

class OFTBinary(Field): pass

# OFTDate, OFTTime, OFTDateTime fields.

class OFTDate(Field):

    @property

    def value(self):

        "Returns a Python `date` object for the OFTDate field."

        try:

            yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

            return date(yy.value, mm.value, dd.value)

        except (ValueError, OGRException):

            return None

class OFTDateTime(Field):

    @property

    def value(self):

        "Returns a Python `datetime` object for this OFTDateTime field."

        # TODO: Adapt timezone information.

        #  See http://lists.maptools.org/pipermail/gdal-dev/2006-February/007990.html

        #  The `tz` variable has values of: 0=unknown, 1=localtime (ambiguous), 

        #  100=GMT, 104=GMT+1, 80=GMT-5, etc.

        try:

            yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

            return datetime(yy.value, mm.value, dd.value, hh.value, mn.value, ss.value)

        except (ValueError, OGRException):

            return None

class OFTTime(Field):

    @property

    def value(self):

        "Returns a Python `time` object for this OFTTime field."

        try:

            yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

            return time(hh.value, mn.value, ss.value)

        except (ValueError, OGRException):

            return None

# List fields are also just subclasses

class OFTIntegerList(Field): pass

class OFTRealList(Field): pass

class OFTStringList(Field): pass

class OFTWideStringList(Field): pass

# Class mapping dictionary for OFT Types and reverse mapping.

OGRFieldTypes = { 0 : OFTInteger,

                  1 : OFTIntegerList,

                  2 : OFTReal,

                  3 : OFTRealList,

                  4 : OFTString,

                  5 : OFTStringList,

                  6 : OFTWideString,

                  7 : OFTWideStringList,

                  8 : OFTBinary,

                  9 : OFTDate,

                 10 : OFTTime,

                 11 : OFTDateTime,

                  }

ROGRFieldTypes = dict([(cls, num) for num, cls in OGRFieldTypes.items()])