"""

This module is for inspecting OGR data sources and generating either

models for GeoDjango and/or mapping dictionaries for use with the

`LayerMapping` utility.

Author: Travis Pinney, Dane Springmeyer, & Justin Bronn

"""

from itertools import izip

# Requires GDAL to use.

from django.contrib.gis.gdal import DataSource

from django.contrib.gis.gdal.field import OFTDate, OFTDateTime, OFTInteger, OFTReal, OFTString, OFTTime

def mapping(data_source, geom_name='geom', layer_key=0, multi_geom=False):

    """

    Given a DataSource, generates a dictionary that may be used 

    for invoking the LayerMapping utility.

    Keyword Arguments:

     `geom_name` => The name of the geometry field to use for the model.

     `layer_key` => The key for specifying which layer in the DataSource to use;

       defaults to 0 (the first layer).  May be an integer index or a string

       identifier for the layer.

     `multi_geom` => Boolean (default: False) - specify as multigeometry.

    """

    if isinstance(data_source, basestring):

        # Instantiating the DataSource from the string.

        data_source = DataSource(data_source)

    elif isinstance(data_source, DataSource):

        pass

    else:

        raise TypeError('Data source parameter must be a string or a DataSource object.')

    # Creating the dictionary.

    _mapping = {}

    # Generating the field name for each field in the layer.

    for field in data_source[layer_key].fields:

        mfield = field.lower()

        if mfield[-1:] == '_': mfield += 'field'

        _mapping[mfield] = field

    gtype = data_source[layer_key].geom_type

    if multi_geom and gtype.num in (1, 2, 3): prefix = 'MULTI'

    else: prefix = ''

    _mapping[geom_name] = prefix + str(gtype).upper()

    return _mapping

def ogrinspect(*args, **kwargs):

    """

    Given a data source (either a string or a DataSource object) and a string

    model name this function will generate a GeoDjango model.

    Usage:

    >>> from django.contrib.gis.utils import ogrinspect

    >>> ogrinspect('/path/to/shapefile.shp','NewModel')

    ...will print model definition to stout

    or put this in a python script and use to redirect the output to a new

    model like:

    $ python generate_model.py > myapp/models.py

    # generate_model.py 

    from django.contrib.gis.utils import ogrinspect

    shp_file = 'data/mapping_hacks/world_borders.shp'

    model_name = 'WorldBorders'

    print ogrinspect(shp_file, model_name, multi_geom=True, srid=4326,

                     geom_name='shapes', blank=True)

    Required Arguments

     `datasource` => string or DataSource object to file pointer

     `model name` => string of name of new model class to create

    Optional Keyword Arguments

     `geom_name` => For specifying the model name for the Geometry Field. 

       Otherwise will default to `geom`

     `layer_key` => The key for specifying which layer in the DataSource to use;

       defaults to 0 (the first layer).  May be an integer index or a string

       identifier for the layer.

     `srid` => The SRID to use for the Geometry Field.  If it can be determined,

       the SRID of the datasource is used.

     `multi_geom` => Boolean (default: False) - specify as multigeometry.

     `name_field` => String - specifies a field name to return for the

       `__unicode__` function (which will be generated if specified).

     `imports` => Boolean (default: True) - set to False to omit the 

       `from django.contrib.gis.db import models` code from the 

       autogenerated models thus avoiding duplicated imports when building

       more than one model by batching ogrinspect()

     `decimal` => Boolean or sequence (default: False).  When set to True

       all generated model fields corresponding to the `OFTReal` type will

       be `DecimalField` instead of `FloatField`.  A sequence of specific

       field names to generate as `DecimalField` may also be used.

     `blank` => Boolean or sequence (default: False).  When set to True all

       generated model fields will have `blank=True`.  If the user wants to 

       give specific fields to have blank, then a list/tuple of OGR field

       names may be used.

     `null` => Boolean (default: False) - When set to True all generated

       model fields will have `null=True`.  If the user wants to specify

       give specific fields to have null, then a list/tuple of OGR field

       names may be used.

    Note: This routine calls the _ogrinspect() helper to do the heavy lifting.

    """

    return '\n'.join(s for s in _ogrinspect(*args, **kwargs))

def _ogrinspect(data_source, model_name, geom_name='geom', layer_key=0, srid=None,

                multi_geom=False, name_field=None, imports=True, 

                decimal=False, blank=False, null=False):

    """

    Helper routine for `ogrinspect` that generates GeoDjango models corresponding

    to the given data source.  See the `ogrinspect` docstring for more details.

    """

    # Getting the DataSource

    if isinstance(data_source, str):

        data_source = DataSource(data_source)

    elif isinstance(data_source, DataSource):

        pass

    else:

        raise TypeError('Data source parameter must be a string or a DataSource object.')

    # Getting the layer corresponding to the layer key and getting

    # a string listing of all OGR fields in the Layer.

    layer = data_source[layer_key]

    ogr_fields = layer.fields

    # Creating lists from the `null`, `blank`, and `decimal`

    # keyword arguments.

    def process_kwarg(kwarg):

        if isinstance(kwarg, (list, tuple)):

            return [s.lower() for s in kwarg] 

        elif kwarg:

            return [s.lower() for s in ogr_fields]

        else:

            return []

    null_fields = process_kwarg(null)

    blank_fields = process_kwarg(blank)

    decimal_fields = process_kwarg(decimal)

    # Gets the `null` and `blank` keywords for the given field name.

    def get_kwargs_str(field_name):

        kwlist = []

        if field_name.lower() in null_fields: kwlist.append('null=True')

        if field_name.lower() in blank_fields: kwlist.append('blank=True')

        if kwlist: return ', ' + ', '.join(kwlist)

        else: return ''

    # For those wishing to disable the imports.

    if imports:

        yield '# This is an auto-generated Django model module created by ogrinspect.'

        yield 'from django.contrib.gis.db import models'

        yield ''

    yield 'class %s(models.Model):' % model_name

    for field_name, width, precision, field_type in izip(ogr_fields, layer.field_widths, layer.field_precisions, layer.field_types):

        # The model field name.

        mfield = field_name.lower()

        if mfield[-1:] == '_': mfield += 'field'

        # Getting the keyword args string.

        kwargs_str = get_kwargs_str(field_name)

        if field_type is OFTReal:

            # By default OFTReals are mapped to `FloatField`, however, they

            # may also be mapped to `DecimalField` if specified in the 

            # `decimal` keyword.

            if field_name.lower() in decimal_fields:

                yield '    %s = models.DecimalField(max_digits=%d, decimal_places=%d%s)' % (mfield, width, precision, kwargs_str)

            else:

                yield '    %s = models.FloatField(%s)' % (mfield, kwargs_str[2:])

        elif field_type is OFTInteger:

            yield '    %s = models.IntegerField(%s)' % (mfield, kwargs_str[2:])

        elif field_type is OFTString:

            yield '    %s = models.CharField(max_length=%s%s)' % (mfield, width, kwargs_str)

        elif field_type is OFTDate:

            yield '    %s = models.DateField(%s)' % (mfield, kwargs_str[2:])

        elif field_type is OFTDateTime:

            yield '    %s = models.DateTimeField(%s)' % (mfield, kwargs_str[2:])

        elif field_type is OFTDate:

            yield '    %s = models.TimeField(%s)' % (mfield, kwargs_str[2:])

        else:

            raise TypeError('Unknown field type %s in %s' % (fld_type, mfield))

    # TODO: Autodetection of multigeometry types (see #7218).

    gtype = layer.geom_type

    if multi_geom and gtype.num in (1, 2, 3):

        geom_field = 'Multi%s' % gtype.django

    else:

        geom_field = gtype.django

    # Setting up the SRID keyword string.

    if srid is None:

        if layer.srs is None:

            srid_str = 'srid=-1'

        else:

            srid = layer.srs.srid

            if srid is None:

                srid_str = 'srid=-1'

            elif srid == 4326:

                # WGS84 is already the default.

                srid_str = ''

            else:

                srid_str = 'srid=%s' % srid

    else:

        srid_str = 'srid=%s' % srid

    yield '    %s = models.%s(%s)' % (geom_name, geom_field, srid_str)

    yield '    objects = models.GeoManager()'

    if name_field:

        yield ''

        yield '    def __unicode__(self): return self.%s' % name_field