import argparse

from django.contrib.gis import gdal
from django.core.management.base import BaseCommand, CommandError
from django.utils.inspect import get_func_args


class LayerOptionAction(argparse.Action):
    """
    Custom argparse action for the `ogrinspect` `layer_key` keyword option
    which may be an integer or a string.
    """

    def __call__(self, parser, namespace, value, option_string=None):
        try:
            setattr(namespace, self.dest, int(value))
        except ValueError:
            setattr(namespace, self.dest, value)


class ListOptionAction(argparse.Action):
    """
    Custom argparse action for `ogrinspect` keywords that require
    a string list. If the string is 'True'/'true' then the option
    value will be a boolean instead.
    """

    def __call__(self, parser, namespace, value, option_string=None):
        if value.lower() == "true":
            setattr(namespace, self.dest, True)
        else:
            setattr(namespace, self.dest, value.split(","))


class Command(BaseCommand):
    help = (
        "Inspects the given OGR-compatible data source (e.g., a shapefile) and "
        "outputs\na GeoDjango model with the given model name. For example:\n"
        " ./manage.py ogrinspect zipcode.shp Zipcode"
    )

    requires_system_checks = []

    def add_arguments(self, parser):
        parser.add_argument("data_source", help="Path to the data source.")
        parser.add_argument("model_name", help="Name of the model to create.")
        parser.add_argument(
            "--blank",
            action=ListOptionAction,
            default=False,
            help="Use a comma separated list of OGR field names to add "
            "the `blank=True` option to the field definition. Set to `true` "
            "to apply to all applicable fields.",
        )
        parser.add_argument(
            "--decimal",
            action=ListOptionAction,
            default=False,
            help="Use a comma separated list of OGR float fields to "
            "generate `DecimalField` instead of the default "
            "`FloatField`. Set to `true` to apply to all OGR float fields.",
        )
        parser.add_argument(
            "--geom-name",
            default="geom",
            help="Specifies the model name for the Geometry Field (defaults to `geom`)",
        )
        parser.add_argument(
            "--layer",
            dest="layer_key",
            action=LayerOptionAction,
            default=0,
            help="The key for specifying which layer in the OGR data "
            "source to use. Defaults to 0 (the first layer). May be "
            "an integer or a string identifier for the layer.",
        )
        parser.add_argument(
            "--multi-geom",
            action="store_true",
            help="Treat the geometry in the data source as a geometry collection.",
        )
        parser.add_argument(
            "--name-field",
            help="Specifies a field name to return for the __str__() method.",
        )
        parser.add_argument(
            "--no-imports",
            action="store_false",
            dest="imports",
            help="Do not include `from django.contrib.gis.db import models` statement.",
        )
        parser.add_argument(
            "--null",
            action=ListOptionAction,
            default=False,
            help="Use a comma separated list of OGR field names to add "
            "the `null=True` option to the field definition. Set to `true` "
            "to apply to all applicable fields.",
        )
        parser.add_argument(
            "--srid",
            help="The SRID to use for the Geometry Field. If it can be "
            "determined, the SRID of the data source is used.",
        )
        parser.add_argument(
            "--mapping",
            action="store_true",
            help="Generate mapping dictionary for use with `LayerMapping`.",
        )

    def handle(self, *args, **options):
        data_source, model_name = options.pop("data_source"), options.pop("model_name")

        # Getting the OGR DataSource from the string parameter.
        try:
            ds = gdal.DataSource(data_source)
        except gdal.GDALException as msg:
            raise CommandError(msg)

        # Returning the output of ogrinspect with the given arguments
        # and options.
        from django.contrib.gis.utils.ogrinspect import _ogrinspect, mapping

        # Filter options to params accepted by `_ogrinspect`
        ogr_options = {
            k: v
            for k, v in options.items()
            if k in get_func_args(_ogrinspect) and v is not None
        }
        output = [s for s in _ogrinspect(ds, model_name, **ogr_options)]

        if options["mapping"]:
            # Constructing the keyword arguments for `mapping`, and
            # calling it on the data source.
            kwargs = {
                "geom_name": options["geom_name"],
                "layer_key": options["layer_key"],
                "multi_geom": options["multi_geom"],
            }
            mapping_dict = mapping(ds, **kwargs)
            # This extra legwork is so that the dictionary definition comes
            # out in the same order as the fields in the model definition.
            rev_mapping = {v: k for k, v in mapping_dict.items()}
            output.extend(
                [
                    "",
                    "",
                    "# Auto-generated `LayerMapping` dictionary for %s model"
                    % model_name,
                    "%s_mapping = {" % model_name.lower(),
                ]
            )
            output.extend(
                "    '%s': '%s'," % (rev_mapping[ogr_fld], ogr_fld)
                for ogr_fld in ds[options["layer_key"]].fields
            )
            output.extend(
                [
                    "    '%s': '%s',"
                    % (options["geom_name"], mapping_dict[options["geom_name"]]),
                    "}",
                ]
            )
        return "\n".join(output)