"""
Helper objects needed by multiple CLI commands.
"""
from functools import partial
import json
import math
import warnings

from munch import munchify


warnings.simplefilter('default')


def obj_gen(lines):
    """Return a generator of JSON objects loaded from ``lines``."""
    first_line = next(lines)
    if first_line.startswith(u'\x1e'):
        def gen():
            buffer = first_line.strip(u'\x1e')
            for line in lines:
                if line.startswith(u'\x1e'):
                    if buffer:
                        yield json.loads(buffer)
                    buffer = line.strip(u'\x1e')
                else:
                    buffer += line
            else:
                yield json.loads(buffer)
    else:
        def gen():
            yield json.loads(first_line)
            for line in lines:
                yield json.loads(line)
    return gen()


def nullable(val, cast):
    if val is None:
        return None
    else:
        return cast(val)


def eval_feature_expression(feature, expression):
    safe_dict = {'f': munchify(feature)}
    safe_dict.update({
        'sum': sum,
        'pow': pow,
        'min': min,
        'max': max,
        'math': math,
        'bool': bool,
        'int': partial(nullable, int),
        'str': partial(nullable, str),
        'float': partial(nullable, float),
        'len': partial(nullable, len),
    })
    try:
        from shapely.geometry import shape
        safe_dict['shape'] = shape
    except ImportError:
        pass
    return eval(expression, {"__builtins__": None}, safe_dict)


def make_ld_context(context_items):
    """Returns a JSON-LD Context object.

    See http://json-ld.org/spec/latest/json-ld."""
    ctx = {
      "@context": {
        "geojson": "http://ld.geojson.org/vocab#",
        "Feature": "geojson:Feature",
        "FeatureCollection": "geojson:FeatureCollection",
        "GeometryCollection": "geojson:GeometryCollection",
        "LineString": "geojson:LineString",
        "MultiLineString": "geojson:MultiLineString",
        "MultiPoint": "geojson:MultiPoint",
        "MultiPolygon": "geojson:MultiPolygon",
        "Point": "geojson:Point",
        "Polygon": "geojson:Polygon",
        "bbox": {
          "@container": "@list",
          "@id": "geojson:bbox"
        },
        "coordinates": "geojson:coordinates",
        "datetime": "http://www.w3.org/2006/time#inXSDDateTime",
        "description": "http://purl.org/dc/terms/description",
        "features": {
          "@container": "@set",
          "@id": "geojson:features"
        },
        "geometry": "geojson:geometry",
        "id": "@id",
        "properties": "geojson:properties",
        "start": "http://www.w3.org/2006/time#hasBeginning",
        "stop": "http://www.w3.org/2006/time#hasEnding",
        "title": "http://purl.org/dc/terms/title",
        "type": "@type",
        "when": "geojson:when"
      }
    }
    for item in context_items or []:
        t, uri = item.split("=")
        ctx[t.strip()] = uri.strip()
    return ctx


def id_record(rec):
    """Converts a record's id to a blank node id and returns the record."""
    rec['id'] = '_:f%s' % rec['id']
    return rec