import enum
import datetime
import json
import shapely
import shapefile

from nexrad.db    import DatabaseTable
from nexrad.coord import COORD_SYSTEM

def parse_timestamp(text: str):
    size = len(text)

    if size == 8:
        fmt = '%Y%m%d'
    elif size == 10:
        fmt = '%Y%m%d%H'
    elif size == 12:
        fmt = '%Y%m%d%H%M'
    elif size == 14:
        fmt = '%Y%m%d%H%M%S'

    return datetime.datetime.strptime(text, fmt).astimezone(datetime.UTC)

def shape_to_geojson(shape: shapefile.Shape):
    return json.dumps(shape.__geo_interface__)

class VTECType(enum.StrEnum):
    OPERATIONAL       = 'O'
    TEST              = 'T'
    EXPERIMENTAL      = 'E'
    EXPERIMENTAL_VTEC = 'X'

class VTEC(DatabaseTable):
    __table__ = 'nexrad_vtec_event'
    __key__   = 'id'

    __columns__ = (
        'id', 'timestamp_issued', 'timestamp_expired',
        'timestamp_init_iss', 'timestamp_init_exp',
        'timestamp_updated', 'timestamp_poly_start',
        'timestamp_poly_end', 'event_id', 'wfo', 'sig', 'phenom',
        'status', 'hail_size', 'tornado_tag', 'damage_tag', 'poly'
    )

    __columns_read__ = {
        'poly': 'ST_AsText(poly) as poly'
    }

    __values_write__ = {
        'poly': shapely.from_wkt
    }

    __columns_write__ = {
        'poly': 'SetSRID(GeomFromGeoJSON(:poly), {crs})'.format(crs=COORD_SYSTEM)
    }

    __values_write__ = {
        'poly': lambda v: {'poly': shape_to_geojson(v)}
    }

    id:       int
    poly:     shapefile.Shape
    event_id: int

    @staticmethod
    def from_shapefile_record(record, shape):
        vtec = VTEC()
        vtec.id = None

        vtec.timestamp_issued     = parse_timestamp(record['ISSUED'])
        vtec.timestamp_expired    = parse_timestamp(record['EXPIRED'])
        vtec.timestamp_init_iss   = parse_timestamp(record['INIT_ISS'])
        vtec.timestamp_init_exp   = parse_timestamp(record['INIT_EXP'])
        vtec.timestamp_updated    = parse_timestamp(record['UPDATED'])
        vtec.timestamp_poly_start = parse_timestamp(record['POLY_BEG'])
        vtec.timestamp_poly_end   = parse_timestamp(record['POLY_END'])

        vtec.event_id   = int(record['ETN']) if (record['ETN'] is not None and record['ETN'] != '')  else None
        vtec.hail_size  = float(record['HAILTAG']) if record['HAILTAG'] is not None else None
        vtec.wind_speed = float(record['WINDTAG']) if record['WINDTAG'] is not None else None

        vtec.status      = record['STATUS']
        vtec.wfo         = record['WFO']
        vtec.phenom      = record['PHENOM']
        vtec.sig         = record['SIG']
        vtec.tornado_tag = record['TORNTAG']
        vtec.damage_tag  = record['DAMAGTAG']
        vtec.poly        = shape

        return vtec

    @staticmethod
    def each_from_shapefile(path: str):
        sf = shapefile.Reader(path)

        for i in range(0, sf.numRecords):
            record = sf.record(i)

            if record['GTYPE'] != 'P':
                continue

            yield VTEC.from_shapefile_record(record, sf.shape(i))