195 lines
6.1 KiB
Python
195 lines
6.1 KiB
Python
"""
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Methods for interacting with database files
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"""
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from builtins import map
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from builtins import object
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import json
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import os
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import sys
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from math import radians, cos, sqrt
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from shutil import copyfile
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from time import strftime
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from ordigi import constants
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class Db(object):
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"""A class for interacting with the JSON files database."""
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def __init__(self, target_dir):
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# Create dir for target database
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dirname = os.path.join(target_dir, '.ordigi')
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if not os.path.exists(dirname):
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try:
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os.makedirs(dirname)
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except OSError:
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pass
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# self.hash_db = constants.hash_db
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self.hash_db_file = os.path.join(dirname, constants.hash_db)
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self.check_db(self.hash_db_file)
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self.hash_db = {}
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# We know from above that this file exists so we open it
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# for reading only.
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with open(self.hash_db_file, 'r') as f:
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try:
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self.hash_db = json.load(f)
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except ValueError:
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pass
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# self.location_db_file = constants.location_db
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self.location_db_file = os.path.join(dirname, constants.location_db)
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self.check_db(self.location_db_file)
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self.location_db = []
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# We know from above that this file exists so we open it
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# for reading only.
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with open(self.location_db_file, 'r') as f:
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try:
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self.location_db = json.load(f)
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except ValueError:
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pass
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def check_db(self, db_file):
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'''Load db from file'''
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# If the hash db doesn't exist we create it.
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# Otherwise we only open for reading
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if not os.path.isfile(db_file):
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with open(db_file, 'a'):
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os.utime(db_file, None)
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def add_hash(self, key, value, write=False):
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"""Add a hash to the hash db.
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:param str key:
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:param str value:
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:param bool write: If true, write the hash db to disk.
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"""
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self.hash_db[key] = value
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if(write is True):
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self.update_hash_db()
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# Location database
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# Currently quite simple just a list of long/lat pairs with a name
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# If it gets many entries a lookup might take too long and a better
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# structure might be needed. Some speed up ideas:
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# - Sort it and inter-half method can be used
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# - Use integer part of long or lat as key to get a lower search list
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# - Cache a small number of lookups, images are likely to be taken in
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# clusters around a spot during import.
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def add_location(self, latitude, longitude, place, write=False):
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"""Add a location to the database.
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:param float latitude: Latitude of the location.
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:param float longitude: Longitude of the location.
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:param str place: Name for the location.
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:param bool write: If true, write the location db to disk.
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"""
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data = {}
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data['lat'] = latitude
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data['long'] = longitude
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data['name'] = place
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self.location_db.append(data)
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if(write is True):
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self.update_location_db()
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def backup_hash_db(self):
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"""Backs up the hash db."""
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# TODO
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if os.path.isfile(self.hash_db_file):
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mask = strftime('%Y-%m-%d_%H-%M-%S')
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backup_file_name = '%s-%s' % (self.hash_db_file, mask)
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copyfile(self.hash_db_file, backup_file_name)
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return backup_file_name
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def check_hash(self, key):
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"""Check whether a hash is present for the given key.
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:param str key:
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:returns: bool
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"""
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return key in self.hash_db
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def get_hash(self, key):
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"""Get the hash value for a given key.
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:param str key:
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:returns: str or None
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"""
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if(self.check_hash(key) is True):
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return self.hash_db[key]
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return None
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def get_location_name(self, latitude, longitude, threshold_m):
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"""Find a name for a location in the database.
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:param float latitude: Latitude of the location.
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:param float longitude: Longitude of the location.
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:param int threshold_m: Location in the database must be this close to
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the given latitude and longitude.
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:returns: str, or None if a matching location couldn't be found.
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"""
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last_d = sys.maxsize
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name = None
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for data in self.location_db:
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# As threshold is quite small use simple math
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# From http://stackoverflow.com/questions/15736995/how-can-i-quickly-estimate-the-distance-between-two-latitude-longitude-points # noqa
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# convert decimal degrees to radians
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lon1, lat1, lon2, lat2 = list(map(
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radians,
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[longitude, latitude, data['long'], data['lat']]
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))
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r = 6371000 # radius of the earth in m
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x = (lon2 - lon1) * cos(0.5 * (lat2 + lat1))
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y = lat2 - lat1
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d = r * sqrt(x * x + y * y)
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# Use if closer then threshold_km reuse lookup
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if(d <= threshold_m and d < last_d):
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name = data['name']
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last_d = d
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return name
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def get_location_coordinates(self, name):
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"""Get the latitude and longitude for a location.
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:param str name: Name of the location.
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:returns: tuple(float), or None if the location wasn't in the database.
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"""
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for data in self.location_db:
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if data['name'] == name:
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return (data['lat'], data['long'])
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return None
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def all(self):
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"""Generator to get all entries from self.hash_db
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:returns tuple(string)
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"""
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for checksum, path in self.hash_db.items():
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yield (checksum, path)
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def reset_hash_db(self):
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self.hash_db = {}
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def update_hash_db(self):
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"""Write the hash db to disk."""
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with open(self.hash_db_file, 'w') as f:
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json.dump(self.hash_db, f)
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def update_location_db(self):
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"""Write the location db to disk."""
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with open(self.location_db_file, 'w') as f:
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json.dump(self.location_db, f)
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