"""
A caching proxy for CDS' Simbad object resolver.
"""

#c Copyright 2008-2020, the GAVO project
#c
#c This program is free software, covered by the GNU GPL.  See the
#c COPYING file in the source distribution.


import json
import os
import socket
from urllib import request, parse

if __name__=="__main__":
	# see below on why this doesn't have normal unit tests.
	os.environ["GAVO_OOTTEST"] = "dontcare"
	from gavo.helpers import testhelpers

from gavo import base
from gavo.utils import ElementTree



class ObjectCache(object):
	"""a cache for simbad queries kept in dc.metastore.

	This used to be file-based, and used different keys for different
	purposes.  The different keys didn't seem to be useful, so they're
	ignored now.

	This only caches positive responses; there's too much that can
	go wrong when caching negatives, and the expectation is that negatives
	are so varying that there's little to win anyway.

	The values passed in are json-encoded (for simbad, these are dictionaries).
	"""
	def addItem(self, key, value):
		"""adds an item to the cache.

		value is json-encoded before writing it.
		"""
		with base.getWritableAdminConn() as conn:
			base.setDBMeta(conn, 
				'simbad:'+key,
				json.dumps(value))
	
	def getItem(self, key):
		"""returns a previously stored object of key.

		This raises a KeyError if nothing has been stored before.
		"""
		return json.loads(base.getDBMeta('simbad:'+key))


class Sesame(object):
	"""is a simple interface to the simbad name resolver.
	"""
	# we're using several simbad mirrors if we have to, and only give
	# up if all of them fail.
	svc_urls = [
		"http://cdsweb.u-strasbg.fr/cgi-bin/nph-sesame/-ox/SN?",
		"http://vizier.cfa.harvard.edu/viz-bin/nph-sesame/-ox/SN?"]

	def __init__(self):
		self.cache = ObjectCache()

	def _parseXML(self, simbadXML):
		try:
			et = ElementTree.fromstring(simbadXML)
		except Exception as msg: # simbad returned weird XML
			base.ui.notifyWarning("Bad XML from simbad (%s)"%str(msg))
			return None
	
		res = {}
		nameMatch = et.find("Target/name")
		if nameMatch is None:
			# no such object, return a negative
			return None

		res["oname"] = nameMatch.text
		firstResponse = et.find("Target/Resolver")
		if not firstResponse:
			return None

		res["otype"] = getattr(firstResponse.find("otype"), "text", None)
		try:
			res["RA"] = float(firstResponse.find("jradeg").text)
			res["dec"] = float(firstResponse.find("jdedeg").text)
		except (ValueError, AttributeError):
			# presumably null position
			return None
		return res

	def query(self, ident):
		try:
			return self.cache.getItem(ident)
		except KeyError:
			# cache miss, fall through to actually querying sesame
			pass

		for svc_url in self.svc_urls:
			try:
				with request.urlopen(svc_url+parse.quote(ident)) as f:
					newOb = self._parseXML(f.read())
				self.cache.addItem(ident, newOb)
				return newOb
			except socket.error: 
				# Try next mirror
				pass
		else:
			# all mirrors fail
			raise base.ui.logOldExc(base.ValidationError(
				"Simbad is offline, cannot query.",
				"hscs_pos", # really, this should be added by the widget
				hint="If this problem persists, complain to us rather than simbad."))
	
	def getPositionFor(self, identifier):
		rec = self.query(identifier)
		if not rec:
			raise KeyError(identifier)
		return float(rec["RA"]), float(rec["dec"])
	

def getSimbadPositions(identifier):
	"""returns ra and dec from Simbad for identifier.

	It raises a KeyError if Simbad doesn't know identifier.
	"""
	return base.caches.getSesame("").getPositionFor(identifier)


# This used to accept a "key" to separate different uses of Sesame.
# That's not turned out to be useful, so we're now ignoring the
# key.
base.caches.makeCache("getSesame", lambda key="ignored": Sesame())


############## ADQL ufunc

from gavo import adql

@adql.userFunction("gavo_simbadpoint",
	"(identifier TEXT) -> POINT",
	"""
	gavo_simbadpoint queries simbad for an identifier and returns the 
	corresponding point.  Note that identifier can only be a literal,
	i.e., as simple string rather than a column name. This is because
	our database cannot query simbad, and we probably wouldn't want
	to fire off millions of simbad queries anyway; use simbad's own
	TAP service for this kind of applications.
	""",
	"point", ucd="pos.eq;src")
def _simbadpoint(args):
	from gavo.adql import nodes

	if len(args)!=1 or args[0].type!="characterStringLiteral":
		raise adql.UfuncError(
			"gavo_simbadpoint takes exactly one string literal as argument")

	object = args[0].value

	resolver = base.caches.getSesame()
	try:
		alpha, delta = resolver.getPositionFor(object)
	except KeyError:
		raise adql.UfuncError("No simbad position for '%s'"%object)

	raise nodes.ReplaceNode(nodes.Point(cooSys=None, 
		x=nodes.Factor([repr(alpha)]), y=nodes.Factor([repr(delta)])))


def _getTestSuite():
	import unittest

	with base.getWritableAdminConn() as conn:
		conn.execute("DELETE FROM dc.metastore WHERE key LIKE 'simbad:%%'")
	
	sc = base.caches.getSesame("anything")

	# NOTE: all these tests assume the cache has been cleared before
	# them, and that the configured mirrors are up.
	# Cache clearing happens a few lines up.
	class QueryTest(testhelpers.VerboseTest):
		def testBasic(self):
			res = getSimbadPositions("Antares")
			self.assertAlmostEqual(res[0], 247.351915, 5)
			self.assertAlmostEqual(res[1], -26.432002, 5)

		def testCaching(self):
			res = getSimbadPositions("M31")
			self.assertAlmostEqual(res[0], 10.684708, 5)
			self.assertAlmostEqual(res[1], 41.26875, 5)

			tmp = Sesame.svc_urls
			Sesame.svcs_urls = []
			try:
				res = getSimbadPositions("M31")
				self.assertAlmostEqual(res[0], 10.684708, 5)
				self.assertAlmostEqual(res[1], 41.26875, 5)
			finally:
				Sesame.svcs_urls = tmp

		def testMirrorFailover(self):
			tmp = Sesame.svc_urls[0]
			Sesame.svc_urls[0] = "http://localhost:39293?"
			
			try:
				res = getSimbadPositions("epsilon Eri")
				self.assertAlmostEqual(res[0], 53.232687, 5) 
				self.assertAlmostEqual(res[1], -9.458258, 5)
			finally: 
				Sesame.svc_urls[0] = tmp

		def testCacheInstallation(self):
			res = base.caches.getSesame("anything").getPositionFor("ε Eri")
			self.assertAlmostEqual(res[0], 53.232687, 5) 
			self.assertAlmostEqual(res[1], -9.458258, 5)
	
	l = locals()
	tests = [l[name] for name in l 
		if isinstance(l[name], type) and issubclass(l[name], unittest.TestCase)]
	loader = unittest.TestLoader()
	suite = unittest.TestSuite([loader.loadTestsFromTestCase(t)
		for t in tests])
	return suite


if __name__=="__main__":
	# we don't want to test this as part of the normal unit tests, as 
	# there's little to sensibly test without a live network connection
	# (and we don't want to require that for the unit tests).
	import unittest
	suite = _getTestSuite()
	unittest.TextTestRunner().run(suite)