"""
Common functions and classes for services and cores.
"""

#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 re
import os

import pkg_resources

from gavo import base
from gavo import utils
from gavo.formal import nevowc


class Error(base.ExecutiveAction):
	def __init__(self, msg, rd=None, hint=None):
		self.rd = rd
		self.msg = msg
		self.hint = hint
		base.ExecutiveAction.__init__(self, msg)


class BadMethod(Error):
	"""raised to generate an HTTP 405 response.
	"""
	def __str__(self):
		return "This resource cannot respond to the HTTP '%s' method"%self.msg


class UnknownURI(Error, base.NotFoundError):
	"""raised to generate an HTTP 404 response.
	"""
	def __str__(self):
		return Error.__str__(self)


class ForbiddenURI(Error):
	"""raised to generate an HTTP 403 response.
	"""


class Authenticate(Error):
	"""raised to initiate an authentication request.

	Authenticates are optionally constructed with the realm the user 
	shall authenticate in.  If you leave the realm out, the DC-wide default
	will be used.
	"""
	def __init__(self, realm=base.getConfig("web", "realm"), hint=None):
		self.realm = realm
		Error.__init__(self, "This is a request to authenticate against %s"%realm,
			hint=hint)


class RedirectBase(Error):
	def __init__(self, dest, hint=None):
		if isinstance(dest, bytes):
			dest = dest.decode("utf-8")

		self.rawDest = dest
		dest = str(dest)
		if not dest.startswith("http"):
			dest = base.getConfig("web", "serverURL")+base.makeSitePath(dest)
		self.dest = dest
		Error.__init__(self, "This is supposed to redirect to %s"%dest,
			hint=hint)


class WebRedirect(RedirectBase):
	"""raised to redirect a user agent to a different resource (HTTP 301).

	WebRedirectes are constructed with the destination URL that can be
	relative (to webRoot) or absolute (starting with http).
	"""


class SeeOther(RedirectBase):
	"""raised to redirect a user agent to a different resource (HTTP 303).

	SeeOthers are constructed with the destination URL that can be
	relative (to webRoot) or absolute (starting with http).

	They are essentially like WebRedirect, except they put out a 303 
	instead of a 301.
	"""


class Found(RedirectBase):
	"""raised to redirect a user agent to a different resource (HTTP 302).

	Found instances are constructed with the destination URL that can be
	relative (to webRoot) or absolute (starting with http).

	They are essentially like WebRedirect, except they put out a 302 
	instead of a 301.
	"""


def parseServicePath(serviceParts):
	"""returns a tuple of resourceDescriptor, serviceName.

	A serivce id consists of an inputsDir-relative path to a resource 
	descriptor, a slash, and the name of a service within this descriptor.

	This function returns a tuple of inputsDir-relative path and service name.
	It raises a gavo.Error if sid has an invalid format.  The existence of
	the resource or the service are not checked.
	"""
	return "/".join(serviceParts[:-1]), serviceParts[-1]


class QueryMeta(dict):
	"""A class keeping information on the query environment.

	It is constructed with a plain dictionary (there are alternative
	constructors for t.w requests are below) mapping 
	certain keys (you'll currently have to figure out which from the 
	source) to values, mostly strings, except for the keys listed in 
	listKeys, which should be sequences of strings.
	
	If you pass an empty dict, some sane defaults will be used.  You
	can get that "empty" query meta as common.emptyQueryMeta, but make
	sure you don't mutate it.

	QueryMetas constructed from request will have the user and password
	items filled out.

	If you're using formal, you should set the formal_data item
	to the dictionary created by formal.  This will let people use
	the parsed parameters in templates.

	Note: You cannot trust qm["user"] -- it is not validated against
	any credentials.
	"""
	
	# a set of keys handled by query meta to be ignored in parameter
	# lists because they are used internally.  This covers everything 
	# QueryMeta interprets, but also keys by introduced by certain gwidgets
	# and the formal infrastructure
	metaKeys = set(["_FILTER", "_OUTPUT", "_charset_", "_ADDITEM",
		"__nevow_form__", "_FORMAT", "_VERB", "_TDENC", "formal_data",
		"_SET", "_TIMEOUT", "_VOTABLE_VERSION", "FORMAT"])

	# a set of keys that have sequences as values (needed for construction
	# from t.w request.strargs)
	listKeys = set(["_ADDITEM", "_DBOPTIONS_ORDER", "_SET"])

	def __init__(self, initArgs=None, defaultLimit=None):
		if initArgs is None:
			initArgs = {}
		self.ctxArgs = utils.CaseSemisensitiveDict(initArgs)
		if defaultLimit is None:
			self.defaultLimit = base.getConfig("db", "defaultLimit")
		else:
			self.defaultLimit = defaultLimit
		self["formal_data"] = {}
		self["user"] = self["password"] = None
		self["accept"] = {}
		self["inputTable"] = None
		self._fillOutput(self.ctxArgs)
		self._fillDbOptions(self.ctxArgs)
		self._fillSet(self.ctxArgs)

	@classmethod
	def fromRequestArgs(cls, inArgs, **kwargs):
		"""constructs a QueryMeta from a gavo.web.common.Request.strargs
		"""
		args = {}
		for key, value in inArgs.items():
			# defense against broken legacy code: listify if necessary
			if not isinstance(value, list):
				value = [value]

			if key in cls.listKeys:
				args[key] = value
			else:
				if value:
					args[key] = value[0]
		return cls(args, **kwargs)

	@classmethod
	def fromRequest(cls, request, **kwargs):
		"""constructs a QueryMeta from a gavo.web.common.Request.

		In addition to getting information from the arguments, this
		also sets user and password.
		"""
		res = cls.fromRequestArgs(request.strargs, **kwargs)
		res["accept"] = utils.parseAccept(request.getHeader("accept"))
		res["user"] = request.getUser() or None
		res["password"] = utils.debytify(request.getPassword(), "utf-8") or None
		return res
	
	def _fillOutput(self, args):
		"""interprets values left by the OutputFormat widget.
		"""
		if "RESPONSEFORMAT" in args:
			self["format"] = args["RESPONSEFORMAT"]
		else:
			self["format"] = args.get("_FORMAT", "HTML")

		try:
# prefer fine-grained "verbosity" over _VERB or VERB
# Hack: malformed _VERBs result in None verbosity, which is taken to
# mean about "use fields of HTML".  Absent _VERB or VERB, on the other
# hand, means VERB=2, i.e., a sane default
			if "verbosity" in args:
				self["verbosity"] = int(args["verbosity"])
			elif "_VERB" in args:  # internal verb parameter
				self["verbosity"] = int(args["_VERB"])*10
			elif "VERB" in args:   # verb parameter for SCS and such
				self["verbosity"] = int(args["VERB"])*10
			else:
				self["verbosity"] = 20
		except ValueError:
			self["verbosity"] = "HTML"  # VERB given, but not an int.

		self["tdEnc"] = base.getConfig("ivoa", "votDefaultEncoding")=="td"
		if "_TDENC" in args:
			try:
				self["tdEnc"] = base.parseBooleanLiteral(args["_TDENC"])
			except ValueError:
				pass

		try:
			self["VOTableVersion"] = tuple(int(v) for v in
				args["_VOTABLE_VERSION"].split("."))
		except:  # simple ignore malformed version specs
			pass

		self["additionalFields"] = args.get("_ADDITEM", [])

	def _fillSet(self, args):
		"""interprets the output of a ColumnSet widget.
		"""
		self["columnSet"] = None
		if "_SET" in args:
			self["columnSet"] = set(args["_SET"])

	def _fillDbOptions(self, args):
		self["dbSortKeys"] = [s.strip() 
			for s in args.get("_DBOPTIONS_ORDER", []) if s.strip()]

		self["direction"] = {"ASC": "ASC", "DESC": "DESC"}[
			args.get("_DBOPTIONS_DIR", "ASC")]

		try:
			self["dbLimit"] = int(args["MAXREC"])
		except (ValueError, KeyError):
			self["dbLimit"] = self.defaultLimit

		try:
			self["timeout"] = max(float(args["_TIMEOUT"]), 0.001)
		except (ValueError, KeyError):
			self["timeout"] = base.getConfig("web", "sqlTimeout")

	def overrideDbOptions(self, sortKeys=None, limit=None, sortFallback=None,
			direction=None):
		if sortKeys is not None:
			self["dbSortKeys"] = sortKeys
		if not self["dbSortKeys"] and sortFallback is not None:
			self["dbSortKeys"] = sortFallback.split(",")
		if limit is not None:
			self["dbLimit"] = int(limit)
		if direction is not None:
			self["direction"] = direction

	def asSQL(self):
		"""returns the dbLimit and dbSortKey values as an SQL fragment.
		"""
		frag, pars = [], {}
		sortKeys = self["dbSortKeys"]
		dbLimit = self["dbLimit"]
# TODO: Sorting needs a thorough redesign, presumably giving column instance
# as column keys.  These could carry "default up" or "default down" in
# properties.  Meanwhile, there should be a UI to let users decide on
# sort direction.
# Meanwhile, let's do an emergency hack.
		if sortKeys:
			# Ok, we need to do some emergency securing here.  There should be
			# pre-validation that we're actually seeing a column key, but
			# just in case let's make sure we're seeing an SQL identifier.
			# (We can't rely on dbapi's escaping since we're not talking values here)
			frag.append("ORDER BY %s %s"%(",".join(
					re.sub('[^A-Za-z0-9"_]+', "", key) for key in sortKeys),
				self["direction"]))
		if dbLimit:
			frag.append("LIMIT %(_matchLimit)s")
			pars["_matchLimit"] = int(dbLimit)+1
		return " ".join(frag), pars


emptyQueryMeta = QueryMeta()


def getTemplatePath(key):
	"""see loadSystemTemplate.
	"""
	userPath = os.path.join(base.getConfig("rootDir"), "web/templates", key)
	if os.path.exists(userPath):
		return userPath
	else:
		resPath = "resources/templates/"+key
		if pkg_resources.resource_exists('gavo', resPath):
			return pkg_resources.resource_filename('gavo', resPath)
		else:
			raise base.NotFoundError(key, "template", "system templates")


def loadSystemTemplate(key):
	"""returns a nevow template for system pages from key.

	path is interpreted as relative to gavo_root/web/templates (first)
	and package internal (last).  If no template is found, None is
	returned (this harmonizes with the fallback in CustomTemplateMixin).
	"""
	try:
		tp = getTemplatePath(key)
		if tp is not None:
			return nevowc.XMLFile(tp)
	except IOError:
		pass