queries.py

"""
:Author: Franziska Koehn
:Created: 2015/01/13

This module includes functions around sending and defining queries.

to query the xnat server define:

one string including one Root-Type like:

.. sourcecode:: python

   'xnat:mrScanData'

one list including the search-constraints like:

.. code-block:: python

    [
        ('xnat:mrScanData/TYPE', 'LIKE', '%t2%'),
        ('xnat:mrScanData/PARAMETERS_FLIP', '>=', '10'),
        'AND',
        [('xnat:mrScanData/PARAMETERS_TE', '>', '2.0'),
         ('xnat:mrScanData/PARAMETERS_TE', '<', '2.0'),
         'OR'
         ]
    ]

a list of search-fields like:

.. code-block:: python

    [ 'xnat:mrScanData/TYPE','xnat:mrScanData/ID']

"""


from threading import Lock
import xsa.errors
requests_lock = Lock()

def get_query_methods():
    """Returns all applicable methods for creating a query."""
    return ["AND", "OR"]

def get_operators():
    """Returns all applicable Operators for creating a query."""
    return ["LIKE", ">", "<", "<=", ">=", "="]


def download_async(result, host, creds, rest, dest_folder='', cb=(lambda *_: None), cb_args=()):
    """
    Downloads file by using threads (So the GUI will not be blocked while downloading).

    **Parameters**
        :result: dict, resultset from which will be downloaded
        :host: str, address of host
        :creds: tuple (username, userpassword), credentials (including user-name and -password)
        :rest: str, REST-API definition
        :dest_folder: str, folder where the downloaded files will be saved
        :cb: function, that will be called, when download is finished with the arguments from cb_args
        :cb_args: args for function cb
    """
    from threading import Thread
    download_thread = Thread(target=download, args=(result, host, creds, rest, dest_folder, cb, cb_args))
    download_thread.start()
    return download_thread

def download(result, host, creds, rest, dest_folder='', cb=(lambda *_: None), cb_args=()):
    """
    Downloads a Result.

    **Parameters**
        :result: dict, resultset from which will be downloaded
        :host: str, address of host
        :creds: tuple (username, userpassword), credentials (including user-name and -password)
        :rest: str, REST-API definition
        :dest_folder: str, folder where the downloaded files will be saved
        :cb: function, that will be called, when download is finished with the arguments from cb_args
        :cb_args: args for function cb
    """

    requests_lock.acquire()

    import re
    import os

    names=[]
    def subfunc(f):
        key = f.group(0).strip("{}")
        r = result[key]
        names.append(r)
        return r
    ret = re.sub('\{\w+\}', subfunc, rest)

    path = os.path.join(dest_folder, '-'.join(names))
    url = "%s%s" % (host, ret)

    download_file(url, creds, path)
    requests_lock.release()
    cb(*cb_args)

def download_file(url, creds, path):
    """
    Downloads a file from given 'url' and saves it to 'path'.

    Returns True if download was finished without problems
    Returns False if download raised an exception.

    **Parameters**
        :url: str, host/REST-API with filled values
        :creds: tuple(user-name, user-password), credentials
        :path: str, folder where the downloaded files will be saved
    """

    import requests
    from base64 import b64encode
    from requests.auth import HTTPBasicAuth

    if not path.endswith(".zip"):
        path += ".zip"

    user, passw = creds

    try:
        with open(path, 'wb') as handle:
            response = requests.get(url, stream=True, auth=HTTPBasicAuth(user, passw))
            if not response.ok:
                raise ValueError(response.status_code)
            for block in response.iter_content(1024):
                if not block:
                    break
                handle.write(block)
        return True
    except IOError as e:
        raise xsa.errors.WritingError("Error writing file %s, %s" % (path, e))
    except ValueError as e:
        raise xsa.errors.DownloadError("Error downloading file %s, Status Code %s" % (url, e))
    return False

def retry_qry(fun):
    def retry(*args, **kwargs):
        last_exception = None
        retries = 1
        while retries >= 0:
            try:
                return fun(*args, **kwargs)
            except Exception as e:
                print(("wrapped", e))
                if type(last_exception) is type(e):
                    raise e
                last_exception = e
            finally:
                retries -= 1
    return retry

@retry_qry
def query_for_additional_data(rest, result, host, creds):

    import requests
    from requests.auth import HTTPBasicAuth
    from xml.etree import ElementTree
    import re

    def subfunc(f):
        key = f.group(0).strip("{}")
        return result[key]
    ret = re.sub('\{\w+\}', subfunc, rest)
    user, passw = creds
    url = "%s%s" % (host, ret)

    r = requests.get(url, auth=HTTPBasicAuth(user, passw))
    exp = ElementTree.fromstring(r.text)

    new_fields = exp.findall(".//xnat:field", {"xnat": "http://nrg.wustl.edu/xnat"})
    new_result = result.copy()
    for f in new_fields:
        fieldname = f.get("name")
        value = exp.find(".//xnat:field[@name='"+fieldname+"']", {"xnat": "http://nrg.wustl.edu/xnat"})
        new_result[fieldname] = ''.join(value.text).replace("\n","")
    return new_result


@retry_qry
def search_for(host, root_element, constraints, search_fields, user, passw):
    """
    Does a search for given values. raises xsa-Exceptions

    **Parameters**
        :host: str, host-address
        :root_element: str, Root-Type of search
        :constraints: list, constraints of query
        :search_fields: list of str, fields which will be returned from server
        :user: str, user-name
        :passw: str, user-password

    **Raises**
        :xsa.errors.ServerNotFoundError:
        :xsa.errors.UnauthorizedError:
        :xsa.errors.ResponseNotReady:
        :xsa.errors.QueryError:

    """
    import requests
    from requests.auth import HTTPBasicAuth
    from tempfile import NamedTemporaryFile
    from xsa.jsonutil import JsonTable
    import json

    url= "%s%s" % (host, "/data/search?format=json")

    with NamedTemporaryFile(suffix=".xml") as tmp:
        tree = create_xml_tree(root_element, constraints, search_fields)
        tree.write(tmp, xml_declaration=True)
        tmp.flush()
        r = requests.post(url, files={'file': open(tmp.name, 'rb')}, auth=HTTPBasicAuth(user, passw))

    if r.status_code == requests.codes.ok:
        json_file=(json.loads(r.text))['ResultSet']['Result']
        return JsonTable(json_file)


def create_xml_tree(root_type, query, fields):
    import xml.etree.cElementTree as ET

    search_attributes = {"ID":"", "allow-diff-columns":"0", "secure":"false", "brief-description":"MR Sessions", "xmlns:xdat":"http://nrg.wustl.edu/security", "xmlns:xsi":"http://www.w3.org/2001/XMLSchema-instance"}
    root = ET.Element("xdat:search", attrib=search_attributes)
    ET.SubElement(root, "xdat:root_element_name").text = root_type

    for field in fields:
        element, field_id = field.split("/")
        field = ET.SubElement(root, "xdat:search_field")
        ET.SubElement(field, "xdat:element_name").text = element
        ET.SubElement(field, "xdat:field_ID").text = field_id

    def create_criterias(parent, element, iterator):
        try:
            if isinstance(element, str):
                element = parent.set("method", element)
                create_criterias(parent, next(iterator), iterator)
            elif isinstance(element, tuple):
                if len(element) != 3:
                    raise errors.QueryError("The query-definition is incorrect.")
                else:
                    citeria = ET.SubElement(parent, "xdat:criteria", attrib={"override_value_formatting":"0"})
                    ET.SubElement(citeria, "xdat:schema_field").text=element[0]
                    ET.SubElement(citeria, "xdat:comparison_type").text=element[1]
                    ET.SubElement(citeria, "value").text=element[2]
                    create_criterias(parent, next(iterator), iterator)
            elif isinstance(element, list):
                child = ET.SubElement(parent, "xdat:child_set", method="AND")
                iter_child = iter(element)
                create_criterias(child, next(iter_child), iter_child)
        except StopIteration:
            pass

    iter_query = iter(query)
    where = ET.SubElement(root, "xdat:search_where", method="AND")
    create_criterias(where, next(iter_query), iter_query)

    return ET.ElementTree(root)