query interface
===============

The query interface allows to programmatically search for products in
the macsserver database. This is done by HTTP request to specially crafted URLs.

query format
------------

The base url for querying is::

   http://macsserver/query

After this prefix, the user can add key-value parameters in the following form::

   /key[_modifier]:value

Where ``key`` is the field to search for and ``value`` the value to match the query.
The ``modifier`` is optional, when ommitted, the query seraches for an exact match.
The following ``key``s are currently supported:

* ``_oid``: object id (str)
* ``sensorId``: sensor id (str)
* ``campaign`` == ``userMeta.campaign``: campaign id (str)
* ``intent`` == ``userMeta.intent``: intent id (str)
* ``mountOptions`` == ``userMeta.mountOptions``: mount option id (str)
* ``productType``: product type id (str)
* ``date``: date and time of capture (milliseconds since the epoch == JavaScript convention)

The modifiers will alter the query in the following manner:

* ``min``: Match all attributes which are greater or equal.
* ``max``: Match all attributes which are less or equal.

Additionally, there are special keys, which are written in all uppercase.
The following special keys are currently supported:

* ``LIMIT``: Maximum number of results to return.
* ``OFS``: Number of results to skip.

The special keys ``LIMIT`` and ``OFS`` can be used for pagination.

So if the user wants to query for all SWIR data from ACRIDICON 2014
from 27.08.2014 00:00:00+01:00 until 01.09.2014 00:00:00+01:00,
with a maximum of 90 results, starting from the beginning,
the correct query would be::

    http://macsserver/query/campaign:acridicon2014/sensorId:410043/date_min:1409090400000/date_max:1409522400000/LIMIT:90/OFS:0

answer from the server
----------------------

The server will return JSON data in the following form::

   {"count": NUMBER OF TOTAL RESULTS,
    "result": [RES_0, RES_1, RES_2, ...]}

Where ``count`` will always give the number of results for the query, without considering
``LIMIT`` or ``OFS``. The ``result`` list will contain objects containing:

* ``_oid``: object id (str)
* ``date``: date and time (ISO 8601)
* ``sensorId``: sensor id (str)
* ``userMeta``: object containing user defined metadata