a8_jsonurl
=======

Introduction
------------

a8_jsonurl is a simple library for managing the serialisation and deserialisation of URL query strings which represent hierarchically structured data.

It will take python data structures which can be represented in JSON and convert them to flat key/value pairs for use in URL query strings, and it will take URL query strings and parse them into hierarchical data structures.

This is convenient if you wish to pass structured data around in the URL itself rather than in a POST body.  This may complement a web API which also accepts JSON strings in the body of a POST request, providing equivalent functionality using GET without constructing URLs which include url-encoded json objects.


Usage
-----

    >>> import jsonurl

### Converting Data Structures

A simple flat dictionary

    >>> d = {"one" : 1, "two" : 2}
    
    >>> jsonurl.query_string(d)
    'one=1&two=2'

A dictionary with a nested dictionary

    >>> d = {"one" : {"two" : 2, "three" : 3}, "four" : 4}
    >>> q = jsonurl.query_string(d)
    >>> q
    'four=4&one.three=3&one.two=2'

We can also get a flat dictionary as a proxy for the hierarchic one, if we do not want a8_jsonurl to actually prepare the query part of the URL for us

    >>> jsonurl.dict_to_args(d)
    {'four': '4', 'one.three': '3', 'one.two': '2'}

We can parse the query string back into a python dictionary object

    >>> jsonurl.parse_query(q)
    {'four': 4, 'one': {'three': 3, 'two': 2}}

We can also serialise nested lists:

    >>> d = {"one" : 1, "two" : [2,3,4]}

The flattened data structure:

    >>> jsonurl.dict_to_args(d)
    {'two.1': '3', 'two.0': '2', 'two.2': '4', 'one': '1'}

The query string itself:

    >>> q = jsonurl.query_string(d)
    >>> q
    'one=1&two.0=2&two.1=3&two.2=4'

This can be comfortably parsed back into a python data structure

    >>> jsonurl.parse_query(q)
    {'two': [2, 3, 4], 'one': 1}

We can go on to serialise arbitrarily complex data structures

    >>> d = {"one" : [ {"two" : 2, "three" : 3}, 4 ]}
    >>> q = jsonurl.query_string(d)
    >>> q
    'one.0.three=3&one.0.two=2&one.1=4'

### Escape Characters

a8_jsonurl will also handle url-escaping:

    >>> q = {"escape_me" : "I'll need escaping"}
    >>> s = jsonurl.query_string(q)
    >>> s
    'escape_me=I%27ll+need+escaping'

a8_jsonurl uses "+" for a space instead of %20 to improve readability

It also unescapes everything during parse:

    >>> jsonurl.parse_query(s)
    {'escape_me': "I'll need escaping"}

Since a8_jsonurl uses "." as its separator, dictionary keys with "." in the name are escaped.  We prefix each "." with another during serialisation:

    >>> d = {"user.names" : ["richard", "jones"]}
    >>> q = jsonurl.query_string(d)
    >>> q
    'user..names.0=richard&user..names.1=jones'

".." is then converted back during parsing:

    >>> jsonurl.parse_query(q)
    {'user.names': ['richard', 'jones']}


### Parameter Ordering

It orders the query parameters, to make it easier to read long query strings:

    >>> d = {"b" : "last", "a" : [1,2,3]}
    >>> jsonurl.query_string(d)
    'a.0=1&a.1=2&a.2=3&b=last'