# Source code for fastjsonschema

    #    ___
    #    \./     DANGER: This project implements some code generation
    # .--.O.--.          techniques involving string concatenation.
    #  \/   \/           If you look at it, you might die.
    #

    r"""
    Installation
    ************

    .. code-block:: bash

        pip install fastjsonschema

    Support only for Python 3.3 and higher.

    About
    *****

    ``fastjsonschema`` implements validation of JSON documents by JSON schema.
    The library implements JSON schema drafts 04, 06 and 07. The main purpose is
    to have a really fast implementation. See some numbers:

     * Probably most popular ``jsonschema`` can take up to 5 seconds for valid inputs
       and 1.2 seconds for invalid inputs.
     * Second most popular ``json-spec`` is even worse with up to 7.2 and 1.7 seconds.
     * Last ``validictory``, now deprecated, is much better with 370 or 23 milliseconds,
       but it does not follow all standards and it can be still slow for some purposes.

    With this library you can gain big improvements as ``fastjsonschema`` takes
    only about 25 milliseconds for valid inputs and 2 milliseconds for invalid ones.
    Pretty amazing, right? :-)

    Technically it works by generating the most stupid code on the fly which is fast but
    is hard to write by hand. The best efficiency is achieved when compiled once and used
    many times, of course. It works similarly like regular expressions. But you can also
    generate the code to the file which is even slightly faster.

    You can do the performance on your computer or server with an included script:

    .. code-block:: bash

        $ make performance
        fast_compiled        valid      ==>  0.0464646
        fast_compiled        invalid    ==>  0.0030227
        fast_file            valid      ==>  0.0461219
        fast_file            invalid    ==>  0.0030608
        fast_not_compiled    valid      ==> 11.4627202
        fast_not_compiled    invalid    ==>  2.5726230
        jsonschema           valid      ==>  7.5844927
        jsonschema           invalid    ==>  1.9204665
        jsonschema_compiled  valid      ==>  0.6938364
        jsonschema_compiled  invalid    ==>  0.0359244
        jsonspec             valid      ==>  9.0715843
        jsonspec             invalid    ==>  2.1650488
        validictory          valid      ==>  0.4874793
        validictory          invalid    ==>  0.0232244

    This library follows and implements `JSON schema draft-04, draft-06, and draft-07
    <http://json-schema.org>`_. Sometimes it's not perfectly clear so I recommend also
    check out this `understanding JSON schema <https://spacetelescope.github.io/understanding-json-schema>`_.

    Note that there are some differences compared to JSON schema standard:

     * Regular expressions are full Python ones, not only what JSON schema allows. It's easier
       to allow everything and also it's faster to compile without limits. So keep in mind that when
       you will use a more advanced regular expression, it may not work with other library or in
       other languages.
     * Because Python matches new line for a dollar in regular expressions (``a$`` matches ``a`` and ``a\\n``),
       instead of ``$`` is used ``\Z`` and all dollars in your regular expression are changed to ``\\Z``
       as well. When you want to use dollar as regular character, you have to escape it (``\$``).
     * JSON schema says you can use keyword ``default`` for providing default values. This implementation
       uses that and always returns transformed input data.

    API
    ***
    """

    from .draft04 import CodeGeneratorDraft04
    from .draft06 import CodeGeneratorDraft06
    from .draft07 import CodeGeneratorDraft07
    from .exceptions import JsonSchemaException, JsonSchemaValueException, JsonSchemaDefinitionException
    from .ref_resolver import RefResolver
    from .version import VERSION

    __all__ = (
        'VERSION',
        'JsonSchemaException',
        'JsonSchemaValueException',
        'JsonSchemaDefinitionException',
        'validate',
        'compile',
        'compile_to_code',
    )

    def validate(definition, data, handlers={}, formats={}, use_default=True):
        """
        Validation function for lazy programmers or for use cases, when you need
        to call validation only once, so you do not have to compile it first.
        Use it only when you do not care about performance (even thought it will
        be still faster than alternative implementations).

        .. code-block:: python

            import fastjsonschema

            fastjsonschema.validate({'type': 'string'}, 'hello')
            # same as: compile({'type': 'string'})('hello')

        Preferred is to use :any:`compile` function.
        """
        return compile(definition, handlers, formats, use_default)(data)

    #TODO: Change use_default to False when upgrading to version 3.
    # pylint: disable=redefined-builtin,dangerous-default-value,exec-used
    def compile(definition, handlers={}, formats={}, use_default=True):
        """
        Generates validation function for validating JSON schema passed in ``definition``.
        Example:

        .. code-block:: python

            import fastjsonschema

            validate = fastjsonschema.compile({'type': 'string'})
            validate('hello')

        This implementation supports keyword ``default`` (can be turned off
        by passing `use_default=False`):

        .. code-block:: python

            validate = fastjsonschema.compile({
                'type': 'object',
                'properties': {
                    'a': {'type': 'number', 'default': 42},
                },
            })

            data = validate({})
            assert data == {'a': 42}

        Supported implementations are draft-04, draft-06 and draft-07. Which version
        should be used is determined by `$draft` in your ``definition``. When not
        specified, the latest implementation is used (draft-07).

        .. code-block:: python

            validate = fastjsonschema.compile({
                '$schema': 'http://json-schema.org/draft-04/schema',
                'type': 'number',
            })

        You can pass mapping from URI to function that should be used to retrieve
        remote schemes used in your ``definition`` in parameter ``handlers``.

        Also, you can pass mapping for custom formats. Key is the name of your
        formatter and value can be regular expression which will be compiled or
        callback returning `bool` (or you can raise your own exception).

        .. code-block:: python

            validate = fastjsonschema.compile(definition, formats={
                'foo': r'foo|bar',
                'bar': lambda value: value in ('foo', 'bar'),
            })

        Exception :any:`JsonSchemaDefinitionException` is raised when generating the
        code fails (bad definition).

        Exception :any:`JsonSchemaValueException` is raised from generated function when
        validation fails (data do not follow the definition).
        """
        resolver, code_generator = _factory(definition, handlers, formats, use_default)
        global_state = code_generator.global_state
        # Do not pass local state so it can recursively call itself.
        exec(code_generator.func_code, global_state)
        return global_state[resolver.get_scope_name()]

    # pylint: disable=dangerous-default-value
    def compile_to_code(definition, handlers={}, formats={}, use_default=True):
        """
        Generates validation code for validating JSON schema passed in ``definition``.
        Example:

        .. code-block:: python

            import fastjsonschema

            code = fastjsonschema.compile_to_code({'type': 'string'})
            with open('your_file.py', 'w') as f:
                f.write(code)

        You can also use it as a script:

        .. code-block:: bash

            echo "{'type': 'string'}" | python3 -m fastjsonschema > your_file.py
            python3 -m fastjsonschema "{'type': 'string'}" > your_file.py

        Exception :any:`JsonSchemaDefinitionException` is raised when generating the
        code fails (bad definition).
        """
        _, code_generator = _factory(definition, handlers, formats, use_default)
        return (
            'VERSION = "' + VERSION + '"\n' +
            code_generator.global_state_code + '\n' +
            code_generator.func_code
        )

    def _factory(definition, handlers, formats={}, use_default=True):
        resolver = RefResolver.from_schema(definition, handlers=handlers)
        code_generator = _get_code_generator_class(definition)(
            definition,
            resolver=resolver,
            formats=formats,
            use_default=use_default,
        )
        return resolver, code_generator

    def _get_code_generator_class(schema):
        # Schema in from draft-06 can be just the boolean value.
        if isinstance(schema, dict):
            schema_version = schema.get('$schema', '')
            if 'draft-04' in schema_version:
                return CodeGeneratorDraft04
            if 'draft-06' in schema_version:
                return CodeGeneratorDraft06
        return CodeGeneratorDraft07