# -*- coding: utf-8 -*-
"""
    jinja2.environment
    ~~~~~~~~~~~~~~~~~~

    Provides a class that holds runtime and parsing time options.

    :copyright: (c) 2017 by the Jinja Team.
    :license: BSD, see LICENSE for more details.
"""
import os
import sys
import weakref
from functools import reduce, partial
from jinja2 import nodes
from jinja2.defaults import BLOCK_START_STRING, \
     BLOCK_END_STRING, VARIABLE_START_STRING, VARIABLE_END_STRING, \
     COMMENT_START_STRING, COMMENT_END_STRING, LINE_STATEMENT_PREFIX, \
     LINE_COMMENT_PREFIX, TRIM_BLOCKS, NEWLINE_SEQUENCE, \
     DEFAULT_FILTERS, DEFAULT_TESTS, DEFAULT_NAMESPACE, \
     DEFAULT_POLICIES, KEEP_TRAILING_NEWLINE, LSTRIP_BLOCKS
from jinja2.lexer import get_lexer, TokenStream
from jinja2.parser import Parser
from jinja2.nodes import EvalContext
from jinja2.compiler import generate, CodeGenerator
from jinja2.runtime import Undefined, new_context, Context
from jinja2.exceptions import TemplateSyntaxError, TemplateNotFound, \
     TemplatesNotFound, TemplateRuntimeError
from jinja2.utils import import_string, LRUCache, Markup, missing, \
     concat, consume, internalcode, have_async_gen
from jinja2._compat import imap, ifilter, string_types, iteritems, \
     text_type, reraise, implements_iterator, implements_to_string, \
     encode_filename, PY2, PYPY


# for direct template usage we have up to ten living environments
_spontaneous_environments = LRUCache(10)

# the function to create jinja traceback objects.  This is dynamically
# imported on the first exception in the exception handler.
_make_traceback = None


def get_spontaneous_environment(*args):
    """Return a new spontaneous environment.  A spontaneous environment is an
    unnamed and unaccessible (in theory) environment that is used for
    templates generated from a string and not from the file system.
    """
    try:
        env = _spontaneous_environments.get(args)
    except TypeError:
        return Environment(*args)
    if env is not None:
        return env
    _spontaneous_environments[args] = env = Environment(*args)
    env.shared = True
    return env


def create_cache(size):
    """Return the cache class for the given size."""
    if size == 0:
        return None
    if size < 0:
        return {}
    return LRUCache(size)


def copy_cache(cache):
    """Create an empty copy of the given cache."""
    if cache is None:
        return None
    elif type(cache) is dict:
        return {}
    return LRUCache(cache.capacity)


def load_extensions(environment, extensions):
    """Load the extensions from the list and bind it to the environment.
    Returns a dict of instantiated environments.
    """
    result = {}
    for extension in extensions:
        if isinstance(extension, string_types):
            extension = import_string(extension)
        result[extension.identifier] = extension(environment)
    return result


def fail_for_missing_callable(string, name):
    msg = string % name
    if isinstance(name, Undefined):
        try:
            name._fail_with_undefined_error()
        except Exception as e:
            msg = '%s (%s; did you forget to quote the callable name?)' % (msg, e)
    raise TemplateRuntimeError(msg)


def _environment_sanity_check(environment):
    """Perform a sanity check on the environment."""
    assert issubclass(environment.undefined, Undefined), 'undefined must ' \
        'be a subclass of undefined because filters depend on it.'
    assert environment.block_start_string != \
        environment.variable_start_string != \
        environment.comment_start_string, 'block, variable and comment ' \
        'start strings must be different'
    assert environment.newline_sequence in ('\r', '\r\n', '\n'), \
        'newline_sequence set to unknown line ending string.'
    return environment


class Environment(object):
    r"""The core component of Jinja is the `Environment`.  It contains
    important shared variables like configuration, filters, tests,
    globals and others.  Instances of this class may be modified if
    they are not shared and if no template was loaded so far.
    Modifications on environments after the first template was loaded
    will lead to surprising effects and undefined behavior.

    Here are the possible initialization parameters:

        `block_start_string`
            The string marking the beginning of a block.  Defaults to ``'{%'``.

        `block_end_string`
            The string marking the end of a block.  Defaults to ``'%}'``.

        `variable_start_string`
            The string marking the beginning of a print statement.
            Defaults to ``'{{'``.

        `variable_end_string`
            The string marking the end of a print statement.  Defaults to
            ``'}}'``.

        `comment_start_string`
            The string marking the beginning of a comment.  Defaults to ``'{#'``.

        `comment_end_string`
            The string marking the end of a comment.  Defaults to ``'#}'``.

        `line_statement_prefix`
            If given and a string, this will be used as prefix for line based
            statements.  See also :ref:`line-statements`.

        `line_comment_prefix`
            If given and a string, this will be used as prefix for line based
            comments.  See also :ref:`line-statements`.

            .. versionadded:: 2.2

        `trim_blocks`
            If this is set to ``True`` the first newline after a block is
            removed (block, not variable tag!).  Defaults to `False`.

        `lstrip_blocks`
            If this is set to ``True`` leading spaces and tabs are stripped
            from the start of a line to a block.  Defaults to `False`.

        `newline_sequence`
            The sequence that starts a newline.  Must be one of ``'\r'``,
            ``'\n'`` or ``'\r\n'``.  The default is ``'\n'`` which is a
            useful default for Linux and OS X systems as well as web
            applications.

        `keep_trailing_newline`
            Preserve the trailing newline when rendering templates.
            The default is ``False``, which causes a single newline,
            if present, to be stripped from the end of the template.

            .. versionadded:: 2.7

        `extensions`
            List of Jinja extensions to use.  This can either be import paths
            as strings or extension classes.  For more information have a
            look at :ref:`the extensions documentation <jinja-extensions>`.

        `optimized`
            should the optimizer be enabled?  Default is ``True``.

        `undefined`
            :class:`Undefined` or a subclass of it that is used to represent
            undefined values in the template.

        `finalize`
            A callable that can be used to process the result of a variable
            expression before it is output.  For example one can convert
            ``None`` implicitly into an empty string here.

        `autoescape`
            If set to ``True`` the XML/HTML autoescaping feature is enabled by
            default.  For more details about autoescaping see
            :class:`~jinja2.utils.Markup`.  As of Jinja 2.4 this can also
            be a callable that is passed the template name and has to
            return ``True`` or ``False`` depending on autoescape should be
            enabled by default.

            .. versionchanged:: 2.4
               `autoescape` can now be a function

        `loader`
            The template loader for this environment.

        `cache_size`
            The size of the cache.  Per default this is ``400`` which means
            that if more than 400 templates are loaded the loader will clean
            out the least recently used template.  If the cache size is set to
            ``0`` templates are recompiled all the time, if the cache size is
            ``-1`` the cache will not be cleaned.

            .. versionchanged:: 2.8
               The cache size was increased to 400 from a low 50.

        `auto_reload`
            Some loaders load templates from locations where the template
            sources may change (ie: file system or database).  If
            ``auto_reload`` is set to ``True`` (default) every time a template is
            requested the loader checks if the source changed and if yes, it
            will reload the template.  For higher performance it's possible to
            disable that.

        `bytecode_cache`
            If set to a bytecode cache object, this object will provide a
            cache for the internal Jinja bytecode so that templates don't
            have to be parsed if they were not changed.

            See :ref:`bytecode-cache` for more information.

        `enable_async`
            If set to true this enables async template execution which allows
            you to take advantage of newer Python features.  This requires
            Python 3.6 or later.
    """

    #: if this environment is sandboxed.  Modifying this variable won't make
    #: the environment sandboxed though.  For a real sandboxed environment
    #: have a look at jinja2.sandbox.  This flag alone controls the code
    #: generation by the compiler.
    sandboxed = False

    #: True if the environment is just an overlay
    overlayed = False

    #: the environment this environment is linked to if it is an overlay
    linked_to = None

    #: shared environments have this set to `True`.  A shared environment
    #: must not be modified
    shared = False

    #: these are currently EXPERIMENTAL undocumented features.
    exception_handler = None
    exception_formatter = None

    #: the class that is used for code generation.  See
    #: :class:`~jinja2.compiler.CodeGenerator` for more information.
    code_generator_class = CodeGenerator

    #: the context class thatis used for templates.  See
    #: :class:`~jinja2.runtime.Context` for more information.
    context_class = Context

    def __init__(self,
                 block_start_string=BLOCK_START_STRING,
                 block_end_string=BLOCK_END_STRING,
                 variable_start_string=VARIABLE_START_STRING,
                 variable_end_string=VARIABLE_END_STRING,
                 comment_start_string=COMMENT_START_STRING,
                 comment_end_string=COMMENT_END_STRING,
                 line_statement_prefix=LINE_STATEMENT_PREFIX,
                 line_comment_prefix=LINE_COMMENT_PREFIX,
                 trim_blocks=TRIM_BLOCKS,
                 lstrip_blocks=LSTRIP_BLOCKS,
                 newline_sequence=NEWLINE_SEQUENCE,
                 keep_trailing_newline=KEEP_TRAILING_NEWLINE,
                 extensions=(),
                 optimized=True,
                 undefined=Undefined,
                 finalize=None,
                 autoescape=False,
                 loader=None,
                 cache_size=400,
                 auto_reload=True,
                 bytecode_cache=None,
                 enable_async=False):
        # !!Important notice!!
        #   The constructor accepts quite a few arguments that should be
        #   passed by keyword rather than position.  However it's important to
        #   not change the order of arguments because it's used at least
        #   internally in those cases:
        #       -   spontaneous environments (i18n extension and Template)
        #       -   unittests
        #   If parameter changes are required only add parameters at the end
        #   and don't change the arguments (or the defaults!) of the arguments
        #   existing already.

        # lexer / parser information
        self.block_start_string = block_start_string
        self.block_end_string = block_end_string
        self.variable_start_string = variable_start_string
        self.variable_end_string = variable_end_string
        self.comment_start_string = comment_start_string
        self.comment_end_string = comment_end_string
        self.line_statement_prefix = line_statement_prefix
        self.line_comment_prefix = line_comment_prefix
        self.trim_blocks = trim_blocks
        self.lstrip_blocks = lstrip_blocks
        self.newline_sequence = newline_sequence
        self.keep_trailing_newline = keep_trailing_newline

        # runtime information
        self.undefined = undefined
        self.optimized = optimized
        self.finalize = finalize
        self.autoescape = autoescape

        # defaults
        self.filters = DEFAULT_FILTERS.copy()
        self.tests = DEFAULT_TESTS.copy()
        self.globals = DEFAULT_NAMESPACE.copy()

        # set the loader provided
        self.loader = loader
        self.cache = create_cache(cache_size)
        self.bytecode_cache = bytecode_cache
        self.auto_reload = auto_reload

        # configurable policies
        self.policies = DEFAULT_POLICIES.copy()

        # load extensions
        self.extensions = load_extensions(self, extensions)

        self.enable_async = enable_async
        self.is_async = self.enable_async and have_async_gen

        _environment_sanity_check(self)

    def add_extension(self, extension):
        """Adds an extension after the environment was created.

        .. versionadded:: 2.5
        """
        self.extensions.update(load_extensions(self, [extension]))