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

    Runtime helpers.

    :copyright: (c) 2017 by the Jinja Team.
    :license: BSD.
"""
import sys

from itertools import chain
from types import MethodType

from jinja2.nodes import EvalContext, _context_function_types
from jinja2.utils import Markup, soft_unicode, escape, missing, concat, \
     internalcode, object_type_repr, evalcontextfunction, Namespace
from jinja2.exceptions import UndefinedError, TemplateRuntimeError, \
     TemplateNotFound
from jinja2._compat import imap, text_type, iteritems, \
     implements_iterator, implements_to_string, string_types, PY2, \
     with_metaclass, abc


# these variables are exported to the template runtime
__all__ = ['LoopContext', 'TemplateReference', 'Macro', 'Markup',
           'TemplateRuntimeError', 'missing', 'concat', 'escape',
           'markup_join', 'unicode_join', 'to_string', 'identity',
           'TemplateNotFound', 'Namespace']

#: the name of the function that is used to convert something into
#: a string.  We can just use the text type here.
to_string = text_type

#: the identity function.  Useful for certain things in the environment
identity = lambda x: x

_first_iteration = object()
_last_iteration = object()


def markup_join(seq):
    """Concatenation that escapes if necessary and converts to unicode."""
    buf = []
    iterator = imap(soft_unicode, seq)
    for arg in iterator:
        buf.append(arg)
        if hasattr(arg, '__html__'):
            return Markup(u'').join(chain(buf, iterator))
    return concat(buf)


def unicode_join(seq):
    """Simple args to unicode conversion and concatenation."""
    return concat(imap(text_type, seq))


def new_context(environment, template_name, blocks, vars=None,
                shared=None, globals=None, locals=None):
    """Internal helper to for context creation."""
    if vars is None:
        vars = {}
    if shared:
        parent = vars
    else:
        parent = dict(globals or (), **vars)
    if locals:
        # if the parent is shared a copy should be created because
        # we don't want to modify the dict passed
        if shared:
            parent = dict(parent)
        for key, value in iteritems(locals):
            if value is not missing:
                parent[key] = value
    return environment.context_class(environment, parent, template_name,
                                     blocks)


class TemplateReference(object):
    """The `self` in templates."""

    def __init__(self, context):
        self.__context = context

    def __getitem__(self, name):
        blocks = self.__context.blocks[name]
        return BlockReference(name, self.__context, blocks, 0)

    def __repr__(self):
        return '<%s %r>' % (
            self.__class__.__name__,
            self.__context.name
        )


def _get_func(x):
    return getattr(x, '__func__', x)


class ContextMeta(type):

    def __new__(cls, name, bases, d):
        rv = type.__new__(cls, name, bases, d)
        if bases == ():
            return rv

        resolve = _get_func(rv.resolve)
        default_resolve = _get_func(Context.resolve)
        resolve_or_missing = _get_func(rv.resolve_or_missing)
        default_resolve_or_missing = _get_func(Context.resolve_or_missing)

        # If we have a changed resolve but no changed default or missing
        # resolve we invert the call logic.
        if resolve is not default_resolve and \
           resolve_or_missing is default_resolve_or_missing:
            rv._legacy_resolve_mode = True
        elif resolve is default_resolve and \
             resolve_or_missing is default_resolve_or_missing:
            rv._fast_resolve_mode = True

        return rv


def resolve_or_missing(context, key, missing=missing):
    if key in context.vars:
        return context.vars[key]
    if key in context.parent:
        return context.parent[key]
    return missing


class Context(with_metaclass(ContextMeta)):
    """The template context holds the variables of a template.  It stores the
    values passed to the template and also the names the template exports.
    Creating instances is neither supported nor useful as it's created
    automatically at various stages of the template evaluation and should not
    be created by hand.

    The context is immutable.  Modifications on :attr:`parent` **must not**
    happen and modifications on :attr:`vars` are allowed from generated
    template code only.  Template filters and global functions marked as
    :func:`contextfunction`\\s get the active context passed as first argument
    and are allowed to access the context read-only.

    The template context supports read only dict operations (`get`,
    `keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
    `__getitem__`, `__contains__`).  Additionally there is a :meth:`resolve`
    method that doesn't fail with a `KeyError` but returns an
    :class:`Undefined` object for missing variables.
    """
    # XXX: we want to eventually make this be a deprecation warning and
    # remove it.
    _legacy_resolve_mode = False
    _fast_resolve_mode = False

    def __init__(self, environment, parent, name, blocks):
        self.parent = parent
        self.vars = {}
        self.environment = environment
        self.eval_ctx = EvalContext(self.environment, name)
        self.exported_vars = set()
        self.name = name

        # create the initial mapping of blocks.  Whenever template inheritance
        # takes place the runtime will update this mapping with the new blocks
        # from the template.
        self.blocks = dict((k, [v]) for k, v in iteritems(blocks))

        # In case we detect the fast resolve mode we can set up an alias
        # here that bypasses the legacy code logic.
        if self._fast_resolve_mode:
            self.resolve_or_missing = MethodType(resolve_or_missing, self)

    def super(self, name, current):
        """Render a parent block."""
        try:
            blocks = self.blocks[name]
            index = blocks.index(current) + 1
            blocks[index]
        except LookupError:
            return self.environment.undefined('there is no parent block '
                                              'called %r.' % name,
                                              name='super')
        return BlockReference(name, self, blocks, index)

    def get(self, key, default=None):
        """Returns an item from the template context, if it doesn't exist
        `default` is returned.
        """
        try:
            return self[key]
        except KeyError:
            return default

    def resolve(self, key):
        """Looks up a variable like `__getitem__` or `get` but returns an
        :class:`Undefined` object with the name of the name looked up.
        """
        if self._legacy_resolve_mode:
            rv = resolve_or_missing(self, key)
        else:
            rv = self.resolve_or_missing(key)
        if rv is missing:
            return self.environment.undefined(name=key)
        return rv

    def resolve_or_missing(self, key):
        """Resolves a variable like :meth:`resolve` but returns the
        special `missing` value if it cannot be found.
        """
        if self._legacy_resolve_mode:
            rv = self.resolve(key)
            if isinstance(rv, Undefined):
                rv = missing
            return rv
        return resolve_or_missing(self, key)

    def get_exported(self):
        """Get a new dict with the exported variables."""
        return dict((k, self.vars[k]) for k in self.exported_vars)

    def get_all(self):
        """Return the complete context as dict including the exported
        variables.  For optimizations reasons this might not return an
        actual copy so be careful with using it.
        """
        if not self.vars:
            return self.parent
        if not self.parent:
            return self.vars
        return dict(self.parent, **self.vars)

    @internalcode
    def call(__self, __obj, *args, **kwargs):
        """Call the callable with the arguments and keyword arguments
        provided but inject the active context or environment as first
        argument if the callable is a :func:`contextfunction` or
        :func:`environmentfunction`.
        """
        if __debug__:
            __traceback_hide__ = True  # noqa

        # Allow callable classes to take a context
        if hasattr(__obj, '__call__'):
            fn = __obj.__call__
            for fn_type in ('contextfunction',
                            'evalcontextfunction',
                            'environmentfunction'):
                if hasattr(fn, fn_type):
                    __obj = fn
                    break

        if isinstance(__obj, _context_function_types):
            if getattr(__obj, 'contextfunction', 0):
                args = (__self,) + args
            elif getattr(__obj, 'evalcontextfunction', 0):
                args = (__self.eval_ctx,) + args
            elif getattr(__obj, 'environmentfunction', 0):
                args = (__self.environment,) + args
        try:
            return __obj(*args, **kwargs)
        except StopIteration:
            return __self.environment.undefined('value was undefined because '
                                                'a callable raised a '
                                                'StopIteration exception')

    def derived(self, locals=None):
        """Internal helper function to create a derived context.  This is
        used in situations where the system needs a new context in the same
        template that is independent.
        """
        context = new_context(self.environment, self.name, {},
                              self.get_all(), True, None, locals)
        context.eval_ctx = self.eval_ctx
        context.blocks.update((k, list(v)) for k, v in iteritems(self.blocks))
        return context

    def _all(meth):
        proxy = lambda self: getattr(self.get_all(), meth)()
        proxy.__doc__ = getattr(dict, meth).__doc__
        proxy.__name__ = meth
        return proxy

    keys = _all('keys')
    values = _all('values')
    items = _all('items')

    # not available on python 3
    if PY2:
        iterkeys = _all('iterkeys')
        itervalues = _all('itervalues')
        iteritems = _all('iteritems')
    del _all

    def __contains__(self, name):
        return name in self.vars or name in self.parent

    def __getitem__(self, key):
        """Lookup a variable or raise `KeyError` if the variable is
        undefined.
        """
        item = self.resolve_or_missing(key)
        if item is missing:
            raise KeyError(key)
        return item

    def __repr__(self):
        return '<%s %s of %r>' % (
            self.__class__.__name__,
            repr(self.get_all()),
            self.name
        )


abc.Mapping.register(Context)


class BlockReference(object):
    """One block on a template reference."""

    def __init__(self, name, context, stack, depth):
        self.name = name
        self._context = context
        self._stack = stack
        self._depth = depth

    @property
    def super(self):
        """Super the block."""
        if self._depth + 1 >= len(self._stack):
            return self._context.environment. \
                undefined('there is no parent block called %r.' %
                          self.name, name='super')
        return BlockReference(self.name, self._context, self._stack,
                              self._depth + 1)

    @internalcode
    def __call__(self):
        rv = concat(self._stack[self._depth](self._context))
        if self._context.eval_ctx.autoescape:
            rv = Markup(rv)
        return rv