"""Default tags used by the template system, available to all templates."""
from __future__ import unicode_literals

import os
import re
import sys
import warnings
from datetime import datetime
from itertools import cycle as itertools_cycle, groupby

from django.conf import settings
from django.utils import six, timezone
from django.utils.deprecation import RemovedInDjango110Warning
from django.utils.encoding import force_text, smart_text
from django.utils.html import conditional_escape, format_html
from django.utils.lorem_ipsum import paragraphs, words
from django.utils.safestring import mark_safe

from .base import (
    BLOCK_TAG_END, BLOCK_TAG_START, COMMENT_TAG_END, COMMENT_TAG_START,
    SINGLE_BRACE_END, SINGLE_BRACE_START, VARIABLE_ATTRIBUTE_SEPARATOR,
    VARIABLE_TAG_END, VARIABLE_TAG_START, Context, Node, NodeList, Template,
    TemplateSyntaxError, VariableDoesNotExist, kwarg_re,
    render_value_in_context, token_kwargs,
)
from .defaultfilters import date
from .library import Library
from .smartif import IfParser, Literal

register = Library()


class AutoEscapeControlNode(Node):
    """Implements the actions of the autoescape tag."""
    def __init__(self, setting, nodelist):
        self.setting, self.nodelist = setting, nodelist

    def render(self, context):
        old_setting = context.autoescape
        context.autoescape = self.setting
        output = self.nodelist.render(context)
        context.autoescape = old_setting
        if self.setting:
            return mark_safe(output)
        else:
            return output


class CommentNode(Node):
    def render(self, context):
        return ''


class CsrfTokenNode(Node):
    def render(self, context):
        csrf_token = context.get('csrf_token')
        if csrf_token:
            if csrf_token == 'NOTPROVIDED':
                return format_html("")
            else:
                return format_html("<input type='hidden' name='csrfmiddlewaretoken' value='{}' />", csrf_token)
        else:
            # It's very probable that the token is missing because of
            # misconfiguration, so we raise a warning
            if settings.DEBUG:
                warnings.warn(
                    "A {% csrf_token %} was used in a template, but the context "
                    "did not provide the value.  This is usually caused by not "
                    "using RequestContext."
                )
            return ''


class CycleNode(Node):
    def __init__(self, cyclevars, variable_name=None, silent=False):
        self.cyclevars = cyclevars
        self.variable_name = variable_name
        self.silent = silent

    def render(self, context):
        if self not in context.render_context:
            # First time the node is rendered in template
            context.render_context[self] = itertools_cycle(self.cyclevars)
        cycle_iter = context.render_context[self]
        value = next(cycle_iter).resolve(context)
        if self.variable_name:
            context[self.variable_name] = value
        if self.silent:
            return ''
        return render_value_in_context(value, context)


class DebugNode(Node):
    def render(self, context):
        from pprint import pformat
        output = [force_text(pformat(val)) for val in context]
        output.append('\n\n')
        output.append(force_text(pformat(sys.modules)))
        return ''.join(output)


class FilterNode(Node):
    def __init__(self, filter_expr, nodelist):
        self.filter_expr, self.nodelist = filter_expr, nodelist

    def render(self, context):
        output = self.nodelist.render(context)
        # Apply filters.
        with context.push(var=output):
            return self.filter_expr.resolve(context)


class FirstOfNode(Node):
    def __init__(self, variables, asvar=None):
        self.vars = variables
        self.asvar = asvar

    def render(self, context):
        for var in self.vars:
            value = var.resolve(context, True)
            if value:
                first = render_value_in_context(value, context)
                if self.asvar:
                    context[self.asvar] = first
                    return ''
                return first
        return ''


class ForNode(Node):
    child_nodelists = ('nodelist_loop', 'nodelist_empty')

    def __init__(self, loopvars, sequence, is_reversed, nodelist_loop, nodelist_empty=None):
        self.loopvars, self.sequence = loopvars, sequence
        self.is_reversed = is_reversed
        self.nodelist_loop = nodelist_loop
        if nodelist_empty is None:
            self.nodelist_empty = NodeList()
        else:
            self.nodelist_empty = nodelist_empty

    def __repr__(self):
        reversed_text = ' reversed' if self.is_reversed else ''
        return "<For Node: for %s in %s, tail_len: %d%s>" % \
            (', '.join(self.loopvars), self.sequence, len(self.nodelist_loop),
             reversed_text)

    def __iter__(self):
        for node in self.nodelist_loop:
            yield node
        for node in self.nodelist_empty:
            yield node

    def render(self, context):
        if 'forloop' in context:
            parentloop = context['forloop']
        else:
            parentloop = {}
        with context.push():
            try:
                values = self.sequence.resolve(context, True)
            except VariableDoesNotExist:
                values = []
            if values is None:
                values = []
            if not hasattr(values, '__len__'):
                values = list(values)
            len_values = len(values)
            if len_values < 1:
                return self.nodelist_empty.render(context)
            nodelist = []
            if self.is_reversed:
                values = reversed(values)
            num_loopvars = len(self.loopvars)
            unpack = num_loopvars > 1
            # Create a forloop value in the context.  We'll update counters on each
            # iteration just below.
            loop_dict = context['forloop'] = {'parentloop': parentloop}
            for i, item in enumerate(values):
                # Shortcuts for current loop iteration number.
                loop_dict['counter0'] = i
                loop_dict['counter'] = i + 1
                # Reverse counter iteration numbers.
                loop_dict['revcounter'] = len_values - i
                loop_dict['revcounter0'] = len_values - i - 1
                # Boolean values designating first and last times through loop.
                loop_dict['first'] = (i == 0)
                loop_dict['last'] = (i == len_values - 1)

                pop_context = False
                if unpack:
                    # If there are multiple loop variables, unpack the item into
                    # them.

                    # To complete this deprecation, remove from here to the
                    # try/except block as well as the try/except itself,
                    # leaving `unpacked_vars = ...` and the "else" statements.
                    if not isinstance(item, (list, tuple)):
                        len_item = 1
                    else:
                        len_item = len(item)
                    # Check loop variable count before unpacking
                    if num_loopvars != len_item:
                        warnings.warn(
                            "Need {} values to unpack in for loop; got {}. "
                            "This will raise an exception in Django 1.10."
                            .format(num_loopvars, len_item),
                            RemovedInDjango110Warning)
                    try:
                        unpacked_vars = dict(zip(self.loopvars, item))
                    except TypeError:
                        pass
                    else:
                        pop_context = True
                        context.update(unpacked_vars)
                else:
                    context[self.loopvars[0]] = item

                for node in self.nodelist_loop:
                    nodelist.append(node.render_annotated(context))

                if pop_context:
                    # The loop variables were pushed on to the context so pop them
                    # off again. This is necessary because the tag lets the length
                    # of loopvars differ to the length of each set of items and we
                    # don't want to leave any vars from the previous loop on the
                    # context.
                    context.pop()
        return mark_safe(''.join(force_text(n) for n in nodelist))


class IfChangedNode(Node):
    child_nodelists = ('nodelist_true', 'nodelist_false')

    def __init__(self, nodelist_true, nodelist_false, *varlist):
        self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
        self._varlist = varlist

    def render(self, context):
        # Init state storage
        state_frame = self._get_context_stack_frame(context)
        if self not in state_frame:
            state_frame[self] = None

        nodelist_true_output = None
        try:
            if self._varlist:
                # Consider multiple parameters.  This automatically behaves
                # like an OR evaluation of the multiple variables.
                compare_to = [var.resolve(context, True) for var in self._varlist]
            else:
                # The "{% ifchanged %}" syntax (without any variables) compares the rendered output.
                compare_to = nodelist_true_output = self.nodelist_true.render(context)
        except VariableDoesNotExist:
            compare_to = None

        if compare_to != state_frame[self]:
            state_frame[self] = compare_to
            # render true block if not already rendered
            return nodelist_true_output or self.nodelist_true.render(context)
        elif self.nodelist_false:
            return self.nodelist_false.render(context)
        return ''

    def _get_context_stack_frame(self, context):
        # The Context object behaves like a stack where each template tag can create a new scope.
        # Find the place where to store the state to detect changes.
        if 'forloop' in context:
            # Ifchanged is bound to the local for loop.
            # When there is a loop-in-loop, the state is bound to the inner loop,
            # so it resets when the outer loop continues.
            return context['forloop']
        else:
            # Using ifchanged outside loops. Effectively this is a no-op because the state is associated with 'self'.
            return context.render_context


class IfEqualNode(Node):
    child_nodelists = ('nodelist_true', 'nodelist_false')

    def __init__(self, var1, var2, nodelist_true, nodelist_false, negate):
        self.var1, self.var2 = var1, var2
        self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
        self.negate = negate

    def __repr__(self):
        return "<IfEqualNode>"

    def render(self, context):
        val1 = self.var1.resolve(context, True)
        val2 = self.var2.resolve(context, True)
        if (self.negate and val1 != val2) or (not self.negate and val1 == val2):
            return self.nodelist_true.render(context)
        return self.nodelist_false.render(context)


class IfNode(Node):

    def __init__(self, conditions_nodelists):
        self.conditions_nodelists = conditions_nodelists

    def __repr__(self):
        return "<IfNode>"

    def __iter__(self):
        for _, nodelist in self.conditions_nodelists:
            for node in nodelist:
                yield node

    @property
    def nodelist(self):
        return NodeList(node for _, nodelist in self.conditions_nodelists for node in nodelist)

    def render(self, context):
        for condition, nodelist in self.conditions_nodelists:

            if condition is not None:           # if / elif clause
                try:
                    match = condition.eval(context)
                except VariableDoesNotExist:
                    match = None
            else:                               # else clause
                match = True

            if match:
                return nodelist.render(context)

        return ''


class LoremNode(Node):
    def __init__(self, count, method, common):
        self.count, self.method, self.common = count, method, common

    def render(self, context):
        try:
            count = int(self.count.resolve(context))
        except (ValueError, TypeError):
            count = 1
        if self.method == 'w':
            return words(count, common=self.common)
        else:
            paras = paragraphs(count, common=self.common)
        if self.method == 'p':
            paras = ['<p>%s</p>' % p for p in paras]