from django.template import Lexer, Parser, tag_re, NodeList, VariableNode, TemplateSyntaxError

from django.utils.encoding import force_unicode

from django.utils.html import escape

from django.utils.safestring import SafeData, EscapeData

class DebugLexer(Lexer):

    def __init__(self, template_string, origin):

        super(DebugLexer, self).__init__(template_string, origin)

    def tokenize(self):

        "Return a list of tokens from a given template_string"

        result, upto = [], 0

        for match in tag_re.finditer(self.template_string):

            start, end = match.span()

            if start > upto:

                result.append(self.create_token(self.template_string[upto:start], (upto, start), False))

                upto = start

            result.append(self.create_token(self.template_string[start:end], (start, end), True))

            upto = end

        last_bit = self.template_string[upto:]

        if last_bit:

            result.append(self.create_token(last_bit, (upto, upto + len(last_bit)), False))

        return result

    def create_token(self, token_string, source, in_tag):

        token = super(DebugLexer, self).create_token(token_string, in_tag)

        token.source = self.origin, source

        return token

class DebugParser(Parser):

    def __init__(self, lexer):

        super(DebugParser, self).__init__(lexer)

        self.command_stack = []

    def enter_command(self, command, token):

        self.command_stack.append( (command, token.source) )

    def exit_command(self):

        self.command_stack.pop()

    def error(self, token, msg):

        return self.source_error(token.source, msg)

    def source_error(self, source,msg):

        e = TemplateSyntaxError(msg)

        e.source = source

        return e

    def create_nodelist(self):

        return DebugNodeList()

    def create_variable_node(self, contents):

        return DebugVariableNode(contents)

    def extend_nodelist(self, nodelist, node, token):

        node.source = token.source

        super(DebugParser, self).extend_nodelist(nodelist, node, token)

    def unclosed_block_tag(self, parse_until):

        command, source = self.command_stack.pop()

        msg = "Unclosed tag '%s'. Looking for one of: %s " % (command, ', '.join(parse_until))

        raise self.source_error(source, msg)

    def compile_function_error(self, token, e):

        if not hasattr(e, 'source'):

            e.source = token.source

class DebugNodeList(NodeList):

    def render_node(self, node, context):

        try:

            result = node.render(context)

        except TemplateSyntaxError, e:

            if not hasattr(e, 'source'):

                e.source = node.source

            raise

        except Exception, e:

            from sys import exc_info

            wrapped = TemplateSyntaxError(u'Caught an exception while rendering: %s' % force_unicode(e, errors='replace'))

            wrapped.source = node.source

            wrapped.exc_info = exc_info()

            raise wrapped

        return result

class DebugVariableNode(VariableNode):

    def render(self, context):

        try:

            output = force_unicode(self.filter_expression.resolve(context))

        except TemplateSyntaxError, e:

            if not hasattr(e, 'source'):

                e.source = self.source

            raise

        except UnicodeDecodeError:

            return ''

        if (context.autoescape and not isinstance(output, SafeData)) or isinstance(output, EscapeData):

            return escape(output)

        else:

            return output