#
# Licensed to the Apache Software Foundation (ASF) under one
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# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
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"""
Useful transforms for dom objects.
"""
from . import dom
from io import StringIO


class Visitor:

    def descend(self, node):
        for child in node.children:
            child.dispatch(self)

    def node(self, node):
        self.descend(node)

    def leaf(self, leaf):
        pass


class Identity:

    def descend(self, node):
        result = []
        for child in node.children:
            result.append(child.dispatch(self))
        return result

    def default(self, tag):
        result = dom.Tag(tag.name, *tag.attrs)
        result.extend(self.descend(tag))
        return result

    def tree(self, tree):
        result = dom.Tree()
        result.extend(self.descend(tree))
        return result

    def tag(self, tag):
        return self.default(tag)

    def leaf(self, leaf):
        return leaf.__class__(leaf.data)


class Sexp(Identity):

    def __init__(self):
        self.stack = []
        self.level = 0
        self.out = ""

    def open(self, s):
        self.out += "(%s" % s
        self.level += len(s) + 1
        self.stack.append(s)

    def line(self, s=""):
        self.out = self.out.rstrip()
        self.out += "\n" + " " * self.level + s

    def close(self):
        s = self.stack.pop()
        self.level -= len(s) + 1
        self.out = self.out.rstrip()
        self.out += ")"

    def tree(self, tree):
        self.open("+ ")
        for child in tree.children:
            self.line()
            child.dispatch(self)
        self.close()

    def tag(self, tag):
        self.open("Node(%s) " % tag.name)
        for child in tag.children:
            self.line()
            child.dispatch(self)
        self.close()

    def leaf(self, leaf):
        self.line("%s(%s)" % (leaf.__class__.__name__, leaf.data))


class Output:

    def descend(self, node):
        out = StringIO()
        for child in node.children:
            out.write(child.dispatch(self))
        return out.getvalue()

    def default(self, tag):
        out = StringIO()
        out.write("<%s" % tag.name)
        for k, v in tag.attrs:
            out.write(' %s="%s"' % (k, v))
        out.write(">")
        out.write(self.descend(tag))
        if not tag.singleton:
            out.write("</%s>" % tag.name)
        return out.getvalue()

    def tree(self, tree):
        return self.descend(tree)

    def tag(self, tag):
        return self.default(tag)

    def data(self, leaf):
        return leaf.data

    def entity(self, leaf):
        return "&%s;" % leaf.data

    def character(self, leaf):
        raise Exception("TODO")

    def comment(self, leaf):
        return "<!-- %s -->" % leaf.data


class Empty(Output):

    def tag(self, tag):
        return self.descend(tag)

    def data(self, leaf):
        return ""

    def entity(self, leaf):
        return ""

    def character(self, leaf):
        return ""

    def comment(self, leaf):
        return ""


class Text(Empty):

    def data(self, leaf):
        return leaf.data

    def entity(self, leaf):
        return "&%s;" % leaf.data

    def character(self, leaf):
        # XXX: is this right?
        return "&#%s;" % leaf.data