import copy
from fs.errors import ResourceNotFoundError
import logging
import os
import sys
from lxml import etree
from path import path

from pkg_resources import resource_string
from xblock.fields import Scope, String, Boolean, List
from xmodule.editing_module import EditingDescriptor
from xmodule.html_checker import check_html
from xmodule.stringify import stringify_children
from xmodule.x_module import XModule
from xmodule.xml_module import XmlDescriptor, name_to_pathname
import textwrap
from xmodule.contentstore.content import StaticContent
from xblock.core import XBlock

log = logging.getLogger("edx.courseware")

# Make '_' a no-op so we can scrape strings
_ = lambda text: text


class HtmlFields(object):
    display_name = String(
        display_name=_("Display Name"),
        help=_("This name appears in the horizontal navigation at the top of the page."),
        scope=Scope.settings,
        # it'd be nice to have a useful default but it screws up other things; so,
        # use display_name_with_default for those
        default="Text"
    )
    data = String(help=_("Html contents to display for this module"), default=u"", scope=Scope.content)
    source_code = String(help=_("Source code for LaTeX documents. This feature is not well-supported."), scope=Scope.settings)
    use_latex_compiler = Boolean(
        help=_("Enable LaTeX templates?"),
        default=False,
        scope=Scope.settings
    )
    editor = String(
        help=_("Select Visual to enter content and have the editor automatically create the HTML. Select Raw to edit HTML directly. If you change this setting, you must save the component and then re-open it for editing."),
        display_name=_("Editor"),
        default="visual",
        values=[
            {"display_name": "Visual", "value": "visual"},
            {"display_name": "Raw", "value": "raw"}
        ],
        scope=Scope.settings
    )


class HtmlModule(HtmlFields, XModule):
    js = {
        'coffee': [
            resource_string(__name__, 'js/src/javascript_loader.coffee'),
            resource_string(__name__, 'js/src/html/display.coffee'),
        ],
        'js': [
            resource_string(__name__, 'js/src/collapsible.js'),
            resource_string(__name__, 'js/src/html/imageModal.js'),
            resource_string(__name__, 'js/common_static/js/vendor/draggabilly.pkgd.js'),
        ]
    }
    js_module_name = "HTMLModule"
    css = {'scss': [resource_string(__name__, 'css/html/display.scss')]}

    def get_html(self):
        if self.system.anonymous_student_id:
            return self.data.replace("%%USER_ID%%", self.system.anonymous_student_id)
        return self.data


class HtmlDescriptor(HtmlFields, XmlDescriptor, EditingDescriptor):
    """
    Module for putting raw html in a course
    """
    mako_template = "widgets/html-edit.html"
    module_class = HtmlModule
    filename_extension = "xml"
    template_dir_name = "html"

    js = {'coffee': [resource_string(__name__, 'js/src/html/edit.coffee')]}
    js_module_name = "HTMLEditingDescriptor"
    css = {'scss': [resource_string(__name__, 'css/editor/edit.scss'), resource_string(__name__, 'css/html/edit.scss')]}

    # VS[compat] TODO (cpennington): Delete this method once all fall 2012 course
    # are being edited in the cms
    @classmethod
    def backcompat_paths(cls, path):
        if path.endswith('.html.xml'):
            path = path[:-9] + '.html'  # backcompat--look for html instead of xml
        if path.endswith('.html.html'):
            path = path[:-5]  # some people like to include .html in filenames..
        candidates = []
        while os.sep in path:
            candidates.append(path)
            _, _, path = path.partition(os.sep)

        # also look for .html versions instead of .xml
        nc = []
        for candidate in candidates:
            if candidate.endswith('.xml'):
                nc.append(candidate[:-4] + '.html')
        return candidates + nc

    @classmethod
    def filter_templates(cls, template, course):
        """
        Filter template that contains 'latex' from templates.

        Show them only if use_latex_compiler is set to True in
        course settings.
        """
        return (not 'latex' in template['template_id'] or course.use_latex_compiler)

    def get_context(self):
        """
        an override to add in specific rendering context, in this case we need to
        add in a base path to our c4x content addressing scheme
        """
        _context = EditingDescriptor.get_context(self)
        # Add some specific HTML rendering context when editing HTML modules where we pass
        # the root /c4x/ url for assets. This allows client-side substitutions to occur.
        _context.update({
            'base_asset_url': StaticContent.get_base_url_path_for_course_assets(self.location.course_key),
            'enable_latex_compiler': self.use_latex_compiler,
            'editor': self.editor
        })
        return _context

    # NOTE: html descriptors are special.  We do not want to parse and
    # export them ourselves, because that can break things (e.g. lxml
    # adds body tags when it exports, but they should just be html
    # snippets that will be included in the middle of pages.

    @classmethod
    def load_definition(cls, xml_object, system, location):
        '''Load a descriptor from the specified xml_object:

        If there is a filename attribute, load it as a string, and
        log a warning if it is not parseable by etree.HTMLParser.

        If there is not a filename attribute, the definition is the body
        of the xml_object, without the root tag (do not want <html> in the
        middle of a page)
        '''
        filename = xml_object.get('filename')
        if filename is None:
            definition_xml = copy.deepcopy(xml_object)
            cls.clean_metadata_from_xml(definition_xml)
            return {'data': stringify_children(definition_xml)}, []
        else:
            # html is special.  cls.filename_extension is 'xml', but
            # if 'filename' is in the definition, that means to load
            # from .html
            # 'filename' in html pointers is a relative path
            # (not same as 'html/blah.html' when the pointer is in a directory itself)
            pointer_path = "{category}/{url_path}".format(
                category='html',
                url_path=name_to_pathname(location.name)
            )
            base = path(pointer_path).dirname()
            # log.debug("base = {0}, base.dirname={1}, filename={2}".format(base, base.dirname(), filename))
            filepath = "{base}/{name}.html".format(base=base, name=filename)
            # log.debug("looking for html file for {0} at {1}".format(location, filepath))

            # VS[compat]
            # TODO (cpennington): If the file doesn't exist at the right path,
            # give the class a chance to fix it up. The file will be written out
            # again in the correct format.  This should go away once the CMS is
            # online and has imported all current (fall 2012) courses from xml
            if not system.resources_fs.exists(filepath):
                candidates = cls.backcompat_paths(filepath)
                # log.debug("candidates = {0}".format(candidates))
                for candidate in candidates:
                    if system.resources_fs.exists(candidate):
                        filepath = candidate
                        break

            try:
                with system.resources_fs.open(filepath) as file:
                    html = file.read().decode('utf-8')
                    # Log a warning if we can't parse the file, but don't error
                    if not check_html(html) and len(html) > 0:
                        msg = "Couldn't parse html in {0}, content = {1}".format(filepath, html)
                        log.warning(msg)
                        system.error_tracker("Warning: " + msg)

                    definition = {'data': html}

                    # TODO (ichuang): remove this after migration
                    # for Fall 2012 LMS migration: keep filename (and unmangled filename)
                    definition['filename'] = [filepath, filename]

                    return definition, []

            except (ResourceNotFoundError) as err:
                msg = 'Unable to load file contents at path {0}: {1} '.format(
                    filepath, err)
                # add more info and re-raise
                raise Exception(msg), None, sys.exc_info()[2]

    # TODO (vshnayder): make export put things in the right places.

    def definition_to_xml(self, resource_fs):
        ''' Write <html filename="" [meta-attrs="..."]> to filename.xml, and the html
        string to filename.html.
        '''

        # Write html to file, return an empty tag
        pathname = name_to_pathname(self.url_name)
        filepath = u'{category}/{pathname}.html'.format(
            category=self.category,
            pathname=pathname
        )

        resource_fs.makedir(os.path.dirname(filepath), recursive=True, allow_recreate=True)
        with resource_fs.open(filepath, 'w') as filestream:
            html_data = self.data.encode('utf-8')
            filestream.write(html_data)

        # write out the relative name
        relname = path(pathname).basename()

        elt = etree.Element('html')
        elt.set("filename", relname)
        return elt

    @property
    def non_editable_metadata_fields(self):
        non_editable_fields = super(HtmlDescriptor, self).non_editable_metadata_fields
        non_editable_fields.append(HtmlDescriptor.use_latex_compiler)
        return non_editable_fields


class AboutFields(object):
    display_name = String(
        help=_("Display name for this module"),
        scope=Scope.settings,
        default="overview",
    )
    data = String(
        help=_("Html contents to display for this module"),
        default=u"",
        scope=Scope.content
    )


@XBlock.tag("detached")
class AboutModule(AboutFields, HtmlModule):
    """
    Overriding defaults but otherwise treated as HtmlModule.
    """
    pass


@XBlock.tag("detached")
class AboutDescriptor(AboutFields, HtmlDescriptor):
    """
    These pieces of course content are treated as HtmlModules but we need to overload where the templates are located
    in order to be able to create new ones
    """
    template_dir_name = "about"
    module_class = AboutModule


class StaticTabFields(object):
    """
    The overrides for Static Tabs
    """
    display_name = String(
        display_name=_("Display Name"),
        help=_("This name appears in the horizontal navigation at the top of the page."),
        scope=Scope.settings,
        default="Empty",
    )
    data = String(
        default=textwrap.dedent(u"""\
            <p>Add the content you want students to see on this page.</p>
        """),
        scope=Scope.content,
        help=_("HTML for the additional pages")
    )


@XBlock.tag("detached")
class StaticTabModule(StaticTabFields, HtmlModule):
    """
    Supports the field overrides
    """
    pass


@XBlock.tag("detached")
class StaticTabDescriptor(StaticTabFields, HtmlDescriptor):
    """
    These pieces of course content are treated as HtmlModules but we need to overload where the templates are located
    in order to be able to create new ones
    """
    template_dir_name = None
    module_class = StaticTabModule


class CourseInfoFields(object):
    """
    Field overrides
    """
    items = List(
        help=_("List of course update items"),
        default=[],
        scope=Scope.content
    )
    data = String(
        help=_("Html contents to display for this module"),
        default=u"<ol></ol>",
        scope=Scope.content
    )


@XBlock.tag("detached")
class CourseInfoModule(CourseInfoFields, HtmlModule):
    """
    Just to support xblock field overrides
    """
    # statuses
    STATUS_VISIBLE = 'visible'
    STATUS_DELETED = 'deleted'


@XBlock.tag("detached")
class CourseInfoDescriptor(CourseInfoFields, HtmlDescriptor):
    """
    These pieces of course content are treated as HtmlModules but we need to overload where the templates are located
    in order to be able to create new ones
    """
    template_dir_name = None
    module_class = CourseInfoModule
