"""
Methods for exporting course data to XML
"""

import logging
import lxml.etree
from xblock.fields import Scope
from xmodule.contentstore.content import StaticContent
from xmodule.exceptions import NotFoundError
from xmodule.modulestore import EdxJSONEncoder, ModuleStoreEnum
from xmodule.modulestore.inheritance import own_metadata
from fs.osfs import OSFS
from json import dumps
import json
import os
from path import path
import shutil
from xmodule.modulestore.draft_and_published import DIRECT_ONLY_CATEGORIES

DRAFT_DIR = "drafts"
PUBLISHED_DIR = "published"
EXPORT_VERSION_FILE = "format.json"
EXPORT_VERSION_KEY = "export_format"

DEFAULT_CONTENT_FIELDS = ['metadata', 'data']


def export_to_xml(modulestore, contentstore, course_key, root_dir, course_dir):
    """
    Export all modules from `modulestore` and content from `contentstore` as xml to `root_dir`.

    `modulestore`: A `ModuleStore` object that is the source of the modules to export
    `contentstore`: A `ContentStore` object that is the source of the content to export, can be None
    `course_key`: The `CourseKey` of the `CourseModuleDescriptor` to export
    `root_dir`: The directory to write the exported xml to
    `course_dir`: The name of the directory inside `root_dir` to write the course content to
    """

    course = modulestore.get_course(course_key)

    fsm = OSFS(root_dir)
    export_fs = course.runtime.export_fs = fsm.makeopendir(course_dir)

    root = lxml.etree.Element('unknown')

    # export only the published content
    with modulestore.branch_setting(ModuleStoreEnum.Branch.published_only, course_key):
        course.add_xml_to_node(root)

    with export_fs.open('course.xml', 'w') as course_xml:
        lxml.etree.ElementTree(root).write(course_xml)

    # export the static assets
    policies_dir = export_fs.makeopendir('policies')
    if contentstore:
        contentstore.export_all_for_course(
            course_key,
            root_dir + '/' + course_dir + '/static/',
            root_dir + '/' + course_dir + '/policies/assets.json',
        )

        # If we are using the default course image, export it to the
        # legacy location to support backwards compatibility.
        if course.course_image == course.fields['course_image'].default:
            try:
                course_image = contentstore.find(
                    StaticContent.compute_location(
                        course.id,
                        course.course_image
                    ),
                )
            except NotFoundError:
                pass
            else:
                output_dir = root_dir + '/' + course_dir + '/static/images/'
                if not os.path.isdir(output_dir):
                    os.makedirs(output_dir)
                with OSFS(output_dir).open('course_image.jpg', 'wb') as course_image_file:
                    course_image_file.write(course_image.data)

    # export the static tabs
    export_extra_content(export_fs, modulestore, course_key, 'static_tab', 'tabs', '.html')

    # export the custom tags
    export_extra_content(export_fs, modulestore, course_key, 'custom_tag_template', 'custom_tags')

    # export the course updates
    export_extra_content(export_fs, modulestore, course_key, 'course_info', 'info', '.html')

    # export the 'about' data (e.g. overview, etc.)
    export_extra_content(export_fs, modulestore, course_key, 'about', 'about', '.html')

    # export the grading policy
    course_run_policy_dir = policies_dir.makeopendir(course.location.name)
    with course_run_policy_dir.open('grading_policy.json', 'w') as grading_policy:
        grading_policy.write(dumps(course.grading_policy, cls=EdxJSONEncoder))

    # export all of the course metadata in policy.json
    with course_run_policy_dir.open('policy.json', 'w') as course_policy:
        policy = {'course/' + course.location.name: own_metadata(course)}
        course_policy.write(dumps(policy, cls=EdxJSONEncoder))

    # NOTE: this code assumes that verticals are the top most draftable container
    # should we change the application, then this assumption will no longer be valid
    # NOTE: we need to explicitly implement the logic for setting the vertical's parent
    # and index here since the XML modulestore cannot load draft modules
    draft_verticals = modulestore.get_items(
        course_key,
        category='vertical',
        revision=ModuleStoreEnum.RevisionOption.draft_only
    )
    if len(draft_verticals) > 0:
        draft_course_dir = export_fs.makeopendir(DRAFT_DIR)
        for draft_vertical in draft_verticals:
            parent_loc = modulestore.get_parent_location(
                draft_vertical.location,
                revision=ModuleStoreEnum.RevisionOption.draft_preferred
            )
            # Don't try to export orphaned items.
            if parent_loc is not None:
                logging.debug('parent_loc = {0}'.format(parent_loc))
                if parent_loc.category in DIRECT_ONLY_CATEGORIES:
                    draft_vertical.xml_attributes['parent_sequential_url'] = parent_loc.to_deprecated_string()
                    sequential = modulestore.get_item(parent_loc)
                    index = sequential.children.index(draft_vertical.location)
                    draft_vertical.xml_attributes['index_in_children_list'] = str(index)
                draft_vertical.runtime.export_fs = draft_course_dir
                node = lxml.etree.Element('unknown')
                draft_vertical.add_xml_to_node(node)


def _export_field_content(xblock_item, item_dir):
    """
    Export all fields related to 'xblock_item' other than 'metadata' and 'data' to json file in provided directory
    """
    module_data = xblock_item.get_explicitly_set_fields_by_scope(Scope.content)
    if isinstance(module_data, dict):
        for field_name in module_data:
            if field_name not in DEFAULT_CONTENT_FIELDS:
                # filename format: {dirname}.{field_name}.json
                with item_dir.open('{0}.{1}.{2}'.format(xblock_item.location.name, field_name, 'json'),
                                   'w') as field_content_file:
                    field_content_file.write(dumps(module_data.get(field_name, {}), cls=EdxJSONEncoder))


def export_extra_content(export_fs, modulestore, course_key, category_type, dirname, file_suffix=''):
    items = modulestore.get_items(course_key, category=category_type)

    if len(items) > 0:
        item_dir = export_fs.makeopendir(dirname)
        for item in items:
            with item_dir.open(item.location.name + file_suffix, 'w') as item_file:
                item_file.write(item.data.encode('utf8'))

                # export content fields other then metadata and data in json format in current directory
                _export_field_content(item, item_dir)


def convert_between_versions(source_dir, target_dir):
    """
    Converts a version 0 export format to version 1, and vice versa.

    @param source_dir: the directory structure with the course export that should be converted.
       The contents of source_dir will not be altered.
    @param target_dir: the directory where the converted export should be written.
    @return: the version number of the converted export.
    """
    def convert_to_version_1():
        """ Convert a version 0 archive to version 0 """
        os.mkdir(copy_root)
        with open(copy_root / EXPORT_VERSION_FILE, 'w') as f:
            f.write('{{"{export_key}": 1}}\n'.format(export_key=EXPORT_VERSION_KEY))

        # If a drafts folder exists, copy it over.
        copy_drafts()

        # Now copy everything into the published directory
        published_dir = copy_root / PUBLISHED_DIR
        shutil.copytree(path(source_dir) / course_name, published_dir)
        # And delete the nested drafts directory, if it exists.
        nested_drafts_dir = published_dir / DRAFT_DIR
        if nested_drafts_dir.isdir():
            shutil.rmtree(nested_drafts_dir)

    def convert_to_version_0():
        """ Convert a version 1 archive to version 0 """
        # Copy everything in "published" up to the top level.
        published_dir = path(source_dir) / course_name / PUBLISHED_DIR
        if not published_dir.isdir():
            raise ValueError("a version 1 archive must contain a published branch")

        shutil.copytree(published_dir, copy_root)

        # If there is a DRAFT branch, copy it. All other branches are ignored.
        copy_drafts()

    def copy_drafts():
        """
        Copy drafts directory from the old archive structure to the new.
        """
        draft_dir = path(source_dir) / course_name / DRAFT_DIR
        if draft_dir.isdir():
            shutil.copytree(draft_dir, copy_root / DRAFT_DIR)

    root = os.listdir(source_dir)
    if len(root) != 1 or (path(source_dir) / root[0]).isfile():
        raise ValueError("source archive does not have single course directory at top level")

    course_name = root[0]

    # For this version of the script, we simply convert back and forth between version 0 and 1.
    original_version = get_version(path(source_dir) / course_name)
    if original_version not in [0, 1]:
        raise ValueError("unknown version: " + str(original_version))
    desired_version = 1 if original_version is 0 else 0

    copy_root = path(target_dir) / course_name

    if desired_version == 1:
        convert_to_version_1()
    else:
        convert_to_version_0()

    return desired_version


def get_version(course_path):
    """
    Return the export format version number for the given
    archive directory structure (represented as a path instance).

    If the archived file does not correspond to a known export
    format, None will be returned.
    """
    format_file = course_path / EXPORT_VERSION_FILE
    if not format_file.isfile():
        return 0
    with open(format_file, "r") as f:
        data = json.load(f)
        if EXPORT_VERSION_KEY in data:
            return data[EXPORT_VERSION_KEY]

    return None
