import urllib.parse
from collections import namedtuple
from collections.abc import Mapping, Sequence
from functools import partial
from os import path

from tornado import template

from ..__version__ import __version__ as version
from ..exceptions import PyWebIOWarning
from ..utils import isgeneratorfunction, iscoroutinefunction, get_function_name, get_function_doc, \
    get_function_seo_info

DEFAULT_CDN = "https://cdn.jsdelivr.net/gh/wang0618/PyWebIO-assets@v{version}/"

AppMeta = namedtuple('App', 'title description')

_here_dir = path.dirname(path.abspath(__file__))
_index_page_tpl = template.Template(open(path.join(_here_dir, 'tpl', 'index.html')).read())


def render_page(app, protocol, cdn):
    """渲染前端页面的HTML框架, 支持SEO

    :param callable app: PyWebIO app
    :param str protocol: 'ws'/'http'
    :param bool/str cdn: Whether to use CDN, also accept string as custom CDN URL
    :return: bytes content of rendered page
    """
    assert protocol in ('ws', 'http')
    meta = parse_app_metadata(app)
    if cdn is True:
        cdn = DEFAULT_CDN.format(version=version)
    elif not cdn:
        cdn = ''
    return _index_page_tpl.generate(title=meta.title or 'PyWebIO Application',
                                    description=meta.description, protocol=protocol,
                                    script=True, content='', base_url=cdn)


def cdn_validation(cdn, level='warn'):
    """CDN availability check

    :param bool/str cdn: cdn parameter
    :param level: warn or error
    """
    assert level in ('warn', 'error')

    if cdn is True and 'dev' in version:
        if level == 'warn':
            import warnings
            warnings.warn("Default CDN is not supported in dev version. Ignore the CDN setting", PyWebIOWarning,
                          stacklevel=3)
            return False
        else:
            raise ValueError("Default CDN is not supported in dev version. Please host static files by yourself.")

    return cdn


def parse_app_metadata(func):
    """解析pywebio app元数据"""
    seo_info = get_function_seo_info(func)
    if seo_info:
        return AppMeta(*seo_info)

    doc = get_function_doc(func)
    parts = doc.strip().split('\n\n', 1)
    if len(parts) == 2:
        title, description = parts
    else:
        title, description = parts[0], ''

    return AppMeta(title, description)


_app_list_tpl = template.Template("""
<h1>Applications index</h1>
<ul>
    {% for name,meta in apps_info.items() %}
    <li>
        {% if other_arguments is not None %}
            <a href="?app={{name}}{{other_arguments}}">{{ meta.title or name }}</a>:
        {% else %}
            <a href="javascript:WebIO.openApp('{{ name }}', true)">{{ meta.title or name }}</a>:
        {% end %}
        
        {% if meta.description %}
            {{ meta.description }} 
        {% else %}
            <i>No description.</i>
        {% end %}
    </li>
    {% end %}
</ul>
""".strip())


def get_static_index_content(apps, query_arguments=None):
    """生成默认的静态主页

    :param callable apps: PyWebIO apps
    :param str query_arguments: Url Query Arguments。为None时，表示使用WebIO.openApp跳转
    :return: bytes
    """
    apps_info = {
        name: parse_app_metadata(func)
        for name, func in apps.items()
    }

    qs = urllib.parse.parse_qs(query_arguments)
    qs.pop('app', None)
    other_arguments = urllib.parse.urlencode(qs, doseq=True)

    if other_arguments:
        other_arguments = '&' + other_arguments
    else:
        other_arguments = None
    content = _app_list_tpl.generate(apps_info=apps_info, other_arguments=other_arguments).decode('utf8')
    return content


def _generate_default_index_app(apps):
    """默认的主页任务函数"""
    content = get_static_index_content(apps)

    def index():
        from pywebio.output import put_html
        put_html(content)

    return index


def make_applications(applications):
    """格式化 applications 为 任务名->任务函数 的映射, 并提供默认主页

    :param applications: 接受 单一任务函数、字典、列表 类型
    :return dict: 任务名->任务函数 的映射
    """

    if isinstance(applications, Sequence):  # 列表 类型
        applications, app_list = {}, applications
        for func in app_list:
            name = get_function_name(func)
            if name in applications:
                raise ValueError("Duplicated application name:%r" % name)
            applications[name] = func
    elif not isinstance(applications, Mapping):  # 单一任务函数 类型
        applications = {'index': applications}

    # covert dict key to str
    applications = {str(k): v for k, v in applications.items()}

    for app in applications.values():
        assert iscoroutinefunction(app) or isgeneratorfunction(app) or callable(app), \
            "Don't support application type:%s" % type(app)

    if 'index' not in applications:
        applications['index'] = _generate_default_index_app(applications)

    return applications


def seo(title, description=None, app=None):
    '''Set the SEO information of the PyWebIO application (web page information provided when indexed by search engines)

    :param str title: Application title
    :param str description: Application description
    :param callable app: PyWebIO task function

    If not ``seo()`` is not used, the `docstring <https://www.python.org/dev/peps/pep-0257/>`_ of the task function will be regarded as SEO information by default.

    ``seo()`` can be used in 2 ways: direct call and decorator::

        @seo("title", "description")
        def foo():
            pass

        def bar():
            pass

        def hello():
            """Application title

            Application description...
            (A empty line is used to separate the description and title)
            """

        start_server([
            foo,
            hello,
            seo("title", "description", bar),
        ])


    '''
    if app is not None:
        return seo(title, description)(app)

    def decorator(func):
        try:
            func = partial(func)
            func._pywebio_title = title
            func._pywebio_description = description or ''
        except Exception:
            pass
        return func

    return decorator