"""Various HTML "components"."""

from email.headerregistry import (
    Address,
    BaseHeader,
    UniqueAddressHeader,
)
from .html_render import HTML
from typing import cast, Optional
from urllib.parse import urlencode
from email.message import EmailMessage
from typing import Iterable


def dl(entries: Iterable[tuple[HTML, HTML]]) -> HTML:
    """Build a description list."""
    items = []
    for k, v in entries:
        items += [('dt', k),
                  ('dd', v)]
    return ('dl', items)


def format_email(addr: Address) -> list[HTML]:
    """Format an email address suitable for the headers of the message view."""
    mail_addr = f'{addr.username}@{addr.domain}'
    return [addr.display_name, ' <', mailto(mail_addr), '>']


def mailto(addr: str) -> HTML:
    """Construct a mailto anchor element."""
    return ('a', {'href': f'mailto:{addr}'}, addr)


def header_format(key: str, value: BaseHeader) -> HTML:
    """
    Format email headers to HTML.

    https://docs.python.org/3/library/email.headerregistry.html#email.headerregistry.HeaderRegistry
    """
    if key in ['to', 'cc', 'bcc']:
        assert isinstance(value, UniqueAddressHeader), \
            f"Expected UniqueAddressHeader, got {type(value)}"
        return ('ul', *[('li', *format_email(addr))
                        for addr in value.addresses])
    elif key == 'from':
        assert isinstance(value, UniqueAddressHeader), \
            f"Expected UniqueAddressHeader, got {type(value)}"
        return format_email(value.addresses[0])
    elif key == 'in-reply-to':
        id = str(value).strip("<>")
        return ['<', ('a', {'href': '?' + urlencode({'id': id})}, id), '>']
    else:
        return str(value)


def attachement_tree(id: str,
                     mail: EmailMessage,
                     idx: int = 0) -> tuple[HTML, int]:
    """Construct a tree of all attachements for the given mail."""
    ct = mail.get_content_type()
    fn = mail.get_filename()

    children = []
    _idx = idx
    for child in mail.iter_parts():
        tree, idx = attachement_tree(id, cast(EmailMessage, child), idx + 1)
        children.append(tree)

    content: HTML
    if children:
        content = ('ul', *children)
    else:
        content = []

    if fn:
        body = f'{ct} {fn}'
    else:
        body = str(ct)
    download = {}
    if mail.get_content_type() == 'application/octet-stream':
        download['download'] = mail.get_filename() or ''
    return ('li', ('a', {'data-idx': str(_idx),
                         'href': '/part?' + urlencode({'id': id,
                                                       'idx': _idx}),
                         **download,
                         }, body), content), idx


def login_page(returnto: Optional[str] = None) -> HTML:
    """HTML form for the login page."""
    return ('form', {'action': '/login', 'method': 'POST', 'class': 'loginform'},
            ('label', {'for': 'username'}, 'Användarnamn'),
            ('input', {'id': 'username', 'name': 'username', 'placeholder': 'Användarnamn'}),
            ('label', {'for': 'password'}, 'Lösenord'),
            ('input', {'id': 'password', 'name': 'password',
                       'placeholder': 'Lösenord',
                       'type': 'password'}),
            ('div',
            ('input', {'id': 'remember', 'name': 'remember', 'type': 'checkbox'}),
            ('label', {'for': 'remember'}, 'Kom ihåg mig')),
            ('input', {'type': 'hidden',
                       'name': 'returnto',
                       'value': returnto}) if returnto else [],
            ('input', {'type': 'submit', 'value': 'Logga in'}),
            )


def user_info(username: str) -> HTML:
    """
    Return user info for top bar.

    Includes the users name, and a button for logging out.
    """
    return [('span', username),
            ('form', {'action': '/logout', 'method': 'POST'},
             ('input', {'type': 'submit', 'value': 'Logga ut'}))]


def login_prompt() -> HTML:
    """Return link to the login page."""
    return ('a', {'href': '/login'}, 'Logga in')


def flashed_messages(messages: list[str] | list[tuple[str, str]]) -> HTML:
    """
    Return Flasks flashed messages, formatted as a list.

    :param messages:
        Either a list of messages, or a list of (category, message)
        messages. See `flask.get_flashed_messages` for more information.
    """
    if not messages:
        return []
    if isinstance(messages[0], tuple):
        messages = cast(list[tuple[str, str]], messages)
        return ('ul', {'class': 'flashes'},
                *[('li', msg) for (_, msg) in messages])
    else:
        return ('ul', {'class': 'flashes'},
                *[('li', msg) for msg in messages])


def include_stylesheet(path: str) -> HTML:
    """Return HTML for including a stylesheet inside the <head>."""
    return ('link', {'type': 'text/css',
                     'rel': 'stylesheet',
                     'href': path})


def search_field(q: str) -> HTML:
    """Build large search form for search page."""
    return ('form', {'id': 'searchform',
                     'action': '/search',
                     'method': 'GET'},
            ('label', {'for': 'search'},
             'Sökförfrågan till Mu'),
            ('input', {'id': 'search',
                       'type': 'text',
                       'placeholder': 'Sök...',
                       'name': 'q',
                       'value': q}),
            ('input', {'type': 'Submit', 'value': 'Sök'}))