#!/usr/bin/env python3
# -*- coding: utf-8 -*-

"""
    Query and control an archive of messages stored on a server using
    XEP-0313: Message Archive Management(MAM).
"""

import random
from datetime import datetime, timedelta, timezone
from hashlib import md5
from typing import Optional, Callable

from slixmpp import JID
from slixmpp.exceptions import IqError, IqTimeout
from poezio.theming import get_theme
from poezio import tabs
from poezio import xhtml, colors
from poezio.config import config
from poezio.text_buffer import TextBuffer


class DiscoInfoException(Exception): pass
class MAMQueryException(Exception): pass
class NoMAMSupportException(Exception): pass


def add_line(
        tab,
        text_buffer: TextBuffer,
        text: str,
        time: datetime,
        nick: str,
        top: bool,
    ) -> None:
    """Adds a textual entry in the TextBuffer"""

    # Convert to local timezone
    time = time.replace(tzinfo=timezone.utc).astimezone(tz=None)
    time = time.replace(tzinfo=None)

    deterministic = config.get_by_tabname('deterministic_nick_colors', tab.jid.bare)
    if isinstance(tab, tabs.MucTab):
        nick = nick.split('/')[1]
        user = tab.get_user_by_name(nick)
        if deterministic:
            if user:
                color = user.color
            else:
                theme = get_theme()
                if theme.ccg_palette:
                    fg_color = colors.ccg_text_to_color(theme.ccg_palette, nick)
                    color = fg_color, -1
                else:
                    mod = len(theme.LIST_COLOR_NICKNAMES)
                    nick_pos = int(md5(nick.encode('utf-8')).hexdigest(), 16) % mod
                    color = theme.LIST_COLOR_NICKNAMES[nick_pos]
        else:
            color = random.choice(list(xhtml.colors))
            color = xhtml.colors.get(color)
            color = (color, -1)
    else:
        nick = nick.split('/')[0]
        color = get_theme().COLOR_OWN_NICK
    text_buffer.add_message(
        txt=text,
        time=time,
        nickname=nick,
        nick_color=color,
        history=True,
        user=None,
        highlight=False,
        top=top,
        identifier=None,
        str_time=None,
        jid=None,
    )


async def query(
        core,
        groupchat: bool,
        remote_jid: JID,
        amount: int,
        reverse: bool,
        start: Optional[datetime] = None,
        end: Optional[datetime] = None,
        before: Optional[str] = None,
        callback: Optional[Callable] = None,
    ) -> None:
    try:
        iq = await core.xmpp.plugin['xep_0030'].get_info(jid=remote_jid)
    except (IqError, IqTimeout):
        raise DiscoInfoException
    if 'urn:xmpp:mam:2' not in iq['disco_info'].get_features():
        raise NoMAMSupportException

    args = {
        'iterator': True,
        'reverse': reverse,
    }

    if groupchat:
        args['jid'] = remote_jid
    else:
        args['with_jid'] = remote_jid

    args['rsm'] = {'max': amount}
    if reverse:
        if before is not None:
            args['rsm']['before'] = before
        else:
            args['end'] = end
    else:
        args['rsm']['start'] = start
        if before is not None:
            args['rsm']['end'] = end
    try:
        results = core.xmpp['xep_0313'].retrieve(**args)
    except (IqError, IqTimeout):
        raise MAMQueryException
    if callback is not None:
        callback(results)

    return results


async def add_messages_to_buffer(tab, top: bool, results, amount: int) -> bool:
    """Prepends or appends messages to the tab text_buffer"""

    text_buffer = tab._text_buffer
    msg_count = 0
    msgs = []
    async for rsm in results:
        if top:
            for msg in rsm['mam']['results']:
                if msg['mam_result']['forwarded']['stanza'] \
                .xml.find('{%s}%s' % ('jabber:client', 'body')) is not None:
                    msgs.append(msg)
                if msg_count == amount:
                    tab.core.refresh_window()
                    return False
                msg_count += 1
            msgs.reverse()
            for msg in msgs:
                forwarded = msg['mam_result']['forwarded']
                timestamp = forwarded['delay']['stamp']
                message = forwarded['stanza']
                tab.last_stanza_id = msg['mam_result']['id']
                nick = str(message['from'])
                add_line(tab, text_buffer, message['body'], timestamp, nick, top)
        else:
            for msg in rsm['mam']['results']:
                forwarded = msg['mam_result']['forwarded']
                timestamp = forwarded['delay']['stamp']
                message = forwarded['stanza']
                nick = str(message['from'])
                add_line(tab, text_buffer, message['body'], timestamp, nick, top)
                tab.core.refresh_window()
    return False


async def fetch_history(tab, end: Optional[datetime] = None, amount: Optional[int] = None):
    remote_jid = tab.jid
    before = tab.last_stanza_id
    if end is None:
        end = datetime.now()
    tzone = datetime.now().astimezone().tzinfo
    end = end.replace(tzinfo=tzone).astimezone(tz=timezone.utc)
    end = end.replace(tzinfo=None)
    end = datetime.strftime(end, '%Y-%m-%dT%H:%M:%SZ')

    if amount >= 100:
        amount = 99

    groupchat = isinstance(tab, tabs.MucTab)

    results = await query(
        tab.core,
        groupchat,
        remote_jid,
        amount,
        reverse=True,
        end=end,
        before=before,
    )
    query_status = await add_messages_to_buffer(tab, True, results, amount)
    tab.query_status = query_status


async def on_tab_open(tab) -> None:
    amount = 2 * tab.text_win.height
    end = datetime.now()
    tab.query_status = True
    for message in tab._text_buffer.messages:
        time = message.time
        if time < end:
            end = time
    end = end + timedelta(seconds=-1)
    try:
        await fetch_history(tab, end=end, amount=amount)
    except (NoMAMSupportException, MAMQueryException, DiscoInfoException):
        tab.query_status = False
        return None


async def on_scroll_up(tab) -> None:
    tw = tab.text_win

    # If position in the tab is < two screen pages, then fetch MAM, so that we
    # keep some prefetched margin. A first page should also be prefetched on
    # join if not already available.
    total, pos, height = len(tw.built_lines), tw.pos, tw.height
    rest = (total - pos) // height
    # Not resetting the state of query_status here, it is changed only after the
    # query is complete (in fetch_history)
    # This is done to stop message repetition, eg: if the user presses PageUp continuously.
    tab.query_status = True

    if rest > 1:
        return None

    try:
        # XXX: Do we want to fetch a possibly variable number of messages?
        # (InfoTab changes height depending on the type of messages, see
        # `information_buffer_popup_on`).
        await fetch_history(tab, amount=height)
    except NoMAMSupportException:
        tab.core.information('MAM not supported for %r' % tab.jid, 'Info')
        return None
    except (MAMQueryException, DiscoInfoException):
        tab.core.information('An error occured when fetching MAM for %r' % tab.jid, 'Error')
        return None