"""

Litecord
Copyright (C) 2018-2019  Luna Mendes

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""

from typing import Optional
from collections import defaultdict
from dataclasses import dataclass

from logbook import Logger

from litecord.voice.lvsp_conn import LVSPConnection

log = Logger(__name__)


@dataclass
class Region:
    """Voice region data."""

    id: str
    vip: bool


class LVSPManager:
    """Manager class for Litecord Voice Server Protocol (LVSP) connections.

    Spawns :class:`LVSPConnection` as needed, etc.
    """

    def __init__(self, app, voice):
        self.app = app
        self.voice = voice

        # map servers to LVSPConnection
        self.conns = {}

        # maps regions to server hostnames
        self.servers = defaultdict(list)

        # maps Union[GuildID, DMId, GroupDMId] to server hostnames
        self.assign = {}

        # quick storage for Region dataclass instances.
        self.regions = {}

        self.app.sched.spawn(self.refresh_regions())

    async def refresh_regions(self):
        """Spawn LVSPConnection for each region."""
        regions = await self.app.db.fetch(
            """
            SELECT id, vip
            FROM voice_regions
            WHERE deprecated = false
            """
        )

        regions = [Region(r["id"], r["vip"]) for r in regions]

        if not regions:
            log.warning("no regions are setup")
            return

        for region in regions:
            # this function can be run multiple times, and so we ignore
            # regions that are already in self.regions, since they already have
            # their lvsp connections spawned.
            if region.id in self.regions:
                continue

            self.regions[region.id] = region
            self.app.loop.create_task(self._spawn_region(region))

    async def _spawn_region(self, region: Region):
        """Spawn a region. Involves fetching all the hostnames
        for the regions and spawning a LVSPConnection for each."""
        servers = await self.app.db.fetch(
            """
        SELECT hostname
        FROM voice_servers
        WHERE region_id = $1
        """,
            region.id,
        )

        if not servers:
            log.warning("region {} does not have servers", region)
            return

        servers = [r["hostname"] for r in servers]
        self.servers[region.id] = servers

        for hostname in servers:
            conn = LVSPConnection(self, region.id, hostname)
            self.conns[hostname] = conn

            self.app.loop.create_task(conn.run())

    async def del_conn(self, conn):
        """Delete a connection from the connection pool."""
        try:
            self.servers[conn.region].remove(conn.hostname)
        except KeyError:
            pass

        try:
            self.conns.pop(conn.hostname)
        except KeyError:
            pass

    async def guild_region(self, guild_id: int) -> Optional[str]:
        """Return the voice region of a guild."""
        return await self.app.db.fetchval(
            """
        SELECT region
        FROM guilds
        WHERE id = $1
        """,
            guild_id,
        )

    def get_health(self, hostname: str) -> float:
        """Get voice server health, given hostname."""
        try:
            conn = self.conns[hostname]
        except KeyError:
            return -1

        return conn.health

    async def get_guild_server(self, guild_id: int) -> Optional[str]:
        """Get a voice server for the given guild, assigns
        one if there isn't any"""

        try:
            hostname = self.assign[guild_id]
        except KeyError:
            region = await self.guild_region(guild_id)

            # sort connected servers by health
            sorted_servers = sorted(self.servers[region], key=self.get_health)

            try:
                hostname = sorted_servers[0]
            except IndexError:
                return None

        return hostname

    async def assign_conn(self, key: int, hostname: str):
        """Assign a connection to a given key in the assign map"""
        self.assign[key] = hostname

    def region(self, region_id: str) -> Optional[Region]:
        """Get a :class:`Region` instance"""
        return self.regions.get(region_id)