from pathlib import Path
import json
import hmac
from typing import Annotated
import secrets
import random
from enum import Enum
from dataclasses import dataclass
import io
import datetime
from contextlib import asynccontextmanager
from typing import Any
from collections.abc import AsyncGenerator, Sequence

from sqlalchemy import select, String
from sqlalchemy.exc import IntegrityError, NoResultFound
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
from sqlalchemy.dialects.postgresql import ARRAY

from litestar import Litestar, get, post, Request
from litestar.contrib.jinja import JinjaTemplateEngine
from litestar.exceptions import HTTPException, ValidationException, NotFoundException, NotAuthorizedException
from litestar.template.config import TemplateConfig
from litestar.response import Template, Redirect
from litestar.response.file import ASGIFileResponse
from litestar.response.streaming import ASGIStreamingResponse
from litestar.static_files import create_static_files_router
from litestar.enums import RequestEncodingType
from litestar.params import Body
from litestar import Request
from litestar.datastructures import State

import ics

class Base(DeclarativeBase):
    pass

class Event(Base):
    __tablename__ = "events"

    def __init__(self, iden, password, title, time, location, description):
        self.iden = iden
        self.password = password
        self.title = title
        self.time = time
        self.location = location
        self.description = description
        self.invites = '[]'

    iden: Mapped[str] = mapped_column(primary_key=True)
    password: Mapped[str]
    title: Mapped[str]
    time: Mapped[datetime.datetime]
    location: Mapped[str]
    description: Mapped[str]
    invites: Mapped[str]

    def get_invites(self):
        return json.loads(self.invites)

    def to_ics(self):
        fmt = "%Y%m%dT%H%M%S"
        start = self.time.strftime(fmt)
        now = datetime.datetime.now().strftime(fmt)
        return f'''BEGIN:VCALENDAR
VERSION:2.0
PRODID:custom
BEGIN:VEVENT
DESCRIPTION:{self.description}
LOCATION:{self.location}
DTSTART:{start}
DTSTAMP:{now}
SUMMARY:{self.title}
UID:{self.iden}
END:VEVENT
END:VCALENDAR'''

@asynccontextmanager
async def db_connection(app: Litestar) -> AsyncGenerator[None, None]:
    engine = getattr(app.state, "engine", None)
    if engine is None:
        engine = create_async_engine("sqlite+aiosqlite:///symposium.sqlite", echo=True)
        app.state.engine = engine
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    try:
        yield
    finally:
        await engine.dispose()

sessionmaker = async_sessionmaker(expire_on_commit=False)

parts = [
    "Oxbow", "Limber", "Steadfast", "Regicide", "Swarm", "Weave", "Bough", "Canopy", "Herald", "Scorn",
    "Alder", "Aerial", "Welkin", "Acrid", "Kindling", "Rapture", "Myrtle", "Envy", "Solstice",
    "Juniper", "Cleaving", "Stream", "Reaper", "Sluice", "Conduit", "Disdain", "Sylvan", "Ravish", "Atrium",
    "Thresh", "Harvest", "Water", "Renewal", "Rosy", "Frieze", "Portal", "Vespers", "Litany", "Serpent",
    "Primate", "Incite", "Canon", "Acquiese", "Mirror", "Script", "Seal", "Privy",
    "Piercing", "Heresy", "Subduct", "Sceptre", "Arrogance", "Ivory", "Accrete", "Cluster",
    "Sepulchre", "Summon", "Pleading", "Myriad", "Exalted", "Sentry", "Shriven", "River", "Threshold"
]

def gen_iden():
    return "-".join(random.choices(parts, k=8))

def error(msg) -> Template:
    return Template(template_name="error.html", context=dict(error=msg))

def auth_error() -> Template:
    return error("Unauthorized.")

def check_auth(password, event):
    return password and hmac.compare_digest(event.password, password)

@get("/")
async def index() -> Template:
    return Template(template_name="index.html")

@get("/event/{iden:str}", name="event")
async def event(state: State, iden: str, password: str = "") -> Template:
    async with sessionmaker(bind=state.engine) as session:
        async with session.begin():
            query = select(Event).where(Event.iden == iden)
            result = await session.execute(query)
            try:
                event = result.scalar_one()
            except NoResultFound:
                return error("Not found.")

    manage = False
    if password:
        if not check_auth(password, event):
            return auth_error()
        manage = True

    context = dict(event=event, manage=manage)
    return Template(template_name="event.html", context=context)

@get("/event/{iden:str}/calendar")
async def calendar(state: State, iden: str) -> ASGIStreamingResponse:
    async with sessionmaker(bind=state.engine) as session:
        async with session.begin():
            query = select(Event).where(Event.iden == iden)
            result = await session.execute(query)
            try:
                event = result.scalar_one()
            except NoResultFound:
                return error("Not found.")
    ics = event.to_ics()
    f = io.StringIO(ics)
    return ASGIStreamingResponse(iterator=f, media_type='text/plain', headers={
        'Content-Disposition': 'attachment; filename=event.ics',
    })

@dataclass
class EditRequest:
    title: str
    when: str
    where: str
    what: str

@post("/event/create")
async def create(request: Request, state: State, data: Annotated[EditRequest, Body(media_type=RequestEncodingType.URL_ENCODED)]) -> Redirect:
    iden = gen_iden()
    password = secrets.token_bytes(16).hex()
    event = Event(iden, password, data.title, datetime.datetime.fromisoformat(data.when), data.where, data.what)

    async with sessionmaker(bind=state.engine) as session:
        try:
            async with session.begin():
                session.add(event)
        except IntegrityError:
            return error("Iden already exists.")

    return Redirect("/symposium" + request.app.route_reverse('event', iden=iden) + "?password=" + event.password)

@post("/event/{iden:str}/edit")
async def edit(state: State, request: Request, iden: str, password: str, data: Annotated[EditRequest, Body(media_type=RequestEncodingType.URL_ENCODED)]) -> Redirect:
    async with sessionmaker(bind=state.engine) as session:
        async with session.begin():
            query = select(Event).where(Event.iden == iden)
            result = await session.execute(query)
            try:
                event = result.scalar_one()
            except NoResultFound:
                return error("Not found.")

            if not check_auth(password, event):
                return auth_error()

            event.title = data.title
            event.time = datetime.datetime.fromisoformat(data.when)
            event.location = data.where
            event.description = data.what

    return Redirect("/symposium" + request.app.route_reverse('event', iden=iden) + "?password=" + event.password)

@dataclass
class RemoveRequest:
    name: str

@post("/event/{iden:str}/remove")
async def remove(state: State, request: Request, iden: str, data: Annotated[RemoveRequest, Body(media_type=RequestEncodingType.URL_ENCODED)], password: str = "") -> Redirect:
    async with sessionmaker(bind=state.engine) as session:
        async with session.begin():
            query = select(Event).where(Event.iden == iden)
            result = await session.execute(query)
            try:
                event = result.scalar_one()
            except NoResultFound:
                return error("Not found.")

            if not check_auth(password, event):
                return auth_error()

            name = data.name
            invites = json.loads(event.invites)
            if name in invites:
                invites.remove(name)
                event.invites = json.dumps(invites)
    return Redirect("/symposium" + request.app.route_reverse('event', iden=iden) + "?password=" + event.password)

@dataclass
class JoinRequest:
    name: str

@post("/event/{iden:str}/join")
async def join(state: State, request: Request, iden: str, data: Annotated[JoinRequest, Body(media_type=RequestEncodingType.URL_ENCODED)], password: str = "") -> Redirect:
    async with sessionmaker(bind=state.engine) as session:
        async with session.begin():
            query = select(Event).where(Event.iden == iden)
            result = await session.execute(query)
            try:
                event = result.scalar_one()
            except NoResultFound:
                return error("Not found.")

            name = data.name
            if len(name) > 50:
                return error("Name too long.")
            if len(name) == 0:
                return error("Name too short.")
            invites = json.loads(event.invites)
            if name in invites:
                return error("Name already exists in event.")
            invites.append(name)
            event.invites = json.dumps(invites)

    url = "/symposium" + request.app.route_reverse('event', iden=iden)
    if password:
        url += "?password=" + password
    return Redirect(path=url)

app = Litestar(
    route_handlers=[
        index,
        event,
        calendar,
        create,
        edit,
        remove,
        join,
        create_static_files_router(path='/static', directories=['static']),
    ],
    template_config=TemplateConfig(
        directory=Path("templates"),
        engine=JinjaTemplateEngine,
    ),
    lifespan=[db_connection],
)