import uuid
from typing import cast
from urllib.parse import urlsplit

import sqlalchemy as sa
import sqlalchemy.exc as sa_exc
from flask import (
    Blueprint,
    Response,
    abort,
    flash,
    redirect,
    render_template,
    request,
    url_for,
)
from flask.typing import ResponseReturnValue
from flask_login import current_user, login_required, login_user, logout_user

from . import DATABASE as db
from . import forms
from .models import ReceivedWebmention, User
from .tasks.receiver import verify_webmention

root_page = Blueprint("root", __name__)


@root_page.route("/")
def index() -> ResponseReturnValue:
    return redirect(url_for("root.received"))


@root_page.route("/login", methods=["GET", "POST"])
def login() -> ResponseReturnValue:
    if current_user.is_authenticated:
        return redirect(url_for("root.index"))

    form = forms.LoginForm()

    if form.validate_on_submit():
        user = db.session.scalar(
            sa.select(User).where(User.username == form.username.data)
        )

        if user is None or not user.check_password(form.password.data):
            flash("Invalid username or password", "danger")
            return redirect(url_for("root.login"))

        login_user(user)

        next_page = request.args.get("next")
        if not next_page or urlsplit(next_page).netloc != "":
            next_page = url_for("root.index")
        return redirect(next_page)

    return render_template("login.html", form=form)


@root_page.route("/logout")
def logout() -> ResponseReturnValue:
    logout_user()
    return redirect(url_for("root.index"))


@root_page.route("/received")
@login_required
def received() -> ResponseReturnValue:
    webmentions = db.paginate(
        sa.select(ReceivedWebmention).order_by(ReceivedWebmention.uuid.desc()),
        per_page=25,
    )

    return render_template(
        "received.html",
        title="Received Webmentions",
        webmentions=webmentions,
    )


@root_page.route("/endpoint", methods=["POST"])
def endpoint() -> ResponseReturnValue:
    form = forms.EndpointForm(meta={"csrf": False})

    if not form.validate_on_submit():
        return form.errors, 400

    source = cast(str, form.source.data)
    target = cast(str, form.target.data)

    webmention = db.session.execute(
        sa.select(ReceivedWebmention).where(
            ReceivedWebmention.source == source,
            ReceivedWebmention.target == target,
        )
    ).scalar_one_or_none()

    if webmention is None:
        identifier = uuid.uuid7()

        webmention = ReceivedWebmention(
            uuid=identifier,
            source=source,
            target=target,
        )

        db.session.add(webmention)

        try:
            db.session.commit()
        except sa_exc.IntegrityError:
            db.session.rollback()

            # Another request may have inserted the same source/target pair
            # after our SELECT but before our COMMIT.
            webmention = db.session.execute(
                sa.select(ReceivedWebmention).where(
                    ReceivedWebmention.source == source,
                    ReceivedWebmention.target == target,
                )
            ).scalar_one()

            identifier = webmention.uuid
            webmention.status = "received"
            webmention.failure_reason = None

            db.session.commit()

    else:
        identifier = webmention.uuid

        # Re-sent webmention: re-verify the existing row.
        webmention.status = "received"
        webmention.failure_reason = None

        db.session.commit()

    verify_webmention(webmention.uuid)

    status_url = url_for(
        "root.status",
        identifier=str(identifier),
        _external=True,
    )

    return Response(
        status=201,
        headers={"Location": status_url},
    )


@root_page.route("/status/<uuid:identifier>")
def status(identifier: uuid.UUID) -> ResponseReturnValue:
    webmention = db.session.get(ReceivedWebmention, identifier)

    if webmention is None:
        return abort(404)

    return render_template(
        "status.html", title="Webmention status", webmention=webmention
    )