import { error, json, redirect, type Handle } from '@sveltejs/kit';
import { readSession, readSessionHash, recordAudit, setupRequired } from './index.js';
import {
    authBody,
    authError,
    requireSameOrigin,
    requireUserTransport,
    sessionCookie
} from './http.js';
import { roleAllows, routePermission, type RoutePermission } from './access.js';
import { withRequestUsername } from './request-context.js';

function publicAsset(routeId: string | null, path: string, method: string) {
    return (
        routeId === null &&
        ['GET', 'HEAD'].includes(method) &&
        (path.startsWith('/_app/') ||
            path === '/favicon.svg' ||
            [
                '/agent/ec-agent.py',
                '/agent/ec-agent-update.py',
                '/agent/install.sh',
                '/agent/manifest.json'
            ].includes(path))
    );
}

/** Streaming responses must lose access when the underlying session does. */
export function protectEventStream(
    response: Response,
    tokenHash: string,
    permission: RoutePermission,
    signal: AbortSignal
): Response {
    if (!response.body) return response;
    const reader = response.body.getReader();
    let timer: ReturnType<typeof setInterval> | undefined;
    let closed = false;
    let closeStream: () => void = () => {};
    const cleanup = () => {
        if (timer) clearInterval(timer);
        signal.removeEventListener('abort', closeStream);
    };
    const stream = new ReadableStream<Uint8Array>({
        start(controller) {
            closeStream = () => {
                if (closed) return;
                closed = true;
                cleanup();
                void reader.cancel().catch(() => {});
                controller.close();
            };
            timer = setInterval(() => {
                try {
                    const current = readSessionHash(tokenHash);
                    if (
                        !current ||
                        current.user.mustChangePassword ||
                        !roleAllows(current.user.role, permission)
                    )
                        closeStream();
                } catch {
                    closeStream();
                }
            }, 15_000);
            signal.addEventListener('abort', closeStream, { once: true });
            if (signal.aborted) {
                closeStream();
                return;
            }
        },
        async pull(controller) {
            try {
                const next = await reader.read();
                if (closed) return;
                if (next.done) {
                    closed = true;
                    cleanup();
                    controller.close();
                } else controller.enqueue(next.value);
            } catch (cause) {
                if (!closed) {
                    closed = true;
                    cleanup();
                    controller.error(cause);
                }
            }
        },
        cancel() {
            closed = true;
            cleanup();
            return reader.cancel();
        }
    });
    return new Response(stream, {
        status: response.status,
        statusText: response.statusText,
        headers: response.headers
    });
}

export const authenticationHandle: Handle = async ({ event, resolve }) => {
    event.locals.user = null;
    event.locals.sessionHash = null;
    const routeId = event.route.id;
    const method = event.request.method.toUpperCase();
    if (publicAsset(routeId, event.url.pathname, method)) return resolve(event);
    const permission = routePermission(routeId, method);
    if (
        !routeId?.startsWith('/api/agent/') &&
        /^Bearer ec_(?:host|enroll)_/i.test(event.request.headers.get('authorization') ?? '')
    ) {
        return json(
            { error: 'Host credentials only authorize the host agent API.' },
            { status: 403 }
        );
    }
    if (permission === 'machine') return resolve(event);
    const api = routeId?.startsWith('/api/') || event.url.pathname.startsWith('/api/');
    try {
        requireUserTransport(event.url);
        if (!['GET', 'HEAD', 'OPTIONS'].includes(method))
            requireSameOrigin(event.request, event.url);
    } catch (cause) {
        if (api) return authError(cause);
        throw cause;
    }

    const session = readSession(event.cookies.get(sessionCookie(event.url)));
    event.locals.user = session?.user ?? null;
    event.locals.sessionHash = session?.tokenHash ?? null;
    const setup = setupRequired();
    if (permission !== 'public') {
        if (!session) {
            if (api)
                return json(
                    {
                        error: setup
                            ? 'Complete administrator setup before using the management API.'
                            : 'Sign in to continue.',
                        setupRequired: setup
                    },
                    { status: 401, headers: { 'Cache-Control': 'no-store' } }
                );
            redirect(
                303,
                setup
                    ? '/setup'
                    : `/login?next=${encodeURIComponent(event.url.pathname + event.url.search)}`
            );
        }
        if (session.user.mustChangePassword && permission !== 'authenticated') {
            if (api)
                return json(
                    {
                        error: 'Change your temporary password from Account before continuing.',
                        mustChangePassword: true
                    },
                    { status: 403, headers: { 'Cache-Control': 'no-store' } }
                );
            redirect(303, '/account');
        }
        if (!roleAllows(session.user.role, permission)) {
            const message =
                permission === 'admin'
                    ? 'Administrator access is required.'
                    : 'Operator access is required for this action.';
            if (api)
                return json(
                    { error: message },
                    { status: 403, headers: { 'Cache-Control': 'no-store' } }
                );
            error(403, message);
        }
        // Launch APIs can also save credentials. Operators may launch with saved
        // keys, but only administrators may introduce or replace server keys.
        if (
            session.user.role === 'operator' &&
            method === 'POST' &&
            ['/api/servers', '/api/deployment-collections'].includes(routeId ?? '')
        ) {
            try {
                const body = await authBody(event.request.clone(), 1024 * 1024);
                if (
                    body.plutoKey ||
                    (body.keys &&
                        typeof body.keys === 'object' &&
                        Object.values(body.keys).some(Boolean))
                ) {
                    return json(
                        {
                            error: 'An administrator must save server keys before an operator launches these servers.'
                        },
                        { status: 403 }
                    );
                }
            } catch (cause) {
                return authError(cause);
            }
        }
    } else if (['/login', '/setup'].includes(routeId ?? '')) {
        if (session) redirect(303, session.user.mustChangePassword ? '/account' : '/');
        if (routeId === '/setup' && !setup) redirect(303, '/login');
        if (routeId === '/login' && setup) redirect(303, '/setup');
    }

    let response = await withRequestUsername(session?.user.username ?? null, () => resolve(event));
    if (session && !['GET', 'HEAD', 'OPTIONS'].includes(method) && response.status < 400) {
        recordAudit(session.user.id, 'request', routeId, {
            method,
            status: response.status,
            path: event.url.pathname
        });
    }
    if (session && response.headers.get('content-type')?.startsWith('text/event-stream')) {
        response = protectEventStream(
            response,
            session.tokenHash,
            permission,
            event.request.signal
        );
    }
    const headers = new Headers(response.headers);
    headers.set('Cache-Control', 'no-store');
    headers.set('Vary', [headers.get('Vary'), 'Cookie'].filter(Boolean).join(', '));
    headers.set('Referrer-Policy', 'same-origin');
    headers.set('X-Content-Type-Options', 'nosniff');
    headers.set('X-Frame-Options', 'DENY');
    return new Response(response.body, {
        status: response.status,
        statusText: response.statusText,
        headers
    });
};