import lurid from '@andyburke/lurid';
import { get_session, get_user, PRECHECK_TABLE, require_user, user_has_write_permission_for_event } from '../../../utils/prechecks.ts';
import * as CANNED_RESPONSES from '../../../utils/canned_responses.ts';
import { EVENT, EVENTS, VALIDATE_EVENT } from '../../../models/event.ts';
import parse_body from '../../../utils/bodyparser.ts';
import { FSDB_SEARCH_OPTIONS, WALK_ENTRY } from '@andyburke/fsdb';
import { WATCH, WATCHES } from '../../../models/watch.ts';
import { flatten } from '../../../utils/object_helpers.ts';
import { CHANNEL, CHANNELS } from '../../../models/channel.ts';

export const PRECHECKS: PRECHECK_TABLE = {};

// GET /api/events - get events
// query parameters:
//   partial_id: the partial id subset you would like to match (remember, lurids are lexigraphically sorted)
PRECHECKS.GET = [get_session, get_user, require_user];
export async function GET(request: Request, meta: Record<string, any>): Promise<Response> {
	const sorts = EVENTS.sorts;
	const sort_name: string = meta.query.sort ?? 'newest';
	const key = sort_name as keyof typeof sorts;
	const sort: any = sorts[key];
	if (!sort) {
		return Response.json({
			error: {
				message: 'You must specify a sort: newest, oldest, latest, stalest',
				cause: 'invalid_sort'
			}
		}, {
			status: 400
		});
	}

	const options: FSDB_SEARCH_OPTIONS<EVENT> = {
		...(meta.query ?? {}),
		limit: Math.min(parseInt(meta.query?.limit ?? '100', 10), 1_000),
		offset: Math.max(parseInt(meta.query?.offset ?? '0', 10), 0),
		sort,
		filter: (entry: WALK_ENTRY<EVENT>) => {
			const {
				event_type,
				event_id
			} = /^.*\/events\/(?<event_type>.*?)\/.*\/(?<event_id>[A-Za-z-]+)\.json$/.exec(entry.path)?.groups ?? {};

			if (meta.query.after_id && event_id <= meta.query.after_id) {
				return false;
			}

			if (meta.query.before_id && event_id >= meta.query.before_id) {
				return false;
			}

			if (meta.query.type && !meta.query.type.split(',').includes(event_type)) {
				return false;
			}

			return true;
		}
	};

	const headers = {
		'Cache-Control': 'no-cache, must-revalidate'
	};

	const results = (await EVENTS.all(options))
		.map((entry: WALK_ENTRY<EVENT>) => entry.load())
		.filter((event) => typeof event.channel === 'undefined') // channel events must be queried via the channel's api
		.sort((lhs_item: EVENT, rhs_item: EVENT) => rhs_item.timestamps.created.localeCompare(lhs_item.timestamps.created));

	// long-polling support
	if (results.length === 0 && meta.query.wait) {
		return new Promise((resolve, reject) => {
			function on_create(create_event: any) {
				if (meta.query.type && !meta.query.type.split(',').includes(create_event.item.type)) {
					return;
				}

				results.push(create_event.item);
				clearTimeout(timeout);
				EVENTS.off('create', on_create);

				return resolve(Response.json(results, {
					status: 200,
					headers
				}));
			}

			const timeout = setTimeout(() => {
				EVENTS.off('create', on_create);
				return resolve(Response.json(results, {
					status: 200,
					headers
				}));
			}, 60_000); // 60 seconds
			EVENTS.on('create', on_create);
			request.signal.addEventListener('abort', () => {
				EVENTS.off('create', on_create);
				clearTimeout(timeout);
				reject(new Error('request aborted'));
			});
			Deno.addSignalListener('SIGINT', () => {
				EVENTS.off('create', on_create);
				clearTimeout(timeout);
				return resolve(Response.json(results, {
					status: 200,
					headers
				}));
			});
		});
	}

	return Response.json(results, {
		status: 200,
		headers
	});
}

async function update_watches(event: EVENT) {
	const limit = 100;

	let more_to_process;
	let offset = 0;
	do {
		const watches: WATCH[] = (await WATCHES.all({
			limit,
			offset
		})).map((entry) => entry.load());

		for (const watch of watches) {
			if (typeof watch.type === 'string' && event.type !== watch.type) {
				continue;
			}

			if (typeof watch.parent_id === 'string' && event.parent_id !== watch.parent_id) {
				continue;
			}

			if (typeof watch.channel === 'string' && event.channel !== watch.channel) {
				continue;
			}

			if (typeof watch.topic === 'string' && event.topic !== watch.topic) {
				continue;
			}

			if (typeof watch.tags !== 'undefined' && !watch.tags.every((tag) => event.tags?.includes(tag))) {
				continue;
			}

			if (typeof watch.data !== 'undefined') {
				const event_data = flatten(event.data ?? {});
				for (const [key, value] of Object.entries(flatten(watch.data))) {
					const matcher = new RegExp(value);
					if (!matcher.test(event_data[key])) {
						continue;
					}
				}
			}

			if (event.id < watch.last_id_seen) {
				continue;
			}

			watch.last_id_seen = event.id;

			// TODO: send a notification
			console.dir({
				notification: {
					watch,
					event
				}
			});
		}

		offset += watches.length;
		more_to_process = watches.length === limit;
	} while (more_to_process);
}

// POST /api/events - Create an event
PRECHECKS.POST = [get_session, get_user, require_user, (_req: Request, meta: Record<string, any>): Response | undefined => {
	const user_can_create_events = meta.user.permissions.some((permission: string) => permission.indexOf('events.create') === 0);

	if (!user_can_create_events) {
		return CANNED_RESPONSES.permission_denied();
	}
}];
export async function POST(req: Request, meta: Record<string, any>): Promise<Response> {
	try {
		const now = new Date().toISOString();

		const body = await parse_body(req);
		const event: EVENT = {
			type: 'unknown',
			...body,
			creator_id: meta.user.id,
			timestamps: {
				created: now,
				updated: now
			}
		};

		event.id = `${event.type}:${lurid()}`;

		const errors = VALIDATE_EVENT(event);
		if (errors) {
			return Response.json({
				errors
			}, {
				status: 400
			});
		}

		if (!user_has_write_permission_for_event(meta.user, event)) {
			return CANNED_RESPONSES.permission_denied();
		}

		if (event.channel) {
			const channel: CHANNEL | null = await CHANNELS.get(event.channel);
			if (!channel) {
				return Response.json({
					errors: [{
						cause: 'missing_channel',
						message: 'No such channel exists.'
					}]
				}, {
					status: 400
				});
			}

			const user_can_write_events_to_channel = channel.permissions.events.write.length === 0 ? true : channel.permissions.events.write.includes(meta.user.id);

			if (!user_can_write_events_to_channel) {
				return CANNED_RESPONSES.permission_denied();
			}
		}

		await EVENTS.create(event);

		update_watches(event);

		return Response.json(event, {
			status: 201
		});
	} catch (error) {
		return Response.json({
			error: {
				message: (error as Error).message ?? 'Unknown Error!',
				cause: (error as Error).cause ?? 'unknown'
			}
		}, { status: 500 });
	}
}