import { Request as ExpressRequest, Response as ExpressResponse } from "express";
import { Option, tryDo } from "@shared/common/async_utils";
import { rpcClient } from "src/utils/rpc";
import { eventLogger } from "src/utils/logging";
import { QueryOptions } from "winston";

export interface LogEvent {
    _id: string;
    label: string;
    level: string;
    message: string;
    timestamp: string;
}

export interface PollOptions {
    limit?: string;
}

function zip(obj: Record<string, unknown[]>): unknown[] {
    return Object.values(obj).reduce((prev, cur) => [...prev, ...cur], []);
}

function isNumber(val: unknown): val is number {
    return !Number.isNaN(Number.parseInt(val as string, 10));
}

function queryEvents(opts?: QueryOptions | { includeIds?: boolean }):
        Promise<Record<string, unknown[]>> {
    return new Promise((resolve, reject) => {
        eventLogger.query(opts as QueryOptions, (error, results) => {
            if (error) {
                reject(error);
            } else {
                resolve(results);
            }
        });
    });
}

export type PollResult = Option<{ events: LogEvent[] }, { error: string }>;
type GetResult = Promise<ExpressResponse<PollResult>>;
export const get = async (req: ExpressRequest, res: ExpressResponse): GetResult => {
    const params = req.query as PollOptions;
    if (!req.session?.userId) {
        return res.json({
            ok: false,
            error: "Not logged in, please log in",
        });
    }

    const { authorised } = await rpcClient.userAuthorised({ userId: req.session.userId });
    if (!authorised) {
        return res.json({
            ok: false,
            error: "Not authorised, please log in",
        });
    }

    const DEFAULT_LIMIT = 50;
    const result = await tryDo(queryEvents({
        fields: ["level", "message", "label", "timestamp"],
        limit: isNumber(params.limit) ? +params.limit : DEFAULT_LIMIT,
        includeIds: true,
    }));

    if (!result.ok) {
        return res.json({
            ok: false,
            error: `Failed to query events. Error: ${result.error}`,
        });
    }

    return res.json({ ok: true, events: zip(result.result) });
};