import { Worker } from 'node:worker_threads';
import { resolve } from 'node:path';
import { config } from '../config.js';
import { db } from '../db/index.js';
import type { MetricsQuery, MetricsData } from '../../metrics.js';
import type {
    LeaderboardOptions,
    LeaderboardResponse,
    PlayerProfile,
    LeaderboardEntry
} from '../../leaderboard.js';
import type { CapacityHistory, CapacityQuery } from '../../capacity.js';
import { ensureHostSchema } from '../hosts/schema.js';

class ReportWorker {
    private worker: Worker | null = null;
    private sequence = 0;
    private pending = new Map<
        number,
        // eslint-disable-next-line @typescript-eslint/no-explicit-any -- Pending requests hold resolvers for different report result types.
        { resolve: (value: any) => void; reject: (error: Error) => void; timer: NodeJS.Timeout }
    >();
    // eslint-disable-next-line @typescript-eslint/no-explicit-any -- Each request key identifies a caller-specific report result type.
    private flights = new Map<string, Promise<any>>();
    async close() {
        const worker = this.worker;
        this.worker = null;
        for (const pending of this.pending.values()) {
            clearTimeout(pending.timer);
            pending.reject(new Error('Report service stopped'));
        }
        this.pending.clear();
        this.flights.clear();
        await worker?.terminate();
    }
    run<T>(kind: string, input: unknown): Promise<T> {
        const requestInput = input as { query?: unknown; now?: number };
        const timed = kind === 'metrics' || kind === 'capacity';
        const key = JSON.stringify(
            timed
                ? [kind, requestInput.query, Math.floor(requestInput.now! / 30_000)]
                : [kind, input]
        );
        const flight = this.flights.get(key);
        if (flight) return flight;
        if (this.pending.size >= 64)
            return Promise.reject(new Error('Reports are busy. Please retry shortly.'));
        db(); // Finish migrations before opening the independent reader.
        if (!this.worker) {
            const worker = (this.worker = new Worker(
                resolve(
                    process.env.NODE_ENV === 'production'
                        ? 'build/reports/worker.mjs'
                        : '.svelte-kit/reports/worker.mjs'
                ),
                { workerData: { dbPath: resolve(config.dbPath) } }
            ));
            worker.on('message', ({ id, value, error, elapsedMs, cached }) => {
                const pending = this.pending.get(id);
                if (!pending) return;
                clearTimeout(pending.timer);
                this.pending.delete(id);
                if (process.env.EC_PERF_LOG === 'true')
                    console.info('[report]', { kind, elapsedMs, cached });
                if (error) pending.reject(new Error(error));
                else pending.resolve(value);
                if (!this.pending.size) worker.unref();
            });
            const fail = (error: Error) => {
                if (this.worker !== worker) return;
                this.worker = null;
                for (const pending of this.pending.values()) {
                    clearTimeout(pending.timer);
                    pending.reject(error);
                }
                this.pending.clear();
                void worker.terminate();
            };
            worker.on('error', fail);
            worker.on('exit', () => fail(new Error('Report worker stopped. Please retry.')));
        }
        this.worker.ref();
        const id = ++this.sequence;
        const promise = new Promise<T>((resolve, reject) => {
            const timer = setTimeout(() => {
                // Reset the worker rather than leaving an expensive abandoned query queued.
                const worker = this.worker;
                this.worker = null;
                for (const item of this.pending.values()) {
                    clearTimeout(item.timer);
                    item.reject(new Error('Report timed out. Please retry.'));
                }
                this.pending.clear();
                void worker?.terminate();
            }, 60_000);
            this.pending.set(id, { resolve, reject, timer });
            this.worker!.postMessage({ id, kind, input });
        }).finally(() => {
            if (this.flights.get(key) === promise) this.flights.delete(key);
        });
        this.flights.set(key, promise);
        return promise;
    }
}
const metrics = new ReportWorker();
const leaderboard = new ReportWorker();
const capacity = new ReportWorker();
export const metricsReport = (query: MetricsQuery) =>
    metrics.run<MetricsData>('metrics', { query, now: Date.now() });
export const leaderboardReport = (query: LeaderboardOptions) =>
    leaderboard.run<LeaderboardResponse>('leaderboard', query);
export const playerReport = (guid: string, offset: number, options: LeaderboardOptions) =>
    leaderboard.run<{ profile: PlayerProfile | null; entry: LeaderboardEntry | null }>('player', {
        guid,
        offset,
        options
    });
export const capacityHistoryReport = (query: CapacityQuery) => {
    ensureHostSchema(db());
    // Game changes current placement estimates, not measured host resources.
    return capacity.run<CapacityHistory>('capacity', {
        query: { ...query, game: 'all' },
        now: Date.now()
    });
};
export async function closeReports() {
    await Promise.all([metrics.close(), leaderboard.close(), capacity.close()]);
}