import { createHmac } from 'node:crypto';

import type { WebhookConfig, WebhookEvent } from '../config.js';

/** Sous-ensemble du logger Fastify utilisé par le notifieur. */
export interface NotifierLogger {
  debug(details: Record<string, unknown>, message: string): void;
  warn(details: Record<string, unknown>, message: string): void;
}

/** Données d'un upload finalisé, avant enrichissement par le notifieur. */
export interface UploadCompletedInput {
  target: string;
  /** Nom simple, ou chemin relatif `dossier/sous/fichier.ext` (mode dossier). */
  storedName: string;
  originalName?: string;
  size: number;
  mimeType: string;
  /** `sub` de l'utilisateur, si la session est lisible. */
  user?: string;
  /** Chemin ayant produit l'upload. */
  via: 'direct' | 'chunked';
}

/** Données d'un échec d'upload (route `/upload*` terminée en 4xx/5xx). */
export interface UploadFailedInput {
  message: string;
  statusCode: number;
  method: string;
  path: string;
  target?: string;
  user?: string;
}

export interface Notifier {
  /** Notifie les webhooks abonnés à `upload`. Ne lève jamais ; n'attend pas la livraison. */
  uploadCompleted(input: UploadCompletedInput): void;
  /** Notifie les webhooks abonnés à `error`. Ne lève jamais ; n'attend pas la livraison. */
  uploadFailed(input: UploadFailedInput): void;
  /** Attend la fin des livraisons en cours (arrêt propre). */
  close(): Promise<void>;
}

const MAX_ATTEMPTS = 2;
const RETRY_DELAY_MS = 500;
const USER_AGENT = 'mediaDrop-webhook';
const SIZE_UNITS = ['o', 'Ko', 'Mo', 'Go', 'To'] as const;

function formatBytes(bytes: number): string {
  let value = bytes;
  let unit = 0;
  while (value >= 1024 && unit < SIZE_UNITS.length - 1) {
    value /= 1024;
    unit += 1;
  }
  const shown = value < 10 && unit > 0 ? value.toFixed(1) : String(Math.round(value));
  return `${shown} ${SIZE_UNITS[unit] ?? 'o'}`;
}

function delay(ms: number): Promise<void> {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function errorText(error: unknown): string {
  return error instanceof Error ? error.message : String(error);
}

function uploadSummary(input: UploadCompletedInput): string {
  return `✅ Upload terminé : ${input.storedName} (${formatBytes(input.size)}) — cible « ${input.target} »`;
}

function errorSummary(input: UploadFailedInput): string {
  return `⚠️ Échec d'upload (${String(input.statusCode)}) : ${input.message} [${input.method} ${input.path}]`;
}

function uploadBody(input: UploadCompletedInput): Record<string, unknown> {
  const summary = uploadSummary(input);
  return {
    event: 'upload' satisfies WebhookEvent,
    timestamp: new Date().toISOString(),
    target: input.target,
    storedName: input.storedName,
    ...(input.originalName !== undefined ? { originalName: input.originalName } : {}),
    size: input.size,
    mimeType: input.mimeType,
    ...(input.user !== undefined ? { user: input.user } : {}),
    via: input.via,
    // `text` (Slack) et `content` (Discord) : même résumé lisible.
    text: summary,
    content: summary,
  };
}

function errorBody(input: UploadFailedInput): Record<string, unknown> {
  const summary = errorSummary(input);
  return {
    event: 'error' satisfies WebhookEvent,
    timestamp: new Date().toISOString(),
    message: input.message,
    statusCode: input.statusCode,
    method: input.method,
    path: input.path,
    ...(input.target !== undefined ? { target: input.target } : {}),
    ...(input.user !== undefined ? { user: input.user } : {}),
    text: summary,
    content: summary,
  };
}

function buildHeaders(
  webhook: WebhookConfig,
  event: WebhookEvent,
  body: string,
): Record<string, string> {
  const headers: Record<string, string> = {
    ...webhook.headers,
    'content-type': 'application/json',
    'user-agent': USER_AGENT,
    'x-mediadrop-event': event,
  };
  if (webhook.secret !== undefined) {
    const digest = createHmac('sha256', webhook.secret).update(body).digest('hex');
    headers['x-mediadrop-signature'] = `sha256=${digest}`;
  }
  return headers;
}

async function deliver(
  webhook: WebhookConfig,
  event: WebhookEvent,
  body: string,
  log: NotifierLogger,
): Promise<void> {
  const headers = buildHeaders(webhook, event, body);

  for (let attempt = 1; attempt <= MAX_ATTEMPTS; attempt += 1) {
    try {
      const response = await fetch(webhook.url, {
        method: 'POST',
        headers,
        body,
        signal: AbortSignal.timeout(webhook.timeoutMs),
      });
      // Vider le corps pour libérer la connexion (keep-alive).
      await response.text().catch(() => '');

      if (response.ok) {
        log.debug({ url: webhook.url, status: response.status, event }, 'Webhook livré');
        return;
      }
      const retriable = response.status === 429 || response.status >= 500;
      if (!retriable) {
        log.warn({ url: webhook.url, status: response.status, event }, 'Webhook rejeté (abandon)');
        return;
      }
      log.warn({ url: webhook.url, status: response.status, event, attempt }, 'Webhook en échec');
    } catch (error) {
      log.warn({ url: webhook.url, err: errorText(error), event, attempt }, 'Webhook injoignable');
    }

    if (attempt < MAX_ATTEMPTS) {
      await delay(RETRY_DELAY_MS);
    }
  }
}

/**
 * Crée un notifieur qui POSTe un corps JSON à chaque webhook abonné, à chaque
 * upload finalisé (`upload`) et à chaque échec d'upload (`error`).
 *
 * Livraison en parallèle, sans bloquer la réponse HTTP : chaque webhook a son
 * propre délai d'attente, une nouvelle tentative sur erreur réseau / 429 / 5xx,
 * et les échecs sont seulement journalisés. `close()` attend les envois en cours.
 * Sans webhook configuré, toutes les méthodes sont des non-opérations.
 */
export function createNotifier(webhooks: readonly WebhookConfig[], log: NotifierLogger): Notifier {
  if (webhooks.length === 0) {
    return {
      uploadCompleted(): void {},
      uploadFailed(): void {},
      close: (): Promise<void> => Promise.resolve(),
    };
  }

  const pending = new Set<Promise<void>>();

  const dispatch = (event: WebhookEvent, body: Record<string, unknown>): void => {
    const json = JSON.stringify(body);
    for (const webhook of webhooks) {
      if (!webhook.events.includes(event)) {
        continue;
      }
      const task = deliver(webhook, event, json, log).finally(() => {
        pending.delete(task);
      });
      pending.add(task);
    }
  };

  return {
    uploadCompleted(input): void {
      dispatch('upload', uploadBody(input));
    },
    uploadFailed(input): void {
      dispatch('error', errorBody(input));
    },
    close: async (): Promise<void> => {
      await Promise.allSettled([...pending]);
    },
  };
}