import { createHash } from "node:crypto";

/**
 * Limitation de débit en mémoire (fenêtre glissante) — adaptée à une instance
 * unique (PM2 fork / Node). Pour plusieurs instances, remplacer par un store
 * partagé (Redis) en conservant l'interface `RateLimiter`.
 */
export interface RateLimiter {
  check(key: string, now?: number): { allowed: boolean; retryAfterS: number };
}

export function createMemoryRateLimiter(limit: number, windowS: number): RateLimiter {
  const hits = new Map<string, number[]>();
  const windowMs = windowS * 1000;
  let lastSweep = 0;
  return {
    check(key, now = Date.now()) {
      if (now - lastSweep > windowMs) {
        for (const [k, arr] of hits) {
          const kept = arr.filter((t) => now - t < windowMs);
          if (kept.length) hits.set(k, kept);
          else hits.delete(k);
        }
        lastSweep = now;
      }
      const arr = (hits.get(key) ?? []).filter((t) => now - t < windowMs);
      if (arr.length >= limit) {
        const retryAfterS = Math.ceil((arr[0] + windowMs - now) / 1000);
        hits.set(key, arr);
        return { allowed: false, retryAfterS: Math.max(1, retryAfterS) };
      }
      arr.push(now);
      hits.set(key, arr);
      return { allowed: true, retryAfterS: 0 };
    },
  };
}

/** IP cliente derrière un reverse proxy de confiance (Caddy / nginx). */
export function clientIp(headers: Headers): string {
  const fwd = headers.get("x-forwarded-for");
  if (fwd) return fwd.split(",")[0].trim();
  return headers.get("x-real-ip") ?? "unknown";
}

/** Empreinte non réversible pour la journalisation (pas de donnée personnelle en clair). */
export function fingerprint(value: string): string {
  return createHash("sha256").update(value).digest("hex").slice(0, 12);
}

/** Dédoublonnage court : même expéditeur + même message dans la fenêtre. */
export function createDedupe(windowS: number) {
  const seen = new Map<string, number>();
  return {
    isDuplicate(key: string, now = Date.now()): boolean {
      for (const [k, t] of seen) if (now - t > windowS * 1000) seen.delete(k);
      if (seen.has(key)) return true;
      seen.set(key, now);
      return false;
    },
  };
}

/** Politique de sécurité de contenu (CSP) du site. */
export function contentSecurityPolicy(): string {
  return [
    "default-src 'self'",
    "script-src 'self' 'unsafe-inline'", // inline requis par l'hydratation Next (scripts d'amorçage)
    "style-src 'self' 'unsafe-inline'",
    "img-src 'self' data: blob:",
    "font-src 'self' data:",
    "connect-src 'self'",
    "frame-ancestors 'none'",
    "base-uri 'self'",
    "form-action 'self'",
    "object-src 'none'",
  ].join("; ");
}

export const securityHeaders = [
  { key: "Content-Security-Policy", value: contentSecurityPolicy() },
  { key: "X-Content-Type-Options", value: "nosniff" },
  { key: "X-Frame-Options", value: "DENY" },
  { key: "Referrer-Policy", value: "strict-origin-when-cross-origin" },
  {
    key: "Permissions-Policy",
    value: "camera=(), microphone=(), geolocation=(), interest-cohort=()",
  },
  {
    key: "Strict-Transport-Security",
    value: "max-age=31536000; includeSubDomains",
  },
];