import { cookies } from "next/headers";
import { createHash, createHmac, timingSafeEqual } from "crypto";
import { prisma } from "../db";

/* Sessions for the operations console.
 *
 * A third kind of session, kept apart from the other two the same way lib/staffsession.ts keeps
 * the wearer's apart from the coordinator's: its own cookie, a signing key derived from a
 * separate secret with a separate domain string, and a payload claim named `oid` where the others
 * carry `uid` and `sid`. A coordinator or staff cookie pasted into tc_ops fails signature
 * verification, and even if it somehow didn't, readOpsToken() rejects a payload with no `oid`.
 * There is no arrangement of the other two tokens that becomes this one — not because a condition
 * says no, but because the three are not the same shape.
 *
 * ⛔ The secret is OPS_SESSION_SECRET, never SESSION_SECRET. SESSION_SECRET also derives the key
 * that encrypts every customer's TOTP secret, so if this console shared it, a compromised operator
 * credential would force a rotation that destroys every facility's second factor. The console
 * must be revocable on its own.
 *
 * ⛔ The cookie is host-only — no Domain attribute — so it is sent to ops.threadcount.tech and
 * nowhere else. Domain=.threadcount.tech would hand it to analytics. and errors.threadcount.tech,
 * both real applications this product's CSP already trusts.
 *
 * ⛔ Nothing in here, and nothing in the console, may mint a coordinator or staff session. The
 * demo route shows how few lines that takes; an operator signing in as a customer is the data
 * plane by another door, and the product's privacy page says it never happens.
 */

export const OPS_COOKIE = "tc_ops";
// Eight hours: an owner console is tuned the opposite way from the two convenience sessions.
const MAX_AGE = 60 * 60 * 8;

function secret() {
  const s = process.env.OPS_SESSION_SECRET;
  if (!s) throw new Error("OPS_SESSION_SECRET not set");
  // Domain separation, and a different master secret underneath it.
  return createHash("sha256").update("threadcount:ops:v1:" + s).digest();
}

function b64url(buf: Buffer) {
  return buf.toString("base64").replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

/** Short fingerprint of the password hash: a password change invalidates every older token. */
export function opsPwVersion(passwordHash: string) {
  return createHash("sha256").update(passwordHash).digest("base64url").slice(0, 12);
}

/** `sso` marks a session that Cloudflare Access already put a second factor behind. */
export function signOpsSession(oid: string, passwordHash: string, sso = false, maxAge = MAX_AGE) {
  const payload = b64url(Buffer.from(JSON.stringify({ oid, pv: opsPwVersion(passwordHash), sso, exp: Date.now() + maxAge * 1000 })));
  const sig = b64url(createHmac("sha256", secret()).update(payload).digest());
  return `${payload}.${sig}`;
}

export function readOpsToken(raw: string | undefined): { oid: string; pv: string; sso: boolean } | null {
  if (!raw) return null;
  const [payload, sig] = raw.split(".");
  if (!payload || !sig) return null;
  const expect = b64url(createHmac("sha256", secret()).update(payload).digest());
  const a = Buffer.from(sig), b = Buffer.from(expect);
  if (a.length !== b.length || !timingSafeEqual(a, b)) return null;
  try {
    const data = JSON.parse(Buffer.from(payload.replace(/-/g, "+").replace(/_/g, "/"), "base64").toString());
    if (!data.oid || !data.exp || data.exp < Date.now()) return null;
    return { oid: data.oid, pv: String(data.pv || ""), sso: data.sso === true };
  } catch {
    return null;
  }
}

export async function setOpsCookie(oid: string, passwordHash: string, sso = false) {
  const jar = await cookies();
  jar.set(OPS_COOKIE, signOpsSession(oid, passwordHash, sso), {
    httpOnly: true,
    sameSite: "lax",
    secure: process.env.NODE_ENV === "production",
    path: "/",
    maxAge: MAX_AGE,
  });
}

export async function clearOpsCookie() {
  const jar = await cookies();
  jar.set(OPS_COOKIE, "", { httpOnly: true, sameSite: "lax", path: "/", maxAge: 0 });
}

export type OperatorRole = "OWNER" | "SUPPORT";

export type OperatorSession = {
  id: string;
  email: string;
  name: string;
  role: OperatorRole;
  /** The second factor was proven at the identity provider, not here. */
  viaSso: boolean;
  totpEnabled: boolean;
};

/** Re-read per request rather than trusting the token beyond an id, like currentUser(). */
export async function currentOperator(): Promise<OperatorSession | null> {
  const jar = await cookies();
  const tok = readOpsToken(jar.get(OPS_COOKIE)?.value);
  if (!tok) return null;
  const o = await prisma.operator.findUnique({
    where: { id: tok.oid },
    select: { id: true, email: true, name: true, role: true, inactive: true, passwordHash: true, totpEnabledAt: true },
  });
  if (!o || o.inactive) return null;
  if (tok.pv !== opsPwVersion(o.passwordHash)) return null; // password changed since this token was minted
  return { id: o.id, email: o.email, name: o.name, role: o.role, viaSso: tok.sso, totpEnabled: !!o.totpEnabledAt };
}

const RANK: Record<OperatorRole, number> = { SUPPORT: 1, OWNER: 2 };

/** Throws rather than returns null so a route cannot forget to check. */
export async function requireOperator(minRole: OperatorRole = "SUPPORT"): Promise<OperatorSession> {
  const o = await currentOperator();
  if (!o) throw new Error("UNAUTHENTICATED");
  if (RANK[o.role] < RANK[minRole]) throw new Error("FORBIDDEN");
  return o;
}

/* The trail. Every write the console makes goes through here, and so does every reveal and every
 * sign-in. Never awaited by callers and never throws — a trail that could fail the action it
 * records would be a reason to skip recording it. `facilityId` is a plain string on purpose (see
 * the schema): a facility that leaves cannot take the record of what was looked at with it. */
export function logOperatorEvent(e: { operatorId: string; action: string; facilityId?: string; subject?: string; detail?: string; ip?: string }): void {
  prisma.operatorEvent.create({
    data: {
      operatorId: e.operatorId,
      action: e.action.slice(0, 60),
      facilityId: (e.facilityId || "").slice(0, 40),
      subject: (e.subject || "").slice(0, 200),
      detail: (e.detail || "").slice(0, 400),
      ip: (e.ip || "").slice(0, 60),
    },
  }).catch(() => { /* the trail must not fail the action */ });
}