// What claude-code does on a node, written against two things it is handed — a way to ask a tool on the
// bus and a way to emit an event — so every path is tested without a bus (novox/hq design 36 §4–§5,
// ADR 0183, ADR 0198).
//
// **Over NATS, in two kinds** (design 32 §10): an event says that something happened and carries no
// secret, because a stream keeps it; a token travels on a request, which nothing keeps. So:
//   - the licence manager's `licence.rotated` and `licence.switched` events tell this module to ask the
//     seat for its current token, sealed to the key it sends with the request;
//   - a login a person made here — a refresh token this module never writes — is offered to the seat at
//     once, sealed to the seat's key: the one moment a refresh token travels, because the login made the
//     manager's stale;
//   - an MCP server registered for more nodes than this one is an `mcp.registered` event every node's
//     claude-code consumes, so a node that was off takes it when it is back.

import { chmodSync, existsSync, readFileSync, rmSync, writeFileSync } from "node:fs";
import { join } from "node:path";

import { render, entryProblem, MANAGED_DIR, type Binding, type Facts, type Settings, type Servers } from "./render.js";
import { generateKeyPair, open, seal, type SealedBox } from "./seal.js";
import { decideApply, grantOf, holdsLogin, readCredentials, replacedBy, withGrant, writeCredentials, type Grant } from "./grant.js";
import { readIdentity, writeIdentity, type Identity } from "./identity.js";

export const SEAT = "anthropic-licence-manager";

export interface Paths {
  state: string;
  facts: string;
  settings: string;
  home: string;
  node: string;
}

/** A tool on the bus: its address and arguments in, its JSON answer out. */
export type Ask = (address: string, args: Record<string, unknown>) => Promise<unknown>;
/** An event of this module's, by its local name. */
export type Emit = (type: string, body: unknown) => Promise<void>;
/** Write one managed file; answers what happened. */
export type WriteManaged = (name: string, content: string) => string;

export const readJson = <T>(p: string, fallback: T): T => {
  try {
    return JSON.parse(readFileSync(p, "utf8")) as T;
  } catch {
    return fallback;
  }
};

const credentialsPath = (p: Paths) => join(p.home, ".claude", ".credentials.json");
const accountPath = (p: Paths) => join(p.home, ".claude.json");
const bindingPath = (p: Paths) => join(p.state, "licence.json");
const apiKeyPath = (p: Paths) => join(p.state, "api-key");
export const helperPath = (p: Paths) => join(p.state, "api-key-helper");
const keyPath = (p: Paths) => join(p.state, "key.pem");
const pubPath = (p: Paths) => join(p.state, "key.pub.pem");
const registryPath = (p: Paths) => join(p.state, "mcp-servers.json");

export function keypair(p: Paths): { publicKey: string; privateKey: string } {
  if (!existsSync(keyPath(p))) {
    const k = generateKeyPair();
    writeFileSync(keyPath(p), k.privateKey, { mode: 0o600 });
    writeFileSync(pubPath(p), k.publicKey, { mode: 0o644 });
  }
  return { privateKey: readFileSync(keyPath(p), "utf8"), publicKey: readFileSync(pubPath(p), "utf8") };
}

export function registered(p: Paths): Servers {
  return readJson<Servers>(registryPath(p), {});
}

export function renderNow(p: Paths, write: WriteManaged): string[] {
  const facts = readJson<Facts | null>(p.facts, null);
  if (!facts?.console) throw new Error(`the mesh has not rendered ${p.facts} yet; nothing to write`);
  const files = render(facts, readJson<Settings>(p.settings, {}), readJson<Binding | null>(bindingPath(p), null),
    helperPath(p), registered(p));
  return Object.entries(files).map(([name, content]) => write(name, content));
}

// ---- the licence ----------------------------------------------------------------------------------

/** What the seat answers to `current`: the licence this node is bound to and its token, sealed. */
export interface Current {
  licence: string;
  kind: "subscription" | "api-key";
  sealed: SealedBox;
  identity?: Identity | null;
}

/** Ask the seat for this node's current token and apply it. */
export async function pull(p: Paths, ask: Ask, write: WriteManaged): Promise<Record<string, unknown>> {
  const answer = (await ask(`${SEAT}.current`, { node: p.node, public_key: keypair(p).publicKey })) as Current | null;
  if (!answer?.sealed) return { applied: false, reason: "the seat holds no licence for this node" };
  return apply(p, answer, write);
}

/** Apply what the seat handed over. A switch replaces the grant whole and cleans up after the old licence. */
export function apply(p: Paths, handed: Current, write: WriteManaged): Record<string, unknown> {
  const plain = open(handed.sealed, keypair(p).privateKey);
  const previous = readJson<Binding | null>(bindingPath(p), null);
  const switched = previous?.licence !== handed.licence;
  let outcome: Record<string, unknown> = { applied: true, licence: handed.licence, kind: handed.kind, switched };
  if (handed.kind === "api-key") {
    writeFileSync(apiKeyPath(p), plain.trim() + "\n", { mode: 0o600 });
    writeFileSync(helperPath(p), `#!/bin/sh\nexec cat '${apiKeyPath(p)}'\n`, { mode: 0o700 });
    chmodSync(helperPath(p), 0o700);
  } else {
    const grant = JSON.parse(plain) as Grant;
    const local = readCredentials(credentialsPath(p));
    const d = decideApply(grantOf(local), grant, switched ? "switch" : "rotation");
    if (d.apply) writeCredentials(credentialsPath(p), switched ? replacedBy(local, grant) : withGrant(local, grant));
    else outcome = { applied: false, licence: handed.licence, reason: d.reason };
    // Away from the API key: it goes, with its helper.
    rmSync(apiKeyPath(p), { force: true });
    rmSync(helperPath(p), { force: true });
  }
  if (switched && handed.identity?.accountUuid) {
    outcome.account = writeIdentity(accountPath(p), handed.identity) ? "updated" : "unchanged";
  }
  writeFileSync(bindingPath(p), JSON.stringify({ licence: handed.licence, kind: handed.kind }) + "\n", { mode: 0o600 });
  try {
    outcome.rendered = renderNow(p, write); // the key-helper comes or goes with the licence's kind
  } catch (err) {
    outcome.rendered = { failed: err instanceof Error ? err.message : String(err) };
  }
  return outcome;
}

/** A licence event from the manager: is it for this node? */
export function concerns(p: Paths, type: string, body: { licence?: string; node?: string }): boolean {
  if (type.endsWith("licence.switched")) return body.node === p.node;
  if (type.endsWith("licence.rotated")) return body.licence === readJson<Binding | null>(bindingPath(p), null)?.licence;
  return false;
}

/** A refresh token in the credentials file is a login: this module never writes one. Offer it to the seat. */
export async function offerLogin(p: Paths, ask: Ask): Promise<Record<string, unknown> | null> {
  const creds = readCredentials(credentialsPath(p));
  if (!holdsLogin(creds)) return null;
  const key = (await ask(`${SEAT}.public_key`, {})) as { public_key?: string } | null;
  if (!key?.public_key) throw new Error("the licence manager did not say what key to seal a login to");
  return (await ask(`${SEAT}.adopt`, {
    node: p.node,
    identity: readIdentity(accountPath(p)),
    sealed: seal(JSON.stringify(creds!.claudeAiOauth), key.public_key),
  })) as Record<string, unknown>;
}

// ---- MCP servers ----------------------------------------------------------------------------------

export interface Registration {
  name: string;
  entry?: Record<string, unknown>;
  /** Which nodes: this one (absent), every node running the module ("all"), or a list. */
  nodes?: "all" | string[];
}

function setRegistered(p: Paths, name: string, entry: Record<string, unknown> | null): boolean {
  const list = { ...registered(p) } as Record<string, Record<string, unknown>>;
  const before = JSON.stringify(list[name] ?? null);
  if (entry) list[name] = entry;
  else delete list[name];
  if (JSON.stringify(list[name] ?? null) === before) return false;
  writeFileSync(registryPath(p), JSON.stringify(list, null, 2) + "\n", { mode: 0o600 });
  return true;
}

const targets = (p: Paths, nodes: Registration["nodes"]) =>
  nodes === "all" ? true : Array.isArray(nodes) ? nodes.includes(p.node) : false;

/** Register (or with no entry, unregister) here, and announce it for the other nodes asked for. */
export async function registerServer(p: Paths, r: Registration, emit: Emit, write: WriteManaged,
                                     others: () => Promise<string[]>): Promise<Record<string, unknown>> {
  if (r.entry) {
    const problem = entryProblem(r.name, r.entry);
    if (problem) return { registered: false, reason: problem };
  }
  const here = r.nodes === undefined || targets(p, r.nodes);
  const changed = here ? setRegistered(p, r.name, r.entry ?? null) : false;
  const rendered = here && changed ? renderNow(p, write) : [];
  if (r.nodes !== undefined) {
    await emit(r.entry ? "mcp.registered" : "mcp.unregistered", { name: r.name, entry: r.entry ?? null, nodes: r.nodes });
  }
  const answer: Record<string, unknown> = {
    [r.entry ? "registered" : "unregistered"]: r.name,
    on: r.nodes === undefined ? [p.node] : r.nodes,
    here: here ? (changed ? "changed" : "already so") : "not this node",
    rendered,
  };
  if (r.nodes === undefined) {
    // The question the operator wanted asked: here only, or more?
    const elsewhere = (await others().catch(() => [] as string[])).filter((n) => n !== p.node);
    answer.also = elsewhere.length
      ? `claude-code also runs on ${elsewhere.join(", ")}. To ${r.entry ? "register" : "unregister"} it there too, call again with nodes: "all" or a list of those nodes.`
      : `To do the same on every node running claude-code, call again with nodes: "all".`;
  }
  return answer;
}

/** An `mcp.registered`/`mcp.unregistered` event from any node's claude-code: apply it if it names this node. */
export function onServerEvent(p: Paths, type: string, body: Registration, write: WriteManaged): string | null {
  if (!body?.name || !targets(p, body.nodes)) return null;
  const entry = type.endsWith("mcp.registered") ? body.entry ?? null : null;
  if (entry && entryProblem(body.name, entry)) return null;
  if (!setRegistered(p, body.name, entry)) return null;
  renderNow(p, write);
  return `${entry ? "registered" : "unregistered"} ${body.name} from an event`;
}

export { MANAGED_DIR };