// 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 through this module is **state, not an event** (novox/hq ADR 0202): one
//     key per server in the module's `servers` bucket — `all.<server>` for every node, `<node>.<server>`
//     for one — which every node watches. A node that joins later, or was off, reads the whole current set
//     at start; unregistering is a delete. A secret never goes in an entry: the runtime refuses one.

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: "reason" in d ? d.reason : undefined }; // narrowed by hand: the build compiles without strict
    // 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[];
}

/** The `servers` state, as this module reaches it through the runtime (`state("servers")` in the SDK). */
export interface ServerState {
  put(key: string, value: Record<string, unknown>): Promise<number>;
  delete(key: string): Promise<void>;
  keys(): Promise<string[]>;
}

/** One change to the `servers` state, as a watch hands it over. */
export interface ServerChange {
  key: string;
  op: "put" | "delete";
  value?: Record<string, unknown>;
}

/** The key a registration lives at: `all.<server>` for every node, `<node>.<server>` for one. */
export const keyOf = (scope: string, name: string) => `${scope}.${name}`;

/**
 * What this node takes from the `servers` state: the entries for every node and for this one, by key —
 * kept in memory from the watch, and written through to the module's own file whenever what applies here
 * changes, so the managed directory can be rendered without the bus.
 */
export class ServerView {
  private readonly entries = new Map<string, Record<string, unknown>>();
  constructor(private readonly p: Paths) {}

  /** Take one change; answers whether what applies to this node changed. */
  take(c: ServerChange): boolean {
    const dot = c.key.indexOf(".");
    const scope = c.key.slice(0, dot), name = c.key.slice(dot + 1);
    if (dot <= 0 || (scope !== "all" && scope !== this.p.node)) return false;
    if (c.op === "put" && c.value && entryProblem(name, c.value) === null) this.entries.set(c.key, c.value);
    else this.entries.delete(c.key);
    return this.writeThrough();
  }

  /** What applies here: every node's entries, with this node's own laid over them by server name. */
  effective(): Servers {
    const out: Record<string, Record<string, unknown>> = {};
    for (const scope of ["all", this.p.node]) {
      for (const [key, entry] of [...this.entries].sort(([a], [b]) => a.localeCompare(b))) {
        if (key.startsWith(scope + ".")) out[key.slice(scope.length + 1)] = entry;
      }
    }
    return out;
  }

  private writeThrough(): boolean {
    const now = JSON.stringify(this.effective(), null, 2) + "\n";
    let before = "";
    try {
      before = readFileSync(registryPath(this.p), "utf8");
    } catch {
      /* none yet */
    }
    if (now === before) return false;
    writeFileSync(registryPath(this.p), now, { mode: 0o600 });
    return true;
  }
}

/** A change from the watch: take it, and render when what applies here changed. */
export function onServerChange(view: ServerView, c: ServerChange, p: Paths, write: WriteManaged): string | null {
  if (!view.take(c)) return null;
  renderNow(p, write);
  return `${c.op === "put" ? "registered" : "unregistered"} ${c.key}`;
}

const scopesOf = (p: Paths, nodes: Registration["nodes"]): string[] =>
  nodes === undefined ? [p.node] : nodes === "all" ? ["all"] : nodes;

/**
 * Register (or with no entry, unregister) a server: a put (or delete) per scope in the `servers` state.
 * Taken into this node's view at once, so the answer says what it did here; every other node takes it
 * from its watch, and a node that joins later from the current state.
 */
export async function registerServer(p: Paths, r: Registration, servers: ServerState, view: ServerView,
                                     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 scopes = scopesOf(p, r.nodes);
  // Compared before and after rather than read from take(): this node's own watch may hand the view the
  // same change first, and then take() here finds nothing new although this call made it.
  const before = JSON.stringify(view.effective());
  for (const scope of scopes) {
    const key = keyOf(scope, r.name);
    if (r.entry) await servers.put(key, r.entry);
    else await servers.delete(key);
    view.take({ key, op: r.entry ? "put" : "delete", value: r.entry });
  }
  const changedHere = JSON.stringify(view.effective()) !== before;
  const here = scopes.includes("all") || scopes.includes(p.node);
  const answer: Record<string, unknown> = {
    [r.entry ? "registered" : "unregistered"]: r.name,
    on: r.nodes === undefined ? [p.node] : r.nodes,
    here: here ? (changedHere ? "changed" : "already so") : "not this node",
    rendered: changedHere ? renderNow(p, write) : [],
  };
  if (!r.entry && view.effective()[r.name]) {
    answer.still = `${r.name} still applies here from another registration (for every node, or for this one); unregister that too`;
  }
  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;
}

export { MANAGED_DIR };