// The tool runtime — the thin per-node process that makes a module's tools actually serve. It
// binds the mesh broker, loads the assigned modules' tool entrypoints (each of which calls
// registerModuleTools as it imports), and hands them to the sdk's serving harness. Everything hard
// — dispatch, collection, duplicate-name safety — is the sdk's; this is the wrapper.

import { pathToFileURL } from "node:url";
import { resolve } from "node:path";
import { useBroker } from "@novox/mesh-sdk/messaging";
import { collectTools, toolKey } from "@novox/mesh-sdk/tools";
import type { Broker } from "@novox/mesh-sdk/messaging";
import { seatToolSubject, type Credential, type RuntimeBroker } from "./broker-nats.js";

/**
 * The one verb every module's runtime answers for it (novox/hq ADR 0152, design 34 §3): the
 * module's tool names, descriptions and argument schemas, from the code that answers them and
 * from nowhere else. Discovery asks the module, because a copy kept anywhere else drifts.
 */
export const TOOLS_VERB = "tools";

/** What `tools` answers for one module. */
export interface ToolsAnswer {
  module: string;
  tools: {
    name: string;
    description: string;
    input: Readonly<Record<string, unknown>>;
    /** Where this tool is answered, as the mesh issued it (ADR 0160): the module's plain subject
     *  first when there is one, then this machine's. A caller composes nothing. */
    subjects?: string[];
  }[];
}

export interface RuntimeOptions {
  /** The mesh broker to serve over. */
  broker: Broker;
  /** Absolute paths to the assigned modules' compiled tool entrypoints (e.g. .../umami/tools/index.js). */
  moduleEntrypoints: string[];
  /** The credential the mesh delivered, for what it says about the seats this module claims
   *  (novox/hq ADR 0159). Absent for a runtime started by hand, which then serves no seat. */
  credential?: Credential;
}

/** Load the modules, bind the broker, and serve. Returns a stop function that unhooks serving. */
export async function runTools(opts: RuntimeOptions): Promise<() => void> {
  useBroker(() => opts.broker);

  for (const entry of opts.moduleEntrypoints) {
    // Importing the entrypoint runs its registerModuleTools(...) — that is the whole handshake.
    await import(pathToFileURL(resolve(entry)).href);
  }

  // Serve the RPC endpoint only if a module actually registered a tool. A pure-events module (the
  // audit logger) registers none, and its scoped account may not declare the serve queue — so a
  // runtime that always served would fail for exactly the modules that never needed it.
  // A registration under a seat's name is the module's implementation of that seat's verbs
  // (ADR 0159, 0160): served on the seat's subjects by serveClaimedSeats, never as a module's
  // tools and never listed among them. Everything else is the module's own.
  // A module named like its seat (the catalogue is the mesh-catalog seat) registers once and is
  // both: its tools are the module's and the seat's verbs alike.
  const self = opts.credential?.module;
  const seatNames = new Set((opts.credential?.claims ?? []).map((c) => c.seat));
  const ownRegistrations = collectTools().filter(({ module }) => module === self || !seatNames.has(module));
  const tools = ownRegistrations.flatMap(({ module, tools: own }) => own.map((t) => ({ module, name: t.name })));
  const stops: Array<() => void> = [];
  const stop = (): void => stops.splice(0).forEach((s) => s());
  // Each tool on its own key, namespaced by its module (ADR 0047); where that key is answered is
  // the broker's to know from the membership (ADR 0160).
  for (const { module, tools: own } of ownRegistrations) {
    const seen = new Set<string>();
    for (const t of own) {
      if (seen.has(t.name)) {
        stop();
        throw new Error(`${module} exposes two tools named ${t.name} — refused`);
      }
      seen.add(t.name);
      stops.push(await opts.broker.handle(toolKey(module, t.name), (args: Record<string, unknown> | undefined) => t.run(args ?? {})));
    }
  }

  // And, for every module that serves any, the verb that says what it serves. Refused before
  // anything is bound if a module named a tool of its own `tools`: one name answering two things
  // is the fault nobody can diagnose afterwards, and the runtime is the only place that sees both.
  const runtime = opts.broker as RuntimeBroker;
  for (const { module, tools: own } of ownRegistrations) {
    if (own.length === 0) continue;
    if (own.some((t) => t.name === TOOLS_VERB)) {
      stop();
      throw new Error(
        `${module} names a tool "${TOOLS_VERB}", which is the verb the runtime answers for every ` +
          "module with what it serves (novox/hq ADR 0152) — refused, rename it",
      );
    }
    const subjectsOf = (tool: string): string[] | undefined => {
      const issued = typeof runtime.membership === "function" ? runtime.membership() : undefined;
      if (!issued) return undefined;
      const plain = issued.serves.filter((s) => s.queue).map((s) => s.subject.replace("{tool}", tool));
      const mine = issued.serves.filter((s) => !s.queue).map((s) => s.subject.replace("{tool}", tool));
      return [...plain, ...mine];
    };
    const answer: ToolsAnswer = {
      module,
      tools: own.map((t) => ({ name: t.name, description: t.description, input: t.input, subjects: subjectsOf(t.name) })),
    };
    stops.push(await opts.broker.handle(toolKey(module, TOOLS_VERB), async () => answer));
  }

  console.log(`[mesh-tools] serving ${tools.length} tool(s): ${tools.map((t) => t.name).join(", ") || "(none)"}`);
  stops.push(await serveClaimedSeats(opts.broker as RuntimeBroker, opts.credential));
  return () => {
    for (const s of stops) s();
  };
}

/**
 * Holding a seat means serving its tools (design 33 §3, novox/hq ADR 0159). The credential names the
 * seats this module claims and the verbs each promises; each verb is served on the seat's own
 * subject by the module's tool of the same name. Whether this instance *holds* the seat is the bus's
 * to decide: only the holder's account may subscribe the seat's subjects, so a claimant that does not
 * hold it here is refused the subscription and serves nothing — never a failure of its own tools.
 */
async function serveClaimedSeats(broker: RuntimeBroker, credential?: Credential): Promise<() => void> {
  const claims = credential?.claims ?? [];
  if (claims.length === 0 || typeof broker.handleSubject !== "function") return () => {};
  // A seat's verbs are the role's, not the software's (ADR 0159): implemented under the seat's
  // name — `registerModuleTools("mesh-store", …)` — and never confused with the module's own tools.
  const implementations = new Map<string, Map<string, (args: Record<string, unknown>) => Promise<unknown>>>();
  for (const { module, tools } of collectTools()) {
    if (!claims.some((c) => c.seat === module)) continue;
    const verbs = new Map<string, (args: Record<string, unknown>) => Promise<unknown>>();
    for (const t of tools) verbs.set(t.name, (args) => t.run(args));
    implementations.set(module, verbs);
  }
  let stops: (() => void)[] = [];
  const serve = async (): Promise<void> => {
    stops.forEach((s) => s());
    stops = [];
    const issued = typeof broker.membership === "function" ? broker.membership() : undefined;
    for (const claim of claims) {
      const verbs = implementations.get(claim.seat);
      for (const verb of claim.serves ?? []) {
        const run = verbs?.get(verb);
        if (!run) {
          console.log(`[mesh-tools] claims ${claim.seat} and implements no ${verb}, which that seat promises; not served`);
          continue;
        }
        // Where the mesh issued the verb when it has; the derived shape until then.
        const subject = issued?.seats?.find((s) => s.seat === claim.seat && s.verb === verb)?.subject
          ?? seatToolSubject(claim.seat, verb, claim.scope, credential?.node);
        stops.push(await broker.handleSubject(subject, run));
        console.log(`[mesh-tools] serving ${claim.seat}'s ${verb} on ${subject}, admitted where this module holds the seat`);
      }
    }
  };
  await serve();
  if (typeof broker.onMembership === "function") broker.onMembership(() => void serve());
  return () => stops.forEach((s) => s());
}