/**
 * FIN-link sandbox (gap-analysis v2 §7.1 / §10.6).
 *
 * The SWIFT generators under `services/swift/` produce strings — but
 * the architecture note §4.3 requires an actual transport. Until a
 * production FIN-link / Alliance Access integration ships, this
 * sandbox service stands in as the outbound transport so the full
 * lifecycle (dispatch → ack → accept → settle) can be exercised end
 * to end in dev + E2E.
 *
 * The sandbox:
 *
 *   1. Accepts an outbound SWIFT/ISO payload via POST /dispatch.
 *   2. Assigns a FIN reference, stores the message in memory, and
 *      returns a synchronous ack (200).
 *   3. Advances the message through a deterministic lifecycle:
 *        received -> acknowledged -> accepted -> settled
 *      on each tick of an internal clock (configurable via
 *      setTickIntervalMs for tests).
 *   4. Exposes GET /messages/:reference + GET /messages for polling.
 *   5. Optionally POSTs a webhook on each state change when a caller
 *      supplies `webhookUrl` in the dispatch request.
 *
 * The sandbox is intentionally process-local. Production transports
 * should back this interface with a real FIN queue / Alliance Web
 * Platform gateway.
 */

import { createHmac, randomBytes } from "crypto";
import express, { Router, type Request, type Response } from "express";

export type FinMessageState =
  | "received"
  | "acknowledged"
  | "accepted"
  | "settled"
  | "rejected";

export type FinMessageType =
  | "MT760"
  | "MT202"
  | "pacs.009"
  | "pacs.008"
  | "camt.025"
  | "camt.054"
  | "unknown";

export interface FinMessage {
  reference: string;
  messageType: FinMessageType;
  payload: string;
  state: FinMessageState;
  receivedAt: string;
  updatedAt: string;
  stateHistory: Array<{ state: FinMessageState; at: string }>;
  webhookUrl?: string;
  planId?: string;
  endToEndId?: string;
}

export interface DispatchRequest {
  messageType: FinMessageType;
  payload: string;
  planId?: string;
  endToEndId?: string;
  webhookUrl?: string;
}

export interface DispatchResponse {
  reference: string;
  state: FinMessageState;
  ackedAt: string;
}

const store = new Map<string, FinMessage>();

// Deterministic lifecycle progression.
const ORDER: FinMessageState[] = [
  "received",
  "acknowledged",
  "accepted",
  "settled",
];

function nextState(current: FinMessageState): FinMessageState | null {
  const idx = ORDER.indexOf(current);
  if (idx < 0 || idx === ORDER.length - 1) return null;
  return ORDER[idx + 1];
}

function genReference(): string {
  return `FIN-${randomBytes(6).toString("hex").toUpperCase()}`;
}

export function finSignature(payload: string): string {
  const secret = process.env.FIN_SANDBOX_SECRET || "fin-sandbox-dev-secret";
  return createHmac("sha256", secret).update(payload).digest("hex");
}

export function recordDispatch(req: DispatchRequest): FinMessage {
  const reference = genReference();
  const now = new Date().toISOString();
  const msg: FinMessage = {
    reference,
    messageType: req.messageType,
    payload: req.payload,
    state: "received",
    receivedAt: now,
    updatedAt: now,
    stateHistory: [{ state: "received", at: now }],
    webhookUrl: req.webhookUrl,
    planId: req.planId,
    endToEndId: req.endToEndId,
  };
  store.set(reference, msg);
  return msg;
}

export async function advance(reference: string): Promise<FinMessage | null> {
  const msg = store.get(reference);
  if (!msg) return null;
  const next = nextState(msg.state);
  if (!next) return msg;
  const at = new Date().toISOString();
  msg.state = next;
  msg.updatedAt = at;
  msg.stateHistory.push({ state: next, at });
  if (msg.webhookUrl) {
    await emitWebhook(msg).catch(() => undefined);
  }
  return msg;
}

export function rejectMessage(
  reference: string,
  reason: string,
): FinMessage | null {
  const msg = store.get(reference);
  if (!msg) return null;
  const at = new Date().toISOString();
  msg.state = "rejected";
  msg.updatedAt = at;
  msg.stateHistory.push({ state: "rejected", at });
  (msg as FinMessage & { rejectionReason?: string }).rejectionReason = reason;
  return msg;
}

export function getMessage(reference: string): FinMessage | undefined {
  return store.get(reference);
}

export function listMessages(filter?: { planId?: string }): FinMessage[] {
  const all = Array.from(store.values());
  if (!filter?.planId) return all;
  return all.filter((m) => m.planId === filter.planId);
}

export function resetSandboxForTests(): void {
  store.clear();
}

async function emitWebhook(msg: FinMessage): Promise<void> {
  if (!msg.webhookUrl) return;
  const body = JSON.stringify({
    reference: msg.reference,
    messageType: msg.messageType,
    state: msg.state,
    updatedAt: msg.updatedAt,
    planId: msg.planId,
    endToEndId: msg.endToEndId,
  });
  const signature = finSignature(body);
  try {
    await fetch(msg.webhookUrl, {
      method: "POST",
      headers: {
        "content-type": "application/json",
        "x-fin-sandbox-signature": signature,
      },
      body,
    });
  } catch {
    // swallow — the sandbox is best-effort in dev
  }
}

// ---------------------------------------------------------------------------
// HTTP router
// ---------------------------------------------------------------------------

export function buildSandboxRouter(): Router {
  const r = Router();
  r.use(express.json({ limit: "5mb" }));

  r.post("/dispatch", (req: Request, res: Response) => {
    const body = req.body as Partial<DispatchRequest>;
    if (
      !body ||
      typeof body.payload !== "string" ||
      typeof body.messageType !== "string"
    ) {
      return res.status(400).json({
        error: "messageType and payload are required",
      });
    }
    const msg = recordDispatch({
      messageType: body.messageType as FinMessageType,
      payload: body.payload,
      planId: body.planId,
      endToEndId: body.endToEndId,
      webhookUrl: body.webhookUrl,
    });
    const response: DispatchResponse = {
      reference: msg.reference,
      state: msg.state,
      ackedAt: msg.updatedAt,
    };
    return res.status(202).json(response);
  });

  r.post("/advance/:reference", async (req: Request, res: Response) => {
    const msg = await advance(req.params.reference);
    if (!msg) return res.status(404).json({ error: "not found" });
    return res.json(msg);
  });

  r.post("/reject/:reference", (req: Request, res: Response) => {
    const reason =
      typeof req.body?.reason === "string" ? req.body.reason : "rejected";
    const msg = rejectMessage(req.params.reference, reason);
    if (!msg) return res.status(404).json({ error: "not found" });
    return res.json(msg);
  });

  r.get("/messages/:reference", (req: Request, res: Response) => {
    const msg = getMessage(req.params.reference);
    if (!msg) return res.status(404).json({ error: "not found" });
    return res.json(msg);
  });

  r.get("/messages", (req: Request, res: Response) => {
    const planId =
      typeof req.query.planId === "string" ? req.query.planId : undefined;
    return res.json({ messages: listMessages({ planId }) });
  });

  return r;
}

// ---------------------------------------------------------------------------
// Timer-driven auto-progress (optional; off by default in tests)
// ---------------------------------------------------------------------------

let tickTimer: NodeJS.Timeout | null = null;

export function startAutoProgress(intervalMs = 2_000): void {
  stopAutoProgress();
  tickTimer = setInterval(() => {
    for (const msg of store.values()) {
      if (msg.state !== "settled" && msg.state !== "rejected") {
        void advance(msg.reference);
      }
    }
  }, intervalMs);
  // Allow the Node process to exit while this timer is pending.
  if (typeof tickTimer.unref === "function") tickTimer.unref();
}

export function stopAutoProgress(): void {
  if (tickTimer) {
    clearInterval(tickTimer);
    tickTimer = null;
  }
}