import { randomUUID } from 'node:crypto';
import { lstat, readFile } from 'node:fs/promises';
import { z } from 'zod';
import { parseAtomicXmr, XMR_RPC_UINT64_MAX } from '../../shared/xmr-amount.ts';
import { validateXmrAddress } from './xmr.ts';

const MAX_CONFIG_BYTES = 4096;
const MAX_RESPONSE_BYTES = 1024 * 1024;
const RPC_TIMEOUT_MS = 5000;
const MAX_TRANSFERS = 4096;
const configSchema = z.object({
  network: z.literal('mainnet'),
  url: z.string().min(1).max(2048),
  username: z.string().min(1).max(256),
  password: z.string().min(1).max(1024),
}).strict();
const rpcEnvelopeSchema = z.object({
  jsonrpc: z.literal('2.0'), id: z.string().uuid(), result: z.record(z.string(), z.unknown()),
}).strict();
const integerString = z.string().regex(/^(0|[1-9]\d{0,19})$/);
const heightResultSchema = z.object({ height: integerString, status: z.literal('OK') }).passthrough();
const addressResultSchema = z.object({ address: z.string().length(95), addresses: z.array(z.unknown()).optional(), status: z.literal('OK') }).passthrough();
const incomingTransferSchema = z.object({
  txid: z.string().regex(/^[a-f0-9]{64}$/),
  address: z.string().length(95),
  amount: integerString,
  height: integerString,
  timestamp: integerString,
  unlock_time: integerString,
  locked: z.boolean(),
  double_spend_seen: z.boolean(),
  subaddr_index: z.object({ major: integerString, minor: integerString }).strict(),
}).passthrough();
const transfersResultSchema = z.object({
  in: z.array(incomingTransferSchema).max(MAX_TRANSFERS).default([]),
  status: z.literal('OK'),
}).passthrough();

export type MoneroIncomingObservation = {
  observationId: string;
  transactionId: string;
  address: string;
  amountAtomicXmr: string;
  height: number;
  confirmations: number;
  timestamp: number;
  unlockTime: string;
  accountIndex: number;
  addressIndex: number;
  locked: boolean;
  doubleSpendSeen: boolean;
};
export type MoneroObservationPage = {
  network: 'mainnet';
  walletHeight: number;
  fromHeight: number;
  throughHeight: number;
  primaryAddress: string;
  incoming: MoneroIncomingObservation[];
};
export type MoneroFixtureTransport = (url: string, init: RequestInit) => Promise<Response>;

function integer(value: string, maximum: bigint, name: string): number {
  const parsed = BigInt(value);
  if (parsed > maximum || parsed > BigInt(Number.MAX_SAFE_INTEGER)) throw new Error(`Invalid Monero ${name}`);
  return Number(parsed);
}

/** JSON.parse rounds uint64 amounts. Convert JSON numeric tokens to strings before parsing,
 * preserving exact wallet-RPC integer text so all monetary values can be checked as bigint. */
function parseLosslessJson(text: string): unknown {
  let output = '', inString = false, escaped = false;
  for (let i = 0; i < text.length;) {
    const char = text[i];
    if (inString) {
      output += char;
      if (escaped) escaped = false;
      else if (char === '\\') escaped = true;
      else if (char === '"') inString = false;
      i++;
      continue;
    }
    if (char === '"') { inString = true; output += char; i++; continue; }
    if (char === '-' || (char >= '0' && char <= '9')) {
      const match = /^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/.exec(text.slice(i));
      if (!match) throw new Error('Invalid JSON numeric token');
      output += JSON.stringify(match[0]); i += match[0].length; continue;
    }
    output += char; i++;
  }
  return JSON.parse(output) as unknown;
}

function validateEndpoint(value: string): URL {
  let url: URL;
  try { url = new URL(value); } catch { throw new Error('Invalid Monero wallet-RPC endpoint'); }
  if (url.username || url.password || url.search || url.hash || url.pathname !== '/json_rpc') {
    throw new Error('Monero wallet-RPC endpoint must be a bare /json_rpc URL');
  }
  const loopback = url.hostname === '127.0.0.1' || url.hostname === '[::1]';
  if (url.protocol !== 'https:' && !(url.protocol === 'http:' && loopback)) {
    throw new Error('Wallet RPC requires HTTPS, except loopback-only HTTP');
  }
  if (!url.port && !['http:', 'https:'].includes(url.protocol)) throw new Error('Invalid Monero wallet-RPC port');
  return url;
}

export async function loadMoneroObserverConfig(env: NodeJS.ProcessEnv = process.env) {
  if (env.WIKIDECK_MONERO_OBSERVER !== '1') throw new Error('Monero observer is disabled');
  const path = env.WIKIDECK_MONERO_WALLET_RPC_CONFIG_FILE;
  if (!path) throw new Error('Monero wallet-RPC config file is required');
  try {
    const info = await lstat(path);
    if (!info.isFile() || info.isSymbolicLink() || info.size < 1 || info.size > MAX_CONFIG_BYTES) throw new Error();
    if (process.platform !== 'win32' && (info.mode & 0o077) !== 0) throw new Error();
    const parsed = configSchema.parse(JSON.parse(await readFile(path, 'utf8')));
    validateEndpoint(parsed.url);
    if (/[\r\n\x00]/.test(parsed.username) || /[\r\n\x00]/.test(parsed.password)) throw new Error();
    return parsed;
  } catch {
    throw new Error('Invalid or inaccessible Monero wallet-RPC config; credentials must be in a protected regular file');
  }
}

/** Restricted read-only surface. No generic RPC method, subaddress creation, transfer or sweep API exists. */
export function createMoneroWalletObserver(config: z.infer<typeof configSchema>, transport: MoneroFixtureTransport = fetch) {
  const endpoint = validateEndpoint(config.url);
  const authorization = `Basic ${Buffer.from(`${config.username}:${config.password}`).toString('base64')}`;
  async function rpc(method: 'get_height' | 'get_address' | 'get_transfers', params: Record<string, unknown> = {}) {
    const id = randomUUID(), controller = new AbortController();
    const timeout = setTimeout(() => controller.abort(), RPC_TIMEOUT_MS); timeout.unref();
    const abort = new Promise<never>((_, reject) => controller.signal.addEventListener('abort',
      () => reject(new Error('Monero wallet-RPC deadline exceeded')), { once: true }));
    const operation = (async () => {
      let response: Response;
      try {
        response = await transport(endpoint.href, { method: 'POST', redirect: 'error', signal: controller.signal,
          headers: { authorization, accept: 'application/json', 'content-type': 'application/json' },
          body: JSON.stringify({ jsonrpc: '2.0', id, method, params }) });
      } catch { throw new Error('Monero wallet-RPC request failed'); }
      if (!response.ok || response.redirected || !response.body ||
          !/^application\/json(?:\s*;|$)/i.test(response.headers.get('content-type') ?? '')) {
        await response.body?.cancel(); throw new Error('Monero wallet-RPC response rejected');
      }
      const contentLength = response.headers.get('content-length');
      if (contentLength !== null && (!/^\d+$/.test(contentLength) || Number(contentLength) > MAX_RESPONSE_BYTES)) {
        await response.body.cancel(); throw new Error('Monero wallet-RPC response exceeds size limit');
      }
      const reader = response.body.getReader(), chunks: Uint8Array[] = []; let size = 0;
      try {
        for (;;) {
          const part = await reader.read(); if (part.done) break;
          size += part.value.byteLength;
          if (size > MAX_RESPONSE_BYTES) throw new Error('Monero wallet-RPC response exceeds size limit');
          chunks.push(part.value);
        }
      } finally { await reader.cancel(); reader.releaseLock(); }
      let raw: unknown;
      try { raw = parseLosslessJson(new TextDecoder('utf-8', { fatal: true }).decode(Buffer.concat(chunks))); }
      catch { throw new Error('Monero wallet-RPC returned malformed JSON'); }
      const envelope = rpcEnvelopeSchema.parse(raw);
      if (envelope.id !== id) throw new Error('Monero wallet-RPC response ID mismatch');
      return envelope.result;
    })();
    try { return await Promise.race([operation, abort]); }
    finally { clearTimeout(timeout); }
  }
  return {
    async verifyMainnetWallet(): Promise<string> {
      const result = addressResultSchema.parse(await rpc('get_address', { account_index: 0 }));
      return validateXmrAddress(result.address);
    },
    async scanIncoming(fromHeight: number): Promise<MoneroObservationPage> {
      if (!Number.isSafeInteger(fromHeight) || fromHeight < 0) throw new Error('Invalid Monero scan height');
      const [heightRaw, primaryAddress] = await Promise.all([
        rpc('get_height'), this.verifyMainnetWallet(),
      ]);
      const walletHeight = integer(heightResultSchema.parse(heightRaw).height, BigInt(Number.MAX_SAFE_INTEGER), 'height');
      if (fromHeight > walletHeight) throw new Error('Monero observer cursor is ahead of wallet height');
      const transferRaw = transfersResultSchema.parse(await rpc('get_transfers', {
        in: true, filter_by_height: true, min_height: fromHeight, max_height: walletHeight,
      }));
      if (transferRaw.in.length >= MAX_TRANSFERS) throw new Error('Monero transfer page reached its safety limit; refusing to advance scan cursor');
      const incoming = await Promise.all(transferRaw.in.map(async item => {
        const amount = BigInt(item.amount);
        if (amount <= 0n || amount > XMR_RPC_UINT64_MAX) throw new Error('Invalid incoming Monero amount');
        const address = item.address;
        await validateXmrAddress(address);
        const height = integer(item.height, BigInt(Number.MAX_SAFE_INTEGER), 'transfer height');
        if (height < fromHeight || height > walletHeight) throw new Error('Wallet returned transfer outside requested height range');
        const major = integer(item.subaddr_index.major, 0xffffffffn, 'account index');
        const minor = integer(item.subaddr_index.minor, 0xffffffffn, 'address index');
        return { observationId: `${item.txid}:${major}:${minor}`, transactionId: item.txid, address,
          amountAtomicXmr: amount.toString(), height, confirmations: walletHeight - height + 1,
          timestamp: integer(item.timestamp, BigInt(Number.MAX_SAFE_INTEGER), 'timestamp'),
          unlockTime: item.unlock_time, accountIndex: major, addressIndex: minor,
          locked: item.locked, doubleSpendSeen: item.double_spend_seen };
          }));
      const unique = new Set(incoming.map(row => row.observationId));
      if (unique.size !== incoming.length) throw new Error('Duplicate Monero wallet output observation');
      return { network: 'mainnet', walletHeight, fromHeight, throughHeight: walletHeight, primaryAddress, incoming };
    },
  };
}