// Storage left on the Sia account: the indexer's GET /account, signed with
// the app key s3d registered at login (it lives in s3d's own database, and
// is only read here to sign this one request; it is never sent anywhere).
// The signature scheme is indexd's (api/app/auth.go requestHash + client.go
// sign): BLAKE2b-256 over method, host, path and the expiry, Ed25519-signed,
// passed as ?sv=<unix expiry>&sc=<pubkey>&ss=<signature> (URL-safe base64).
import crypto from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';

// ---- BLAKE2b-256 (RFC 7693) ----------------------------------------------
// Node only ships blake2b512, and Sia hashes are the 256-bit variant, which
// is a different parameter block, not a truncation. Inputs here are tiny,
// so plain BigInt arithmetic is fine.
const M64 = (1n << 64n) - 1n;
const IV = [
  0x6a09e667f3bcc908n, 0xbb67ae8584caa73bn, 0x3c6ef372fe94f82bn, 0xa54ff53a5f1d36f1n,
  0x510e527fade682d1n, 0x9b05688c2b3e6c1fn, 0x1f83d9abfb41bd6bn, 0x5be0cd19137e2179n,
];
const SIGMA = [
  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15], [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3],
  [11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4], [7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8],
  [9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13], [2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9],
  [12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11], [13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10],
  [6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5], [10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0],
];
const rotr = (x, n) => ((x >> BigInt(n)) | (x << BigInt(64 - n))) & M64;

export function blake2b256(data) {
  const outLen = 32;
  const h = IV.slice();
  h[0] ^= 0x01010000n ^ BigInt(outLen);
  const buf = Buffer.from(data);
  const blocks = Math.max(1, Math.ceil(buf.length / 128));
  for (let b = 0; b < blocks; b++) {
    const last = b === blocks - 1;
    const block = Buffer.alloc(128);
    buf.copy(block, 0, b * 128, Math.min(buf.length, (b + 1) * 128));
    const m = Array.from({ length: 16 }, (_, i) => block.readBigUInt64LE(i * 8));
    const t = BigInt(last ? buf.length : (b + 1) * 128);
    const v = [...h, ...IV];
    v[12] ^= t & M64;
    v[13] ^= t >> 64n;
    if (last) v[14] ^= M64;
    const G = (a, bb, c, d, x, y) => {
      v[a] = (v[a] + v[bb] + x) & M64; v[d] = rotr(v[d] ^ v[a], 32);
      v[c] = (v[c] + v[d]) & M64; v[bb] = rotr(v[bb] ^ v[c], 24);
      v[a] = (v[a] + v[bb] + y) & M64; v[d] = rotr(v[d] ^ v[a], 16);
      v[c] = (v[c] + v[d]) & M64; v[bb] = rotr(v[bb] ^ v[c], 63);
    };
    for (let r = 0; r < 12; r++) {
      const s = SIGMA[r % 10];
      G(0, 4, 8, 12, m[s[0]], m[s[1]]); G(1, 5, 9, 13, m[s[2]], m[s[3]]);
      G(2, 6, 10, 14, m[s[4]], m[s[5]]); G(3, 7, 11, 15, m[s[6]], m[s[7]]);
      G(0, 5, 10, 15, m[s[8]], m[s[9]]); G(1, 6, 11, 12, m[s[10]], m[s[11]]);
      G(2, 7, 8, 13, m[s[12]], m[s[13]]); G(3, 4, 9, 14, m[s[14]], m[s[15]]);
    }
    for (let i = 0; i < 8; i++) h[i] ^= v[i] ^ v[i + 8];
  }
  const out = Buffer.alloc(64);
  h.forEach((x, i) => out.writeBigUInt64LE(x, i * 8));
  return out.subarray(0, outLen);
}

// ---- indexd request signing ---------------------------------------------------
const PKCS8_ED25519 = Buffer.from('302e020100300506032b657004220420', 'hex');

export function signIndexerUrl(appKey, method, endpointUrl, validUntilSec) {
  const u = new URL(endpointUrl);
  const until = Buffer.alloc(8);
  until.writeBigUInt64LE(BigInt(validUntilSec));
  const hash = blake2b256(Buffer.concat([Buffer.from(method), Buffer.from(u.host), Buffer.from(u.pathname), until]));
  const seed = Buffer.from(appKey).subarray(0, 32); // a Sia private key is seed || public key
  const key = crypto.createPrivateKey({ key: Buffer.concat([PKCS8_ED25519, seed]), format: 'der', type: 'pkcs8' });
  const pub = crypto.createPublicKey(key).export({ format: 'der', type: 'spki' }).subarray(-32);
  const sig = crypto.sign(null, hash, key);
  const b64 = (b) => Buffer.from(b).toString('base64').replace(/\+/g, '-').replace(/\//g, '_');
  u.searchParams.set('sv', String(validUntilSec));
  u.searchParams.set('sc', b64(pub));
  u.searchParams.set('ss', b64(sig));
  return u;
}

// ---- s3d's app key -------------------------------------------------------------
export async function readAppKey(dataDir) {
  const file = path.join(dataDir, 's3d.db');
  if (!fs.existsSync(file)) return null;
  let DatabaseSync;
  try { ({ DatabaseSync } = await import('node:sqlite')); } catch { return null; }
  const db = new DatabaseSync(file, { readOnly: true });
  try {
    const row = db.prepare('SELECT app_key, indexer_url FROM global_settings LIMIT 1').get();
    if (!row || !row.app_key) return null;
    return { appKey: Buffer.from(row.app_key), indexerUrl: String(row.indexer_url || '') };
  } finally { db.close(); }
}

// { maxPinnedData, pinnedData, remainingStorage } in bytes, from the indexer.
export async function accountSpace(dataDir, { fetchImpl = fetch } = {}) {
  const k = await readAppKey(dataDir);
  if (!k || !k.indexerUrl) return null;
  const base = k.indexerUrl.replace(/\/+$/, '');
  const url = signIndexerUrl(k.appKey, 'GET', `${base}/account`, Math.floor(Date.now() / 1000) + 120);
  k.appKey.fill(0);
  const res = await fetchImpl(url, { headers: { accept: 'application/json' }, signal: AbortSignal.timeout(15_000) });
  if (!res.ok) throw new Error(`indexer answered ${res.status}: ${(await res.text()).slice(0, 200)}`);
  const j = await res.json();
  return { maxPinnedData: Number(j.maxPinnedData), pinnedData: Number(j.pinnedData), remainingStorage: Number(j.remainingStorage), indexer: new URL(base).host };
}