/**
 * Server-side VOID credit ledger.
 * Stored in var/server-ledger.json (gitignored, created on first write).
 * Uses atomic rename for writes — safe on a single Next.js server.
 *
 * VOID credits are the authoritative balance for tool unlocks.
 * Rate: VOID_CREDIT_SATS_PER env var (default 1000 sats = 1 VOID).
 */

import fs from "fs";
import path from "path";
import os from "os";

// ─── Types ──────────────────────────────────────────────────────────────────

export type ToolUnlockRecord = {
  toolId: string;
  unlockedAt: number;
  voidSpent: number;
};

export type HandleRecord = {
  voidCredits: number;
  claimedInvoices: Record<string, number>; // invoiceId → void amount credited
  unlockedTools: ToolUnlockRecord[];
};

type LedgerData = {
  v: 1;
  handles: Record<string, HandleRecord>;
  /** invoiceId → handle — written at invoice creation so webhook can credit the right account */
  invoiceIndex: Record<string, string>;
};

// ─── File paths ──────────────────────────────────────────────────────────────

const VAR_DIR = path.join(process.cwd(), "var");
const LEDGER_PATH = path.join(VAR_DIR, "server-ledger.json");

// ─── Helpers ─────────────────────────────────────────────────────────────────

function ensureVarDir() {
  if (!fs.existsSync(VAR_DIR)) fs.mkdirSync(VAR_DIR, { recursive: true });
}

function emptyLedger(): LedgerData {
  return { v: 1, handles: {}, invoiceIndex: {} };
}

function emptyHandle(): HandleRecord {
  return { voidCredits: 0, claimedInvoices: {}, unlockedTools: [] };
}

// ─── I/O ─────────────────────────────────────────────────────────────────────

export function readLedger(): LedgerData {
  try {
    if (!fs.existsSync(LEDGER_PATH)) return emptyLedger();
    const raw = fs.readFileSync(LEDGER_PATH, "utf8");
    const parsed = JSON.parse(raw) as LedgerData;
    if (parsed?.v !== 1) return emptyLedger();
    parsed.handles ??= {};
    parsed.invoiceIndex ??= {};
    return parsed;
  } catch {
    return emptyLedger();
  }
}

function writeLedger(data: LedgerData): void {
  ensureVarDir();
  const tmp = path.join(os.tmpdir(), `cyberlux-ledger-${Date.now()}-${Math.random().toString(36).slice(2)}.json`);
  fs.writeFileSync(tmp, JSON.stringify(data, null, 2), "utf8");
  fs.renameSync(tmp, LEDGER_PATH); // atomic on same filesystem
}

function handleKey(handle: string): string {
  return handle.trim().toLowerCase();
}

// ─── Public API ───────────────────────────────────────────────────────────────

export function getVoidBalance(handle: string): number {
  const ledger = readLedger();
  return ledger.handles[handleKey(handle)]?.voidCredits ?? 0;
}

export function getHandleRecord(handle: string): HandleRecord {
  const ledger = readLedger();
  return ledger.handles[handleKey(handle)] ?? emptyHandle();
}

/** Register invoice → handle mapping when invoice is created. */
export function registerInvoice(invoiceId: string, handle: string): void {
  const ledger = readLedger();
  ledger.invoiceIndex[invoiceId] = handleKey(handle);
  writeLedger(ledger);
}

/** Look up which handle owns an invoice. */
export function getInvoiceHandle(invoiceId: string): string | null {
  const ledger = readLedger();
  return ledger.invoiceIndex[invoiceId] ?? null;
}

/** Whether this invoice has already been credited (prevents double-credit). */
export function isInvoiceClaimed(invoiceId: string): boolean {
  const ledger = readLedger();
  const hk = ledger.invoiceIndex[invoiceId];
  if (!hk) return false;
  return invoiceId in (ledger.handles[hk]?.claimedInvoices ?? {});
}

/**
 * Credit VOID credits to a handle for a settled invoice.
 * Returns false if invoice already credited.
 */
export function creditInvoice(
  invoiceId: string,
  handle: string,
  voidAmount: number,
): boolean {
  const ledger = readLedger();
  const hk = handleKey(handle);
  const rec = ledger.handles[hk] ?? emptyHandle();

  if (invoiceId in rec.claimedInvoices) return false;

  rec.voidCredits = Math.max(0, (rec.voidCredits ?? 0) + Math.max(0, Math.floor(voidAmount)));
  rec.claimedInvoices[invoiceId] = Math.floor(voidAmount);
  ledger.handles[hk] = rec;
  ledger.invoiceIndex[invoiceId] = hk;
  writeLedger(ledger);
  return true;
}

/**
 * Deduct VOID credits and mark a tool as unlocked.
 * Returns { ok: false } if insufficient balance.
 */
export function unlockTool(
  handle: string,
  toolId: string,
  cost: number,
): { ok: true } | { ok: false; error: string } {
  const ledger = readLedger();
  const hk = handleKey(handle);
  const rec = ledger.handles[hk] ?? emptyHandle();

  if (rec.unlockedTools.some((t) => t.toolId === toolId)) {
    return { ok: true }; // already unlocked, idempotent
  }

  if (rec.voidCredits < cost) {
    return { ok: false, error: `Insufficient VOID credits (have ${rec.voidCredits}, need ${cost})` };
  }

  rec.voidCredits -= cost;
  rec.unlockedTools.push({ toolId, unlockedAt: Date.now(), voidSpent: cost });
  ledger.handles[hk] = rec;
  writeLedger(ledger);
  return { ok: true };
}

/** Check if a handle has already unlocked a specific tool. */
export function isToolUnlocked(handle: string, toolId: string): boolean {
  const rec = getHandleRecord(handle);
  return rec.unlockedTools.some((t) => t.toolId === toolId);
}

/**
 * Simple deduction of VOID credits for arbitrary purchases (e.g. raffle tickets).
 * Returns { ok: false } if balance is insufficient.
 */
export function deductVoid(
  handle: string,
  amount: number,
  reason?: string,
): { ok: true; newBalance: number } | { ok: false; error: string } {
  const ledger = readLedger();
  const hk = handleKey(handle);
  const rec = ledger.handles[hk] ?? emptyHandle();
  if (rec.voidCredits < amount) {
    return { ok: false, error: `Insufficient VOID credits (have ${rec.voidCredits}, need ${amount}${reason ? ` for ${reason}` : ""})` };
  }
  rec.voidCredits -= amount;
  ledger.handles[hk] = rec;
  writeLedger(ledger);
  return { ok: true, newBalance: rec.voidCredits };
}

/** Admin: manually add VOID credits to a handle (operator use only). */
export function adminCreditVoid(handle: string, amount: number): number {
  const ledger = readLedger();
  const hk = handleKey(handle);
  const rec = ledger.handles[hk] ?? emptyHandle();
  rec.voidCredits = Math.max(0, rec.voidCredits + Math.max(0, Math.floor(amount)));
  ledger.handles[hk] = rec;
  writeLedger(ledger);
  return rec.voidCredits;
}

/** Return all handle records for admin views. */
export function getAllHandles(): Record<string, HandleRecord> {
  return readLedger().handles;
}

/** Conversion helpers */
export const SATS_PER_VOID = parseInt(process.env.VOID_CREDIT_SATS_PER ?? "1000", 10) || 1000;

export function satsToVoid(sats: number): number {
  return Math.floor(sats / SATS_PER_VOID);
}

export function usdToVoid(usd: number, btcUsdRate: number): number {
  const sats = Math.floor((usd / btcUsdRate) * 1e8);
  return satsToVoid(sats);
}