// Copyright (C) 2026 Whiterun LLC,
// This software is licensed under the GNU Lesser General Public License (LGPL), version 3.0 or later.
// A copy of the license can be found in the LICENSE file or at https://www.gnu.org/licenses/lgpl-3.0.html

/**
 * Dapp-side pubkey state manager.
 *
 * Stores xpub nodes received from the wallet and derives pubkeys on demand.
 *
 * Uses plain `number` for child indices (0=Receive, 1=Change, 7=Cauldron)
 * so this package has no dependency on chain-specific types.
 */

import { deriveHdPublicNodeChild } from "@bitauth/libauth";
import type { HdPublicNodeValid } from "@bitauth/libauth";

export class DappPubkeyStateManager {
  // xpub nodes for on-demand pubkey derivation
  private xpubNodes: Map<number, HdPublicNodeValid> = new Map();

  /** Derive a pubkey on demand from the stored xpub node. */
  getPubkey(childIndex: number, index: bigint): Uint8Array | undefined {
    const xpubNode = this.xpubNodes.get(childIndex);
    if (!xpubNode) return undefined;

    const child = deriveHdPublicNodeChild(xpubNode, Number(index));
    if (typeof child === "string") return undefined;
    return child.publicKey;
  }

  /** Returns true if an xpub node is available for this child index. */
  hasPath(childIndex: number): boolean {
    return this.xpubNodes.has(childIndex);
  }

  setXpubNode(childIndex: number, node: HdPublicNodeValid): void {
    this.xpubNodes.set(childIndex, node);
  }

  getXpubNode(childIndex: number): HdPublicNodeValid | undefined {
    return this.xpubNodes.get(childIndex);
  }
}