From 317e4d73ddd76d80cd50472f89d9f006ac52f736 Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Fri, 22 Aug 2025 02:31:22 -0700
Subject: [PATCH] Implement class to represent Nano addresses.

---
 src/lib/account/address.ts | 74 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 src/lib/account/address.ts

diff --git a/src/lib/account/address.ts b/src/lib/account/address.ts
new file mode 100644
index 0000000..2633ee7
--- /dev/null
+++ b/src/lib/account/address.ts
@@ -0,0 +1,74 @@
+//! SPDX-FileCopyrightText: 2025 Chris Duncan <chris@zoso.dev>
+//! SPDX-License-Identifier: GPL-3.0-or-later
+
+import { ACCOUNT_KEY_HEX_LENGTH, ALPHABET, PREFIX, PREFIX_LEGACY } from "../constants"
+import { base32, bytes, hex } from "../convert"
+import { Blake2b } from "../crypto"
+
+class Address {
+	#address: string
+
+	/**
+	* Converts a public key to a Nano address.
+	*
+	* @param {Uint8Array} publicKey - Public key bytes as Uint8Array
+	* @returns Nano address string using `nano_` prefix
+	*/
+	static fromPublicKey (publicKey: ArrayBuffer | Uint8Array<ArrayBuffer>): string {
+		const checksum = new Blake2b(5).update(publicKey).digest().reverse()
+		const encodedPublicKey = bytes.toBase32(publicKey)
+		const encodedChecksum = bytes.toBase32(checksum)
+		return `${PREFIX}${encodedPublicKey}${encodedChecksum}`
+	}
+
+	constructor (address: string)
+	constructor (publicKey: string | ArrayBuffer | Uint8Array<ArrayBuffer>)
+	constructor (value: unknown) {
+		if (typeof value !== 'string' && !(value instanceof ArrayBuffer) && !(value instanceof Uint8Array)) {
+			throw new TypeError('Invalid address input', { cause: value })
+		}
+		if (typeof value === 'string') {
+			if (RegExp(`^[A-F0-9]{${ACCOUNT_KEY_HEX_LENGTH}}$`, 'i').test(value)) {
+				this.#address = Address.fromPublicKey(hex.toBuffer(value))
+			} else if (RegExp(`^(${PREFIX}|${PREFIX_LEGACY})[13][${ALPHABET}]{59}$`).test(value)) {
+				this.#address = value
+			} else {
+				throw new TypeError('Invalid address input', { cause: value })
+			}
+		} else if (value instanceof ArrayBuffer || value instanceof Uint8Array) {
+			const v = new Uint8Array(value)
+			this.#address = Address.fromPublicKey(v)
+		} else {
+			throw new TypeError('Invalid address input', { cause: value })
+		}
+		this.#address = this.#address.replace(PREFIX_LEGACY, PREFIX)
+	}
+
+	[Symbol.toPrimitive] (hint: string) {
+		if (hint === 'string' || hint === 'default') {
+			return this.#address
+		}
+		throw new SyntaxError('invalid Address syntax')
+	}
+
+	get length (): number { return `${PREFIX}${this.#address}`.length }
+
+	toString (): string { return `${PREFIX}${this.#address}` }
+
+	valueOf (): string { return `${PREFIX}${this.#address}` }
+
+	/**
+	* Converts a Nano address to a public key.
+	*
+	* @returns Public key bytes as ArrayBuffer
+	*/
+	toPublicKey (): ArrayBuffer {
+		const publicKey = base32.toBuffer(this.#address.slice(-60, -8))
+		const checksum = base32.toBuffer(this.#address.slice(-8))
+		const rechecksum = new Blake2b(5).update(publicKey).digest().reverse()
+		if (bytes.toHex(checksum) !== bytes.toHex(rechecksum)) {
+			throw new Error('Checksum mismatch in address')
+		}
+		return publicKey
+	}
+}
-- 
2.47.3