From ca7372b29f07442aae6682c223ad5f0483786c59 Mon Sep 17 00:00:00 2001
From: lwvemike <plamadeala.mihai002@gmail.com>
Date: Wed, 20 Mar 2024 02:36:34 +0200
Subject: [PATCH] feat: create header structure

---
 .vscode/settings.json |   3 +
 eslint.config.js      |   2 +-
 src/index.ts          | 124 ++++++++++++++++++++++++++++++++++++++++++
 test/index.test.ts    |  41 +++++++++++++-
 4 files changed, 166 insertions(+), 4 deletions(-)

diff --git a/.vscode/settings.json b/.vscode/settings.json
index c5632ba..8fbde55 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -37,5 +37,8 @@
     "json",
     "jsonc",
     "yaml"
+  ],
+  "cSpell.words": [
+    "Tacacs"
   ]
 }
diff --git a/eslint.config.js b/eslint.config.js
index 64149c8..da75f40 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -9,7 +9,7 @@ export default antfu(
   },
   {
     rules: {
-      // overrides
+      curly: ['error', 'all'],
     },
   },
 )
diff --git a/src/index.ts b/src/index.ts
index e69de29..cb59390 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -0,0 +1,124 @@
+import type { Buffer } from 'node:buffer'
+
+class TacacsPlusError extends Error {
+  constructor(message: string) {
+    super(`[@noction/tacacs-plus] ${message}`)
+  }
+}
+
+const _DEFAULT_PORT = 49
+const _TAC_PLUS_MAJOR_VER = 0xC
+const _TAC_PLUS_MINOR_VER_DEFAULT = 0x0
+const _TAC_PLUS_MINOR_VER_ONE = 0x1
+
+export enum Flags {
+  TAC_PLUS_UNENCRYPTED_FLAG = 0x01,
+  TAC_PLUS_SINGLE_CONNECT_FLAG = 0x04,
+}
+
+export enum PacketType {
+  TAC_PLUS_AUTHEN = 0x01, // Authentication
+  TAC_PLUS_AUTHOR = 0x02, // Authorization
+  TAC_PLUS_ACCT = 0x03, // Accounting
+}
+
+export class Header {
+  #majorVersion: number // 4 bits
+  #minorVersion: number // 4 bits
+  #type: PacketType // 1 byte
+  #seqNo: number // 1 byte
+  #flags: Flags// 1 byte
+  #sessionId: number // 4 bytes
+  #length: number // 4 bytes
+
+  constructor(
+    majorVersion: number,
+    minorVersion: number,
+    type: PacketType,
+    seqNo: number,
+    flags: number,
+    sessionId: number,
+    length: number,
+  ) {
+    this.#majorVersion = majorVersion
+    this.#minorVersion = minorVersion
+    this.#type = type
+    this.#seqNo = seqNo
+    this.#flags = flags
+    this.#sessionId = sessionId
+    this.#length = length
+  }
+
+  /**
+   * @throws TacacsPlusError
+   * @param raw
+   * @returns
+   */
+  static decodeHeader(raw: Buffer) {
+    if (raw.length !== Header.SIZE) {
+      throw new TacacsPlusError(`Header size must be ${Header.SIZE}, but received ${raw.length}`)
+    }
+
+    let offset = 0
+
+    const versionByte = raw.subarray(offset, 1).readUInt8(0)
+    offset += 1
+
+    const majorVersion = ((versionByte >> 4) & 0xF)
+    const minorVersion = (versionByte & 0xF)
+
+    const type = raw.subarray(offset, 2).readUInt8(0)
+    offset += 1
+
+    const seqNo = raw.subarray(offset, 3).readUInt8(0)
+    offset += 1
+
+    const flags = raw.subarray(offset, 4).readUint8(0)
+    offset += 1
+
+    const sessionId = raw.subarray(offset, 8).readUInt32BE(0)
+    offset += 4
+
+    const length = raw.subarray(offset, 12).readUInt32BE(0)
+
+    return new Header(
+      majorVersion,
+      minorVersion,
+      type,
+      seqNo,
+      flags,
+      sessionId,
+      length,
+    )
+  }
+
+  get majorVersion(): number {
+    return this.#majorVersion
+  }
+
+  get minorVersion(): number {
+    return this.#minorVersion
+  }
+
+  get type(): PacketType {
+    return this.#type
+  }
+
+  get seq_no(): number {
+    return this.#seqNo
+  }
+
+  get flags(): number {
+    return this.#flags
+  }
+
+  get session_id(): number {
+    return this.#sessionId
+  }
+
+  get length(): number {
+    return this.#length
+  }
+
+  static readonly SIZE = 12
+}
diff --git a/test/index.test.ts b/test/index.test.ts
index 401553c..15e9a89 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -1,7 +1,42 @@
+import { Buffer } from 'node:buffer'
 import { describe, expect, it } from 'vitest'
+import { Header, PacketType } from '../src'
 
-describe('should', () => {
-  it('exported', () => {
-    expect(1).toEqual(1)
+describe('@noction/tacacs-plus', () => {
+  describe('header', () => {
+    it('should decode a valid header', () => {
+      const buffer = Buffer.from([
+        0x12,
+        0x01,
+        0x42,
+        0x10,
+        0x00,
+        0x00,
+        0x00,
+        0x01,
+        0x00,
+        0x00,
+        0x00,
+        0x0C,
+      ])
+
+      const header = Header.decodeHeader(buffer)
+
+      expect(header.majorVersion).toBe(1)
+      expect(header.minorVersion).toBe(2)
+      expect(header.type).toBe(PacketType.TAC_PLUS_AUTHEN)
+      expect(header.seq_no).toBe(66)
+      expect(header.flags).toBe(16)
+      expect(header.session_id).toBe(1)
+      expect(header.length).toBe(12)
+    })
+
+    it('should throw an error for an invalid header size', () => {
+      const invalidBuffer = Buffer.from([0x00, 0x01])
+
+      expect(() => Header.decodeHeader(invalidBuffer)).toThrowError(
+        'Header size must be 12, but received 2',
+      )
+    })
   })
 })